Co-reporter:Fang Guo, Na Jiao, Lei Jiang, Yang Li, and Zhaomin Hou
Macromolecules November 14, 2017 Volume 50(Issue 21) pp:8398-8398
Publication Date(Web):October 19, 2017
DOI:10.1021/acs.macromol.7b01668
The polymerization of halide-substituted styrenes (XSt) and their copolymerization with styrene by half-sandwich scandium catalysts with and without a THF ligand have been examined. The THF-free aminobenzyl scandium complex (C5Me4SiMe3)Sc(CH2C6H4NMe2-o)2 (2) in combination with 1 equiv of [Ph3C][B(C6F5)4] showed high activity and excellent syndiotacticity for the polymerization of the halide-substituted styrenes (XSt = p-, o-, and m-ClSt, p-FSt, p-BrSt, and p-ISt). Despite the presence of the electron-withdrawing halogen substituent on the aromatic ring, the polymerization activity reached up to 105 g of polymer molSc–1 h–1 with syndiotacticity (rrrr) up to 99%. This constitutes the first example of the syndiospecific polymerization of halogenated styrenes with high activity and high stereoselectivity. Moreover, the syndiospecific copolymerization of XSt with styrene has also been achieved by this catalyst, which afforded the corresponding syndiotactic copolymers with high molecular weight and a controllable amount of the halogenated styrene units. In contrast, the THF-containing trimethylsilylmethyl scandium complex (C5Me4SiMe3)Sc(CH2SiMe3)2(THF) (1) showed high activity and high syndiotacticity for the polymerization of m-ClSt but gave atactic polymers in the polymerization of p- and o-ClSt, p-BrSt, and p-ISt, while a mixture of syndiotactic and atactic polymers was yielded in the case of p-FSt. The copolymerization of XSt with styrene by complex 1 was also achieved, but the stereoselectivity and comonomer distribution sequences in the resulting copolymers were significantly different from those obtained by using complex 2.
Co-reporter:Li Han, Hongwei Ma, Siqi Zhu, Pibo Liu, Heyu Shen, Lincan Yang, Rui Tan, Wei Huang, and Yang Li
Macromolecules November 14, 2017 Volume 50(Issue 21) pp:8334-8334
Publication Date(Web):October 30, 2017
DOI:10.1021/acs.macromol.7b01952
A series of thermo-tunable liquid crystal block copolymers (LCBCs) with well-designed architectures were successfully synthesized. Linear/star poly[4-(4-vinylphenyl)-1-butene]-block-polybutadiene (PVSt-co-PB) moieties were obtained using living anionic copolymerization of 4-(4-vinylphenyl)-1-butene with butadiene, and topological [PVSt-co-PB]-LCBCs were generated through the adherence of mesogenic moiety via facile hydrosilylation. The PVSt LC block had well-defined grafting densities of approximately 100%, 70%, and 40%, whereas the PB LC block had an asynchronously tunable grafting density. This work included comprehensive studies on their self-assembly and yielded some interesting results. The influences of topologies and compositions on the phase transition behaviors and polarized optical performances of the resulting LCBCs that were driven by asynchronously controlled grafting density were carefully illustrated. The LCBCs with controlled molecular weight (MW) and narrow PDI showed wider LC phase ranges (ΔT) and a high tunability was added into the construction to aid thermos-responsive devices. The wide ΔT and high thermo-stability were demonstrated to be complementary between two LC blocks. However, the response-time and aggregation morphology in POM showed close similarity to LC blocks and showed a gradient in temperature-dependent changes with the PB LC block at a lower temperature and the PVSt LC block at a higher temperature. It is common for LC texture to change with varying temperature, whereas the gradient switching process was unique to LC blocks, which was further confirmed by temperature-dependent WAXD. In particular, the structural reorganization was determined to be driven by asynchronous grafting density by measuring the temperature-variation AFM, in that the asynchronous-tunable motion between LC blocks facilitates small phase separation.
Co-reporter:Yang Yu, Zhiyong Wei, Cheng Zhou, Liuchun Zheng, Xuefei Leng, Yang Li
European Polymer Journal 2017 Volume 92(Volume 92) pp:
Publication Date(Web):1 July 2017
DOI:10.1016/j.eurpolymj.2017.04.036
•Isodimorphism behavior of the resulting aliphatic copolyesters.•Effect of chain length on miscibility and competition of cocrystallization of aliphatic copolyesters.•A chain length inclusion-exclusion model is proposed.•How does the chain length of comonomers regulate the cocrystallization behavior.Four series of random aliphatic copolyesters derived from 1,6-hexanediol and different diacids were designed and synthesized to investigate the effect of chain length of aliphatic diacids on miscibility and competition of cocrystallization behavior. Isodimorphic behaviors were observed from DSC, WAXD and SAXS analyses for the four series of copolyesters. Crystal type transition point at isodimorphism depended on the chain length of comonomeric diacid units in copolyesters, which presented a crystallization competition effect between the two crystal types of parent homopolyesters. The comonomeric diacids with longer chain length had stronger competitive ability in controlling the cocrystallization even when they were present in a minor proportion. Then, the cocrystallization miscibility was qualitatively analyzed by WAXD and SAXS, and further quantificatively investigated by the defect Gibbs energy calculated from the Wendling-Suter method. For HS unit (hexamethylene succinate) incorporated into the crystal type of HL unit (HA, HSu, HSe or HD unit whose chain length of comonomeric diacids gradually lengthens compared to HS unit), the HL with longer chain length has better miscibility with the inserted HS unit. For HL unit squeezed into the crystal lattice of HS unit, HS unit has worse miscibility with the longer inserted HL unit. Moreover, the chain length inclusion-exclusion model on the basis of the Wendling and Suter theory is proposed to give an insight into the mechanism of how does the chain length of comonomers regulate the cocrystallization behavior.For the shorter hexamethylene succinate (HS) comonomer incorporated into the longer unit crystal, the longer chain length comonomer has better miscibility with the inserted HS unit. For the longer comonomers squeezed into the crystal lattice of HS unit, HS unit has worse miscibility with the longer inserted comonomer. The chain length inclusion-exclusion model on the basis of the Wendling and Suter theory is proposed to give an insight into the mechanism of how does the chain length of comonomers regulate the cocrystallization behavior.Download high-res image (237KB)Download full-size image
Co-reporter:Zhenghai Shi;Fang Guo;Rui Tan;Hui Niu;Tingting Li
Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 9) pp:1449-1453
Publication Date(Web):2017/02/28
DOI:10.1039/C6PY02097F
The synthesis of stereoregular star polymers, including star cis-1,4-PB, star cis-1,4-PB-ran-3,4-PI and star cis-1,4-PB-b-syn-PS, through an “arm-first” approach via a living coordination polymerization mechanism is reported in this work for the first time. The half-sandwich scandium catalyst (C5Me4SiMe3)Sc(CH2SiMe3)2(THF) activated with [Ph3C][B(C6F5)4] is used herein. Star cis-1,4-PB compounds with various arm lengths and arm numbers ranging from 1.0 × 104 to 6.5 × 104 g mol−1 and 7.6 to 26.4, respectively, are produced by tuning the polymerization parameters. Additionally, the stereoregular star cis-1,4-PB-ran-3,4-PI and star cis-1,4-PB-b-syn-PS are also explored in the same way with average arm numbers of 21.4 and 16.5 and 35% and 41% star yield, respectively.
Co-reporter:Rui Tan;Zhenghai Shi;Fang Guo;Lv He;Li Han
Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 32) pp:4651-4658
Publication Date(Web):2017/08/15
DOI:10.1039/C7PY00847C
The terpolymerization of ethylene and propylene with isoprene was performed catalyzed by half-sandwich scandium complexes (C5Me4SiMe3)Sc(CH2SiMe3)2(THF) (1) and [1,3-(Me2Si)2C9H5]Sc(CH2SiMe3)2 (THF) (2) in combination with 1 equiv. of [Ph3C][B(C6F5)4]. The terpolymers with ethylene contents of 60–84 mol% and isoprene contents of 5–26 mol% (1,4/3,4 ≈ 50/50) were obtained in the presence of complex 1. In comparison, the terpolymers with ethylene contents of 38–75 mol% and isoprene contents of 4–43 mol% (1,4/3,4 ≈ 70/30) were obtained in the presence of complex 2. Subsequently, a functionalized ethylene–propylene–isoprene terpolymer was prepared by the epoxidation of the 1,4-isoprene units in the terpolymer backbone and further hydroxylation/chlorination through ring-opening reaction of the epoxy groups.
