Mingqing Chen

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Name: 陈明清

Organization: Jiangnan University , China

Department: School of Chemical and Material Engineering

Title: Professor(PhD)

TOPICS

Polymer

Stimuli Responsive Polymers PH Responsive Polymers Stimuli Responsive Polymers Photo Responsive Polymers PH Responsive Polymers

Chemicals
References

A Novel UV-Shielding and Transparent Polymer Film: When Bioinspired Dopamine–Melanin Hollow Nanoparticles Join Polymers

Co-reporter:Yang Wang, Jing Su, Ting Li, Piming Ma, Huiyu Bai, Yi Xie, Mingqing Chen, and Weifu Dong

ACS Applied Materials & Interfaces October 18, 2017 Volume 9(Issue 41) pp:36281-36281

Publication Date(Web):September 25, 2017

DOI:10.1021/acsami.7b08763

Ultraviolet (UV) light is known to be harmful to human health and cause organic materials to undergo photodegradation. In this Research Article, bioinspired dopamine–melanin solid nanoparticles (Dpa-s NPs) and hollow nanoparticles (Dpa-h NPs) as UV-absorbers were introduced to enhance the UV-shielding performance of polymer. First, Dpa-s NPs were synthesized through autoxidation of dopamine in alkaline aqueous solution. Dpa-h NPs were prepared by the spontaneous oxidative polymerization of dopamine solution onto polystyrene (PS) nanospheres template, followed by removal of the template. Poly(vinyl alcohol) (PVA)/Dpa nanocomposite films were subsequently fabricated by a simple casting solvent. UV irradiation protocols were set up, allowing selective study of the extra-shielding effects of Dpa-s versus Dpa-h NPs. In contrast to PVA/Dpa-s films, PVA/Dpa-h films exhibit stronger UV-shielding capabilities and can almost block the complete UV region (200–400 nm). The excellent UV-shielding performance of the PVA/Dpa-h films mainly arises from multiple absorption because of the hollow structure and large specific area of Dpa-h NPs. Moreover, the wall thickness of Dpa-h NPs can be simply controlled from 28 to 8 nm, depending on the ratio between PS and dopamine. The resulting films with Dpa-h NPs (wall thickness = ∼8 nm) maintained relatively high transparency to visible light because of the thinner wall thickness. The results indicate that the prepared Dpa-h NPs can be used as a novel UV absorber for next-generation transparent UV-shielding materials.Keywords: dopamine−melanin; hollow nanoparticles; polymer; transparency; UV-shielding;

Green Antibacterial Nanocomposites from Poly(lactide)/Poly(butylene adipate-co-terephthalate)/Nanocrystal Cellulose–Silver Nanohybrids

Co-reporter:Piming Ma;Long Jiang;Manman Yu;Weifu Dong

ACS Sustainable Chemistry & Engineering December 5, 2016 Volume 4(Issue 12) pp:6417-6426

Publication Date(Web):September 30, 2016

DOI:10.1021/acssuschemeng.6b01106

Silver nanoparticles (AgNPs) with a diameter of 3–6 nm were uniformly reacted onto the surface of nanocrystal cellulose (NCC) via complexation leading to NCC–Ag nanohybrids with an AgNP content of 8 wt %. Subsequently, antibacterial green nanocomposites containing renewable and biodegradable poly(lactide) (PLA), poly(butylene adipate-co-terephthalate) (PBAT) and NCC–Ag nanohybrids were synthesized and investigated. The PBAT as flexibilizer improved the toughness of the PLA matrix while the uniformly dispersed NCC–Ag nanohybrids enhanced the compatibility, thermal stability, crystallization, and antibacterial properties of the PLA/PBAT blends. The crystallization rate and the storage modulus (E′) of the green nanocomposites were increased obviously with increasing content of CNC–Ag nanohybrids. Meanwhile, notably the antibacterial activity of the PLA/PBAT/NCC–Ag nanocomposites was achieved against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus cells. The antibacterial performance was mainly related to the antibacterial nature of the finely dispersed NCC–Ag nanohybrids. The study demonstrates great potential of the green nanocomposites in functional packaging and antibacterial textile applications.Keywords: Antibacterial; Cellulose; Green nanocomposite; Nanohybrids; Poly(lactide);

Rapid Crystallization of Poly(lactic acid) by Using Tailor-Made Oxalamide Derivatives as Novel Soluble-Type Nucleating Agents

Co-reporter:Piming Ma;Weifu Dong;Dawei Wang;Yunsheng Xu

Industrial & Engineering Chemistry Research August 13, 2014 Volume 53(Issue 32) pp:12888-12892

Publication Date(Web):2017-2-22

DOI:10.1021/ie502211j

The crystallization rate and crystallinity of poly(lactic acid) (PLA) was significantly increased by the incorporation of 0.25–1.0 wt % of tailor-made oxalamide derivatives (NAs). The nucleation effect and nucleation mechanisms of the NAs were studied via diferential scanning calorimetry (DSC), polarized optical microscopy (POM), and wide-angle X-ray diffraction (WAXD) techniques. The experimental results convincingly revealed that the NA molecules are soluble in a PLA melt and are capable of self-organizing into fibrils upon cooling. The fibrils as efficient nucleation sites induced rapid growth of α-form PLA crystal along the fibrils, forming shish-kebab-like structures. In isothermal crystallization, very fine PLA sperrulites with high density were obtained in the presence of NAs. The high nucleation efficiency and the simple synthetic routes of the NAs make them promising to be a new generation of nucleating agents for (bio)polymers, e.g., PLA.

