Co-reporter:Bao-jing Luo;Hong-fei Li;Wen-yang Zhang
Chinese Journal of Polymer Science 2017 Volume 35( Issue 5) pp:672-680
Publication Date(Web):2017 May
DOI:10.1007/s10118-017-1912-y
The crystalline structures and crystallization behaviors of iPP containing β nucleation agent TMB-5 (iPP/TMB-5) were investigated by synchrotron radiation wide angel X-ray diffraction (SR-WAXD), differential scanning calorimeter (DSC) and polarized light microscope (PLM). It was found that α-crystallization lagged behind β-crystallization at normal temperatures, but the discrepancy reduced with increasing temperature. TMB-5 could not induce β-iPP when the nucleation agent is wrapped up with α-crystal that crystallized at high temperatures. The polymorphic composition of iPP/TMB-5 was susceptible to the introductory moment of shear. New crystallization process of β-nucleated iPP was proposed to understand the experimental phenomena which could not be explained by those reported in the literature. It was supposed that polymer crystallization initiated from mesophase, and the formations of iPP crystals involved the organization of helical conformation ordering within mesophase. It was proposed that the iPP melt contained mesophases with stereocomplex-type ordering of right-handed and left-handed helical chains which could be disturbed by shear or TMB-5, leading to different polymorphic structures.
Co-reporter:Yunyi Zhang;Cuiyun Zhang;Jian Chen;Yongxin Li;Meiding Yang;Huipeng Zhou;Sohail Anjum Shahzad;Hong Qi;Cong Yu
Journal of Materials Chemistry C 2017 vol. 5(Issue 19) pp:4691-4694
Publication Date(Web):2017/05/18
DOI:10.1039/C6TC04938A
We exploit a real-time perylene probe fluorescence turn-on method to detect acetylcholinesterase (AChE) activity through the selective decomposition of MnO2 nanosheets. The surface of the MnO2 nanosheets is negatively charged. The perylene probe (P-4C+) has four positively charged quaternary ammonium groups. When mixed together, P-4C+ attached to the surface of the MnO2 nanosheets through electrostatic attractive interactions. The fluorescence of P-4C+ was effectively quenched by the MnO2 nanosheets. Acetylthiocholine (ATCh) could be hydrolyzed to thiocholine by AChE. Thiocholine is a reducing agent. It could reduce MnO2 nanosheets to Mn2+ and thus trigger the decomposition of the MnO2 nanosheets. As a result, P-4C+ was released and the fluorescence of P-4C+ was restored. The AChE inhibitor restrained the catalytic activity of AChE and resulted in a reduced fluorescence recovery of P-4C+. Our assay method is simple and selective, with low toxicity and better biocompatibility, which would facilitate biological and biomedical applications associated with AChE activity.
Co-reporter:Feifei Xue;Hongfei Li
RSC Advances (2011-Present) 2017 vol. 7(Issue 53) pp:33355-33363
Publication Date(Web):2017/06/29
DOI:10.1039/C7RA05705A
Lanthanide-based nanotechniques continue to attract considerable attention due to their current range of applications and broad potential in optical devices and biomedicine. Lanthanide ion-loaded block copolymers (BCPs) have gained interest, with questions remaining regarding their luminescence properties and structures. Solutions and films containing polystyrene-block-poly(2-vinylpyridine) (S2VP) and polystyrene-block-poly(4-vinylpyridine) (S4VP) loaded with trivalent lanthanide ions (Ln3+ = Eu3+, Tb3+) were prepared using a solvent displacement method and spin coating approach. Atomic force microscopy and transmission electron microscopy observations confirmed the Ln3+ distribution in the core of S2VP [Ln(x)] micelles and the corona of S4VP[Ln(x)] micelles. The coordination of Ln3+ and the S2VP core segment led to micelle shrinkage and film dewetting with increasing Ln3+ concentration, while the coordination of Ln3+ and the S4VP corona chain swelled the micelle. Photoluminescence investigations of the complex solutions showed typical reddish (Eu3+) and greenish (Tb3+) luminescence, and the emission intensity was enhanced with increasing Ln3+ concentration without typical fluorescence concentration quenching behavior. The luminescence intensity was distinctly enhanced when Ln3+ was distributed in the micellar core. Moreover, the emission spectra of mixed Eu–Tb ions complexes gave addition spectra of the two separated complexes. An orange color emission was observed because Eu3+ was more emissive. These results would improve understanding of ion coordination and lay the foundation for lanthanide ion/BCPs complex applications.
Co-reporter:Wenyang Zhang;Jingqing Li;Yingrui Shang;Hongfei Li;Lijia An
CrystEngComm (1999-Present) 2017 vol. 19(Issue 45) pp:6858-6868
Publication Date(Web):2017/11/20
DOI:10.1039/C7CE01465A
The crystalline structure evolution of poly(butylene terephthalate)/poly(carbonate) (PBT/PC) during stretching was investigated by in situ synchrotron wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS) at 70 °C. The WAXS results demonstrated that the crystallinity and crystallite size (D100) decrease with deformation. The α–β transition was observed during the deformation of PBT/PC blends. The orientation degree of the PBT (100) diffraction increases with strain in the PBT/PC blends. The SAXS data showed that PC is located in the interlamellar region of PBT for the undeformed samples. A structure model was proposed to describe the stretching-induced structure evolution of the PBT/PC blends.
Co-reporter:Wenyang Zhang;Jingqing Li;Yingrui Shang;Hongfei Li;Lijia An
CrystEngComm (1999-Present) 2017 vol. 19(Issue 45) pp:6858-6868
Publication Date(Web):2017/11/20
DOI:10.1039/C7CE01465A
The crystalline structure evolution of poly(butylene terephthalate)/poly(carbonate) (PBT/PC) during stretching was investigated by in situ synchrotron wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS) at 70 °C. The WAXS results demonstrated that the crystallinity and crystallite size (D100) decrease with deformation. The α–β transition was observed during the deformation of PBT/PC blends. The orientation degree of the PBT (100) diffraction increases with strain in the PBT/PC blends. The SAXS data showed that PC is located in the interlamellar region of PBT for the undeformed samples. A structure model was proposed to describe the stretching-induced structure evolution of the PBT/PC blends.
Co-reporter:H. L. Guo;J. F. Bi;Q. Y. Wu;J. Y. Wang;W. Q. Shi;X. Q. Zhang;S. C. Jiang;Z. H. Wu
RSC Advances (2011-Present) 2017 vol. 7(Issue 24) pp:14413-14421
Publication Date(Web):2017/03/03
DOI:10.1039/C7RA01249G
Nd-based ternary catalysts are widely used for the polymerization of isoprene in rubber industry, however structure information during the polymerization of isoprene as well as the catalytic mechanism are still ambiguous. In this paper, the in situ XAFS technique was used to extract the local atomic structure around the Nd center of the catalyst consisting of Nd(vers)3, AlEt3, and Al(iBu)2Cl. Theoretical calculations were used to verify the structure changes in the alkylation process. Four catalysts with different alkylaluminums {AlEt3, Al(nOct)3, Al(iBu)3, and Al(iBu)2H} were, respectively, used for the polymerization of isoprene. The results demonstrate that the substitution of Nd–C for Nd–O bonds is reasonable in the alkylation step. The structural evolutions in the alkylation and chlorination steps, as well as in the polymerization processes of isoprene are all similar for these Nd-based ternary catalysts with different alkylaluminum components. In the polymerization process of isoprene, there are only about 2 Nd–Cl bonds at 2.85 Å and 1–2 Nd–C bonds at 2.42 Å around the Nd centers which are in a monomer state. The Nd–C bonds can be attributed to the contribution of isoprene. This highly-opened structure of the Nd active centers activates greatly the catalytic activity of the Nd-based ternary catalysts. A conjectural catalytic mechanism for the polymerization of isoprene has been deciphered on the basis of the in situ XAFS results. This study is expected to be helpful for the improvement and application of the Nd-based ternary catalysts.
Co-reporter:Cuiyun Zhang, You Fan, Yunyi Zhang, Cong Yu, Hongfei Li, Yu ChenIan W. Hamley, Shichun Jiang
Macromolecules 2017 Volume 50(Issue 4) pp:
Publication Date(Web):February 10, 2017
DOI:10.1021/acs.macromol.6b02331
The self-assembly process of amphiphilic dendritic copolymers (ADPs) with a hydrophilic core and a hydrophobic shell was investigated via laser light scattering. The self-assembly occurs via a fast step and a slow step with different relaxation times. At the critical micelle concentration (CMC), the fusion of small micelles results in the rapid increase of the micelle size in the fast step. The slow step is associated with equilibrium through the fission and fusion of the micelles. The micelle size increases with the unimer concentration, which leads to a lower micelle concentration. The lower micelle concentration makes the relaxation time of the fast step increase with increasing unimer concentration. However, the fusion of larger micelles at higher concentration is more efficient to increase micelle size. The fusion of small micelles with large micelles at higher concentration accelerates the approaching equilibrium of the micelles except for the fission and fusion of micelles. With the increasing degree of amidation (DA), the relaxation time in the fast step increases and in the slow step it decreases.