Co-reporter:Aihui Wang;Hui Niu;Zongke He
Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 31) pp:4494-4502
Publication Date(Web):2017/08/08
DOI:10.1039/C7PY00896A
This study demonstrates an efficient method for the synthesis of thermoreversible cross-linked ethylene/propylene rubbers (EPRs) via two steps; in the first step, a functional olefin monomer containing a furan group (FO) is designed and the ethylene/propylene/FO terpolymerization catalyzed by a traditional Ziegler–Natta catalyst is implemented; in the second step, a cross-linked network is constructed via Diels–Alder (DA) click reaction between the bismaleimide and pendant furan groups in the EPR chains. Via polymerization, the FO content in the copolymers was tailored in relatively wide range from 1.1 mol% to 9.7 mol%; this provided various cross-linking precursory groups for the DA reaction. Moreover, the cross-linking density could be adjusted via not only the amount of the inserted furan group but also the ratio of furan to bismaleimide. These solid thermoreversibile EP rubbers could perform their de-cross-linking above 110 °C and re-form the network below 85 °C in a heating–cooling cycle not only in the static measurement of FTIR, but also in the dynamic test of DMA. The mechanical properties of the resulting products with varied cross-linking densities were compared with that of the non-cross-linked polymer and proved to be of much higher modulus. This thermoreversible cross-linking behavior also provided a new strategy for local-repairing of any crack in rubber products.
Co-reporter:Pibo Liu;Hongwei Ma;Wei Huang;Li Han;Xinyu Hao;Heyu Shen;Yu Bai
Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 11) pp:1778-1789
Publication Date(Web):2017/03/14
DOI:10.1039/C6PY02229D
The amino-functionalized DPE derivative 1-(4-dimethylaminophenyl)-1-phenylethylene (DPE-NMe2) was used in a living anionic copolymerization with styrene (St), and the corresponding sequence structures of the copolymers were investigated using the sequence determination method. The copolymerization of St and DPE-NMe2 was neatly carried out at 24 °C, and a gradient sequence structure was obtained, with the DPE-NMe2 units incrementally distributed along the copolymer chains. For the facile regulation of the sequence distribution of the DPE-NMe2 units in the copolymer chains, the additives tetrahydrofuran (THF) or sodium 2,3-dimethylpentan-3-olate (NaODP) were introduced into the copolymerization reactions. The detailed investigations of the conversions, reactivity ratios, and sequence structures indicated that THF had a restraining effect on the incorporation of DPE-NMe2 units into the copolymer chains, and the variations in the corresponding conversions and reactivity ratios also demonstrated this tendency. In addition, a stimulatory effect was observed in the copolymerization when NaODP was used as an additive. On comparing the sequence distribution of DPE-NMe2 units in the chains among these three copolymerization reactions, it was found that NaODP promoted a higher incorporation of DPE-NMe2 into the chains than the other two conditions. This conclusion was also confirmed by the kinetic results. The values of the reactivity ratios were 9.1, 29.8 and 6.9 for the neat, THF, and NaODP conditions, respectively. For the neat, THF and NaODP conditions, the apparent reactivity ratios for styrene (KSt) were calculated to be 0.0548 min−1, 0.209 min−1 and 0.107 min−1, respectively, while the apparent reactivity ratios for DPE-NMe2 (KDPE) were calculated to be 1.82 × 10−3 min−1, 7.42 × 10−4 min−1 and 6.17 × 10−3 min−1, respectively.
Co-reporter:Rui Tan;Fang Guo
Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 3) pp:615-623
Publication Date(Web):2017/01/17
DOI:10.1039/C6PY01665K
The homopolymerization of propylene and its copolymerization with styrene and ethylene catalyzed by half-sandwich scandium complexes bearing different ligands were carried out. A significant influence of alkyl and THF ligands on the propylene polymerization activity has been observed. The THF-containing trimethylsilylmethyl complex (C5Me4SiMe3)Sc(CH2SiMe3)2(THF) (4) in combination with one equivalent of [Ph3C][B(C6F5)4], can serve as a high activity catalyst for the atactic polymerization of propylene. By using this high activity catalyst, the copolymerization of propylene with styrene has been achieved to afford multi-block propylene–styrene copolymers with syndiotactic styrene–styrene blocks. Moreover, a novel family of random propylene–ethylene–styrene terpolymers with a broad composition range, relatively high molecular weights and narrow molecular weight distributions was effectively obtained by the terpolymerization of propylene with ethylene and styrene in the presence of 4/[Ph3C][B(C6F5)4]. The incorporation of styrene units into atactic polypropylene or ethylene–propylene copolymers can be controlled in a wide range simply by changing the monomer feed ratios.
Co-reporter:Hui Niu, Yuanjie Wang, Xiaoyan Liu, Yanshai Wang, Yang Li
Polymer Testing 2017 Volume 60(Volume 60) pp:
Publication Date(Web):1 July 2017
DOI:10.1016/j.polymertesting.2017.04.007
Ziegler-Natta catalysis was employed to prepare isotactic polypropylenes (iPPs) with various viscosity average molecular weight Mη, where Mη exceeds 1 000 000 g/mol. The viscoelastic properties of the synthesized ultra-high molecular weight iPPs (UHMWiPPs) were investigated by means of oscillatory rheometry. Due to the polydispersity of these polymers that derived from multi-sites catalyst, the UHMWiPPs rheological parameters, including Arrhenius activation energy Ea, plateau modulus GN0, as well as the molecular weight between entanglements Me, were compared with that of the reported monodisperse iPPs. We critically evaluated the typical methods for the experimental determination of GN0 for polydisperse UHMWiPPs with linear architecture and concluded that the preferred method for UHMWiPP was the extrapolation integration method, which gave an average value of GN0 = (4.9 ± 0.3) × 105 Pa and Me = (6300 ± 400) g/mol. The polydipersity was proved to be acceptable for the UHMWiPP system in this research. However, the rheological measurements should be operated with caution because the temperature window was very narrow and the UHMWiPPs were extremely sensitive to thermal oxidative degradation during the tests.
Co-reporter:Wei Sang, Hongwei Ma, Qiuyun Wang, Xinyu Hao, Yubin Zheng, Yurong Wang and Yang Li
Polymer Chemistry 2016 vol. 7(Issue 1) pp:219-234
Publication Date(Web):20 Oct 2015
DOI:10.1039/C5PY01562F
Due to their distinct steric hindrance, 1,1-diphenylethylene (DPE) and its derivatives cannot homopolymerize via living anionic polymerization and thus are advantageous for investigating the sequence structure of the corresponding copolymers. The substitution of functional groups on the benzene rings of DPE derivatives can be used to adjust the reactivity ratios for the copolymerization of styrene and the DPE derivatives. Two types of DPE derivatives, DPE-SiH/OMe and DPE-SiH/NMe2, were designed and prepared in this work. An electron withdrawing substituent and an electron donating substituent are simultaneously present at the para positions of the two phenyl rings of DPE. These derivatives were copolymerized with styrene under Schlenk conditions via living anionic polymerization. The statistical in-chain functionalized copolymers were prepared, and the corresponding average reactivity ratios were 1.42 for DPE-SiH/OMe and 1.79 for DPE-SiH/NMe2. Additionally, a time sampling strategy under high vacuum conditions was used during the copolymerization of the two systems (styrene with DPE-SiH/OMe and styrene with DPE-SiH/NMe2) with [MS]0/[MD]0 = 4. The propagation rate constants and statistical sequence structures were analyzed by 1H NMR spectroscopy, SEC and MALDI-TOF MS, and the average sequential arrangements of the corresponding copolymers were determined. The critical conditions for preparing copolymers with alternating structures were determined and implemented, and the monomer unit ratios were both nearly 1:1.
Co-reporter:Qiuyun Wang, Hongwei Ma, Wei Sang, Li Han, Pibo Liu, Heyu Shen, Wei Huang, Xichen Gong, Lincan Yang, Yurong Wang and Yang Li
Polymer Chemistry 2016 vol. 7(Issue 18) pp:3090-3099
Publication Date(Web):28 Mar 2016
DOI:10.1039/C6PY00085A
Sequence-determined bottlebrush polymers in which the branches are distributed with determined sequential arrangements are precisely, efficiently and conveniently synthesized. Living anionic polymerization and hydrosilylation were used to synthesize the backbones, branches and bottlebrushes. Sequence-determined backbones, which include perfectly alternating and gradient structures, were obtained by controlling the monomer feed ratios during the living anionic copolymerization of styrene and dimethyl(4-(1-phenylvinyl)phenyl)silane (DPE-SiH). In addition, the sequential arrangements of branch points in gradient copolymers, i.e., SiH groups, were precisely determined using the timing-sample method under high-vacuum conditions. Then, the branches were conveniently grafted onto the backbones with a corresponding distribution of SiH groups via efficient hydrosilylation. The overall efficiency of the coupling reaction was greater than 91%. The solution properties of the synthesized bottlebrush polymers were investigated, and the results indicated that the sequence of branches may exert an influence on the branching factor (g′) and the hydrodynamic radius (Rh).