Cellulose-g-poly(d-lactide) nanohybrids induced significant low melt viscosity and fast crystallization of fully bio-based nanocomposites

Co-reporter:Piming Ma, Tianfeng Shen, Long Lin, Weifu Dong, Mingqing Chen

Carbohydrate Polymers 2017 Volume 155() pp:498-506

Publication Date(Web):2 January 2017

DOI:10.1016/j.carbpol.2016.09.003

⿢NCC-g-PDLA nanohybrids were synthesized and used to make nanocomposites.⿢The melt viscosity of PLLA/PHA was significantly reduced by NCC-g-PDLA nanohybrids.⿢The crystallization of PLA was remarkably enhanced by NCC-g-PDLA nanohybrids.⿢Unique core-shell-like microstructures of the nanocomposites were formed.Comb-like nanocrystal cellulose graft poly (d-lactide) (PDLA), i.e., NCC-g-PDLA nanohybrids were synthesized and compounded with poly (l-lactide) (PLLA) and poly (hydroxyalkanoate)s (PHA) to make fully biobased nanocomposites. Surprisingly, the complex viscosity of the PLLA/PHA melts was reduced by more than one order of magnitudes, viz. from 4000 to 100 Pa s by incorporation of 2⿿4 wt% of the NCC-g-PDLA nanohybrids. Meanwhile, the crystallization of the PLLA component was accelerated by the NCC-g-PDLA nanohybrids due to the strong interaction between PDLA and PLLA macromolecules. The significant reduction in melt viscosity associating with unique core-shell-like microstructures due to the synergetic effect of the NCC-g-PDLA nanohybrids and the PHA would facilitate the preparation of complex-shaped biomass articles and fibers under low(er) pressure and temperatures, which is beyond pure academic interest.

Reactive compatibilization of biodegradable poly(butylene succinate)/Spirulina microalgae composites

Co-reporter:Nianqing Zhu;Ming Ye;Dongjian Shi

Macromolecular Research 2017 Volume 25( Issue 2) pp:165-171

Publication Date(Web):2017 February

DOI:10.1007/s13233-017-5025-9

Innovative poly(butylene succinate) (PBS)/Spirulina composites were fabricated by melt blending. Maleic anhydride-grafted PBS (PBS-g-MAH) was synthesized and used as a compatibilizer in the composites. Extra amount of water was added to Spirulina to ensure that it acted as a plastic during blending with PBS. The tensile strength and Young’s modulus of the composites considerably increased after incorporation of PBS-g-MAH due to better interfacial adhesion between the components and better dispersion of Spirulina in the PBS matrix, which were verified by scanning electron microscopy. Fourier transform infrared spectroscopy analysis also indicated the reaction between PBS-g-MAH and Spirulina, which resulted in improved Spirulina-PBS interaction. Differential scanning calorimetry analysis revealed that the crystallization temperature of the composites increased after addition of PBS-g-MAH, especially for the composites with higher Spirulina loading, while the PBS in compatibilized composites exhibited higher enthalpies. However, the compatibilized composites exhibited slight decreases of degradation temperature accompanied by slightly higher weight loss as indicated by thermal gravimetric analysis.

Green synthesis of silver nanoparticles embedded in polyaniline nanofibers via vitamin C for supercapacitor applications

Co-reporter:Li Tang;Fang Duan

Journal of Materials Science: Materials in Electronics 2017 Volume 28( Issue 11) pp:7769-7777

Publication Date(Web):13 March 2017

DOI:10.1007/s10854-017-6472-y

The silver nanoparticles with high dispersion on the surface of polyaniline (PANI/Ag) was acquired by reduction of silver nitrate with the assistance of vitamin C acting as an environmentally friendly reducing agent. The surface morphology of the PANI/Ag composite revealed the PANI nanofibers with bright spots of silver nanoparticles. Specifically, this study could open an avenue for environmentally friendly, simple and cost effective methods in the surface functionalization and generation of silver nanoparticles into the PANI chains. The PANI/Ag composite exhibited the excellent capacitive performance with a specific capacitance as high as 553 F g−1 at 1 A g−1 because of the synergic effect of PANI and silver nanoparticles, which was much higher than that of PANI (316 F g−1). Moreover, its electrical conductivity was 215.8 S cm−1. Eventually, the greatly enhanced capacitive performance was mainly attributed to the silver nanoparticles, which could increase the electrical conductivity and promote the electron transfer between the active components.