Co-reporter:Lina Wang;Lin Xu;Binyuan Liu;Tongfei Shi;Lijia An
Soft Matter (2005-Present) 2017 vol. 13(Issue 17) pp:3091-3098
Publication Date(Web):2017/05/03
DOI:10.1039/C7SM00379J
The dewetting behavior of ring polystyrene (RPS) film and linear polystyrene (LPS) film on silanized Si substrates with different grafting densities and PDMS substrate was investigated. Results showed that polymer architectures greatly influenced the dewetting behavior of the thin polymer film. On the silanized Si substrate with 69% grafting density, RPS chains exhibited stronger adsorption compared with LPS chains, and as a result the wetting layer formed more easily. For LPS films, with a decreased annealing temperature, the stability of the polymer film changed from non-slip dewetting via apparent slip dewetting to apparently stable. However, for RPS films, the polymer film stability switched from apparent slip dewetting to apparently stable. On the silanized Si substrate with 94% grafting density, the chain adsorption became weaker and the dewetting processes were faster than that on the substrate with 69% grafting density at the same experimental temperature for both the LPS and RPS films. Moreover, on the PDMS substrate, LPS films always showed non-slip dewetting, while the dewetting kinetics of RPS films switched from non-slip dewetting to slip dewetting behaviour. Forming the wetting layer strongly influenced the stability and dewetting behavior of the thin polymer films.
Co-reporter:Wenyang Zhang, Jingqing Li, Yingrui Shang, Hongfei Li, Shichun Jiang, Lijia An
Materials & Design 2017 Volume 129(Volume 129) pp:
Publication Date(Web):5 September 2017
DOI:10.1016/j.matdes.2017.04.035
•The effect of temperature on young modulus, fracture strain and yield stress was analyzed for both PBT-100 and PBT-180.•The Ree-Eyring model was used to model the yield behavior.•The causes of stress whitening for PBT-100 and PBT-180 turned to be different.•The effect of temperature on the fracture morphologies was analyzed for both PBT-100 and PBT-180.The tensile behavior of PBT with different crystallinity was investigated at various temperatures. It turned out that the origin of stress whitening is different for PBT crystallized at 100 °C and 180 °C. The deformation of PBT crystallized at 100 °C involves crazing/tearing and fibrillation at different temperatures. The complicated fracture morphologies including brittle fracture, fibrillation and ductile ploughing are linked to the temperature-dependent deformation mode of PBT crystallized at 180 °C. The yield behavior could be described based on the Ree-Eyring model for PBT crystallized at 100 °C and 180 °C. The effect of temperature on Young's modulus, fracture strain and yield stress was analyzed and the fracture morphology was discussed in detail.Download high-res image (159KB)Download full-size image
Co-reporter:Huilong Guo, Jifu Bi, Jiayi Wang, Xuequan Zhang, Shichun Jiang, Zhonghua Wu
Polymer 2017 Volume 119(Volume 119) pp:
Publication Date(Web):16 June 2017
DOI:10.1016/j.polymer.2017.05.028
•Effect of alkylaluminum cocatalyst in Nd-based ternary catalyst was studied.•Isoprene polymerization results based on four catalyst systems shown different for the kind of alkylaluminum.•Local structures around Nd center of the four catalysts were obtained by XAFS technique.•The structural information is beneficial to elucidate the effect of alkylaluminum to the isoprene polymerization.Nd-based ternary catalyst systems are widely used for rubber industry. The effect of alkylaluminum cocatalysts has been investigated for decades. However, there is a lack of structural evidence, especially the quantitative result to illustrate the inner reasons. In the present paper, the effect of different alkylaluminum cocatalysts to the polymerization performance of isoprene has been studied. Catalysts adopted in the present paper all show high 1,4-cis selectivity (above 96%) of polyisoprene and kind of alkylaluminum is not the crucial factor to affect the microstructure of polyisoprene. By comparing the polymerization performance of isoprene and the local atomic structure around Nd centers, it can be concluded that the short carbon-chain in the alkylaluminum cocatalyst is helpful to increase the percent conversion of isoprene. While the carbon-chain length and number in each alkylaluminum cocatalyst can be used to modulate the molecular weight of the synthesized polyisoprene. All the results in the present paper provide a clue to improve the Nd-based ternary catalyst for rubber synthesis.Download high-res image (242KB)Download full-size image
Co-reporter:Cuiyun Zhang, Cong Yu, Yuyuan Lu, Hongfei Li, Yu Chen, Hong Huo, Ian William Hamley and Shichun Jiang
Polymer Chemistry 2016 vol. 7(Issue 18) pp:3126-3133
Publication Date(Web):05 Apr 2016
DOI:10.1039/C6PY00394J
A series of amphiphilic dendritic copolymers (ADPs) with different degrees of amidation (DA) were synthesized by the amidation reaction of polyethyleneimine (HPEI) with dendritic palmitate tails. The hydrodynamic radii (Rh) of the polymers were investigated via dynamic light scattering (DLS). It was found that Rh increased with increasing DA, and a sharp increase was noted when DA was near 51 percent. The intrinsic viscosity was measured using an Ubbelohde capillary viscometer to understand the structure evolution of the ADPs. The results showed that the intrinsic viscosity decreased slowly with increasing DA. The Fox–Flory formula was employed to calculate the radius of gyration (Rg). The ratio of Rg and Rh was around 0.77, which indicated that the ADPs were compact. The solvent effects on Rh were investigated which showed that the Rh in chloroform was bigger than that in a poor solvent for HPEI. However, Rh remained unchanged with the increasing volume fraction of poor solvent for HPEI from twenty percent to eighty percent. The solvent quality has no obvious influence on the relationship between Rh and Mn before DA = 51 percent, but a sharper slope is noted after DA = 51 percent. This phenomenon can be explained by the compact structure of the ADPs. The Rh values remained constant for the synthesized DA within the measured temperature range in chloroform and glycol dimethyl ether.
Co-reporter:Chuanyong Zong;Yan Zhao;Haipeng Ji;Jixun Xie;Xue Han;Juanjuan Wang;Yanping Cao;Conghua Lu;Hongfei Li
Macromolecular Rapid Communications 2016 Volume 37( Issue 15) pp:1288-1294
Publication Date(Web):
DOI:10.1002/marc.201600229
Co-reporter:Chengbo Zhou, Hongfei Li, Wenyang Zhang, Jingqing Li, Shaoyong Huang, Yanfeng Meng, Jesper de Claville Christiansen, Donghong Yu, Zhonghua Wu and Shichun Jiang
CrystEngComm 2016 vol. 18(Issue 18) pp:3237-3246
Publication Date(Web):04 Apr 2016
DOI:10.1039/C6CE00464D
The cold crystallization behaviors and structure evolutions of amorphous PLA stretched within a high-temperature range (100–150 °C) were investigated via in situ synchrotron WAXS and SAXS measurements. The PLA stretched at 120 °C exhibits excellent mechanical properties with the highest modulus, stretching strength and moderate elongation, which is attributed to the coordination effect of thermally-induced initial crystallinity and moderate chain segment mobility. The WAXS results showed that the diffraction peaks of (200/110) and (203) planes shift to higher 2θ values, which indicates the formation of more ordered α′ and α forms during PLA stretching within 100–150 °C. More α forms can be formed from the stretched α′ form and/or from the amorphous phase at 100 °C. The phase diagram of α and α′ forms in stretched PLA with stretching temperature was proposed according to the obtained data of lattice spacing. The crystallinity of stretched PLA increases faster than that which underwent quiescent cold crystallization at the same temperature. The SAXS results indicated that the long period and lamellar thickness along and vertical to the stretching direction of PLA stretched within 100–150 °C exhibit distinct variations, which is attributed to the difference of strain-induced crystallization and lamellar orientation.
Co-reporter:Baojing Luo;Hongfei Li;Chengbo Zhou;Wenyang Zhang;Jingqing Li;Xuehao He
Macromolecular Chemistry and Physics 2016 Volume 217( Issue 12) pp:1354-1360
Publication Date(Web):
DOI:10.1002/macp.201500542
Co-reporter:Xianjing Gong;Dean Shi;Huihui Zeng;Yingkui Yang;Tao Jiang;Qunchao Zhang;Robert K. Y. Li;Yiu-Wing Mai
Macromolecular Chemistry and Physics 2016 Volume 217( Issue 14) pp:1607-1613
Publication Date(Web):
DOI:10.1002/macp.201600040
Co-reporter:Wenyang Zhang;Chengbo Zhou;Yao Zhang;Feifei Xue
Colloid and Polymer Science 2016 Volume 294( Issue 2) pp:321-328
Publication Date(Web):2016 February
DOI:10.1007/s00396-015-3789-z
The deformation behavior is closely related to the structures and mechanical properties of polymers. The structural evolution during deformation is fundamental to understand the deformation mechanism and control the properties of polymers. Deformation-induced structure transitions contain a stable structure to metastable one or metastable structure to a stable one. The structures of the uniaxially stretched poly(butylene succinate) (PBS) at different temperatures were directly investigated by in situ synchrotron wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS). The data reveal the initial strain of the α-β transition increases with the stretching temperatures. A quantitative analysis was performed to explore the crystal transition mechanisms of the stretched PBS.
Co-reporter:Xian-jing Gong;De-an Shi 施德安;Ying-kui Yang
Chinese Journal of Polymer Science 2016 Volume 34( Issue 8) pp:1039-1046
Publication Date(Web):2016 August
DOI:10.1007/s10118-016-1815-3
Cross-linked PEG-based copolymers were obtained via synthesis of polyethylene glycol (PEG) and methoxy polyethylene glycol (MPEG) by the bridging and/or cross-linking agent of 2,4-tolylene diisocyanate (TDI) and/or hexamethylene-1,6-diisocyanate homopolymer (HDI trimer). The effects on the crystallization behaviors of the samples could be found with the changes in molecular weight of MC-PEG and molecular weight of SC-PEG in certain cross-linked density. It is revealed that the samples appear not to crystallize when the molecular weight of MC-PEG and SC-PEG are 1000 g/mol or less than that. The samples begin to crystallize when the molecular weight of either MC-PEG or SC-PEG reaches 2000 g/mol. The crystallinity of crystallized MC-PEG decreases with the increasing molecular weight of uncrystallized SC-PEG and the crystallinity of crystallized SC-PEG declines with the rise of molecular weight of uncrystallizable MC-PEG. The chains of SC-PEG (Mn = 2000 g/mol) can fold and align easilier than those of MC-PEG (Mn = 2000 g/mol), when the content of PEG is the same.