Co-reporter:Yanshai Wang, Zhiyong Wei, Yang Li
European Polymer Journal 2016 Volume 85() pp:92-104
Publication Date(Web):December 2016
DOI:10.1016/j.eurpolymj.2016.10.019
•SBS and epoxidized SBS were used as toughening agent for PLA.•The phase morphologies and mechanical properties of blends were investigated.•Epoxy group of ESBS showed a significant effect in enhancing compatibility.•The impact strength and elongation of PLA/ESBS35.8% (70/30) was 891.0 J/m and 253.8%.Polylactide (PLA) has inherent shortcomings which limit its widespread application: brittleness, low elongation and low melt strength. In this paper, these problems were addressed through melt blending of PLA with an epoxidized thermoplastic elastomer, epoxidized poly(styrene-b-butadiene-b-styrene) (ESBS). ESBS with different epoxidation degree were prepared by an in-situ peroxy-formic acid method. The Tg of ESBS increased while the flexibility decreased with increasing epoxidation degree. The impact strength improved from 29.9 J/m for pure PLA to 891.0 J/m for the blend with 30 wt% ESBS35.8%, meanwhile, the elongation at break increased from 3.5% to 253.8%. In-situ compatibilization of these immiscible blends was achieved via melt blending of PLA with ESBS that led to the formation of graft copolymer architecture at the interface. The compatibility between PLA matrix and ESBS phase increased gradually while the notched impact strength increased firstly and then decreased with increasing epoxidation degree of ESBS. The morphology of PLA/ESBS blends played an important role in notched impact strength and could be controlled by adjusting the epoxidation degree of ESBS. Rheological tests showed a drastic enhancement of melt viscosities for PLA/ESBS blends in oscillatory experiments. Therefore, the mechanical properties could be easily tailored by the epoxidation degree of ESBS.Epoxy group of ESBS shows a significant effect in enhancing compatibility between ESBS phase and PLA matrix.
Co-reporter:Cheng Zhou, Zhiyong Wei, Xuefei Lei and Yang Li
RSC Advances 2016 vol. 6(Issue 68) pp:63508-63514
Publication Date(Web):29 Jun 2016
DOI:10.1039/C6RA08689F
Fully biobased poly(L-lactide)-b-polymyrcene-b-poly(L-lactide) triblock copolymers with PLLA as the hard block and polymyrcene as the soft block were synthesized by the ring opening polymerization of L-lactide in the presence of the dihydroxyl-terminated polymyrcene precursor and organocatalyst. The copolymer composition and molecular weight of these triblock copolymers were confirmed by NMR and GPC results. Two separated glass transition temperatures were detected by both DMA and DSC techniques, indicating an existence of micro-phase separation in these triblock copolymers, which is a typical characteristic of thermoplastic elastomers with the content of soft block increases. Tensile testing revealed that PLLA-b-PM-b-PLLA (200) having 20 wt% polymyrcene show distinct yielding while other samples fracture at low strain without yielding. POM results indicated that all these spherulites show the same characteristic “Maltese cross” patterns. With the increasing content of polymyrcene, the perfection of spherulites decreases, especially for PLLA-b-PM-b-PLLA (200). Considering the current energy and environmental problems, it is expected that these fully biobased thermoplastic elastomers will be of great significance in expanding the applications of PLLA and solving the ecological crisis around us.
Co-reporter:Yingying Ren, Zhiyong Wei, Tong Wu, Yufei Bian, Xuefei Leng, Cheng Zhou and Yang Li
RSC Advances 2016 vol. 6(Issue 51) pp:45791-45801
Publication Date(Web):04 May 2016
DOI:10.1039/C6RA09289F
A large diversity of tailor-made linear-comb and star-comb poly(δ-valerolactone)s (PVL) have been obtained with hydroxylated polybutadiene (HPB) as a macroinitiator and 1,5,7-triazabicyclo-[4.4.0]dec-5-ene (TBD) as a catalyst by a simple “one-step” method. The critical content of this research was to explore systematically the differences in the physicochemistry properties between highly branched PVLs and linear PVLs, including the intrinsic viscosity, rheological properties, and crystallization and melting behavior. Studies of solution behavior and melting behavior elucidated that intrinsic viscosities in solution and complex viscosities in the bulk for comb branched PVLs were much lower compared with their linear and star counterparts. Both WAXD and DSC analysis of PVLs with different topological structures indicated that the comb branched architectures do not alter the structures of the PVL crystallites, but markedly improve the crystallization behavior, e.g. higher crystallinities. Moreover, the influence of the molecular weight of a single arm on the thermal properties and crystallization properties of the obtained linear-comb PVLs was explored. The results demonstrated that the crystallization temperatures (Tcs), melting temperatures (Tms) and crystallinities increased with the increase of molecular weight of a single arm. As such, a structure–property correlation is expected to be constructed which is of great practical importance in the syntheses and applications of highly branched polymers (HBPs).
Co-reporter:Xuefei Leng, Zhiyong Wei, Yingying Ren, Yufei Bian, Qinyi Wang and Yang Li
RSC Advances 2016 vol. 6(Issue 46) pp:40371-40382
Publication Date(Web):12 Apr 2016
DOI:10.1039/C6RA05481A
A series of linear-comb poly(trimethylene carbonate)-block-poly(L-lactide) [lcP(TMC-b-LLA)] with polybutadiene (PB) as backbone and a P(TMC-b-LLA) diblock copolymer as side chain were obtained using controlled synthesis and evaluated as thermoplastic elastomers. The comb-like graft copolymer was achieved using sequential ring-opening polymerization of trimethylene carbonate (TMC) and L-lactide (L-LA) at room temperature (RT) using an organocatalyst, associated with the multi-hydroxyl PB (PB–OH) as a macroinitiator. The thermal and mechanical properties of these graft copolymers were investigated using differential scanning calorimetry, dynamic mechanical analysis and tensile testing. The Young's modulus (E) and the elongation at break (εb) followed predicted trends as the monomer composition changed. Furthermore, well defined linear-comb PLLA-gradient-PTMC [lcP(LLA-grad-TMC)] and linear-comb PLLA-random-PTMC [lcP(LLA-ran-TMC)] were also synthesized for comparison. Results from 1H and 13C-NMR spectroscopy, and gel permeation chromatography confirmed the formation of the chain microstructures. It was found that the properties of the copolymers depended not only on the comonomer content but also on their topologies. The results showed that the gradient and random structure of the side chain could yield unusual properties: the lcP(LLA-grad-TMC) copolymer possessed a distinctive, broad glass transition temperature in comparison with the other two graft copolymers. The lcP(LLA-ran-TMC) random copolymer performed like a typical rubber with a significant high εb value (εb = 1800%) which was even larger than the pure linear-comb PTMC (εb = 865%). Furthermore, this simple “one-pot” method using an organocatalyst to synthesize comb-like graft copolymers with “block”, “gradient” and “random” side chains is demonstrated systematically in this work.
Co-reporter:Xuefei Leng, Zhiyong Wei, Yufei Bian, Yingying Ren, Yurong Wang, Qinyi Wang and Yang Li
RSC Advances 2016 vol. 6(Issue 36) pp:30320-30329
Publication Date(Web):11 Mar 2016
DOI:10.1039/C6RA02697D
Three series of narrowly dispersed comb-like graft poly(L-lactide) (PLLA) with controlled graft length and graft density have been facilely synthesized and characterized. The structural information was determined by means of 1H NMR, GPC, and viscometry, demonstrating the well-defined grafted structure. The effects of grafting parameters on rheological properties, thermal and crystallization behaviors were investigated systematically to illustrate the structure–property relationships. By the analysis of the rheological behavior, the increase of graft length and graft density can both lead to an elevated value of zero-viscosity (η0), enhanced complex modulus (G*) and increased complex viscosity (η*). Comparatively, graft density contributes more to the improvement of rheological properties than graft length does. For thermal properties, DSC results show that the glass transition temperature (Tg), the melting temperature (Tm) and the crystallization enthalpy (ΔHm) of graft PLLA increase with the chain length and decrease with the graft density. Furthermore, spherulite morphologies and growth rates were studied by polarized microscopy (POM), and the observation revealed a remarkable improvement of radius growth rate of the spherulites (G) when graft density increased. The results indicate that G depends more on the molecular weight of each arm (Mn,arm) than the total Mn.