Fabrication of graphene sheets/polyaniline nanofibers composite for enhanced supercapacitor properties

Co-reporter:Li Tang, Zhaokun Yang, Fang Duan, Mingqing Chen

Colloids and Surfaces A: Physicochemical and Engineering Aspects 2017 Volume 520(Volume 520) pp:

Publication Date(Web):5 May 2017

DOI:10.1016/j.colsurfa.2017.01.083

•RGO/PANI composite exhibits excellent capacitive performance and good cycling stability.•The high electrochemical performances were attributed to increasing active sites for the deposition of PANI nanofibers provided by large surface areas of RGO sheets and the synergistic effect between RGO and PANI nanofibers, shortening the ion diffusion paths.•RGO/PANI composite is a quite promising high power supercapacitor material.The graphene/polyaniline nanofibers (RGO/PANI) composite could be prepared by in situ polymerization of aniline in acid solution, followed by reduction of GO with hydrazine in the presence of well-dispersed graphene oxide (GO) and re-oxidation of PANI by strong oxidant. The microscope images indicated that the PANI nanofibers could adsorb on the surface of graphene sheets through a large van der Waal force and hydrogen bonding force. The maximum specific capacitance of RGO/PANI composite achieved 596 F g−1, which was much higher than that of PANI (256 F g−1). Moreover, the RGO/PANI composite also showed a good cycling stability, retaining over 85% of its initial capacitance after 1000 cycles. The good electrochemical performances of RGO/PANI composite were contributed to the modification of RGO sheets surface, the network structure and the synergic effects of the two components. Therefore, this study demonstrates the promising application of RGO/PANI composite as electrode materials for energy storage.Download high-res image (107KB)Download full-size image

Interfacial modification on polyhydroxyalkanoates/starch blend by grafting in-situ

Co-reporter:Pengwu Xu, Qingtao Zeng, Ying Cao, Piming Ma, Weifu Dong, Mingqing Chen

Carbohydrate Polymers 2017 Volume 174(Volume 174) pp:

Publication Date(Web):15 October 2017

DOI:10.1016/j.carbpol.2017.06.048

•Interfacial bonding was in situ created by radical grafting leading to smaller adhesion factor.•Compatibility and interfacial adhesion between PHAs and starch were considerably improved.•A simple way to make blends with low-cost and good performance was provided.The interfacial adhesion between polyhydroxyalkanoates (PHAs) and native starch is poor. To improve the interfacial adhesion, PHAs were in-situ grafted onto starch using dicumyl peroxide (DCP) as a free radical initiator. The grafting reaction was carefully characterized and confirmed by gel analysis and Fourier transform infrared spectroscopy (FT-IR). The gel yield of the PHAs/starch/DCP blend increased with the DCP concentration up to 2 wt%. Meanwhile, obvious plastic deformation (stretched fibrils) was observed at the interface in the PHAs/starch/DCP blend in comparison with complete interfacial debonding in the PHAs/starch physical blend. The improved interfacial adhesion after grafting was further confirmed by a reduction in adhesion factor (Af) obtained from dynamic mechanical analysis (DMA). The mechanical strength and the crystallization rate of the PHAs were deteriorated after incorporation of starch, and were backed up by the interfacial improvement. A linear relationship between the mechanical properties and the gel yield was discovered. In addition, the PHAs/starch/DCP blend exhibited higher decomposition active energy (Ea) and thus better thermal stability in comparison with the PHAs and the PHAs/starch physical blend. Therefore, this study provides a simple route to utilize low-cost starch as a component in biopolymer blend.

Preparation and properties of thermoplastic poly(caprolactone) composites containing high amount of esterified starch without plasticizer

Co-reporter:Yujie Sun, Qiongen Hu, Jiangtao Qian, Ting Li, Piming Ma, Dongjian Shi, Weifu Dong, Mingqing Chen

Carbohydrate Polymers 2016 Volume 139() pp:28-34

Publication Date(Web):30 March 2016

DOI:10.1016/j.carbpol.2015.12.002

•Stearyl chloride was effective to fabricate esterified starch.•The torque of PCL/esterified starch (80/20, wt) was low during melt blending.•PCL/esterified starch (80 wt%) exhibited the improved tensile properties.Based on stearyl chloride and native starch, esterified starch were prepared and the chemical structure was characterized by 1H NMR and FTIR. It was found that stearyl chloride was an efficient agent to fabricate esterified starch with high degree of substitution (DS). During the melt blending of esterified starch (80 wt%) and poly(caprolactone) (PCL, 20 wt%), it was shown the torque of PCL/esterified starch was much lower than that of PCL/native starch without any plasticizer, and further decreased with increasing DS. Compared with PCL/native starch, the tensile properties of PCL/esterified starch composites were significantly enhanced. The tensile strength and elongation at break were increased from 2.7 MPa to 56% for PCL/native starch composites to 9.1 MPa and 626% for PCL/esterified starch ones with DS of 1.50, respectively. SEM observation revealed the esterified starch particles in matrix became smaller and more uniform. In addition, the water resistance and hydrophobic character of PCL/esterified starch composites were improved. PCL composites containing 80 wt% esterified starch with favorable mechanical properties would have great potential applications in broad areas.

