Min Xiao

Name: 肖敏

Organization: Sun Yat-Sen University

Department: The Key Laboratory of Low-carbon Chemistry & Energy Conservation of Guangdong Province /State Key Laboratory of Optoelectronic Materials and Technologies

Title:

TOPICS

Polymer

Polyesters PEEK

Chemicals
References

A Novel Multiblock Copolymer of CO2-Based PPC-mb-PBS: From Simulation to Experiment

Co-reporter:Jiaxiang Qin, Weikeng Luo, Meng Li, Pin Chen, Shuanjin Wang, Shan Ren, Dongmei Han, Min Xiao, and Yuezhong Meng

ACS Sustainable Chemistry & Engineering July 3, 2017 Volume 5(Issue 7) pp:5922-5922

Publication Date(Web):June 4, 2017

DOI:10.1021/acssuschemeng.7b00634

A kind of new biodegradable materials with high performance in a wide range of temperatures was effectively developed via the combination of theoretical calculations and experimental works. The new polymer of poly(propylene carbonate)-multiblock-poly(butylene succinate) (PPC-mb-PBS) was designed and synthesized from poly(propylene carbonate) (PPC) and poly(butylene succinate) (PBS) segments. The simulation was successfully performed based on their multiblock topology structure. On the basis of the calculation, the Tg of PPC-mb-PBS calculated by molecular dynamics (MD) simulation ranges from −42 to −38 °C that is independent of the block size of PPC segments. The end-to-end distance and mean square displacement (MSD) calculations indicate an inversion behavior of the PPC and PBS between hard and soft segments at different temperatures. The stress–strain behavior of PPC-mb-PBS was also calculated by the MD simulation of uniaxial deformation. The simulated stress of PPC-mb-PBS copolyesters is higher than that of pure PPC under uniaxial extension with the same strain and is found to increase with decreasing PPC block size. To verify the validity of the simulation, the PPC-mb-PBS multiblock copolyesters with various designed block length were synthesized and characterized by 1H NMR, DOSY, and GPC. Meantime, their thermal and mechanical properties were determined, respectively, by DSC and tensile testing. The measured Tg data and the variation tendency of tensile strength are in very good agreement with the simulated results, demonstrating the ability of the fully atomic-scale MD simulations to well predict the mechanical properties of the synthesized biodegradable polymers.Keywords: Biodegradable materials; Deformation; Mean square displacement; Mechanical properties; Molecular dynamics simulation; Multiblock copolyester;

Toward Theoretically Cycling-Stable Lithium–Sulfur Battery Using a Foldable and Compositionally Heterogeneous Cathode

Co-reporter:Lei Zhong, Kai Yang, Ruiteng Guan, Liangbin Wang, Shuanjin Wang, Dongmei Han, Min Xiao, and Yuezhong Meng

ACS Applied Materials & Interfaces December 20, 2017 Volume 9(Issue 50) pp:43640-43640

Publication Date(Web):November 27, 2017

DOI:10.1021/acsami.7b13247

Rechargeable lithium–sulfur (Li–S) batteries have been expected for new-generation electrical energy storages, which are attributed to their high theoretical energy density, cost effectiveness, and eco-friendliness. But Li–S batteries still have some problems for practical application, such as low sulfur utilization and dissatisfactory capacity retention. Herein, we designed and fabricated a foldable and compositionally heterogeneous three-dimensional sulfur cathode with integrated sandwich structure. The electrical conductivity of the cathode is facilitated by three different dimension carbons, in which short-distance and long-distance pathways for electrons are provided by zero-dimensional ketjen black (KB), one-dimensional activated carbon fiber (ACF) and two-dimensional graphene (G). The resultant three-dimensional sulfur cathode (T-AKG/KB@S) with an areal sulfur loading of 2 mg cm–2 exhibits a high initial specific capacity, superior rate performance and a reversible discharge capacity of up to 726 mAh g–1 at 3.6 mA cm–2 with an inappreciable capacity fading rate of 0.0044% per cycle after 500 cycles. Moreover, the cathode with a high areal sulfur loading of 8 mg cm–2 also delivers a reversible discharge capacity of 938 mAh g–1 at 0.71 mA cm–2 with a capacity fading rate of 0.15% per cycle and a Coulombic efficiency of almost 100% after 50 cycles.Keywords: 3D cathode structure; cycling stability; fordable cathode; high sulfur loading; lithium−sulfur battery;