Co-reporter:Tingting Li;Li Li;Qiang Xu;Yurong Wang
Journal of Applied Polymer Science 2016 Volume 133( Issue 38) pp:
Publication Date(Web):
DOI:10.1002/app.43979
ABSTRACT
High impact polystyrene (HIPS) resins were obtained with in situ bulk polymerization toughened by styrene–isoprene–butadiene terpolymer rubber (SIBR). SIBR prepolymer was prepared through selective polymerization of styrene (St), isoprene (Ip), and butadiene (Bd) in St with [Nd]/[Al]/[Cl] catalyst. Nd-based catalyst exhibited more favorable activity toward conjugated diene other than St, resulting in St solution of random SIBR with high cis-1,4 stereoregularity and low St content, which was directly exposed to the free radical polymerization of St to generate HIPS. Effect of toughened rubber and the initiators [difunctional (D2) and trifunctional (T3)] were examined to attain HIPS possessing mechanical properties as follow: impact strength, 0.9–24.8 kJ/m2; tensile strength, 16.0–27.5 MPa; and elongation at break, 7.4–107.0%. Increasing SIBR matrix in HIPS improved the impact strength and decreased tensile strength. The fracture surface morphologies of HIPS specimens were studied by notched impact tests and scanning electron microscopy (SEM), illustrating that the incremental SIBR matrix presented synergistic toughening effect of crazing to enhance the ductile fracture behavior. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43979.
Co-reporter:Shaohui Li, Zechao Di, Liang Cheng, Zhongguo Liu, Jicheng Piao, Dongsheng Huang, Zhiyu Zhao, Haitao Cui, Yang Li
Tribology International 2016 Volume 102() pp:319-325
Publication Date(Web):October 2016
DOI:10.1016/j.triboint.2016.05.044
•P and Ca in ATF have a chemical reaction on the steel surface.•P/Ca/O element ratio of the tribofilm is fixed.•It can be inferred that the composition of the tribofilm is calcium phosphate.Automatic transmission fluids (ATF) were tested using a new type disc-on-disc simulation tribo-test-rig Wazau triometer with the aim of studying the tribofilm formation on the steel surfaces during the engagement of wet friction clutches. XPS, SIMS, SEM and EDX were used to investigate the chemical composition of this tribofilm. The result confirms that there exist tribochemical reactions between ATF additives and steel rubbing surfaces. P/Ca/O element ratio of the tribofilm is consistent, which has never been reported before in the tribological field of clutch discs. All the results suggest that the chemical composition of this tribofilm is calcium phosphate. Since calcium phosphate ceramics have excellent mechanical and tribological properties, the friction characteristics of wet clutches must have been changed.
Co-reporter:Tingting Li;Gongqiang He;Zhenghai Shi;Yanming Hu;Fang Guo
Polymer Bulletin 2016 Volume 73( Issue 2) pp:509-518
Publication Date(Web):2016 February
DOI:10.1007/s00289-015-1503-4
Random styrene (St)–butadiene (Bd) copolymer (SBR) was obtained with the catalyst system composed of Nd(P507)3, methylaluminoxane (MAO) and indene. This Nd-based catalyst system showed high activity and selectivity toward the copolymerization. Indene was proven to be the critical component to achieve the high content of St units (~33.0 %). Raising the polymerization temperature was beneficial to enhance the coordination of St to the active center, affording the increased yield and number-average molecular weight (Mn) of SBR. The polymers obtained in aliphatic solvents possessed higher Mn than Mn of SBR generated in toluene. The composition of SBR was controllable by adjusting the feed ratio of St/Bd. NMR and DSC analysis illustrated that the copolymers sustained random distribution even when St incorporation in SBR was up to 33.0 %. SBR was fully characterized by NMR, FTIR, GPC and DSC analysis.
Co-reporter:Yanshai Wang, Zhiyong Wei, Xuefei Leng, Kaihua Shen, Yang Li
Polymer 2016 Volume 92() pp:74-83
Publication Date(Web):1 June 2016
DOI:10.1016/j.polymer.2016.03.081
•Polybutadiene (PB) and epoxidized polybutadiene (EPB) were used as toughening agent for PLA.•The compatibility, phase morphologies, mechanical properties and thermal properties of the PLA/EPB blends were investigated.•Epoxy group of EPB showed a significant effect in enhancing compatibility between rubber phase and PLA matrix.•An excellent toughness-strength balance has been achieved in PLA/EPB blends with low rubber content (10 wt %).Relatively high contents of rubber are commonly required to trigger the brittle-to-ductile transition when using rubber components to toughen polylactide (PLA). However, the strength may drop remarkably after incorporation of large amount of rubber. The main motivation of the present work is to achieve a good toughness-strength balance in a PLA/rubber system with less amount of rubber phase (90/10 w/w). In this study, polybutadiene (PB) was used to toughen PLA due to the flexible molecular chains. In attempt to enhance the compatibility of PB in PLA matrix, epoxidized polybutadiene (EPB) with different epoxidation degree were prepared by an in situ peroxy-formic acid method. The compatibility, phase morphologies, mechanical properties and thermal properties of the PLA/EPB blends were investigated respectively. It was found that epoxy group of EPB showed a significant effect in enhancing compatibility between rubber phase and PLA matrix, giving rise to a remarkable decrease in the particle diameter of rubber phase. When both of the good compatibility and the appropriate particle size of the rubber phase were realized, the impact toughness of PLA/EPB blend was improved by 13 times for that of pure PLA, while the tensile strength still preserved as a level of 77% (based on the value of pure PLA). The interfacial compatibilization between PLA and EPB was achieved through the formation of graft-copolymer being a compatibilizer caused by the in-situ reaction between EPB and PLA in the melt blend process. This result proves the introduction of active groups into PLA blends to be a platform to design their performance via regulating the phase structure.
Co-reporter:Li Han, Hongwei Ma, Yang Li, Siqi Zhu, Lincan Yang, Rui Tan, Pibo Liu, Heyu Shen, Wei Huang, and Xichen Gong
Macromolecules 2016 Volume 49(Issue 15) pp:5350-5365
Publication Date(Web):July 21, 2016
DOI:10.1021/acs.macromol.6b01429
A versatile strategy is highly desired to prepare well-designed side chain liquid crystal polymers (SCLCPs). Two rigid and topological SiH/Vinyl-functionalized polystyrenes (PSs), namely poly(4-vinylphenyldimethylsilane) (PVPDMS) and poly(4-vinylphenyl-1-butene) (PVSt), were synthesized via anionic polymerization (AP) and detailed; subsequently, Vinyl/SiH terminated LCs were treated with PVSt/PVPDMS via hydrosilylation to yield SCLCPs bearing [Si–O–Si]/[Si–C] spacers. Herein, well-designed grafting density, evaluated by 1H NMR, was readily performed by the varying SiH to Vinyl feed mole ratio. The design systematically probes a cooperative effect of architectures on properties and allows for precision in flexible/rigid matrixes. Regardless, PB/PS systems with saturated addition displayed the best performances. Fundamentally, the study compared the dependence of polarized optical and thermal performances on [Si–O–Si] versus [Si–C] spacer, which submitted to be driven by grafting density, providing the first access to tailoring polymer. SCLCPs exhibited essentially constant SmA, but inconsistent dynamic of spacer-induced contribution, in which ΔT was the same in complete addition as if nothing with spacer; surprisingly, followed by decreased grafting density, the decreasing trend in ΔT of [Si–O–Si] as spacer was fast, while that of [Si–C] was slow. This phenomenon was further confirmed by POM. Furthermore, [Si–O–Si] was desired to obtain lower Tg and applicable to the advantageous “decoupling effect”. Endeavor for tailoring SCLCPs and regulating devices, the appropriate spacer and grafting density advanced to an effective role.