Co-reporter:Huilong Guo;Chengbo Zhou;Wenyang Zhang;Jiayi Wang
Colloid and Polymer Science 2016 Volume 294( Issue 12) pp:1983-1988
Publication Date(Web):2016 December
DOI:10.1007/s00396-016-3964-x
The deformation-induced crystalline structure evolutions of isotactic poly-1-butene (iP-1-B) during uniaxial stretching at different temperatures (45 and 75 °C) were investigated with in situ wide-angle X-ray scattering (WAXS) technology. The form I of iP-1-B was employed in this study. The obtained data on structure evolutions revealed that orientations would occur when the applied stress reached a critical value, while the orientation mechanisms are different at the two investigated temperatures. The crystallinity at 75 °C declines fast during deformation, and the orientation is caused by the melting disparity between the crystals parallel and perpendicular to the stretching direction. The high crystalline content during stretching at 45 °C maintains throughout the tensile process and the rotation of crystalline blocks results in the orientation. A brief schematic diagram was given to clarify the routes of orientation at the two temperatures.
Co-reporter:Qing-long Song;Hui-ying Wen 温慧颖
Chinese Journal of Polymer Science 2016 Volume 34( Issue 9) pp:1172-1182
Publication Date(Web):2016 September
DOI:10.1007/s10118-016-1820-6
Poly(trimethylene terephthalate)/polycarbonate (PTT/PC) blends were prepared by solvent mixing to avoid transesterification during high temperature blending. The influences of compositions on the thermal behavior, crystallization morphology and structure of the blends were studied. FTIR results indicated that there was no COO linking to two phenyl groups on each side chain and DSC results supported no transesterification reaction. DSC curves showed that Tc and Tmc increased to maximum range when PC contents were between 7 wt%-15 wt%, however, Tm decreased constantly with the increase of PC contents. It was observed from POM that PTT spherulitic morphology and crystallization kinetics were obviously influenced by the change of PC contents. Structural evolutions during cooling were investigated by SAXS which showed Lc of PTT remained a constant with different PC contents and also fixed during crystallization, nevertheless, it revealed a maximum value of Lnc for sample PTT93. It was concluded that PC chains could be permeated into not only amorphous crystallite structure but also amorphous lamellae structure and 7 wt% PC content was supposed to be the “proper” penetration amount into PTT lamellae structure which led to a maximum capacity of amorphous lamellar layer. Fringedmicelle crystal model was adopted to illustrate semi-crystalline physical structures of the blend in two kinds of component aggregation states.
Co-reporter:Jingqing Li, Peitao Xiao, Hongfei Li, Yao Zhang, Feifei Xue, Baojing Luo, Shaoyong Huang, Yingrui Shang, Huiying Wen, Jesper de Claville Christiansen, Donghong Yu and Shichun Jiang
Polymer Chemistry 2015 vol. 6(Issue 21) pp:3988-4002
Publication Date(Web):16 Apr 2015
DOI:10.1039/C5PY00254K
Poly(L-lactide) (PLLA)/graphene nanosheet (GNS) composites and pure PLLA were prepared by the solution blending method. Crystalline structures and crystallization behaviors of PLLA in the composite were investigated by XRD, POM, SAXS, and DSC. It was found that α′ form PLLA formation seemed to be more preferred than α form PLLA formation in PLLA/GNS composites at crystallization temperatures Tcs within the α′–α crystal formation transition region due to the existence of GNSs, resulting in an obvious shift of the α′–α crystal formation transition of PLLA in PLLA/GNSs towards high Tcs compared with that of pure PLLA. At Tcs below α′–α crystal formation transition, the formed α′ crystal turned to be more imperfect due to GNS addition, while at Tcs above α′–α crystal formation transition, the crystal structure of α form PLLA was not affected by GNSs. Further POM observations at high Tcs with only α crystal formed showed that PLLA spherulites were well formed in both PLLA/GNSs and pure PLLA, however with very different crystallization kinetics while isothermally crystallizing at different Tcs. The PLLA crystallization process of PLLA in PLLA/GNSs was accelerated by GNSs with both the nucleation rate and spherulite growth rate increased mainly because of the increasing segmental mobility of PLLA chains due to GNS addition; whereas, GNSs showed no observable influence on the determined zero growth temperature Tzg of α form PLLA and the Tzg was estimated lower than the equilibrium melting point of PLLA, indicating that the crystal growth of PLLA is mediated by a transient mesophase with the transition temperature of Tzg between the mesophase and melt not influenced by GNSs in PLLA. Synchrotron on-line SAXS results revealed that the long periods of PLLA in PLLA/GNS composites isothermally crystallized at different Tcs are much smaller than those in pure PLLA. The GNSs are helpful in forming more perfect recrystallized α form PLLA after the α′ form PLLA is melted with increasing Tcs. The presence of GNSs resulted in imperfect α form PLLA from melt directly when it is isothermally crystallized at different Tcs within the temperature range of α′–α crystal formation transition.
Co-reporter:Chengbo Zhou, Hongfei Li, Yao Zhang, Feifei Xue, Shaoyong Huang, Huiying Wen, Jingqing Li, Jesper de Claville Christiansen, Donghong Yu, Zhonghua Wu and Shichun Jiang
CrystEngComm 2015 vol. 17(Issue 30) pp:5651-5663
Publication Date(Web):08 Jun 2015
DOI:10.1039/C5CE00669D
Poly(lactic acid) (PLA) is a bio-based and compostable thermoplastic polyester that has rapidly evolved into a competitive commodity material over the last decade. One key bottleneck in expanding the field of application of PLA is the control of its structure and properties. Therefore, in situ investigations under cooling are necessary for understanding the relationship between them. The most intriguing feature of a supercooled liquid is its dramatic rise in viscosity as it is cooled toward the glass transition temperature (Tg) though accompanied by very little change in the structural features observable by typical X-ray experiments. The deformation behaviors and structure evolution of glassy PLA during uniaxially stretching below Tg were investigated in situ by synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) techniques. The stretched samples were measured by differential scanning calorimetry (DSC). The obtained results showed that the deformation and yield stress of glassy PLA are strongly dependent on the stretching temperatures together with the transition from mesophase to mesocrystal and the formation of cavities. With the increase in drawing temperature, the onset of the mesocrystal formation is delayed to a higher strain value, whereas corresponding to the same critical orientation degree of amorphous chains (fam ≈ 0.45). The DSC results indicated that the post-Tg endothermic peak corresponding to the melting of mesocrystal appears and shifts to a higher temperature with increasing stretching temperature, followed by the down-shifts (to a lower temperature) of the exothermic peak of cold crystallization of PLA. The appearance of a small exothermic peak just before the melting peak related to the transition of the α′ to α crystal implies the formation of an α′ crystal during cold crystallization in the drawn PLA samples. The structure evolution of glassy PLA stretched below Tg was discussed in details.
Co-reporter:Huilong Guo, Jifu Bi, Jiayi Wang, Xuequan Zhang, Shichun Jiang and Zhonghua Wu
Dalton Transactions 2015 vol. 44(Issue 19) pp:9130-9139
Publication Date(Web):02 Apr 2015
DOI:10.1039/C5DT01064K
Lanthanide-based catalysts are highly active for isoprene polymerization in hexane. In this paper, a ternary catalyst consisting of neodymium neodecanoate {Nd(vers)3}, Al(iBu)3 and Al(iBu)2Cl was studied by using X-ray-absorption fine-structure (XAFS) technique. A sealed and moisture-proof liquid sample cell with adjustable thickness was designed for Nd LIII-edge XAFS measurements. Based on the XAFS data analysis, detailed structure changes around the Nd center were obtained. It was found that the Nd(vers)3 molecules formed an oligomer structure in hexane solution with two Nd–O subshells (5O @ 2.39 Å and 5O @ 2.54 Å) around the Nd center. The alkylation process by adding Al(iBu)3 to the hexane solution of Nd(vers)3 partially destroyed the aggregation degree of Nd(vers)3 molecules in hexane solution. Al(iBu)3 ligands were bonded to the Nd center by Nd–C bonding. With the Nd:Al ratio increasing from 1:2.5 to 1:10, the O neighbors around Nd decreased from 4 to 2 but with an unchanged Nd–O bond length of 2.38 Å, and the C neighbors around Nd were kept at ca. 4 with Nd–C bond lengths in the range of 2.57–2.58 Å. The Nd–O bonds can be further replaced by Nd–C bonds during the aging process. The chlorination process by adding Al(iBu)2Cl to the mixture solution of Nd(vers)3 and Al(iBu)3 restrained intensively the agglomeration of Nd(vers)3 molecules in hexane solution. Al(iBu)2Cl ligands were bonded to the Nd center by Nd–Cl bonds. There were about 3–4 C neighbors at 2.58 Å, 2 Cl neighbors at 2.87 Å, and 2 Al next-neighbors at 3.14 Å around the Nd center. After allowing the ternary catalyst to stand for 5 days, the coordination numbers of Nd–C and Nd–Cl were all stabilized to 3 without bond length changes, and partial single Cl− anions were also bonded to the Nd center. All these structural details and their change tendency demonstrate that the decrease of aggregation degree of Nd(vers)3 molecules in hexane solution can improve the catalytic activity of the ternary lanthanide-based catalyst system.