A Novel Single-Ion-Conducting Polymer Electrolyte Derived from CO2-Based Multifunctional Polycarbonate

Co-reporter:Shuanjin Wang;Dongmei Han;Shan Ren;Kuirong Deng;Yuezhong Meng

ACS Applied Materials & Interfaces December 14, 2016 Volume 8(Issue 49) pp:33642-33648

Publication Date(Web):November 23, 2016

DOI:10.1021/acsami.6b11384

This work demonstrates the facile and efficient synthesis of a novel environmentally friendly CO2-based multifunctional polycarbonate single-ion-conducting polymer electrolyte with good electrochemistry performance. The terpolymerizations of CO2, propylene epoxide (PO), and allyl glycidyl ether (AGE) catalyzed by zinc glutarate (ZnGA) were performed to generate poly(propylene carbonate allyl glycidyl ether) (PPCAGE) with various alkene groups contents which can undergo clickable reaction. The obtained terpolymers exhibit an alternating polycarbonate structure confirmed by 1H NMR spectra and an amorphous microstructure with glass transition temperatures (Tg) lower than 11.0 °C evidenced by differential scanning calorimetry analysis. The terpolymers were further functionalized with 3-mercaptopropionic acid via efficient thiol–ene click reaction, followed by reacting with lithium hydroxide, to afford single-ion-conducting polymer electrolytes with different lithium contents. The all-solid-state polymer electrolyte with the 41.0 mol % lithium containing moiety shows a high ionic conductivity of 1.61 × 10–4 S/cm at 80 °C and a high lithium ion transference number of 0.86. It also exhibits electrochemical stability up to 4.3 V vs Li+/Li. This work provides an interesting design way to synthesize an all-solid-state electrolyte used for different lithium batteries.Keywords: all-solid-state electrolyte; CO2-based multifunctional polycarbonate; environmentally friendly; ionic conductivity; single-ion-conducting polymer electrolyte; thiol−ene click chemistry;

Network type sp3 boron-based single-ion conducting polymer electrolytes for lithium ion batteries

Co-reporter:Kuirong Deng, Shuanjin Wang, Shan Ren, Dongmei Han, Min Xiao, Yuezhong Meng

Journal of Power Sources 2017 Volume 360(Volume 360) pp:

Publication Date(Web):31 August 2017

DOI:10.1016/j.jpowsour.2017.06.006

•Boron-based single-ion conducting gel polymer electrolytes are designed.•The electrolytes are fabricated by facile in situ thiol-ene click reaction.•Ionic conductivity reaches 1.47 × 10−3 S cm−1 at 25 °C.•High lithium transference number of 0.89 is obtained.•The LiFePO4 cell delivers a capacity of 124 mA h g−1 at 1 C rate after 500 cycles.Electrolytes play a vital role in modulating lithium ion battery performance. An outstanding electrolyte should possess both high ionic conductivity and unity lithium ion transference number. Here, we present a facile method to fabricate a network type sp3 boron-based single-ion conducting polymer electrolyte (SIPE) with high ionic conductivity and lithium ion transference number approaching unity. The SIPE was synthesized by coupling of lithium bis(allylmalonato)borate (LiBAMB) and pentaerythritol tetrakis(2-mercaptoacetate) (PETMP) via one-step photoinitiated in situ thiol-ene click reaction in plasticizers. Influence of kinds and content of plasticizers was investigated and the optimized electrolytes show both outstanding ionic conductivity (1.47 × 10−3 S cm−1 at 25 °C) and high lithium transference number of 0.89. This ionic conductivity is among the highest ionic conductivity exhibited by SIPEs reported to date. Its electrochemical stability window is up to 5.2 V. More importantly, Li/LiFePO4 cells with the prepared single-ion conducting electrolytes as the electrolyte as well as the separator display highly reversible capacity and excellent rate capacity under room temperature. It also demonstrates excellent long-term stability and reliability as it maintains capacity of 124 mA h g−1 at 1 C rate even after 500 cycles without obvious decay.Download high-res image (141KB)Download full-size image

Kinetic and mechanistic investigation for the copolymerization of CO2 and cyclohexene oxide catalyzed by trizinc complexes

Co-reporter:Yonghang Xu;Limiao Lin;Chun-Ting He;Jiaxiang Qin;Zhong Li;Shuanjin Wang;Yuezhong Meng

Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 23) pp:3632-3640

Publication Date(Web):2017/06/13

DOI:10.1039/C7PY00403F

The trizinc complexes Zn3(OAc)4(Ln)2, 1a and 1b, which were coordinated with Schiff-base ligands via a simple and economical method, have been examined and found to be highly effective and efficient toward the copolymerization of CO2 and cyclohexene oxide (CHO). In this work, the kinetics for the copolymerization of CO2 and CHO using 1b as the catalyst was monitored via in situ ATR-FTIR spectroscopy. The reaction orders’ dependencies on catalyst concentration, initial CHO concentration and CO2 pressure, as well as activation energies (Ea) of polycarbonate and cyclic carbonate formation, were investigated in detail. The practical amount of active zinc sites in the copolymerization was calculated using the parameters obtained from 1H NMR and GPC measurements. The initiating reaction details were simulated using density functional theory, and the potential energy surfaces were obtained. Based on the results of all characterizations and kinetic investigations, a unique initiating reaction and copolymerizing mechanism were proposed when using Zn3(OAc)4(Ln)2 as the catalyst.

Ring-opening polymerization of l-lactide and ε-caprolactone catalyzed by versatile tri-zinc complex: Synthesis of biodegradable polyester with gradient sequence structure

Co-reporter:Limiao Lin, Yonghang Xu, Shuanjin Wang, Min Xiao, Yuezhong Meng

European Polymer Journal 2016 Volume 74() pp:109-119

Publication Date(Web):January 2016

DOI:10.1016/j.eurpolymj.2015.09.029

•A gradient poly(lactide-grad-caprolactone) was synthesized at first time.•Both copolymer composition and structure have great impacts on their properties.•This method can be used to synthesize biodegradable aliphatic polyester with a diverse range of properties.An economic and biocompatible Schiff base tri-zinc catalyst was used to synthesize homo/copolymers of l-lactide (LA) and ε-caprolactone (CL) in bulk at first time. Both 1H and 13C NMR analyses show that LA is more active than CL, resulting in a poly(LA-grad-CL) copolymer with gradient sequence structure. A series of copolymers containing varying LA/CL ratios were readily synthesized. The chemical structure of poly(LA-grad-CL) was fully investigated using NMR and GPC technologies. TGA, DSC, DMA and nanoindentation instruments were employed to evaluate thermal and mechanical properties of these polymers. The results indicate that polymer composition and chain structure have a great impact on the crystallization behavior and crystallinity, as well as the thermal and mechanical properties of the copolymers. Therefore, the performance of the copolymer can be then tailored by simply adjusting the ratios of LA to CL.Figure optionsDownload full-size imageDownload as PowerPoint slide

Electrochemical synthesis of dimethyl carbonate from CO2 and methanol over carbonaceous material supported DBU in a capacitor-like cell reactor

Co-reporter:Yingjie Zhou, Zhongwei Fu, Shuanjin Wang, Min Xiao, Dongmei Han and Yuezhong Meng

RSC Advances 2016 vol. 6(Issue 46) pp:40010-40016

Publication Date(Web):18 Apr 2016

DOI:10.1039/C6RA04150G

Electro-assisted dimethyl carbonate (DMC) formation from CO2 and methanol over carbonaceous material supported 1,8-diazabicyclo-[5.4.0]undec-7-ene (DBU) was first performed under solvent-free conditions in a capacitor-like cell reactor designed by our group. The effects of applied voltage modes and conductivities of the catalysts on the catalytic performances were fully investigated. The experiment results demonstrated that the catalytic activities can be obviously boosted when the voltages were applied to the catalyst fixed-bed. The constant working potential presented better catalytic activity than the metabolic voltages, and the higher conductivity of catalysts leads to a better catalytic performance. Furthermore, the supported DBU displayed good recyclable properties in the specially designed electrochemical apparatus. We proposed a reaction mechanism of the electrocatalysis for DMC formation.