Co-reporter:Fang Guo;Bai Wang;Hongwei Ma;Tingting Li
Journal of Polymer Science Part A: Polymer Chemistry 2016 Volume 54( Issue 6) pp:735-739
Publication Date(Web):
DOI:10.1002/pola.27923
Co-reporter:Pibo Liu, Hongwei Ma, Wei Huang, Heyu Shen, Lingling Wu, Yang Li, Yurong Wang
Polymer 2016 Volume 97() pp:167-173
Publication Date(Web):5 August 2016
DOI:10.1016/j.polymer.2016.05.015
•Living anionic copolymerization of styrene and DPE-(NMe2)2 has been investigated.•Sequence distribution of DPE-(NMe2)2 has been determined as gradient increasing.•Low conversation of DPE-(NMe2)2 was exhibited in copolymerization.•Alternating structure for styrene and DPE-(NMe2)2 was scarcely possible to prepare.Sequence distribution in the Living anionic copolymerization of Styrene and strong electron-donating DPE derivative, i.e. the 1,1-bis(4-N,N-dimethylanimophenyl)ethylene (DPE-(NMe2)2), was investigated by a timing-sample method. The target taken samples were characterized by SEC and 1H NMR in detail According to the research data based on integrating all the taken samples, the synthesized copolymer exhibited gradient structure that most polar dimethylamino groups distributed at the end section along whole polymer chains. In addition, the apparent rate constants of styrene and DPE-(NMe2)2 were calculated (at 24 °C) as follows: Kst = 0.036 min−1 (R2 = 0.995), KDPE = 8.40 × 10−5 min−1 (R2 = 0.998), respectively. It is hardly to prepare the alternating structure just through increasing the monomer feed ratios.Download high-res image (205KB)Download full-size image
Co-reporter:Yingying Ren, Zhiyong Wei, Xuefei Leng, Tong Wu, Yufei Bian, and Yang Li
The Journal of Physical Chemistry B 2016 Volume 120(Issue 17) pp:4078-4090
Publication Date(Web):April 11, 2016
DOI:10.1021/acs.jpcb.6b01867
Highly branched polymers (HBPs) are a special class of functional polymeric materials and possess unique properties due to their unique topological structure. A new series of highly branched linear–comb and star–comb amorphous poly(trimethylene carbonate)s (PTMC) and crystalline poly(ε-caprolactone)s (PCL) with well-defined structure and high molecular weight were first synthesized using hydroxylated polybutadiene (HPB) as macroinitiators by simple “one-step” and “graft from” strategies. It is expected that the impact of long-chain, highly branched architecture on the properties of amorphous and crystalline polymers, respectively, is different. We explored systematically for the first time the effect and comparison of branched architectures on the physical and chemical properties of highly branched PTMCs and PCLs, including the intrinsic viscosity, glass transition, thermal degradation, creep property, rheological property, and crystallization and melting behaviors. It is found that the intrinsic viscosities in solution for both comb-branched PTMCs and PCLs were much lower compared with their linear and star counterparts arise from more compact structure and smaller hydrodynamic volumes. For amorphous PTMC, the creep strain and rate increased remarkably with degree of branching increasing due to the shorter side chains making it difficult for the highly branched molecules to entangle. For crystalline PCL, both WAXD and DSC analysis of PCLs with different topological structures indicated that the comb branched architectures have no significant influence on the crystal structure of PCL, but greatly promote the crystallization behavior, e.g., higher crystallinities. The deep understanding of structure–property relationship expects to guide the synthesis of designed functional polymer materials and the processing of polymer products.
Co-reporter:Hongwei Ma;Qiuyun Wang;Wei Sang;Li Han;Pibo Liu;Jun Chen;Yurong Wang
Macromolecular Rapid Communications 2015 Volume 36( Issue 8) pp:726-732
Publication Date(Web):
DOI:10.1002/marc.201400660
Co-reporter:Xuefei Leng, Zhiyong Wei, Yingying Ren, Yang Li, Yurong Wang and Qinyi Wang
RSC Advances 2015 vol. 5(Issue 99) pp:81482-81491
Publication Date(Web):18 Sep 2015
DOI:10.1039/C5RA15141D
In this work, two series of linear-comb and star-comb well defined graft poly(L-lactide) (PLLA) have been synthesized conveniently by one-pot ring-opening polymerization (ROP) of L-lactide using functionalized polybutadiene macroinitiators. The used organocatalyst of 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU) allows the polymerization of L-lactide to proceed rapidly at room temperature. Kinetic studies of the ROP reaction in this system indicate first-order kinetics in monomer concentration. 1H NMR and GPC techniques are employed to characterize the synthesized polymers, validating the formation of the desired comb structures with controllable chain length. Linear-comb and star-comb graft PLLA were comparatively studied as well as with linear PLLA by DSC and POM. The results reveal that the comb structure gives a remarkable improvement of PLLA crystallization ability in both crystallinity and growth rate of spherulites. Furthermore, the more compacted star-comb structure imposes restriction on chain mobility, which weakens the growth effect to some extent. It is found that the glass transition temperature (Tg) and melting temperature (Tm) significantly depend on the side chain length and backbone structure. Rheological studies of both melt and instinct viscosity of the solution show that star-comb PLLA has the lowest hydrodynamic volume compared with linear-comb PLLA and linear PLLA.
Co-reporter:Cheng Zhou, Zhiyong Wei, Yang Yu, Yanshai Wang and Yang Li
RSC Advances 2015 vol. 5(Issue 84) pp:68688-68699
Publication Date(Web):06 Aug 2015
DOI:10.1039/C5RA13177D
In this work, a series of novel biobased copolymers, poly(propylene sebacate-co-isosorbide sebacate) (P(PSe-co-IS)), were synthesized by melt-polycondensation from sebacic acid (SA) and isosorbide (IS) with 1,3-propanediol (PD). In order to analyze the effects of isosorbide on the relative properties of poly(propylene sebacate) (PPSe), the composition, crystal structure, crystallization behavior, multiple melting behavior, and spherulitic morphology of these copolymers were investigated by 1H-NMR, WAXD, DSC, TMDSC and POM, respectively. Results of 1H-NMR indicated that IS have been successfully introduced into the PPSe main chains with the designed molar ratio. DSC data showed that crystallization ability of P(PSe-co-IS) copolymers was retarded with the introduction of IS. With the increment of IS, the overall crystallization rate decreased gradually. Furthermore, crystallization temperature (Tc), crystallization enthalpy (ΔHc), melting temperature (Tm), and equilibrium melting temperature (Tom) of P(PSe-co-IS) copolymers also decreased apparently with the increase of IS content. WAXD suggested that crystal structure of PPSe was not affected by IS, and POM revealed that all spherulites possess the typical “Maltese Cross” image. Furthermore, no obvious ring-banded spherulites could be detected for P(PSe-co-IS) copolymers in the wide temperature range except neat PPSe due to the hindrance of IS. With the increment of IS and crystallization temperature, the number of spherulites decreased rapidly and the size of spherulites increased, respectively.
Co-reporter:Zhiyong Wei, Cheng Zhou, Yang Yu and Yang Li
RSC Advances 2015 vol. 5(Issue 53) pp:42777-42788
Publication Date(Web):29 Apr 2015
DOI:10.1039/C5RA04761G
A series of long chain aliphatic copolyesters poly(decamethylene sebacate-co-isosorbide sebacate) (P(DS-co-IS)) were synthesized from commercially available biobased sebacic acid (SA), 1,10-decanediol (DD) and isosorbide (ISB) through a two-step melt polycondensation method. The molecular weight, composition, and microstructure of the P(DS-co-IS) copolyesters were characterized by GPC, 1H-NMR, and 13C-NMR. The crystallization properties of the P(DS-co-IS) copolyesters were depressed, while the glass transition temperature was enhanced by the incorporation of isosorbide with a bulky rigid structure. The nonisothermal melt crystallization peak temperature and melting point decreased for P(DS-co-IS) with increasing the number of ISB unit; moreover, the equilibrium melting point temperature of P(DS-co-IS) was also reduced. However, the introduction of the ISB segment did not change the crystal structure of P(DS-co-IS), but it gradually decreases the crystallinity. Isothermal crystallization kinetics of neat PDS and its copolyesters indicated that PDS possesses high crystallization ability, which is a characteristic of long chain aliphatic polyesters. The crystallization mechanism remains unchanged for both neat PDS and P(DS-co-IS); however, the crystallization rates of P(DS-co-IS) decreased with increasing ISB composition and crystallization temperature. No evidence of ring-banded spherulites could be detected for this long chain PDS and its copolyesters in a wide temperature range even when supercooled.
Co-reporter:Yingying Ren, Qing Gao, Cheng Zhou, Zhiyong Wei, Yu Zhang and Yang Li
RSC Advances 2015 vol. 5(Issue 35) pp:27421-27430
Publication Date(Web):06 Feb 2015
DOI:10.1039/C4RA17276K
A series of linear-comb highly branched poly(ε-caprolactone) (LC-PCL) with well-defined structure, high molecular weight and narrow polydispersity was synthesized using hydroxylated polybutadiene as macroinitiator and 1,5,7-triazabicyclo-[4.4.0]dec-5-ene (TBD) as catalyst at room temperature. First, the macroinitiator, functionalized hydroxylated polybutadiene was prepared by anionic polymerization of butadiene, epoxidation and ring-opening reaction. Then the hydroxyl groups in the hydroxylated polybutadiene initiated the ring-opening polymerization of ε-caprolactones in the presence of TBD. In an effort to optimize the reaction system, the effects of different reaction factors on the ring-opening polymerization were investigated. The simplicity of the reaction conditions, the ready availability of the catalyst, and the exquisite control over the polymerization were also demonstrated. The arm number, side chain length, and molecular weight of branched LC-PCL were regulated by adjusting the number of hydroxyl groups on macroinitiator and monomer/hydroxyl group feed ratios. Physical properties (thermal property, crystal structure and spherulitic morphology) of the obtained polymers were analyzed by DSC, TGA, WAXD and POM. The results showed that the branched PCL crystallize in the ordinary crystal form similar to linear PCL, and the crystallization and melting behaviors are strongly dependent on the side PCL chain length.