Highly exposed surface area of {001} facets dominated BiOBr nanosheets with enhanced visible light photocatalytic activity

Co-reporter:Fang Duan, Xiaofeng Wang, Tingting Tan and Mingqing Chen

Physical Chemistry Chemical Physics 2016 vol. 18(Issue 8) pp:6113-6121

Publication Date(Web):20 Jan 2016

DOI:10.1039/C5CP06711A

Two groups of BiOBr nanosheets with different sizes and similar exposure percentages of {001} facets were selectively synthesized by simple hydrothermal methods. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflectance spectroscopy (DRS). The photocatalytic activity was estimated from the degradation of organic pollutants under visible-light irradiation. The results indicated that BiOBr nanosheets with similar exposure percentages of {001} facets but smaller sizes exhibited higher photocatalytic activity. Furthermore, the effects of the size, including the thickness and length, of BiOBr nanosheets were also studied. The results showed that the impact of thickness was more significant than that of length. It was found that reducing the thickness of BiOBr nanosheets can significantly increase the exposed surface areas of {001} facets (S{001}), but not necessarily the exposure percentage of {001} facets. Moreover, in our experiment, the photocatalytic activity of BiOBr nanosheets increased linearly with an increase in S{001} in the range of 0.022 to 0.111 nm−1. Therefore, the photocatalytic activity of BiOBr nanosheets depended on the exposed surface areas of {001} facets rather than the exposure percentage of {001} facets. The enhancement of the photocatalytic activity of ultrathin BiOBr nanosheets with large exposed surface areas of {001} facets can be mainly ascribed to their enhanced absorption of visible light and improved separation efficiency of charge carriers.

Silver nanoparticle decorated polyaniline/multiwalled super-short carbon nanotube nanocomposites for supercapacitor applications

Co-reporter:Li Tang, Fang Duan and Mingqing Chen

RSC Advances 2016 vol. 6(Issue 69) pp:65012-65019

Publication Date(Web):04 Jul 2016

DOI:10.1039/C6RA12442A

In order to increase the utilization of the closed pore volumes of carbon nanotubes (CNTs), multilayer super-short carbon nanotubes (SSCNTs) have been synthesized by tailoring the raw multiwalled carbon nanotubes (MWCNTs) with a simple ultrasonic oxidation-cut method. Then silver nanoparticles with high dispersion on the surface of the hybrid nanocomposites (SSCNTs/PANI/Ag) consisting of SSCNTs with polyaniline were acquired by reduction of silver nitrate with Vitamin C. It is found that the final composite exhibits excellent capacitive performance with a specific capacitance as high as 615 F g−1 at 1 A g−1 which is much higher than that of PANI (316 F g−1) and PANI/Ag (454 F g−1). Moreover, it also shows better electrical conductivity (18.5 S cm−1). The greatly enhanced capacitive performance of the nanocomposite is mainly attributed to the introduction of silver nanoparticles, which can increase the electrical conductivities of the nanocomposites and promote the electron transfer between the active components. Furthermore, the open-ended pipes of SSCNTs provide abundant additional transport paths and a short axial dimension so that it can shorten the transmission distance for the electrolyte ions and electrons in the electrode. This study suggests that SSCNTs/PANI/Ag is a promising class of electrode material for high performance energy storage applications.

Selectively cross-linked poly (lactide)/ethylene-glycidyl methacrylate-vinyl acetate thermoplastic elastomers with partial dual-continuous network-like structures and shape memory performances

Co-reporter:Pengwu Xu, Piming Ma, Xiaoxia Cai, Shiqiang Song, Yong Zhang, Weifu Dong, Mingqing Chen

European Polymer Journal 2016 Volume 84() pp:1-12

Publication Date(Web):November 2016

DOI:10.1016/j.eurpolymj.2016.09.004

•The epoxy groups facilitated the selective cross-link of only the EGVA phase.•The TPVs exhibited partially dual-continuous network-like morphology.•The TPVs showed good shape memory behavior.•Superior mechanical properties and tunable hardness of the TPVs are achieved.Bio-based poly (lactide)/ethylene-glycidyl methacrylate-vinyl acetate (PLA/EGVA) thermoplastic vulcanizates (TPVs) with partial dual-continuous network-like structures and shape memory property were made using methylhexahydrophthalic anhydride (MHHPA) as a cross-link agent. Epoxy groups of EGVA facilitated the selective cross-link of the EGVA phase in the PLA/EGVA blends, and two different chemical structures of the TPVs are identified based on the MHHPA content. The TPVs showed a special morphology evolution of the TPV, i.e., from sea-island-type to partial dual-continuous network-like morphology. As a consequence, the PLA/EGVA-based TPVs exhibited excellent shape memory property due to the strong resilience of the selectively cross-linked EGVA phase. The selective cross-link enhanced the complex viscosity (η∗), elasticity (G′) and the solid-like behavior of the PLA/EGVA-based TPVs. Meanwhile, low tensile set (30%), moderate tensile strength (12 MPa) and elongation at break (250%), and tunable hardness (60–75 Shore A) of the TPVs are achieved by tailoring the cross-link density and phase morphology.