Gradient terpolymers with long ε-caprolactone rich sequence derived from propylene oxide, CO2, and ε-caprolactone catalyzed by zinc glutarate

Co-reporter:Wenhan Luo, Min Xiao, Shuanjin Wang, Dongmei Han, Yuezhong Meng

European Polymer Journal 2016 Volume 84() pp:245-255

Publication Date(Web):November 2016

DOI:10.1016/j.eurpolymj.2016.09.029

•One-pot synthesis of terpolymers from PO, CO2 and CL by ZnGA catalyst is described.•Formation rates of PPC and PCL moieties were examined by in situ infrared monitoring.•The terpolymers are a kind of semicrystalline polymers with long CL rich sequence.•The terpolymers show excellent melt processibility and mechanical properties.We report here an efficient one-pot synthesis of terpolymers from propylene oxide (PO), carbon dioxide (CO2), and ε-caprolactone (CL) with long CL rich sequence using zinc glutarate as catalyst. The terpolymer yields increase significantly from 50 to 103 (g polymer per g catalyst) with the introduction of CL as a third monomer. The propylene oxide conversion increases by nearly 44% at relatively low polymerization temperature (60 °C). Moreover, the differences in reaction rates of polycarbonate and polyester moieties were examined by in situ infrared monitoring. 1H NMR, GPC and DOSY NMR results show the as-prepared polymer being a gradient terpolymer. As confirmed by XRD and DSC methods, the synthesized terpolymers are a kind of semicrystalline polymer in which the crystalline domains consist mainly of PCL rich segment. Consequently, the semicrystalline terpolymers exhibit much better thermal properties and superior mechanical strength compared with amorphous polycarbonate PPC.An efficient one-pot synthesis of terpolymers from propylene oxide (PO), carbon dioxide (CO2) and ε-caprolactone (CL) with long CL rich sequence using zinc glutarate as catalyst.

A novel biodegradable polymeric surfactant synthesized from carbon dioxide, maleic anhydride and propylene epoxide

Co-reporter:Yulei Liu, Kuirong Deng, Shuanjin Wang, Min Xiao, Dongmei Han and Yuezhong Meng

Polymer Chemistry 2015 vol. 6(Issue 11) pp:2076-2083

Publication Date(Web):13 Jan 2015

DOI:10.1039/C4PY01801J

Terpolymerizations of CO2, propylene epoxide (PO) and maleic anhydride (MA) using zinc adipate (ZnAA) as a catalyst were carried out in a toluene solution. A series of biodegradable terpolymers (PPCMAs) with different polyester and polycarbonate contents were synthesized. The molecular chain sequence structure of these terpolymers was proved to be a gradient one based on 1H NMR investigation combined with in situ infrared technology monitoring the reaction process. The sulfonation of biodegradable PPCMAs was carried out by the addition of sodium hydrogen sulphite into ethylenic double bonds of the unsaturated polyester unit. The surface activities and the aggregation of these sulfonated biodegradable terpolymers in aqueous solution were investigated by surface tension measurement and dynamic light scattering (DLS) technology. The results indicate that the sulfonated biodegradable terpolymer with comparable hydrophilic and hydrophobic segment contents tends to adsorb at the air/water interface and thus exhibits the best surface activities. The surface tension of the aqueous solution of the polymer with 56.8% hydrophilic segments reaches 47.5 mN m−1 at its critical micelle concentration (CMC).

Semi-crystalline terpolymers with varying chain sequence structures derived from CO2, cyclohexene oxide and ε-caprolactone: one-step synthesis catalyzed by tri-zinc complexes

Co-reporter:Yonghang Xu, Shuanjin Wang, Limiao Lin, Min Xiao and Yuezhong Meng

Polymer Chemistry 2015 vol. 6(Issue 9) pp:1533-1540

Publication Date(Web):01 Dec 2014

DOI:10.1039/C4PY01587H

Novel semi-crystalline terpolymers with varying chain sequence structures derived from cyclohexene oxide (CHO), CO2 and ε-caprolactone (CL) have been firstly synthesized and reported. The terpolymerization is catalyzed by Schiff base tri-zinc complexes via a one-step route. The tri-zinc complexes also exhibit a very high catalytic activity for the homopolymerization of ε-caprolactone in the absence of CHO. A series of terpolymers with varying content of crystalline segments are produced by adjusting the feedstock ratio of CHO/ε-CL. The reactivity of different monomers was investigated by experimental methodology. The results indicate that ε-CL is much more active than CHO in this terpolymerization system. Therefore, the incorporation of ε-CL can dramatically improve the TONs of terpolymer containing ε-CL moieties. Moreover, the thermal properties of the resulting terpolymers were also studied by DSC and TGA. Finally, the polymerization mechanism of this ternary system is extensively discussed based on experimental phenomena. To the best of our knowledge, this is the first report on novel catalysts capable of synthesizing polycarbonates, polyesters and poly (carbonate-ester) via a one-step polymerization.