Co-reporter:Kaihua Shen;Yanfeng Jiang;Zhengxue Liu;Debang Qi;Haiyang Wang
Macromolecular Chemistry and Physics 2015 Volume 216( Issue 20) pp:1990-1996
Publication Date(Web):
DOI:10.1002/macp.201500193
Co-reporter:Li Han, Hongwei Ma, Yang Li, Jian Wu, Hanyan Xu, and Yurong Wang
Macromolecules 2015 Volume 48(Issue 4) pp:925-941
Publication Date(Web):February 10, 2015
DOI:10.1021/acs.macromol.5b00101
A new series of linear–comb and 4-arm star–comb side chain liquid crystalline polymers (Lc-/Sc-SCLCPs) have been synthesized and characterized. The treatment of hydride siloxane-containing terminated liquid crystalline and high 1,2-/1,4- (high vinyl, hv/low vinyl, lv) linear or 4-arm star polybutadienes (L-/S-PBs) was conducted via the methods in combination of living anionic polymerization and “reverse” hydrosilylation to obtain SCLCPs with wide mesomorphic temperature range (ΔT) and narrow polydispersity index (PDI). The possible molecular arrangement model of two analogous hv-/lv-architectures was constructed, that was used to systematically investigate the effects of Lc- and Sc- topological morphology on liquid crystalline (LC) properties and molecular microstructures. SCLCPs exhibited the same smectic A phase around room temperature, but thermal properties were significantly different due to differences of interaction force resulting from different macromolecular side chains packing. Surprisingly, the trend of lv-SCLCP displaying the effects of topology on phase transitions and microstructures was just contrary to that of hv-topology. hv-Sc-SCLCPs containing high density mesogenic composition were desired to generate wider ΔT and higher molecular layer order in comparison with Lc analogues, which provided a unexpected analyzed model that are of interest to be explored. In particular, the uniaue differences of macromolecular aggregation state arrangement in liquid crystal state dependent on free cooling between hv-Lc- and Sc-SCLCPs were observed from POM.
Co-reporter:Yingying Ren, Zhiyong Wei, Xuefei Leng, Yurong Wang, Yang Li
Polymer 2015 Volume 78() pp:51-58
Publication Date(Web):5 November 2015
DOI:10.1016/j.polymer.2015.09.063
•Boric acid is a metal-free biocatalyst for ring-opening polymerization of cyclic esters.•B(OH)3-catalyzed polymerization is a controlled/living polymerization.•B(OH)3-catalyzed polymerization of CL prefers an activated monomer mechanism.Boric acid (1, B(OH)3) was investigated as metal-free biocatalyst for its activity towards the bulk ring-opening polymerization (ROP) of ε-caprolactone (CL) initiated by benzyl alcohol (BnOH). Moreover, other boric acid derivates such as phenylboronic acid (2), 2-thienylboronic acid (3), 2-furanylboronic acid (4) and 5-pyrimidinylboronic acid (5) were also used as acidic catalysts to synthesize poly(ε-caprolactone) (PCL), poly(δ-valerolactone) (PVL) and poly(trimethylene carbonate) (PTMC). The studies on the polymerization kinetics for all catalysts confirm that the reaction rates are first-order with respect to monomer and their catalytic activities follow the order 1 > 3 > 2 ≈ 4 > 5. Furthermore, the block copolymerization of ε-caprolactone (CL) with δ-valerolactone (VL) and trimethylene carbonate (TMC) successfully proceeded by the sequential monomer addition to give PCL-b-PVL and PTMC-b-PCL copolymers, indicating the living nature of the present polymerization system. The end group analysis by 1H NMR and MALDI-TOF MS measurements suggested that the benzyl moiety of initiator inserted into the synthesized polymeric chain. The existence of the interaction between the catalyst B(OH)3 and the monomer CL supports that B(OH)3 catalyzed ROP of CL preferred an activated monomer mechanism. A possible model for the initiation and propagation procedures of ROP of cyclic esters catalyzed by boric acid in the presence of benzyl alcohol was proposed.
Co-reporter:Zhenghai Shi;Fang Guo;Zhaomin Hou
Journal of Polymer Science Part A: Polymer Chemistry 2015 Volume 53( Issue 1) pp:5-9
Publication Date(Web):
DOI:10.1002/pola.27455
Co-reporter:Kaihua Shen, Yibo Wang, Guoqiang Ying, Ming Liang, Yang Li
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2015 Volume 467() pp:216-223
Publication Date(Web):20 February 2015
DOI:10.1016/j.colsurfa.2014.11.057
•Two functionalized poly(styrene–isoprene–butadiene) (PSIB) latexes containing SAN copolymer were synthesized.•The PSIB latex via a seeded-emulsion polymerization was partially miscible with the unimodal distribution of rubber particles.•Bimodal PSIB latex was obtained by agglomerating process with amphiphilic block copolymers.•The PSIB-g-SAN particles with a two-stage seed-emulsion polymerization exhibited a relative homogeneity of distribution in-space.•The PSIB-g-SAN particles being prepared by agglomerating process showed an unequal size structure and an ‘internal-grafting’ characteristic.The poly(styrene–isoprene–butadiene) (PSIB) latexes with large particle diameters were synthesized in a seed-emulsion polymerization or followed by agglomerating with amphiphilic block copolymers, and their granularity uniformities were also investigated through the determination of PSIB grain-size distribution. Resultant PSIB latexes were functionalized with styrene–acrylonitrile random copolymers (SAN) which the chemical graft modification had been investigated as well. The large particle diameter of PSIB latex via a seed-emulsion polymerization showed a continuous and normal distribution, which was improved greatly with the dosages of emulsifier and seed-emulsion concentration. A bimodal PSIB latex with large-sized particles were also prepared by the agglomerating process with a hydrophilic polymer of poly(butylacrylate-methacrylic) acid after the radical emulsion polymerization and was greatly affected with addition of poly(butylacrylate-methacrylic) acid. Moreover, the higher value of graft yield of SAN copolymer onto PSIB latex was observed as compared to the PB latex and the following factors controlled the grafting degree of the particles: (i) the composition of monomers; (ii) the initiator's content; (iii) the conditions for grafting copolymerization. Poly(styrene–isoprene–butadiene-g-SAN) graft copolymers (PSIB-g-SAN) were blended with SAN resins and their toughening properties were tested respectively. The effects of the composite polymer particles and the properties of PSIB-g-SAN particles were also discussed.
Co-reporter:Fang Guo, Rui Meng, Yang Li, Zhaomin Hou
Polymer 2015 Volume 76() pp:159-167
Publication Date(Web):12 October 2015
DOI:10.1016/j.polymer.2015.08.060
•Butadiene–isoprene–styrene terpolymers are synthesized by using a half-sandwich Sc catalyst.•The terpolymers contain atactic polystyrene and cis-1,4-conjugated diene sequences.•The styrene content in the terpolymers is controllable in a range of 17–76 mol%.•Random cis-1,4-copolymerization of butadiene and isoprene is achieved with high activity and regio- and stereoselectivity.We report here the terpolymerization of butadiene (BD), isoprene (IP), and styrene (St) by a half-sandwich scandium catalyst bearing an unsubstituted cyclopentadienyl ligand, (C5H5)Sc(CH2C6H4NMe2-o)2/[Ph3C][B(C6F5)4], which afforded for the first time the BD–IP–St terpolymers containing high cis-1,4-BD and high cis-1,4-IP units and atactic polystyrene blocks. The copolymerization of BD and IP by this catalyst took place in a quasi-living, cis-1,4-selective fashion, yielding the random BD–IP copolymers with high cis-1,4 content of both monomer units (selectivity > 94%), controllable molecular weight (Mn = 5.1 × 104 − 28.7 × 104) and narrow molecular weight distribution (Mw/Mn = 1.18–1.40). The incorporation of atactic polystyrene blocks into high cis-1,4 content BD–IP copolymers was realized in a wide range of St content (17–76 mol%) by carrying out the polymerization in the presence of the three monomers St, BD and IP with varying feed ratios. The NMR and DSC analyses suggest that the resulting copolymers are St–BD–IP terpolymers with atactic polystyrene blocks, high cis-1,4-IP (selectivity up to 98%) and high cis-1,4-BD (selectivity up to 96%) units.