Transparent blown films from poly(lactide) and poly(ethylene-co-vinyl acetate) compounds: Structure and property

Co-reporter:Pengwu Xu, Piming Ma, Martin Hoch, Eric Arnoldi, Xiaoxia Cai, Weifu Dong, Mingqing Chen

Polymer Degradation and Stability 2016 Volume 129() pp:328-337

Publication Date(Web):July 2016

DOI:10.1016/j.polymdegradstab.2016.05.010

The application range of poly(lactide), PLA, films is limited due to the brittleness and notch-sensitivity. In this work, thin films with balanced properties were fabricated by melt blowing of PLA and poly(ethylene-co-vinyl acetate) (EVA) blends. The film thickness is dependent on the taken-up speed and reached to around 10 μm at the taken-up speed over 14 m/min. The presence of EVA not only significantly enhanced the tensile toughness and notch-resistance of the PLA films but also retained high transmittance. The films exhibited anisotropic mechanical performances which were correlated to the micro-morphology differences between the take-up direction (DD) and the transversal direction (TD) as characterized by atomic force microscope. In addition, the EVA with 80 wt% VA units showed better overall modification effect on the PLA films than the EVA with 60 wt% VA units. Superior mechanical properties of PLA/EVA (80/20) blends such as tensile strength of 50–60 MPa, elongation at break up to 230% and tear strength of 85 kN/m were achieved in the DD direction. Meanwhile, balanced properties were also achieved in TD direction. Moreover, a transmittance of around 90% was obtained for the PLA/EVA films which are comparable to neat PLA films. A high enough VA unit content is crucial for superior mechanical properties and high transparency.

Preparation and characterization of innovative cellulose diacetate/epoxy resin blends modified by isophorone diamine

Co-reporter:Ming Ye;Nianqing Zhu;Zhongbin Ni;Weifu Dong

Journal of Applied Polymer Science 2016 Volume 133( Issue 44) pp:

Publication Date(Web):

DOI:10.1002/app.44151

ABSTRACT

Cellulose diacetate (CA)/epoxy resin (EP) blends with excellent mechanical performance were prepared with simple blending followed by curing with isophorone diamine (IPDA). The reaction between the amino groups of IPDA and epoxide groups of EP was confirmed by Fourier transform infrared spectroscopy. Scanning electron microscopy revealed that the cured EP particles gradually became larger and closer to each other to form semi-interpenetrating polymer networks in the CA matrix; this contributed to the improved mechanical properties of the CA/EP blends. Dynamic rheological experiments indicated that the CA/EP blends with semi-interpenetrating polymer networks retained processability. After the introduction of a low content (5–10 phr) of IPDA, the mechanical properties of the CA/EP blends were significantly enhanced. With the addition of 20–30-phr IPDA, the CA/EP blend exhibited a tensile strength of 77 MPa, a flex strength of 65 MPa, a flex modulus of 2.6 GPa, and a hardness of 94 HD; these values were much higher than those of the pristine CA/EP binary blend. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44151.

Biobased Poly(lactide)/ethylene-co-vinyl Acetate Thermoplastic Vulcanizates: Morphology Evolution, Superior Properties, and Partial Degradability

Co-reporter:Piming Ma, Pengwu Xu, Yinghao Zhai, Weifu Dong, Yong Zhang, and Mingqing Chen