Specially designed carbon black nanoparticle-sulfur composite cathode materials with a novel structure for lithium–sulfur battery application

Co-reporter:Zhenjie Sun, Min Xiao, Shuanjin Wang, Dongmei Han, Shuqin Song, Guohua Chen, Yuezhong Meng

Journal of Power Sources 2015 Volume 285() pp:478-484

Publication Date(Web):1 July 2015

DOI:10.1016/j.jpowsour.2015.03.138

•A carbon black-sulfur composite material with a novel structure was synthesized.•The as-prepared cathode material with a high sulfur content of 84 wt%.•The stable capacity retention is of 865 mAh g−1 after 100 cycles.Sulfur is a promising cathode material with a high theoretical capacity of 1672 mAh g−1, but the challenges of the low electrical conductivity of sulfur and the high solubility of polysulfide intermediates still hinder its practical application. In this work, we design and synthesize a special carbon black nanoparticle–sulfur composite cathode material (NCB-S@NCB) with a novel structure and a high sulfur content of 84 wt% for lithium–sulfur battery application. The NCB-S@NCB composite cathode delivers a high initial discharge capacity of 1258 mAh g−1 and still maintains a reversible capacity of 865 mAh g−1 after 100 cycles with a relatively constant Coulombic efficiency around 98.0%.

Sulfur-rich polymeric materials with semi-interpenetrating network structure as a novel lithium–sulfur cathode

Co-reporter:Zhenjie Sun, Min Xiao, Shuanjin Wang, Dongmei Han, Shuqin Song, Guohua Chen and Yuezhong Meng

Journal of Materials Chemistry A 2014 vol. 2(Issue 24) pp:9280-9286

Publication Date(Web):16 Apr 2014

DOI:10.1039/C4TA00779D

Novel polymeric materials with a very high content of sulfur were successfully synthesized via a facile copolymerization of elemental sulfur with 1,3-diethynylbenzene (DEB). For the as-prepared sulfur-rich polymeric materials (C–S copolymer), diynes or polydiynes are chemically cross-linked with a large amount of polymeric sulfur to form a cage-like semi-interpenetrating network (semi-IPN) structure. Due to the strong chemical interaction of sulfur with the carbon framework and the unique cage-like structure in C–S copolymers, the dissolution and diffusion of polysulfides out of the cathode is effectively suppressed through chemical and physical means. As a result, the sulfur-rich C–S polymeric materials with semi-IPN structure exhibit excellent cycling stability and high coulombic efficiency. The initial discharge capacity is 1143 mA h g−1 at a 0.1 C rate. The capacity still remains at 70% even after about 500 cycles at a high current density of 1 C. In addition, a high coulombic efficiency of over 99% is obtained during the entire range of cycling.

Electrostatic shield effect: an effective way to suppress dissolution of polysulfide anions in lithium–sulfur battery

Co-reporter:Zhenjie Sun, Min Xiao, Shuanjin Wang, Dongmei Han, Shuqin Song, Guohua Chen and Yuezhong Meng

Journal of Materials Chemistry A 2014 vol. 2(Issue 38) pp:15938-15944

Publication Date(Web):31 Jul 2014

DOI:10.1039/C4TA03570D

Sulfur has a very high theoretical specific capacity of 1672 mA h g−1 when used in lithium–sulfur batteries. However, the particularly rapid capacity reduction owing to the dissolution of intermediate polysulfide anions into the electrolyte still hinders practical application. In this respect, we report a novel core–shell structured sulfur–poly(sodium p-styrenesulfonate) (S@PSS) composite cathode material with a sulfur content as high as 93 wt% for lithium–sulfur batteries, which is the highest sulfur content disclosed in the literature. Due to the effective transport of lithium cations while blocking polysulfide anions by common ion Coulombic repulsion of the negatively charged –SO3− groups in the PSS protective layer, the S@PSS composite cathode exhibits a high initial specific capacity of 1159 mA h g−1 at a 0.1 C rate, and retains a stable discharge capacity of 972 mA h g−1 after 70 cycles and 845 mA h g−1 after 120 cycles with a high Coulombic efficiency of over 99%. To our knowledge, this new methodology for lithium–sulfur cathodes has not been reported so far; the initial specific capacity is the highest value calculated based on total composite mass, which has not been disclosed in the literature.