Co-reporter:Zhiyong Wei, Ping Song, Lin Sang, Keliang Liu, Cheng Zhou, Yanshai Wang, Yang Li
Polymer 2014 Volume 55(Issue 11) pp:2751-2760
Publication Date(Web):27 May 2014
DOI:10.1016/j.polymer.2014.04.023
A series of biodegradable radiopaque iodinated poly(ester-urethane)s (IPEUs) were synthesized by chain-extension of dihydroxylated poly(butylene succinate) (PBS–OH) and isophorone diisocyanate (IPDI) with iodinated bisphenol-A (IBPA). The effects of IBPA on the crystallization and melting behaviour of IPEUs were investigated by wide-angle X-ray diffraction (WAXD), polarized optical microscope (POM), differential scanning calorimetry (DSC), and temperature-modulated differential scanning calorimetry (TMDSC). WAXD results suggest that the PBS soft segments form only one crystal modification, and that the crystallinity of the samples decreases with increasing the amorphous hard segments. POM observation indicates that the ring-bands of spherulites disappear and then the spherulitic texture is disturbed with increasing the IBPA content. The analysis of isothermal crystallization kinetics shows that the crystallization of IPEUs is retarded by the introduction of IBPA chain extender with bulky pendent groups. In the DSC heating curves, at most four endothermic peaks were observed and their origins were examined. Two recrystallization exothermic peaks were observed for IPEUs in the nonreversible signals of TMDSC. The twice sequential melting–recrystallization–remelting model could be used to explain the multiple melting behaviour of IPEUs.
Co-reporter:Qiang Xu;Li Li;Fang Guo;Zhenghai Shi;Hongwei Ma;Yanshai Wang;Yurong Wang
Polymer Engineering & Science 2014 Volume 54( Issue 8) pp:1858-1863
Publication Date(Web):
DOI:10.1002/pen.23731
The present study focuses on the terpolymer of styrene (St), isoprene (Ip), and butadiene (Bd) synthesized together in cyclohexane at 70°C with neodymium (Nd) compound, alkylaluminum, and chlorinating agent (Cl) rare earth cocatalyst system. The resultants possessed atactic St–St sequences and high cis-1,4 polyconjugated olefins in macromolecular chains besides controllable composition. The composition of the St–Ip–Bd terpolymers and molecular weight (Mw), molecular weight distribution (Mw/Mn) were controlled through the adjustment of Nd compound, alkylalumium, monomers feed ratio (St/Ip/Bd), and [Nd]/[monomers]. With the inventory rating of St raised from 15% to 55%, the content of St in the terpolymers got increased from 2% to 15%. And the content of the Ip segments and Bd segments in the terpolymers increased from 33% to 56% and from 28% to 54%, respectively, with the proportion of Ip/Bd varied from 1/2 to 2/1. As the [Nd]/[monomers] varied from 1.0 × 10−3 to 5.0 × 10−4, the molecular weight increased from 1.3 × 104 to 2.7 × 104. According to the proton nuclear magnetic resonance (1H-NMR) and 13C-NMR, it was proved that both microstructures of polybutadiene segments and polyisoprene segments were high cis-1,4-configuration. A single glass-transition temperature was observed in the differential scanning calorimetry curve. POLYM. ENG. SCI., 54:1858–1863, 2014. © 2013 Society of Plastics Engineers
Co-reporter:Yu Zhang, Fang Guo, Kaihua Shen, Yingying Ren, Yang Li
Polymer 2014 Volume 55(Issue 5) pp:1202-1208
Publication Date(Web):10 March 2014
DOI:10.1016/j.polymer.2014.01.050
A series of multicoumarin-functionalized dendrigraft polybutadienes with linear-comb or star-comb topology were synthesized from generation 0 to 3 (LGn and SGn respectively, n = 0–3) to investigate the dendritic effects on photophysical and fluorescence properties. From the results of SEC-TALLS, SEC and ubbelohde viscometer, the polymer architecture converted from one- or two-dimensional structure to a flexible branched structure, then advanced into a compact structure; meanwhile, the LGn exhibited a relatively looser structure than its SGn analog did. Hypsochromic shifts of the absorption and emission maxima, as well as signal amplifications were observed for both LG3 and SG3, suggesting that encapsulation effect occurred at the third generation resulting from the compact architecture. The fluorescence quantum yield (ΦF) was in the order of LG1 (8.1%) > SG1 (6.4%) > LG2 (5.0%) > SG2 (4.6%) > LG3 (2.3%) > SG3 (2.0%) > SG0 (1.1%) > LG0 (0.7%), indicating that the flexible branched polymer matrix could enhance the fluorescence properties due to the synergistic combination of inter-/intra-molecular fluorescence quenching. Also, the fluorescence properties of polymer with linear-comb architecture were always better than those of star-comb counterpart due to its looser architecture.
Co-reporter:Zhisheng Yu;Chaoxian Wang;Yurong Wang
Journal of Applied Polymer Science 2013 Volume 128( Issue 4) pp:2468-2478
Publication Date(Web):
DOI:10.1002/app.38360
Abstract
A series of low-cis-1,4/high-cis-1,4 polybutadiene composite rubber toughened poly(acrylonitrile-butadiene-styrene) (ABS) terpolymers were prepared and characterized. The morphological analysis shows that specimens exhibit common characteristics of two single rubbers while mechanical measurements reveal that better comprehensive properties can be obtained as more Ni-9004 blended in composite rubber. When increasing Ni-9004/Li-700A ratio, one brittle–ductile transition occurs at 5.0 wt % rubber usage and three transition regions exist under 10.0 wt % usage. In addition, the characteristic force–time curves and fractography demonstrate that failure behavior and crack propagation mode can be effectively evaluated. Conclusively, quasi-brittle fracture can be seen for specimens with obvious cavitation and matrix stripping followed by riverlike fibrous and periodical Wallner stripes, whereas ductile fracture is observed for those with alternate parabolic and firework patterns accompanying stress-whitening and ligament-forming progress. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Co-reporter:Tingting Li;Yanming Hu;Hongxia Zhang;Zhenghai Shi;Gongqiang He;Yurong Wang;Kaihua Shen
Journal of Applied Polymer Science 2013 Volume 130( Issue 3) pp:1772-1777
Publication Date(Web):
DOI:10.1002/app.39327
ABSTRACT
Random styrene-isoprene-butadiene rubber (SIBR) were achieved with the catalyst system composed of neodymium isopropoxide (Nd(OiPr)3), methylaluminoxane (MAO) and indene. This catalyst proved to be highly effective in cyclohexane even at low [Al]/[Nd] ratio (ca. 50) to give styrene-rich terpolymer with high number-average molecular weight (Mn) and narrow molecular weight distribution (Mw/Mn). Indene was critical to improve the coordination of styrene. High temperature was beneficial to increase the yield. Aliphatic solvents (hexane and cyclohexane) achieved a higher Mn of polymer than toluene as a solvent. The glass transition temperature (Tg) and composition of SIBR can be controlled by tuning the feed ratio of monomers. All the products have been fully characterized by NMR spectroscopy, gel permeation chromatograph (GPC), and DSC. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1772–1777, 2013
Co-reporter:Qing Gao;Yanshai Wang;Yingying Ren
Macromolecular Chemistry and Physics 2013 Volume 214( Issue 15) pp:1677-1687
Publication Date(Web):
DOI:10.1002/macp.201300255
Co-reporter:Lingling Wu, Yanshai Wang, Yurong Wang, Kaihua Shen, Yang Li
Polymer 2013 Volume 54(Issue 12) pp:2958-2965
Publication Date(Web):24 May 2013
DOI:10.1016/j.polymer.2013.04.011
In-chain multi-functionalized polystyrene possessing definite geminal dimethylamino groups along the polymer backbone, poly(styrene-co-1,1-bis(4-dimethylaminophenyl)ethylene) (poly(styrene-co-BDADPE)), has been designed and synthesized via living anionic copolymerization of styrene with 1,1-bis(4-dimethylanimophenyl)ethylene in benzene at 50 °C, using sec-butyllithium as initiator. The amine functionality was readily controlled by the monomer feed ratio and molecular weight. Compositions of styrene/BDADPE were 9.0–57.9 when ratios of styrene/BDADPE = 0.45–7.79 and Mn = 4.7–15.5 kg/mol. The incorporation of 1,1-bis(4-dimethylanimophenyl)ethylene unit resulted in an increase in glass transition temperature of copolymer and was hindered in the presence of Lewis base. The monomer reactivity ratio for styrene, r1 = 53.4, was obtained. Such in-chain multi-functionalized polystyrene significantly improved the dispersity of carbon black in the corresponding composites, as verified by SEM observation. This in-chain multi-functionalization of matrix polymer via anionic copolymerization employing 1,1-bis(4-dimethylaminophenyl)ethylene as comonomer provides a facile and effective method to prepare carbon black-based polymer composites with good dispersity.