ACS Sustainable Chemistry & Engineering 2015 Volume 3(Issue 9) pp:2211

Publication Date(Web):July 22, 2015

DOI:10.1021/acssuschemeng.5b00462

Partially biobased thermoplastic vulcanizates (TPV) with novel morphology, superior properties and partial degradability were prepared by dynamic cross-link of saturated poly(lactide) and ethylene-co-vinyl acetate (PLA/EVA) blends using 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (AD) as a free radical initiator. EVA showed higher reactivity with free radicals in comparison with PLA, leading to much higher gel content of the EVA phase (Gf-EVA) than that of the PLA phase (Gf-PLA). However, the Gf-PLA increased more steeply at AD content larger than 1 wt % where the reaction of EVA approached to a saturation point. The competing reaction changed the viscosity ratio of the two components (ηPLA/ηEVA) that resulted in a novel morphology evolution of the TPV, i.e., from sea–island-type morphology to phase inversion via a dual-continuous network-like transition and finally cocontinuity again with increasing the AD content. The cross-link and phase inversion considerably enhanced the melt viscosity (η*), elasticity (G′) and the solid-like behavior of the PLA/EVA-based TPV. Meanwhile, superior tensile strength (σt = 21 MPa), low tensile set (Ts = 30%), moderate elongation (εb = 200%) and suitable stiffness (E′ = 350 MPa, 25 °C) were successfully achieved by tailoring the cross-link structure and phase morphology. In addition, the TPV are partially degradable in aqueous alkali. A degradation rate of approximately 5 wt % was achieved within 10 weeks at 25 °C and the degradation mechanism was investigated from both molecular and macroscopic levels. Therefore, this work provides a new type of partially biobased and degradable materials for substitution of traditional TPV.Keywords: Degradation; Dynamic cross-link; Morphology; Property; Thermoplastic vulcanizate;

Stereocomplexation kinetics of enantiomeric poly(L-lactide)/poly(D-lactide) blends seeded by nanocrystalline cellulose

Co-reporter:Long Jiang, Pei Lv, Piming Ma, Huiyu Bai, Weifu Dong and Mingqing Chen

RSC Advances 2015 vol. 5(Issue 87) pp:71115-71119

Publication Date(Web):12 Aug 2015

DOI:10.1039/C5RA12586C

Stereocomplexation of poly(lactide) was significantly promoted by seeding with nanocrystal cellulose (NCC). A NCC-accelerated and time-dependent stereocomplex crystal (SC) growth are discovered. Moreover, SC-crystallization regime transitions (II–III) were identified and both the nucleation constant (Kg) and transition temperature (Ttr) were strongly increased in the presence of the NCC.

Strong nanocomposite reinforcement effects in poly(vinyl alcohol) with melanin nanoparticles

Co-reporter:Yang Wang, Zhu Wang, Piming Ma, Huiyu Bai, Weifu Dong, Yi Xie and Mingqing Chen

RSC Advances 2015 vol. 5(Issue 89) pp:72691-72698

Publication Date(Web):21 Aug 2015

DOI:10.1039/C5RA12333J

Poly(vinyl alcohol)/melanin nanocomposites with improved tensile strength, Young's modulus and heat distortion temperature (HDT) were prepared by using simple aqueous solution mixing. When incorporated into PVA with low content (0.5–2 wt%), melanin nanoparticles dramatically enhanced the mechanical properties of PVA. With addition of 2 wt% melanin, the nanocomposites exhibited a tensile strength (σ) of 155 MPa and a Young's modulus (E) of 2.95 GPa, which were much higher than these of neat PVA. HDT was enhanced from 56.5 °C to 100 °C. TEM indicated that melanin nanoparticles were uniformly dispersed in PVA without aggregation. The strong hydrogen bonding between the –OH (or –NH–) of melanin and –OH of PVA confirmed by FTIR, which played a key factor to prevent the aggregation of nanoparticles in PVA matrix and made a contribution to the high performance of PVA.

Bio-based poly(lactide)/ethylene-co-vinyl acetate thermoplastic vulcanizates by dynamic crosslinking: structure vs. property

Co-reporter:Piming Ma, Pengwu Xu, Wangcheng Liu, Yinghao Zhai, Weifu Dong, Yong Zhang and Mingqing Chen

RSC Advances 2015 vol. 5(Issue 21) pp:15962-15968

Publication Date(Web):08 Jan 2015

DOI:10.1039/C4RA14194F

Bio-based thermoplastic vulcanizates (TPV) from poly(lactide) (PLA) and ethylene-co-vinyl acetate rubber (EVA) were fabricated using dicumyl peroxide (DCP) as a curing agent; it is the first time that the application of PLA in elastic materials is demonstrated. A two-stage competing reaction mechanism as a function of peroxide content is revealed via gel analysis. The crosslinking of EVA is dominant at low DCP content (<1 wt%), which levels off when the DCP content exceeds 1 wt%. The gel fractions of the EVA and PLA phases can be tuned by the DCP content and fabrication technique. A desirable phase inversion of the PLA/EVA blends due to selective dynamic curing was monitored by both atomic force microscopy (AFM) and dynamic mechanical analysis (DMA). Consequently, PLA/EVA thermoplastic vulcanizates with high strength, high elongation at break, low tensile set and intermediate hardness were obtained. Moreover, their mechanical properties can be tuned by the DCP content and plasticization. The correlation between their structures and properties was investigated.