Co-reporter:Yingrui Shang, Xiaoxing Zhang, Huan Xu, Jingqing Li, Shichun Jiang
Polymer 2015 Volume 77() pp:254-265
Publication Date(Web):23 October 2015
DOI:10.1016/j.polymer.2015.09.017
•The correlation between micro-/meso- structure and properties of amorphous polymers are studied with molecular dynamics simulation•The time-temperature superposition is quantitatively simulated by the MD modeling•The conformational parameters were found to be proportional to T1/2•The in-situ investigation evidenced the structural essence of yielding•The in-situ simulation showed the reason why the yielding points disappear above Tg.•The potential ratio illustrated the abrupt changes in structural elements on yielding.A molecular dynamics model was established to simulate the uniaxial deformation of polymer materials. Efforts were made on revealing the relation of microstructure evolution on mechanical properties of polymers at different temperature and strain rate. The numerical model semi-quantitatively represented the time-temperature equivalence of polymer materials. Conformational parameters such as the bond length, bond angle, and radius of gyration were measured quantitatively, and it showed that the change of mechanical properties with increasing temperature is due to the increase in atomic kinetic energy. And as shown in the simulation, above Tg, the atomic thermal movement surpassed the particle pair-wise potential and chain entanglement. The in-situ simulation was conducted during uniaxial deformation. The results showed that chain segments are constrained around their equilibrium positions in elastic deformation stage. While after yielding, the entanglement density decrease rapidly, the orientation parameter and content of dihedral angles in trans state increase aggressively after yielding, indicating that the pair-wise forces were surpassed and the bonds and bond angles were stretched. The energy analysis of interatomic potentials also showed that the sliding between the macromolecules is dominating after the chains are stretched and extended. The proposed coefficient, potential ratios, parameterized the influences of different structural elements during deformation. All the potential ratios exhibited extremums at yield points, illustrating that the van der Waals potential is dominating before yielding but overwhelmed by bond and angle potentials afterwards. Consequently, Tg can be described as a critical point above which the effects of excess kinetic energy exceed the pair-wise potential, which explains that yielding point turned to vague at temperatures above Tg.
Co-reporter:Benping Wang;Xianjing Gong;Jingqing Li;Yingrui Shang
Journal of Polymer Research 2015 Volume 22( Issue 12) pp:
Publication Date(Web):2015 December
DOI:10.1007/s10965-015-0889-x
Poly (vinylidene fluoride) (PVDF)/graphene composites were prepared through the melt blending method. The growths of PVDF spherulites in the composites at various temperatures were observed by means of polarized optical microscope (POM), and the melting behaviors were investigated with differential scanning calorimetry (DSC). The POM images showed that the spherulites morphology of PVDF in both pure PVDF and the composite samples presented the same well-defined Maltese-cross texture, and the radial growth rates of PVDF spherulites decreased with increasing crystallization temperature. Two equilibrium melting temperatures of PVDF were obtained and the equilibrium melting temperature of the samples crystallized above 160 °C was higher than that crystallized below 160 °C, which was attributed to the different crystal structures. Zero growth temperature of native PVDF spherulite was obtained according to the samples that crystallized above 160 °C. There is no obvious influence of adding graphene on the zero growth temperature of PVDF in the composites.
Co-reporter:Baojing Luo, Hongfei Li, Yao Zhang, Feifei Xue, Peipei Guan, Jing Zhao, Chengbo Zhou, Wenyang Zhang, Jingqing Li, Hong Huo, Dean Shi, Donghong Yu, and Shichun Jiang
Industrial & Engineering Chemistry Research 2014 Volume 53(Issue 34) pp:13513-13521
Publication Date(Web):2017-2-22
DOI:10.1021/ie502062k
Shearing is unavoidable during the polymer process, and isotactic polypropylene (iPP) is one of the most used commercial polymers. iPP mixed with β-nucleating agent TMB-5 was isothermally crystallized at 135 °C from melts under various shear conditions and investigated via synchrotron radiation small-angle and wide-angle X-ray scattering (SAXS and WAXS) techniques with CCD detector. The shear-induced crystalline structure and the orientation of the samples were studied according to the obtained WAXS and SAXS patterns. The results showed that both the crystallinity of α-iPP and β-iPP are in direct proportion to the orientation degree rather than shear rate especially at high shear rate, which proves that wall slip should not be neglected when taking shear effect or rheological behavior into consideration.
Co-reporter:Feifei Xue, Xuesi Chen, Lijia An, Sergio S. Funari and Shichun Jiang
RSC Advances 2014 vol. 4(Issue 99) pp:56346-56354
Publication Date(Web):24 Oct 2014
DOI:10.1039/C4RA09284H
The time dependent hierarchical structures and crystallization behaviors of synthetic crystalline–crystalline symmetric diblock copolymer poly(ethylene oxide)-b-polylactide (PEO-b-PLLA) were investigated by DSC and synchrotron simultaneous small-angle/wide-angle X-ray scattering (SAXS/WAXS)measurements with various isothermal crystallization conditions. DSC measurements indicated that both blocks can crystallize and melt independently. Synchrotron SAXS/WAXS results showed that the structures and crystallization behaviors of PLLA and PEO blocks influence each other and the crystallization of both blocks could induce microphase separation into layer-layer structures, however, the crystalline structures of both blocks are not affected. It is assumed that the final structure of the crystalline–crystalline block copolymer is determined by the crystallization behaviors of the blocks rather than the glass transition temperature of the PLLA block and the theoretical microphase structure of the block copolymers.
Co-reporter:Shaoyong Huang and Shichun Jiang
RSC Advances 2014 vol. 4(Issue 47) pp:24566-24583
Publication Date(Web):23 May 2014
DOI:10.1039/C4RA03043E
Biocompatible and biodegradable block copolymers (BBCPs) have become increasingly important in polymer science, and have many potential applications in polymer materials. The structures of BBCPs, which are determined by the competition between crystallization, microphase separation, kinetics and processing, have a tremendous influence on the final properties and applications. In this review, the most recent advances are highlighted in the crystalline structures and morphologies of BBCPs with at least one crystalline block. Particular emphasis is placed on the influences of chemical composition, molecular architecture, crystallization pathway, and film thickness on the structures and morphologies of the block copolymers. The formation and the characteristics of the structures grown in the block copolymers are helpful for understanding the interplay between crystallization and phase segregation, morphologies, structural evolution and their applications.
Co-reporter:Feifei Xue, Hongfei Li, Jichun You, Conghua Lu, Günter Reiter, Shichun Jiang
Polymer 2014 Volume 55(Issue 22) pp:5801-5810
Publication Date(Web):23 October 2014
DOI:10.1016/j.polymer.2014.09.031
•The crucial role of conformationally restricted effects from micelle to thin film was demonstrated in detail for the first time.•Coalescence process occurred as the result of intermolecular coordination.•A facile one-step procedure for the preparation of block copolymer mesoporous materials was proposed.Block copolymers (BCPs) with inorganic components gained ground as a useful material with a broad range of applications. It is still a matter of discussion what influences of inorganic components on block copolymer structures. In this work we present the critical role of conformationally restricted effect by cadmium acetate (Cd(Ac)2) on microscopic structure and film stability of polystyrene-block-poly(2-vinylpyridine) (S2VP) and polystyrene-block-poly(4-vinylpyridine) (S4VP). The influence of ion concentration, coordination type, as well as physical ageing on micelles and films were investigated and discussed. It was revealed that the coordination type played a critical role in both micelle and thin film morphology. As ion concentration increased, the intermolecular coordination between Cd(Ac)2 and S4VP led to significant micelle coalescence and a decrease of film stability. However, intramolecular coordination between Cd(Ac)2 and S2VP only affected the micelle size. The film prepared from a physically aged low Cd2+ concentration S4VP solution formed mesoporous structure. AFM and GISAXS results showed excellent lateral ordering within mesoporous films. These results suggest a facile procedure for the preparation of block copolymer mesoporous structures which can provide the base for highly functional materials such as highly efficient catalysts, photonic devices, and photovoltaic films.
Co-reporter:Feifei Xue, Hongfei Li, Lijia An, Shichun Jiang
Journal of Colloid and Interface Science 2013 Volume 399() pp:62-67
Publication Date(Web):1 June 2013
DOI:10.1016/j.jcis.2013.02.033
One of the most important issues for spin-coated diblock copolymer thin films is to distinguish the blocks by common techniques, especially for the diblock copolymers containing one block could form active domain. Aiming different estimations on the composition of surface microdomains in polystyrene-block-poly (4-vinylpyridine) (PS-b-P4VP) atomic force microscope (AFM) phase images, AFM, transmission electron microscopy, and droplet shape analyzer were used to identify the constructional details of the polymer thin film morphology. It was confirmed that PS block is harder than P4VP block in symmetric PS-b-P4VP films and corresponds to brighter regions in AFM phase image. It is helpful to distinguish the nanodomains that originate from the different blocks in PS-b-P4VP thin films. The structure evolutions of PS-b-P4VP film annealed with different selective solvents were studied and discussed. The results indicated that the core-corona inversion process is due to the cores of micelles swell and coalesce together rather than local reorganization of the chains.Graphical abstractHighlights► The estimations on the composition of microdomains in PS-b-P4VP film morphology are important. ► The mechanical properties or Tgs of the blocks were used to decide the composition. ► AFM, TEM, and droplet shape analyzer (DSA) were performed to analyze AFM phase image. ► The film morphology evolution with solvent vapor annealing and possible mechanism was proposed.