Activities comparison of Schiff base zinc and tri-zinc complexes for alternating copolymerization of CO2 and epoxides

Co-reporter:Yonghang Xu, Min Xiao, Shuanjin Wang, Mei Pan and Yuezhong Meng

Polymer Chemistry 2014 vol. 5(Issue 12) pp:3838-3846

Publication Date(Web):12 Feb 2014

DOI:10.1039/C4PY00008K

A series of salicylaldiminato-zinc and -tri-zinc complexes containing various Schiff base ligands were prepared using quick methods and then well identified by full characterization. All zinc complexes were examined as catalysts for the copolymerization of CO2 and cyclohexene oxide. Many factors such as electron-donating or -withdrawing substituents on the benzene rings of the ligands, as well as chloride anions or acetate groups bound to the zinc centers, are found to greatly influence on the insertion of CO2 and ring-opening of epoxides. Tri-metallic complexes 2a and 2b exhibited excellent catalytic activities, and thus the copolymerization conditions such as temperature, pressure and reaction time were optimized. The molecular weights of the resulting copolymers determined by gel permeation chromatography display a bimodal distribution with relatively wide polydispersities. The results of the investigation indicate that the catalytic activities of zinc complexes are highly dependent on the electronic density and steric environment around the Zn metal centers.

Mechanism studies of terpolymerization of phthalic anhydride, propylene epoxide, and carbon dioxide catalyzed by ZnGA

Co-reporter:Yulei Liu, Min Xiao, Shuanjin Wang, Liang Xia, Dongmei Hang, Guofeng Cui and Yuezhong Meng

RSC Advances 2014 vol. 4(Issue 19) pp:9503-9508

Publication Date(Web):27 Jan 2014

DOI:10.1039/C3RA46343E

The terpolymerizations of carbon dioxide (CO2), propylene oxide (PO) and phthalic anhydride (PA) using zinc glutarate (ZnGA) as the catalyst were carried out in toluene solution. The monomer reactivity ratios of carbon dioxide and phthalic anhydride (rCO2 = 5.94 and rPA = 0.21) were experimentally evaluated by Fineman–Ross methodology. The results indicate that the reactivity of CO2 is much higher than that of PA, resulting in a random sequence structure of ester and carbonate units in the terpolymer. It is found that the introduction of a small amount of the third monomer PA can significantly increase PO conversion and the molecular weight of the terpolymer. Terpolymers with very high number-average molecular weight (Mn), up to 221 kg mol−1, can be obtained at the optimal reaction conditions (PA/PO molar ratio: 1/8, temperature: 75 °C, CO2 pressure: 5 MPa). This is the highest Mn reported to date for the terpolymerization of CO2, epoxides and cyclic anhydrides, together with very high PO conversion of 72.5%. Moreover, the synthesized terpolymers exhibit a high Tg of about 41 °C and higher thermal stabilities compared with the copolymer of PO and CO2.

Orientation microstructure and properties of poly(propylene carbonate)/poly(butylene succinate) blend films

Co-reporter:G. J. Chen;Y. Y. Wang;S. J. Wang;M. Xiao;Y.Z. Meng

Journal of Applied Polymer Science 2013 Volume 128( Issue 1) pp:390-399

Publication Date(Web):

DOI:10.1002/app.38150

Abstract

The blends of high molecular weight poly(propylene carbonate) (PPC) and poly(butylene succinate) (PBS) were melt blended using triphenylmethane triisocyanate (TTI) as a reactive coupling agent. TTI also serves as a compatibilizer for the blends of PPC and PBS. The blend containing 0.36 wt % TTI showed that the optimal mechanical properties were, therefore, calendared into films with different degrees of orientation. The calendering condition, degree of orientation, morphologies, mechanical properties, crystallization, and thermal behaviors of the films were investigated using wide-angle X-ray diffraction, scanning electron microscopy, tensile testing, and differential scanning calorimetry (DSC) techniques. The result showed that the as-made films exhibited obvious orientation in machine direction (MD). Both tensile strength in MD and the tear strength in transverse direction (TD) increased with increasing the degree of orientation. The orientation of the film also increased the crystallinity and improved the thermal properties of the PPC/PBS blend films. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Mechanical properties of block poly(propylene carbonate-cyclohexyl carbonate) investigated by nanoindentation and DMA methodologies