Multiwalled carbon nanotubes noncovalently functionalized by electro-active amphiphilic copolymer micelles for selective dopamine detection

Co-reporter:Xiaoma Fei, Jing Luo, Ren Liu, Jingcheng Liu, Xiaoya Liu and Mingqing Chen

RSC Advances 2015 vol. 5(Issue 24) pp:18233-18241

Publication Date(Web):02 Feb 2015

DOI:10.1039/C4RA16923A

We have synthesized an electro-active amphiphilic copolymer with carbazole side chains via free radical polymerization using 7-(4-vinylbenzyloxy)-4-methyl coumarin and 9-(4-vinylbenzyl)-9H-carbazole as the monomers. The copolymer can self-assemble to form micelles (termed EACMs) in aqueous solution and can adsorb onto the surfaces of MWCNTs via π–π interactions and thereby cause the efficient dispersion of the MWCNTs in aqueous solution. The coumarin groups in the copolymer undergo UV-induced photo-crosslinking, which further improves the stability of the suspension. Moreover, the electro-active carbazole moieties in the EACMs can undergo electropolymerization to form a conducting network on the MWCNTs that significantly accelerates electron transfer. The EACM/MWCNTs hybrid was applied to the amperometric sensing of dopamine (DA) as a model analyte. After electropolymerization, the electrode exhibited good sensitivity and selectivity toward the determination of dopamine with a 0.2 μM detection limit and a wide linear range. The method described here provides a viable route to water-dispersible and stable carbon nanotubes while preserving their outstanding electrical properties. We presume that the composite described here represents a valuable tool for the construction of electrochemical sensors and electronics.

Reinforcement of transparent ethylene-co-vinyl acetate rubber by nanocrystalline cellulose

Co-reporter:Piming Ma, Long Jiang, Martin Hoch, Weifu Dong, Mingqing Chen

European Polymer Journal 2015 Volume 66() pp:47-56

Publication Date(Web):May 2015

DOI:10.1016/j.eurpolymj.2015.01.037

•Superior mechanical properties of EVA rubber were achieved by addition of 2 phr NCC.•Fine dispersion of NCC can be obtained even without interfacial modification.•Good optical clarity of EVA was maintained after compounding with 1–5 phr NCC.Ethylene-co-vinyl acetate rubber/nanocrystalline cellulose (EVA/NCC) nanocomposites were prepared by solution mixing and static vulcanization in the presence of peroxide. The gel content and crosslink density of the nanocomposites were decreased with increasing NCC loading. However, mechanical properties of the EVA were considerably enhanced, e.g., the tensile strength and the storage modulus were increased by around 75% and 50%, respectively, when 2 phr of the NCC was incorporated. Such significant reinforcement is ascribed to a uniform dispersion of the NCC, the formation of NCC network and the strong EVA–NCC interactions as confirmed by morphology observation (SEM and AFM) and dynamic mechanical thermal analysis (DMA). Moreover, the presence of the NCC did not compromise obviously the optical clarity and the thermal decomposition temperature of the EVA. The highly reinforced ethylene-co-vinyl acetate rubber with high transparence may broaden its application range.

Preparation of polyvinyl alcohol/chitosan hydrogel compounded with graphene oxide to enhance the adsorption properties for Cu(II) in aqueous solution

Co-reporter:Luzhong Li;Zhu Wang;Piming Ma;Huiyu Bai;Weifu Dong

Journal of Polymer Research 2015 Volume 22( Issue 8) pp:

Publication Date(Web):2015 August

DOI:10.1007/s10965-015-0794-3

A novel bio-adsorbent, composite hydrogel beads, composed of polyvinyl alcohol (PVA), chitosan (CS) and graphene oxide (GO) was prepared by an instantaneous gelation method. The micromorphology and thermal stability of the PVA/CS/GO hydrogel beads were characterized by scanning electronic microscope (SEM) and thermo gravimetric analysis (TGA) respectively. Adsorption of Cu(II) onto PVA/CS/GO hydrogel beads was investigated with respect to pH, initial concentration, temperature and adsorption time. Adsorption data were well matched by Langmuir isotherm and pseudo-second-order kinetic model at the optimum pH 5.5. The maximum adsorption capacities of PVA/CS/GO hydrogel beads were found to be 162 mg g−1 for Cu(II) at 30 °C, which was much higher than that of PVA/CS hydrogel. Thermodynamic studies indicated that the adsorption was spontaneous and endothermic process in nature. Besides, desorption efficiency and reusability of the adsorbents were assessed on basis of six consecutive adsorption-desorption cycles. Based on these studies, it can be seen that PVA/CS/GO hydrogel beads will be a potential recyclable adsorbent for removal of hazardous metal ions in waste water.