Co-reporter:Peitao Xiao, Hongfei Li, Shaoyong Huang, Huiying Wen, Donghong Yu, Yingrui Shang, Jingqing Li, Zhonghua Wu, Lijia An and Shichun Jiang
CrystEngComm 2013 vol. 15(Issue 39) pp:7914-7925
Publication Date(Web):01 Aug 2013
DOI:10.1039/C3CE40466H
The shearing effects of sheared polymer melts on their finally formed crystalline structures of poly(L-lactide) (PLLA) were investigated by means of small angle X-ray scattering (SAXS) and wide angle X-ray diffraction (WAXD). The results of WAXD prove that shear has no effects on the crystal structure of PLLA. The SAXS results demonstrate that both of the long period and the thickness of crystalline lamellae increase with rising shear rates when vertical to the shear direction, but remains constant when being parallel to the shear direction. The structural changes for samples prepared with different shear temperature or under the same shear strain but different shear rate were investigated. The mesophase of polymer melts and shearing effects on their pre-ordered phase turned out to be the key factor affecting the crystal structure of PLLA under different shearing conditions.
Co-reporter:Huilong Guo, Yao Zhang, Feifei Xue, Ziwei Cai, Yingrui Shang, Jingqing Li, Yu Chen, Zhonghua Wu and Shichun Jiang
CrystEngComm 2013 vol. 15(Issue 8) pp:1597-1606
Publication Date(Web):29 Nov 2012
DOI:10.1039/C2CE26578H
The crystalline structure evolution of poly(vinylidene fluoride) (PVDF) during tensile deformation at 60 °C, 140 °C and 160 °C, i.e. between the glass transition temperature (Tg) and the melting temperature (Tm), was investigated by in-situ synchrotron SAXS and WAXS techniques. The analysis of the obtained scattering results indicated either yielding or α–β transformation in PVDF occurred and initiated at almost the same strain level with different stretching temperatures. A deformation mechanism was proposed for PVDF to illustrate the structure evolution during uniaxial stretching at high temperature indicating that the initial crystallite and crystalline lamellae structures of stretched PVDF are destroyed and orientated not simultaneously, which is intimately related to the yield point and the initial of α–β transformation on a certain degree of orientation. The long period along tensile direction increases to a maximum and then drops into a lower but stable value during this stage of deformation.
Co-reporter:Feifei Xue and Shichun Jiang
RSC Advances 2013 vol. 3(Issue 46) pp:23895-23908
Publication Date(Web):10 Sep 2013
DOI:10.1039/C3RA43504K
Block copolymers (BCPs) self-assemble into well-ordered morphologies ranging from spheres to cylinders to lamellae depending upon their chemical structures, preparation conditions and dynamic processes. Recently, ion/BCP hybrids have become highly attractive materials due to their flexibility, processability, self-assembling ability and novel features of inorganic components such as electronic, magnetic and optical properties. Therefore, to control the structure and functionalization of ion/BCP hybrids has been a significant challenge in material preparation and manufacturing. The progress of ion/BCP hybrids in bulk and thin films including the influence of ions upon the phase behavior of AB diblock and ABC triblock copolymer bulks has been reviewed, starting from fundamental principles and extending to recent promising developments, along with contributions to aligning block copolymer nanostructures and important applications such as solid-state batteries, fuel cells, nanolithography, templating, and patterning of nanoparticles.
Co-reporter:Ziwei Cai;Yao Zhang;Jingqing Li;Yingrui Shang;Hong Huo;Jiachun Feng;Sergio S. Funari
Journal of Applied Polymer Science 2013 Volume 128( Issue 1) pp:628-635
Publication Date(Web):
DOI:10.1002/app.38181
Abstract
The crystallization behavior of isotactic polypropylene (iPP) induced with various concentrations of the β-form nucleating agent aryl amide derivative (TMB-5) at different temperatures was investigated with synchrotron small-angle X-ray scattering and wide-angle X-ray scattering (WAXS) and polarized optical microscopy. The WAXS results indicate that TMB-5 is a temperature-dependent selective nucleating agent for iPP crystallization. This means that only β crystals or α crystals form at low or high crystallization temperatures, respectively; both β and α crystals can be found at a suitable crystallization temperature. A mechanism was proposed to understand this phenomenon and the crystallization behavior of iPP with the nucleating agent. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Co-reporter:Fei-fei Xue;Xue-si Chen;Li-jia An;Sergio S. Funari
Chinese Journal of Polymer Science 2013 Volume 31( Issue 9) pp:1260-1270
Publication Date(Web):2013 September
DOI:10.1007/s10118-013-1325-5
The real time and in situ investigation of the crystallization process and structure transitions of asymmetric crystalline-crystalline diblock copolymers from the melt was performed with synchrotron simultaneous SAXS/WAXS. The asymmetric poly(ethylene oxide)-b-poly(ɛ-caprolactone) diblock copolymers were chosen for the present study. It was shown that the short blocks crystallized later than the long blocks and final lamellar structure was formed in all of the asymmetric diblock copolymers. The final lamellar structure was confirmed by AFM observation. The SAXS data were analyzed with different methods for the early stage of the crystallization. The Guinier plots indicated that there were no isolated domains formed before the formation of lamellae in the asymmetric diblock copolymers during the crystallization process. Debye-Bueche plots implied the formation of correlated domains during crystallization.
Co-reporter:Yao Zhang;Zhijie Zhang;Hongfei Li;Donghong Yu
Journal of Polymer Research 2013 Volume 20( Issue 12) pp:
Publication Date(Web):2013 December
DOI:10.1007/s10965-013-0312-4
The dielectric relaxation spectroscopy results indicate that the relaxation peak of PCL for pure PCL and PCL/LiClO4 complexes shifts to a lower frequency with increasing crystallization temperature, while the amorphous, condensed structure of PCL for pure PCL and PCL/LiClO4 complexes is slightly affected by crystallization temperature. These findings were obtained from small-angle X-ray scattering (SAXS) measurements. To further understand the effect of crystallization temperature on the relaxation behavior of PCL and PCL/LiClO4 complexes, the isothermal crystallization process of PCL and PCL/LiClO4 was probed in situ by dielectric spectra measurement. The analysis indicated that the relaxation dynamics for pure PCL and PCL/LiClO4 complexes decrease continuously during the isothermal crystallization process, even at the crystallization induction period. This paper presents a detailed discussion of the crystallization mechanisms of the PCL and PCL/LiClO4 complexes, and the probable explanation as to the effect of crystallization temperature on the relaxation dynamics of PCL and PCL/LiClO4 .
Co-reporter:Yi Liu, You Fan, Yuan Yuan, Yu Chen, Fa Cheng and Shi-Chun Jiang
Journal of Materials Chemistry A 2012 vol. 22(Issue 39) pp:21173-21182
Publication Date(Web):22 Aug 2012
DOI:10.1039/C2JM34445A
A series of organo-soluble gold nanoparticles (AuNPs) were prepared through the reduction of HAuCl4 by NaBH4 in the presence of amphiphilic hyperbranched copolymers bearing a hydrophilic hyperbranched polyethylenimine (PEI) core and a hydrophobic dendritic shell. For comparison, the corresponding analogues with a PEI core and a linear shell were also used to prepare the organo-soluble AuNPs. All the obtained AuNPs were characterized by transmission electron microscopy. It was found that under a high feed ratio of polymer to HAuCl4, the average diameter of the obtained small AuNPs was similar, and was independent of the shell morphology of the hyperbranched polymeric stabilizers. Reducing the feed ratio of polymer to HAuCl4 led to the formation of larger AuNPs and irregularly shaped AuNP aggregates. The stability evaluation on the basis of two-month shelf-storage demonstrated that the obtained AuNPs were stable under shelf-storage regardless of whether the shell of the hyperbranched polymeric stabilizer was dendritic or linear. These organo-soluble AuNPs could be used as efficient catalysts for the biphasic catalytic reduction of 4-nitrophenol by NaBH4, and could also be conveniently recovered and reused. The stabilizers with a dendritic shell endowed the AuNP catalyst with a higher performance than the corresponding stabilizers with a linear shell, including: (1) a higher catalytic rate; (2) the ability to be recovered and reused more times; (3) a maximal turnover number of around 23000, which is unprecedented in the catalytic reduction of 4-nitrophenol.
Co-reporter:Yi Liu, You Fan, Xun-Yong Liu, Song-Zi Jiang, Yuan Yuan, Yu Chen, Fa Cheng and Shi-Chun Jiang
Soft Matter 2012 vol. 8(Issue 32) pp:8361-8369
Publication Date(Web):03 Jul 2012
DOI:10.1039/C2SM25732G
The 2,2-bis(hydroxymethyl)propionic acid (BHP)-based generation 1 dendron with two palmitate tails (D1-C16) and the generation 2 dendron with four palmitate tails (D2-C16) were synthesized. The coupling of D1-C16 or D2-C16 with hyperbranched polyethylenimine (PEI) through the amidation reaction resulted in amphiphilic hyperbranched copolymers bearing a hyperbranched PEI core and a dendritic D1-C16 shell or dendritic D2-C16 shell. The structure of the obtained copolymers was verified through Fourier transform infrared (FTIR) and 1H nuclear magnetic resonance (NMR) characterization. Differential scanning calorimetry (DSC) measurement demonstrated that the existence of the branching units in the shell pronouncedly reduced the crystallinity of the hyperbranched copolymers, and the copolymers with less branched shells had a higher melting temperature and melting enthalpy. These novel amphiphilic hyperbranched copolymers could be used as nanocarriers to efficiently accommodate the hydrophilic guests, including Methyl Orange (MO), Congo Red (CR) and Direct Blue 15 (DB), into the hydrophilic amidated PEI core. Each nanocarrier with a branched shell could accommodate a much higher number of guests than the corresponding nanocarriers with linear shells, which indicated that the dendritic structure of the shell played a key role in significantly enhancing the encapsulation capacity of the nanocarriers. As far as the weight ratio of the encapsulated guests to the nanocarriers was concerned, the nanocarriers with branched shells could be modulated to have a similar encapsulation capacity for the small MO with a mono-sulfonate group, but a much superior encapsulation capacity for the large CR and DB guests with multi-sulfonate groups to the nanocarriers with linear shells.