Co-reporter:Shaoyun Chen;Shuanjin Wang;Dongmei Han ;Yuezhong Meng

Journal of Applied Polymer Science 2013 Volume 128( Issue 3) pp:1979-1986

Publication Date(Web):

DOI:10.1002/app.38384

Abstract

To extend the practical application of poly(propylene carbonate) (PPC), the chemical methods were used to improve its mechanical properties. In this connection, random copolymer poly(propylene-cyclohexyl carbonate) (PPCHC) and di-block copolymers poly(propylene carbonate-cyclohexyl carbonate) (PPC-PCHC) were synthesized. Dynamic mechanical analysis (DMA), nanoindentation and nanoscratch test were applied to evaluate their mechanical properties. The storage's modulus, Young's modulus (E) and hardness (H) obtained from DMA and nanoindentation tests showed that the introduction of the third monomer cyclohexene oxide (CHO) can greatly improve the mechanical properties of PPC, and that the block copolymer PPC-PCHC hand better mechanical properties than the random copolymer PPCHC. The annealing treated PPC-PCHCs exhibited deteriorated mechanical properties as compared with untreated PPC-PCHC. From the results of scratch tests, the plastic deformation of PPC-PCHC was smaller than those of PPC and PPCHC. Meanwhile, the plastic deformations of the heat-treated PPC-PCHCs were smaller than the untreated PPC-PCHC because of the possible rearrangement of the molecular chains of PPC-PCHC. The scratch hardness (H_s) of the block copolymer PPC-PCHC is larger than random polymer PPCHC and PPC, but lower than the values of heat-treated samples indicating that the surfaces' hardness of block polymers increase after heat treatment. These different measurement methodologies provide a more precise assessment and understanding for the synthesized block polymers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Effects of Mo promoters on the Cu–Fe bimetal catalysts for the DMC formation from CO2 and methanol

Co-reporter:Ying-Jie Zhou, Min Xiao, Shuan-Jin Wang, Dong-Mei Han, Yi-Xin Lu, Yue-Zhong Meng

Chinese Chemical Letters 2013 Volume 24(Issue 4) pp:307-310

Publication Date(Web):April 2013

DOI:10.1016/j.cclet.2013.02.001

The Mo-promoted Cu–Fe bimetal catalysts were prepared and used for the formation of dimethyl carbonate (DMC) from CO2 and methanol. The catalysts were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR), laser Raman spectra (LRS), energy dispersive spectroscopy (EDS) and temperature programmed desorption (TPD) techniques. The experimental results demonstrated that the Mo promoters can decrease the reducibility and increase the dispersion of Cu–Fe clusters. The concentration balance of base–acid sites can be readily adjusted by changing the Mo content. The moderate concentration balance of acid and base sites was in favor of the DMC formation. Under optimal experimental conditions, the highest methanol conversion of 6.99% with a DMC selectivity of 87.7% can be obtained when 2.5 wt% of Mo was loaded.The concentration balance of base–acid sites of Cu–Fe bimetal catalysts can be readily adjusted and thus the catalytic activities for the formation of dimethyl carbonate (DMC) from CO2 and methanol were significantly enhanced by the introduction of Mo. The highest methanol conversion of 6.99% with a DMC selectivity of 87.7% was obtained when 2.5 wt% Mo was loaded.

Zinc adipate/tertiary amine catalytic system: efficient synthesis of high molecular weight poly(propylene carbonate)

Co-reporter:Lei Tang;Yan Xu;Shuanjin Wang;Yuezhong Meng

Journal of Polymer Research 2013 Volume 20( Issue 7) pp:

Publication Date(Web):2013 July

DOI:10.1007/s10965-013-0190-9

The copolymerization of carbon dioxide and propylene oxide to generate poly (propylene carbonate) (PPC) were efficiently catalyzed by zinc adipate (ZnAA) in the presence of various tertiary amines as cocatalyst. The influences of temperature, pressure as well as cocatalyst concentration on the copolymerization were studied. The ZnAA/4,4′-methylenebis (N,N-dimethylaniline) composite catalyst shows reasonable high polymer productivity (>280 g polymer/g zinc), high selectivity (>95 %, PPC/cyclic carbonate), especially considerable high molecular weight (Mn > 250 k). Because of the high molecular weight, the as-prepared PPC exhibits apparently improved thermal properties as contrast to the one reported elsewhere previously. Furthermore, the effects of the steric and electronic properties of various tertiary amine derivatives on cocatalytic performance have also been discussed. The experimental results suggest that the tertiary amine cocatalysts with the rigid and bulky aromatic structure are more favorable for the copolymerization.