Nanocomposite hydrogel consisting of Na-montmorillonite with enhanced mechanical properties

Co-reporter:Ting Li;Shuangfei Xiang;Piming Ma;Huiyu Bai;Weifu Dong

Journal of Polymer Science Part B: Polymer Physics 2015 Volume 53( Issue 14) pp:1020-1026

Publication Date(Web):

DOI:10.1002/polb.23732

ABSTRACT

A new kind of nanocomposite (NC) hydrogel with Na-montmorillonite (MMT) is presented in this article. The NC hydrogels were synthesized by free radical copolymerization of acrylamide and (3-acrylamidopropyl) trimethylammonium chloride (ATC) in the presence of MMT and N,N′-methylene-bis-acrylamide used as chemical cross-linker. Due to the cation-exchange reaction between MMT and ATC (cationic monomer) during the synthesis of NC hydrogels, MMT platelets were considered chemical “plane” cross-linkers, different from “point” cross-linkers. With increasing amount of MMT, the crosslinking degree enhanced, causing a decrease of the swelling degree at equilibrium. Investigations of mechanical properties indicated that NC hydrogels exhibited enhanced strength and toughness, which resulted from chemical interaction between exfoliated MMT platelets and polymer chains in hydrogels. Dynamic shear measurements showed that both storage modulus and loss modulus increased with increasing MMT content. The idea described here provided a new route to prepare hydrogels with high mechanical properties by using alternative natural Na-MMT. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 1020–1026

Rapid Stereocomplexation between Enantiomeric Comb-Shaped Cellulose-g-poly(l-lactide) Nanohybrids and Poly(d-lactide) from the Melt

Co-reporter:Piming Ma, Long Jiang, Pengwu Xu, Weifu Dong, Mingqing Chen, and Piet J. Lemstra

Biomacromolecules 2015 Volume 16(Issue 11) pp:

Publication Date(Web):October 7, 2015

DOI:10.1021/acs.biomac.5b01135

In this work we report the in situ preparation of fully biobased stereocomplex poly(lactide) (SC-PLA) nanocomposites grafted onto nanocrystalline cellulose (NCC). The stereocomplexation rate by compounding high-molar-mass poly(d-lactide) (PDLA) with comb-like NCC grafted poly(l-lactide) is rather high in comparison with mixtures of PDLA and PLLA. The rapid stereocomplexation was evidenced by a high stereocomplexation temperature (Tc-sc = 145 °C) and a high SC crystallinity (Xc-sc = 38%) upon fast cooling (50 °C/min) from the melt (250 °C for 2 min), which are higher than currently reported values. Moreover, the half-life crystallization time (175–190 °C) of the SC-PLA was shortened by 84–92% in comparison with the PDLA/PLLA blends. The high(er) stereocomplexation rate and the melt stability of the SC in the nanocomposites were ascribed to the nucleation effect of the chemically bonded NCC and the “memory effect” of molecular pairs in the stereocomplex melt because of the confined freedom of the grafted PLLA chains.

Novel poly(xylitol sebacate)/hydroxyapatite bio-nanocomposites via one-step synthesis

Co-reporter:Piming Ma, Ting Li, Wei Wu, Dongjian Shi, Fang Duan, Huiyu Bai, Weifu Dong, Mingqing Chen

Polymer Degradation and Stability 2014 110() pp: 50-55

Publication Date(Web):

DOI:10.1016/j.polymdegradstab.2014.08.014

Strong synergetic effect of fibril-like nucleator and shear flow on the melt crystallization of poly(l-lactide)

Co-reporter:Piming Ma, Qingqing Yu, Tianfeng Shen, Weifu Dong, Mingqing Chen

European Polymer Journal (February 2017) Volume 87() pp:

Publication Date(Web):February 2017

DOI:10.1016/j.eurpolymj.2016.12.026

•Synergetic effect of OXA and shear flow on the crystallization of PLLA is created.•The high-temperature crystallization of PLLA is considerably enhanced.•The morphology evolution and crystallization mechanism are revealed.Bio-based and bio-degradable poly(l-lactide), PLLA, suffers from low crystallization rate. The synergetic effect of fibril-like nucleator (N1,N1′-(ethane-1,2-diyl)bis(N2-phenyloxalamide)) (OXA) and shear flow on speeding up the melt crystallization of the PLLA is the first time reported in this work. The synergetic effect was investigated by using a rheometer. Neither fibril-like OXA nor shear flow showed obvious accelerating effect at 155 °C on the crystallization of PLLA leading to limited crystallinity (Xc) within 70–100 min. In contrast, a crystallinity of more than 40% and an onset crystallization time (tonset) of less than 3 min were achieved by tailoring the shear conditions. The critical shear condition for the fast crystallization of the PLLA/OXA systems at 155 °C is 0.4 rad/s for 10–15 s. A lower shear temperature (e.g., 150 °C in comparison with 155 °C) would increase the crystallization rate much further. Mechanism study revealed that the OXA fibril network and a certain extent of PLLA chain orientation that induced by the shear flow while subsequently stabilized by the OXA fibrils are responsible for the significantly enhanced nucleation and overall melt crystallization kinetics. In addition, the shear flow and fibril-like OXA nucleators not only facilitated the crystallization of PLLA α-form crystals but also promoted the formation of α′- (or δ) and β-form crystals.

Highly exposed surface area of {001} facets dominated BiOBr nanosheets with enhanced visible light photocatalytic activity

Co-reporter:Fang Duan, Xiaofeng Wang, Tingting Tan and Mingqing Chen

Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 8) pp:NaN6121-6121

Publication Date(Web):2016/01/20

DOI:10.1039/C5CP06711A