Co-reporter:Yao Zhang, Hong Huo, Jingqing Li, Yingrui Shang, Yu Chen, Sergio S. Funari and Shichun Jiang
CrystEngComm 2012 vol. 14(Issue 23) pp:7972-7980
Publication Date(Web):23 Aug 2012
DOI:10.1039/C2CE25126D
The crystalline structures and isothermal crystallization behavior of poly(ε-caprolactone) (PCL) and PCL/LiClO4 complexes from the melt were investigated via time-resolved simultaneous synchrotron small-angle and wide-angle X-ray scattering (SAXS/WAXS) measurements in this paper. The influences of Li salts and crystallization temperature on the isothermal crystallization behavior and structural evolution dynamics of PCL were discussed. The results indicated that Li salts affected the crystallization behavior of PCL without changing the structure of the crystalline. It was also shown that the formation of pre-ordered phase (according to SAXS) in the induction stage prior to the appearance of crystalline peaks (according to WAXS) during the isothermal crystallization of PCL and PCL/LiClO4 complexes. The collected SAXS data were analyzed according to Guinier plot and correlation function. By comparing the average radius size of isolated domains formed in the melt obtained from the Guinier plot in the early stage of crystallization with the crystalline lamellar thickness calculated according to the correlation function in the later stage of crystallization, it is concluded that the final crystalline structure may evolve from pre-ordered phase in the initial stage of the melt. Through accurate analysis the PCL and PCL/LiClO4 complexes depicted invariant SAXS intensities, it is found that the LiClO4 coordinated PCL chains mainly locate at the interphase between the crystalline lamellae and amorphous layer. The structural evolution during crystallization in the induction period and subsequent stages of PCL and PCL/LiClO4 were analyzed according to a proposed model.
Co-reporter:Lin Li, Man-Ling Wang, Yu Chen, Shi-Chun Jiang
Journal of Colloid and Interface Science 2012 Volume 387(Issue 1) pp:146-152
Publication Date(Web):1 December 2012
DOI:10.1016/j.jcis.2012.08.009
The terminal hydroxyl groups of amphiphilic multiarm star copolymers with a hydrophilic hyperbranched polyethylenimine (PEI) core and hydrophobic poly(ε-caprolactone) (PCL) arms were partially or completely transformed into the radical-crosslinkable methacrylate (MA) groups (PEI-b-PCL-MA). The resulting PEI-b-PCL-MA polymers with 100% MA substitution self-assembled in water into simple vesicles, whereas those with partial MA substitution aggregated into complex vesicles. These structures could be proved by transmission electron microscopy and dynamic light scattering only after crosslinking the intra-vesicular MA groups that generated the covalently stabilized vesicles (CSVs). The obtained CSVs could be used as host for the formation of gold nanoparticle (AuNP) cluster, and the AuNP clusters stabilized by the CSVs were stable under a wider range of CSV/AuNP feed ratio than those stabilized by the uncrosslinked precursors. The diameter of AuNPs in the clusters was in the range of 4–6 nm, and the distance of adjacent AuNPs could be modulated through altering the feed ratio of CSV/AuNP. The color of the solutions of AuNPs with CSV could be tuned from brown to red, purple, even blue. The composites of CSV and AuNPs could be further used as nanocarriers to accommodate hydrophobic guest of pyrene, and a higher amount of AuNPs in the nanocarriers led to a lower encapsulation capacity for pyrene guests.Graphical abstractHighlights► Covalently stabilized vesicle (CSV) templates the formation of AuNP cluster. ► The distance of AuNPs in the cluster could be tuned. ► The color of solution of composite of AuNPs and CSV could be tuned. ► The composite of AuNPs and CSV could further encapsulate hydrophobic guest.
Co-reporter:Feifei Xue;Xuesi Chen;Lijia An;Sergio S Funari
Polymer International 2012 Volume 61( Issue 6) pp:909-917
Publication Date(Web):
DOI:10.1002/pi.4158
Abstract
The time- and temperature-related crystallization process for the structure transitions of asymmetric crystalline-crystalline diblock copolymers from the melt to crystallites was investigated with synchrotron simultaneous small-angle/wide-angle X-ray scattering. Two asymmetric poly(ethylene oxide)-poly(ε-caprolactone) diblock copolymers were chosen. It is found in the course of the copolymer crystallization that the shorter blocks are uncrystallizable in both of the asymmetric diblock copolymers and final lamellar structures are formed in both of them. The final lamellar structure was confirmed from atomic force microscopy observations. The small-angle X-ray scattering data collected were analyzed with different methods for the early stage of crystallization. Guinier and Debye-Bueche plots indicate that there are neither isolated domains nor correlated domains formed before the formation of lamellae in the asymmetric diblock copolymers during the crystallization process. The structure evolution was calculated according to the correlation function, and the soft nanoconfined crystallization behavior is discussed. Copyright © 2012 Society of Chemical Industry
Co-reporter:Yao Zhang;Jingqing Li;Hong Huo
Journal of Applied Polymer Science 2012 Volume 123( Issue 4) pp:1935-1943
Publication Date(Web):
DOI:10.1002/app.34697
Abstract
Effects of lithium perchlorate (LiClO4) on the crystallization behaviors of poly(ethylene oxide) (PEO) were investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and polarized optical microscopy (POM) in PEO/LiClO4 system. DSC results indicate that there are nucleation effects of LiClO4 on the crystallization of PEO. But, on the other hand, the coordination of lithium ion with the oxygen ether atoms of PEO can obviously reduce the crystallinity and spherulite growth rate of PEO. This contrary effect of LiClO4 on the crystallization of PEO in PEO/LiClO4 complexes system was analyzed and discussed in detail. The Laurizen–Hoffman theory was used to describe the Li-coordinated crystallization kinetics of PEO spherulite. It showed that the nucleation constant (Kg) and folding surface free energy (σe) decreased with increasing LiClO4 contents, and the energy necessary for the transport of segments across the liquid–solid interface (ΔE) increased on increasing the contents of LiClO4. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Co-reporter:De-Yu Zhu, Fa Cheng, Yu Chen, Shi-Chun Jiang
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2012 Volume 397() pp:1-7
Publication Date(Web):5 March 2012
DOI:10.1016/j.colsurfa.2012.01.006
Four sulfonate-containing gemini surfactants, C7–M0–C7, C7–M1–C7, C7–M2–C7 and C11–M1–C11, with long rigid or semi-rigid spacer have been synthesized. Fully rigid spacer of C7–M0–C7 is composed two rigid benzene rings and two rigid carbonyl groups. Besides the rigid moieties as C7–M0–C7, the spacers of C7–M1–C7, C7–M2–C7 and C11–M1–C11 contain one or two flexible methylene units. The characterization by 1H NMR, 13C NMR, electrospray ionization/mass spectrometry (ESI-MS) and Fourier transform infrared (FT-IR) verified the structural characters of these new gemini surfactants. The basic surface properties of these novel gemini surfactants were investigated through measuring the relationship between the surface tension of water and the surfactant concentration, and compared with those of the conventional single-chain surfactant sodium dodecylbenzenesulfonate (SDSB). The curves of surface tension versus logarithm of concentration of C7–Mx–C7 surfactants were unlike the traditional plot exemplified by SDBS. Above the critical micelle concentration (cmc), the surface tension of aqueous solutions of C7–Mx–C7 did not become steady, but still obviously decreased with the concentration increase, which was supposed to be related with the long rigid or semi-rigid spacers. All these gemini surfactants showed lower cmc and C20 (surfactant concentration required for lowering the surface tension of water by 20 mN/m) values, but higher γcmc (surface tension at cmc) value than SDBS. The gemini surfactants with semi-rigid spacers exhibited superior surface activity to that with fully rigid spacer. The aggregation behavior of C7–Mx–C7 in water was investigated using dynamic light scattering (DLS) and transmission electron microscopy (TEM). It was found that the gemini surfactants with long fully rigid spacer preferred to form vesicles, whereas the ones with semi-rigid spacers self-assembled into the mixture of micelles and vesicles at low surfactant concentration and formed vesicles at high surfactant concentration.Graphical abstractHighlights► Gemini surfactants (Cy–Mx–Cy) with long rigid or semi-rigid spacers were synthesized. ► Cy–Mx–Cy had superior surface activities to the single chain SDBS surfactant. ► The curves of γ versus log[Cy–Mx–Cy] were different from that of the traditional SDBS.
Co-reporter:Ziwei Cai, Yao Zhang, Jingqing Li, Feifei Xue, Yingrui Shang, Xuehao He, Jiachun Feng, Zhonghua Wu, Shichun Jiang
Polymer 2012 Volume 53(Issue 7) pp:1593-1601
Publication Date(Web):22 March 2012
DOI:10.1016/j.polymer.2012.02.012
In-situ synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) were carried out to investigate the uniaxial drawing-induced deformation and structure transitions of β form isotactic polypropylene (iPP) at varying temperatures (30 °C, 60 °C, 80 °C, 100 °C and 120 °C). The WAXS results indicated that the initial strain for the strain-induced β–α transformation decreases with the tensile temperature according to the engineering stress–strain curves. The SAXS data showed that the long period increased along the direction perpendicular to the tensile force and changed little along the tensile direction with increasing strain in the elastic deformation stage before the yield point. The analysis of the obtained scattering results indicated that the angle between parent and daughter lamella rotates from initial 40° or 140° to close to 90° accounts for the lateral expansion of the samples with tension, which matches the essential auxetical behavior. A structure deformation and transition mechanism was proposed for β form iPP with uniaxial drawing. The initialization of the crystalline structure transition is after the yield point, then the mechanical loading-induced β–α transition seems to be a gradual process with lamella slippage and breaking which triggers the β–α polymorphic transition.