Co-reporter:Bai Wang, Hong Wei Ma, Kai Hua Shen, Ding Jun, Yang Li
Chinese Chemical Letters 2012 Volume 23(Issue 12) pp:1419-1422
Publication Date(Web):December 2012
DOI:10.1016/j.cclet.2012.10.018
Functional in-chain silyl-hydride (Si-H) SBR copolymers of 4-vinyiphenyldimethylsilanol (VPDMS) and butadiene were synthesized by living anionic polymerization, in which active group Si-H was not lost and its content was controllable. Corresponding self-crosslinking elastomers were obtained by hydrosilation of Si-H group with vinyl bonds in chain. The copolymers and elastomers were characterized by 1H NMR, size exclusion chromatography (SEC), Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and thermogravimetry analysis (TGA) techniques.
Co-reporter:Jun Ding, Yang Li, Kai Hua Shen, Bai Wang, Yu Rong Wang
Chinese Chemical Letters 2012 Volume 23(Issue 6) pp:749-752
Publication Date(Web):June 2012
DOI:10.1016/j.cclet.2012.03.012
The binary random in-chain silyl-hydride multi-functionalized poly(styrene/butadiene/isoprene and dimethyl[4-(1-phenylvinyl) phenyl]silane) (PS-DPESiH, PB-DPESiH, PI-DPESiH) copolymers were successfully synthesized. These functionalized copolymers were prepared in hexane with n-BuLi as the initiator at 50 °C for 4 h. The silyl-hydride groups were introduced into polymer backbones quantitatively by living anionic polymerization. The copolymers were determined through 1H NMR, size exclusion chromatography (SEC) and differential scanning calorimetry (DSC) techniques, while the number of silyl-hydride groups was calculated and discussed.
Co-reporter:Hong Wei Ma, Bai Wang, Chun Qing Zhang, Yang Li, Yan Ming Hu, Yu Rong Wang
Chinese Chemical Letters 2011 Volume 22(Issue 11) pp:1371-1374
Publication Date(Web):November 2011
DOI:10.1016/j.cclet.2011.05.004
The novel functionalized triblock copolymers, poly[(4-vinylphenyl)dimethylsilane]-b-polybutadiene-b-poly[(4-vinylphenyl)- dimethylsilane] (PVPDMS-b-PBd-b-PVPDMS), were synthesized by anionic polymerization method using high vacuum technique. The hydrocarbon-soluble dilithium initiator synthesized from 1,3-di[1-(methylphenyl)ethenyl]benzene (MPEB) was used to synthesize polybutadiene (PBd) precursors and the triblock copolymers in the presence of sec-BuOLi. The precursors and copolymers were characterized by size exclusion chromatography (SEC), 1HNMR and DSC techniques.
Co-reporter:Yanming Hu, Zhongming Jia, Yang Li, Li Chang, Yurong Wang
Materials Science and Engineering: A 2011 528(22–23) pp: 6667-6672
Publication Date(Web):
DOI:10.1016/j.msea.2011.05.061
Co-reporter:Qing Min Zhang, Chuang Chen, Hong Xia Zhang, Chun Qing Zhang, Yang Li, Xi Gao Jian
Chinese Chemical Letters 2010 Volume 21(Issue 11) pp:1370-1373
Publication Date(Web):November 2010
DOI:10.1016/j.cclet.2010.05.013
A novel star-comb styrene/butadiene copolymer (SC-SBC) was synthesized by anionic polymerization and grafting reaction with epoxidized star liquid polybutadiene (ESPB) as coupling agent. The overall shape of the star-comb macromolecules can be altered by changing the molecular weight and number of the side chain. The molecular parameters and mechanical properties of the SC-SBC resins were investigated. The notched izod impact strength of the SC-SBC resins are excellent and reach as high as to 239 J/m.
Co-reporter:Hong Xia Zhang, Yang Li, Chun Qing Zhang, Yan Ming Hu, Yu Rong Wang, Hong Wei Ma, Wei Li
Chinese Chemical Letters 2010 Volume 21(Issue 3) pp:361-364
Publication Date(Web):March 2010
DOI:10.1016/j.cclet.2009.11.031
A novel star-comb polybutadiene (SC–PB) was synthesized with n-butyllithium (n-BuLi) as initiator, epoxidized star liquid polybutadiene (ESPB) as coupling agent, cyclohexane as solvent by living anionic polymerization and grafting-onto technology. The SC–PB was subsequently hydrogenated by homogeneous catalysis (catalytic hydrogenation using nickel naphthenate/triisobutyl aluminum), to transform the SC–PB into the corresponding star-comb poly(ethylene-co-butene) (SC–PEB). The SC–PB was characterized by SEC-TALLS, 1H NMR, DSC and WAXD techniques. The hydrogenation degree and crystallinity degree of SC–PEB were also determined.
Co-reporter:Xuetao Zhang;Chunqing Zhang;Yurong Wang
Polymer Bulletin 2010 Volume 65( Issue 3) pp:201-213
Publication Date(Web):2010 July
DOI:10.1007/s00289-009-0192-2
A series of symmetrical triblock copolymers containing crystallizable high-trans-1,4-polybutadiene (HTPB) were synthesized by sequential anionic polymerization of 1,3-butadiene (Bd) with isoprene (Ip) (or styrene (St)) using barium salt of di(ethylene glycol) ethyl ether/triisobutylaluminium/dilithium (BaDEGEE/TIBA/DLi) as initiation system. The microstructures of the symmetrical triblock copolymers were determined by IR, 1H NMR, and 13C NMR. The results indicated that polyisoprene-block-high-trans-1,4-polybutadiene-block-polyisoprene (IBI) contained HTPB segments and medium 3,4-polyisoprene (PI) segments, and polystyrene-block-HTPB-block-polystrene (SBS) contained HTPB and atatic-polystyrene (PS) segments. The DSC analysis revealed that SBS tended to phase separate but IBI did not. The cold crystallization was observed in IBI but not in SBS.
Co-reporter:Zhisheng Yu;Zhongfu Zhao;Chaoxian Wang;Juan Yang;Chunqing Zhang;Zhansheng Li;Yurong Wang
Polymer Engineering & Science 2009 Volume 49( Issue 11) pp:2249-2256
Publication Date(Web):
DOI:10.1002/pen.21475
Abstract
A series of acrylonitrile–butadiene–styrene (ABS) copolymers were prepared using lithium-catalyzed low-cis rubber (PB700A), nickel-catalyzed high-cis rubber (BR9004), and their compounded rubber (PB700A/BR9004 = 50:50) as toughening agents through bulk polymerization. The effects of molecular structures of rubbers on the dissolving and grafting process of them were investigated. The structure and properties of ABS resins were characterized with FTIR, TEM, and performance measurements. It is shown that the characteristics of rubbers affect their dissolving state and grafting reaction and consequently influence the morphology and properties of ABS materials. BR9004 promotes the formation of irregular microsized rubber particles with special “salami”-like structure and, therefore, presents better mechanical properties. PB700A has much higher 1,2-isomers, which benefits its dispersion and grafting reaction; its toughening effect, however, is unsatisfactory and can be improved by the incorporation of BR9004. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Co-reporter:Hongxia Zhang, Yang Li, Chunqing Zhang, Zhansheng Li, Xin Li and Yurong Wang
Macromolecules 2009 Volume 42(Issue 14) pp:5073-5079
Publication Date(Web):July 2, 2009
DOI:10.1021/ma900870c
A series of dendrigraft star−comb polybutadienes (PBs), from generation zero to four (G0−G4), were synthesized by anionic polymerization and grafting-onto methodology. The 4-arm star PB (G0 PB) with high 1,4-content and narrow molecular weight distribution (MWD) was selectively epoxidized at the 1,4-PB sites to introduce grafting sites randomly along the polymer arms. The G1 PB was prepared by grafting of the epoxidized G0 PB with polybutadienyllithium (PBLi) anions. The dendrigraft star−comb PBs of higher generations (G2, G3, and G4) were synthesized by repeating the epoxidation and grafting reaction cycles. The dendrigraft star−comb PBs had high molecular weights (Mw = 8.3 × 103 −1.4 × 107) and narrow MWDs (Mw/Mn = 1.01−1.20). Moreover, the molecular weight and branching functionality increased geometrically for the successive generations. The solution properties and the characteristic parameters ([η], Rg, Rh, and g′) of the dendrigraft star−comb PBs were determined and compared with those of the corresponding linear PBs. All results pointed to a much higher compactness of the dendrigraft star−comb macromolecular structure.
Co-reporter:Xuetao Zhang, Yang Li, Chunqing Zhang, Yanming Hu, Shunxi Song, Huanhuan Guo, Yurong Wang
Polymer 2009 50(23) pp: 5427-5433
Publication Date(Web):
DOI:10.1016/j.polymer.2009.09.070
Co-reporter:Na Wang, Hui Niu, Yang Li
Polymer (24 March 2017) Volume 113() pp:259-266
Publication Date(Web):24 March 2017
DOI:10.1016/j.polymer.2017.02.075
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