Co-reporter:Peng-Fei Cao;Rong-Xu Zhao;Lin Li;Wen-Wen Yang;Fa Cheng;Yu Chen;Cong-Hua Lu;Shi-Chun Jiang
Journal of Polymer Science Part A: Polymer Chemistry 2012 Volume 50( Issue 2) pp:227-236
Publication Date(Web):
DOI:10.1002/pola.25015
Abstract
The large amount of terminal hydroxyl groups of amphiphilic multiarm star copolymers with hyperbranched polyethylenimine (PEI) as the hydrophilic core and poly(ε-caprolactone) (PCL) arms as the hydrophobic shell were completely transformed into the radical-crosslinkable methacrylate (MA) groups. The resulting PEI-b-PCL-MA polymers could self-assemble into vesicles in water, which was verified by dynamic light scattering (DLS) and transmission electron microscopy (TEM). After crosslinking the intravesicular MA groups, covalently stabilized vesicles (CSVs) were generated. These CSVs were further characterized by DLS and TEM, and it was found that the corona of the vesicles was not the simple double-layer structure, but contained a certain amount of PEI-b-PCL unimolecular micellar units between the double-layer. These CSVs could accommodate both apolar and polar guests using their hydrophobic PCL zones and void cores, respectively. Moreover, these CSVs showed superior capacities for apolar guests to their noncrosslinked precursors and the corresponding traditional amphiphilic multishell star polymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Co-reporter:Rong-Xu Zhao, Lin Li, Bin Wang, Wen-Wen Yang, Yu Chen, Xue-Hao He, Fa Cheng, Shi-Chun Jiang
Polymer 2012 Volume 53(Issue 3) pp:719-727
Publication Date(Web):2 February 2012
DOI:10.1016/j.polymer.2011.12.045
Co-reporter:Xun-Yong Liu, Xu-Ran Mu, Yi Liu, Hua-Ji Liu, Yu Chen, Fa Cheng, and Shi-Chun Jiang
Langmuir 2012 Volume 28(Issue 10) pp:4867-4876
Publication Date(Web):February 22, 2012
DOI:10.1021/la300046w
The salt effects on the water solubility of thermoresponsive hyperbranched polyethylenimine and polyamidoamine possessing large amounts of isobutyramide terminal groups (HPEI-IBAm and HPAMAM-IBAm) were studied systematically. Eight anions with sodium as the counterion and ten cations with chloride as the counterion were used to measure the anion and cation effects on the cloud point temperature (Tcp) of these dendritic polymers in water. It was found that the Tcp of these dendritic polymers was much more sensitive to the addition of salts than that of the traditional thermoresponsive linear polymers. At low anion concentration, the electrostatic interaction between anions and the positively charged groups of these polymers was dominant, resulting in the unusual anion effect on the Tcp of these polymers in water, including (1) Tcp of these dendritic polymers decreasing nonlinearly with the increase of kosmotropic anion concentration; (2) the chaotropic anions showing abnormal salting-out property at low salt concentration and the stronger chaotropes having much pronounced salting-out ability; (3) anti-Hofmeister ordering at low salt concentration. At moderate to high salt concentration, the specific ranking of these anions in reducing the Tcp of HPEI-IBAm and HPAMAM-IBAm polymers was PO43– > CO32– > SO42– > S2O32– > F– > Cl– > Br– > I–, in accordance with the well-known Hofmeister series. At moderate to high salt concentration, the specific ranking order of inorganic cations in reducing the Tcp of HPEI-IBAm polymer was Sr2+ ≈ Ba2+ > Na+ ≈ K+ ≈ Rb+ > Cs+ > NH4+ ≈ Ca2+ > Li+ ≈ Mg2+. This sequence was only partially similar to the typical Hofmeister cation series, whereas at low salt concentration the cation effect on Tcp of the dendritic polymer was insignificant and no obvious specific ranking order could be found.
Co-reporter:Chun-Xiao Zhang, Bin Wang, Yu Chen, Fa Cheng, Shi-Chun Jiang
Polymer 2012 Volume 53(Issue 18) pp:3900-3909
Publication Date(Web):17 August 2012
DOI:10.1016/j.polymer.2012.07.002
The Sn(Oct)2 catalyzed polymerization condition of l-lactide (LLA) and racemic lactide (r-LA) using hyperbranched polyethylenimine (PEI) as the macroinitiator was optimized. Multiarm star polymers bearing PEI core and well-controlled poly(l-lactide) (PLLA) or poly(racemic lactide) (PDLLA) arms were successfully prepared under the optimized condition, including: (1) high concentration of Sn(Oct)2 catalyst was required; (2) with respect to the polymerization of r-LA, the optimal temperature was in the range of 115–130 °C; (3) as for the polymerization of LLA, the optimal temperature was only around 130 °C. Model experiments demonstrated that secondary amine could also effectively initiate the Sn(Oct)2 catalyzed polymerization of LA under the optimized condition, however, its initiation efficiency was usually a little less than 100%, unlike the primary amine and hydroxyl initiators. The results of Gel Permeation Chromatography demonstrated that the obtained multiarm star polymers with PDLLA arms had narrower dispersities than those with PLLA arms. Thermal analyses demonstrated that raising the arm numbers of the stars impaired their thermal stability a little. Stars with PDLLA arm were amorphous. The glass transition temperature of all the PDLLA-based polymers was similar and had no obvious relationship with the arm length, arm number and the molecular architecture. The crystallizability of star polymers with PLLA arm was weaker than that of linear PLLA, and only star polymers with long PLLA arm showed obvious crystallization. The guest encapsulation and release properties of the obtained star polymers were also investigated. It was found that their guest encapsulation capacity had correlation with the PLA arm length, the PEI core size and the degree of quaternization of PEI core, but had no relationship with the type of the PLA arm (PDLLA or PLLA). Whereas the guest release rate was strongly affected by the arm type.Graphical abstract
Co-reporter:Fang Yuan, Hong Pan, Fa Cheng, Yu Chen, Shi-Chun Jiang
Polymer 2012 Volume 53(Issue 11) pp:2175-2182
Publication Date(Web):9 May 2012
DOI:10.1016/j.polymer.2012.03.043
Ethyl cellulose (EC), lactide (LA) and branching comonomer 2,2-bis(hydroxymethyl) butyric acid (BHB) were copolymerized in xylene using Sn(Oct)2 as catalyst. Catalyst amount and polymerization temperature were optimized for the effective introduction of certain amount of branched polylactide (PLA) into the side chains of comb-like copolymers having EC backbone. The characterization of the obtained copolymers by GPC and 1H NMR demonstrated that the influence of polymerization temperature in the range of 110–150 °C on the efficient incorporation of branching units was not pronounced, whereas high amount of catalyst was the key point. The content of branching units in the copolymers could be enhanced by increasing the feed amount of BHB monomer. A plausible mechanism for the polymerization was proposed according to the model experiments. Compared with the comb-like copolymers with merely linear PLA side chains, the ones bearing both branched and linear PLA side chains had the following characters: (1) better solubility in the polar solvent of ethanol; (2) much faster hydrolysis degradation. These characters became more pronounced when the content of branching units in the side chains increased.
Co-reporter:Hu Mao;Hongfei Li;Yingrui Shang;Jingqing Li;Conghua Lu
Journal of Polymer Research 2012 Volume 19( Issue 11) pp:
Publication Date(Web):2012 November
DOI:10.1007/s10965-012-0011-6
Micelle clusters and square slices that formed in different polystyrene-b-poly(ethylene oxide) (PS-b-PEO) solutions were observed with AFM. This diblock copolymer assembled into small spherical micelles and then micelle clusters (diameters: 100–400 nm) after the PS-b-PEO/toluene solution had been aged for 24 h at room temperature. Square slices were obtained from solutions aged for two months. Solvent vapor induced morphological and structural transitions of the micelle clusters and the stability of the square slices on Si wafers were investigated. The results showed that the solvent vapor induced morphology of the sample aged for 24 h was more ordered than that aged for two months. Possible mechanisms for the formation of these structures in the solutions and the vapor-induced structural transition were proposed.
Co-reporter:Huiying Wen;Hua Li;Shuyan Xu;Shengling Xiao;Hongfei Li
Journal of Polymer Research 2012 Volume 19( Issue 1) pp:
Publication Date(Web):2012 January
DOI:10.1007/s10965-011-9801-5
Crystallization behavior of sheared polymer melts of a series of poly(ethylene-co-octene)s with different octene content was investigated by different scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and synchrotron small-angle X-ray scattering (SR-SAXS) techniques. The DSC results indicated that the hexyl branches content had dramatic effects on the thermal properties and crystallinity of polyethylene. It was also found that shear had no obvious effects on the size of either crystallite or lamellae. However, both crystallite and lamellae were oriented by shearing, especially for the lamellae. All obtained results indicate that the initial states of the polymer melt play an important role in affecting the crystallization behaviors. The difference of the shear-induced crystalline structure evolution and the orientation between crystallite and lamellae support the preordered mesomorphic phase of flexible polymer crystallization process proposed by Strobl.
Co-reporter:Jingqing Li;Yao Zhang;Yundan Jiacuo;Yingrui Shang;Hong Huo
Polymer Bulletin 2012 Volume 68( Issue 5) pp:1405-1423
Publication Date(Web):2012 March
DOI:10.1007/s00289-011-0678-6
Poly(ethylene oxide)/poly(ε-caprolactone) (PEO/PCL) blends can be widely used in lithium rechargeable battery area or as medical materials, while the miscibility and phase diagram of the blends are still unclear. The present work attempted to establish the blends’ phase diagram using rheometry and investigated the miscibility. The results showed that a miscibility window of upper critical solution temperature character of the blends is revealed. Meanwhile, the abnormal rheological behavior of PEO at temperatures higher than 130 °C has little influence on the phase diagram determination. Different rheological properties of PEO/PCL blends from those of PEO revealed the existence of interactions between PEO and PCL molecular chains. Whereas shear-induced mixing or shear-induced phase separation might occur in phase diagram determination of PEO/PCL blends using rheometry.
Co-reporter:Shaoyong Huang;Hongfei Li;Xuesi Chen;Lijia An
Polymer Bulletin 2011 Volume 67( Issue 5) pp:885-902
Publication Date(Web):2011 September
DOI:10.1007/s00289-011-0518-8
Morphologies and structures determined by crystallization of the blocks, microphase separation of the copolymers, and vitrification of PLLA block in poly(l-lactide-b-ethylene oxide) (PLLA-b-PEO) copolymers were investigated using microscopic techniques and synchrotron small angle X-ray scattering. The PLLA-b-PEO copolymer films were crystallized from two different annealing processes: melt crystallization (process A) or crystallized from glass state of PLLA block after quenching from melt state (process B). The relationship between the crystalline morphology and microstructure of the copolymers were explored using SAXS. The morphology and phase structure are predominated by crystallization of PLLA block, and greatly influenced by microphase separation of the copolymers. In process B, lozenge-shape and truncated lozenge-shaped PLLA crystals of nanometer scale can be observed. The crystalline morphology is markedly affected by the microstructure formed during the annealing process. Star-shaped morphologies stacked with PLLA single crystals were observed.
Co-reporter:Ruihua Lv, Bing Na, Nana Tian, Shufen Zou, Zhujun Li, Shichun Jiang
Polymer 2011 Volume 52(Issue 21) pp:4979-4984
Publication Date(Web):29 September 2011
DOI:10.1016/j.polymer.2011.08.023
The structural development in the glassy polylactide during stretching and subsequent heating has been investigated by Fourier transform infrared spectroscopy. It is indicated that only when molecular chains in the amorphous phase approach their finite extensibility beyond a critical strain of about 1, accompanied by remarkable conformational ordering, can cohesive mesophase with certain molecular ordering be brought out to trigger strain-induced crystallization. Upon heating cohesive mesophase endures melting during glass transition region where an endothermic peak is observed, and the extent of melting relies on its initial thermal stability and is in particular affected by the subsequent advent of strain-induced crystallization.
Co-reporter:Shaoyong Huang, Shichun Jiang, Xuesi Chen and Lijia An
Langmuir 2009 Volume 25(Issue 22) pp:13125-13132
Publication Date(Web):July 22, 2009
DOI:10.1021/la901827q
The evolution of morphologies of isothermally crystallized thin films with different thicknesses of poly(l-lactide-b-ethylene oxide) diblock copolymer was observed by optical microscopy (OM) and atomic force microscopy (AFM). Dendritic superstructures stacked with lamellae were investigated in thin films with ∼200 nm to ∼400 nm thickness. The lamellar structure was a lozenge- or truncated-lozenge-shaped single crystal of PLLA confirmed by AFM observations. The contour of the dendritic superstructures is hexagonal, and two types of sectors, [110] and [100], can be classified in terms of the chain-folding and crystal growth directions. These phenomena are due to the interplay of the crystallization of the PLLA block, the microphase separation of the block copolymer, and the effect of the film thickness. The growth process of the superstructure can be classified into three steps: the growth of the main branches, the growth of the secondary side branches along the main branch, and the tertiary side branches. PLLA growth rates decrease in copolymer films thinner than 1 μm. Layer−layer phase structure of the copolymer driven by the crystallization of PLLA and the microphase separation of the copolymer appears to be a key factor explaining the crystallization and morphological behavior of this system.
Co-reporter:Yi Liu, You Fan, Yuan Yuan, Yu Chen, Fa Cheng and Shi-Chun Jiang
Journal of Materials Chemistry A 2012 - vol. 22(Issue 39) pp:NaN21182-21182
Publication Date(Web):2012/08/22
DOI:10.1039/C2JM34445A
A series of organo-soluble gold nanoparticles (AuNPs) were prepared through the reduction of HAuCl4 by NaBH4 in the presence of amphiphilic hyperbranched copolymers bearing a hydrophilic hyperbranched polyethylenimine (PEI) core and a hydrophobic dendritic shell. For comparison, the corresponding analogues with a PEI core and a linear shell were also used to prepare the organo-soluble AuNPs. All the obtained AuNPs were characterized by transmission electron microscopy. It was found that under a high feed ratio of polymer to HAuCl4, the average diameter of the obtained small AuNPs was similar, and was independent of the shell morphology of the hyperbranched polymeric stabilizers. Reducing the feed ratio of polymer to HAuCl4 led to the formation of larger AuNPs and irregularly shaped AuNP aggregates. The stability evaluation on the basis of two-month shelf-storage demonstrated that the obtained AuNPs were stable under shelf-storage regardless of whether the shell of the hyperbranched polymeric stabilizer was dendritic or linear. These organo-soluble AuNPs could be used as efficient catalysts for the biphasic catalytic reduction of 4-nitrophenol by NaBH4, and could also be conveniently recovered and reused. The stabilizers with a dendritic shell endowed the AuNP catalyst with a higher performance than the corresponding stabilizers with a linear shell, including: (1) a higher catalytic rate; (2) the ability to be recovered and reused more times; (3) a maximal turnover number of around 23000, which is unprecedented in the catalytic reduction of 4-nitrophenol.
Co-reporter:Huilong Guo, Jifu Bi, Jiayi Wang, Xuequan Zhang, Shichun Jiang and Zhonghua Wu
Dalton Transactions 2015 - vol. 44(Issue 19) pp:NaN9139-9139
Publication Date(Web):2015/04/02
DOI:10.1039/C5DT01064K
Lanthanide-based catalysts are highly active for isoprene polymerization in hexane. In this paper, a ternary catalyst consisting of neodymium neodecanoate {Nd(vers)3}, Al(iBu)3 and Al(iBu)2Cl was studied by using X-ray-absorption fine-structure (XAFS) technique. A sealed and moisture-proof liquid sample cell with adjustable thickness was designed for Nd LIII-edge XAFS measurements. Based on the XAFS data analysis, detailed structure changes around the Nd center were obtained. It was found that the Nd(vers)3 molecules formed an oligomer structure in hexane solution with two Nd–O subshells (5O @ 2.39 Å and 5O @ 2.54 Å) around the Nd center. The alkylation process by adding Al(iBu)3 to the hexane solution of Nd(vers)3 partially destroyed the aggregation degree of Nd(vers)3 molecules in hexane solution. Al(iBu)3 ligands were bonded to the Nd center by Nd–C bonding. With the Nd:Al ratio increasing from 1:2.5 to 1:10, the O neighbors around Nd decreased from 4 to 2 but with an unchanged Nd–O bond length of 2.38 Å, and the C neighbors around Nd were kept at ca. 4 with Nd–C bond lengths in the range of 2.57–2.58 Å. The Nd–O bonds can be further replaced by Nd–C bonds during the aging process. The chlorination process by adding Al(iBu)2Cl to the mixture solution of Nd(vers)3 and Al(iBu)3 restrained intensively the agglomeration of Nd(vers)3 molecules in hexane solution. Al(iBu)2Cl ligands were bonded to the Nd center by Nd–Cl bonds. There were about 3–4 C neighbors at 2.58 Å, 2 Cl neighbors at 2.87 Å, and 2 Al next-neighbors at 3.14 Å around the Nd center. After allowing the ternary catalyst to stand for 5 days, the coordination numbers of Nd–C and Nd–Cl were all stabilized to 3 without bond length changes, and partial single Cl− anions were also bonded to the Nd center. All these structural details and their change tendency demonstrate that the decrease of aggregation degree of Nd(vers)3 molecules in hexane solution can improve the catalytic activity of the ternary lanthanide-based catalyst system.
Co-reporter:Yunyi Zhang, Cuiyun Zhang, Jian Chen, Yongxin Li, Meiding Yang, Huipeng Zhou, Sohail Anjum Shahzad, Hong Qi, Cong Yu and Shichun Jiang
Journal of Materials Chemistry A 2017 - vol. 5(Issue 19) pp:NaN4694-4694
Publication Date(Web):2017/04/10
DOI:10.1039/C6TC04938A
We exploit a real-time perylene probe fluorescence turn-on method to detect acetylcholinesterase (AChE) activity through the selective decomposition of MnO2 nanosheets. The surface of the MnO2 nanosheets is negatively charged. The perylene probe (P-4C+) has four positively charged quaternary ammonium groups. When mixed together, P-4C+ attached to the surface of the MnO2 nanosheets through electrostatic attractive interactions. The fluorescence of P-4C+ was effectively quenched by the MnO2 nanosheets. Acetylthiocholine (ATCh) could be hydrolyzed to thiocholine by AChE. Thiocholine is a reducing agent. It could reduce MnO2 nanosheets to Mn2+ and thus trigger the decomposition of the MnO2 nanosheets. As a result, P-4C+ was released and the fluorescence of P-4C+ was restored. The AChE inhibitor restrained the catalytic activity of AChE and resulted in a reduced fluorescence recovery of P-4C+. Our assay method is simple and selective, with low toxicity and better biocompatibility, which would facilitate biological and biomedical applications associated with AChE activity.
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