Sulfonated poly(fluorenyl ether ketone) ionomers containing aliphatic functional segments for fuel cell applications

Co-reporter:Hang Hu, Wei Liu, Liu Yang, Min Xiao, Shuanjin Wang, Dongmei Han, Yuezhong Meng

International Journal of Hydrogen Energy 2012 Volume 37(Issue 5) pp:4553-4562

Publication Date(Web):March 2012

DOI:10.1016/j.ijhydene.2011.09.085

A series of Sulfonated Poly (fluorenyl ether ketone) ionomers containing aliphatic functional segments were synthesized and characterized. The monomer 4,4′-Dihydroxy-α, ω-diphenoxydecane with aliphatic group was conveniently prepared from hydroquinone and 1,10-dibromodecane. A series of sulfonated aliphatic functional groups containing poly(fluorenyl ether ketone)s with different aliphatic group content were successfully synthesized and characterized in detail, in particular with respect to properties relevant for their application as membrane materials in proton exchange membrane (PEM) fuel cells. Tough and transparent membranes were formed by casting from their solutions. The effects of alkyl groups were investigated by comparison of the PEM properties of the copolymers with different content of aliphatic component on the copolymer chain. The introduction of aliphatic segments can provide an enhanced water uptake, increased proton conductivities, but worse oxidative stability. Transmission electron microscope (TEM) images of j and f revealed an improved phase separation structure under the effect of aliphatic groups. The as-made membranes can also exhibit comparable or much better single cell performance than Nafion@ 117 at 75 °C–95 °C under full or partial relative humidification.

Portable PEMFC stack using sulfonated poly (fluorenyl ether ketone) ionomer as membrane

Co-reporter:S.J. Wang, Y.F. Zhang, D. Shu, S.H. Tian, D.H. Mei, M. Xiao, Y.Z. Meng

International Journal of Hydrogen Energy 2012 Volume 37(Issue 5) pp:4539-4544

Publication Date(Web):March 2012

DOI:10.1016/j.ijhydene.2011.09.138

Portable polymer electrolyte membrane fuel cells (PEMFCs) stack was assembled with sulfonated poly(fluorenyl ether ketone) (SPFEK) ionomer membranes. The portable PEMFC stack was studied by means of cell performance tests at high temperatures under low relatively humidity (RH). The experimental results showed that the output power of the stack increased from 28.74 W to 37.11 W with increasing operating temperature from 30 to 90 °C under 100% RH. When the operating temperature was over 100 °C, the output power decreased with further increasing temperature from 27.68 W (100 °C, 85% RH) to 19.87 W (120 °C, 50% RH). The output at 120 °C and under 50% RH was 69% output power of the stack at 30 °C and under 100% RH. These results demonstrated that the self-prepared SPFEK ionomer membrane was a promising PEM for the application in high-temperature PEMFC.

Synthesis and characterization of high molecular weight poly(1,2-propylene carbonate-co-1,2-cyclohexylene carbonate) using zinc complex catalyst

Co-reporter:Jing-shu Wu 肖敏;Hu He;Shuan-jin Wang

Chinese Journal of Polymer Science 2011 Volume 29( Issue 5) pp:

Publication Date(Web):2011 September

DOI:10.1007/s10118-011-1078-y

Using supported multi-component zinc dicarboxylate catalyst, poly(1,2-propylene carbonate-co-1,2-cyclohexylene carbonate) (PPCHC) was successfully synthesized from carbon dioxide (CO2) with propylene oxide (PO) and cyclohexene oxide (CHO). The conversion of epoxides dramatically increased up to 89.7% (yield: 384.2 g of polymer per g of Zn) with increasing reaction temperature from 60°C to 80°C. The optimized reaction temperature is 80°C. The chemical structure, the molecular weight, as well as thermal and mechanical properties of the resulting terpolymers were investigated extensively. When CHO feed content (mol%) is lower than 10%, the PPCHC terpolymers have number average molecular weight (Mn) ranging from 102 × 103 to 202 × 103 and molecular weight distribution (MWD) values ranging from 2.8 to 3.5. In contrast to poly(propylene carbonate) (PPC), the introduction of small amount of CHO leads to increase in the glass transition temperature from 38.0°C to 42.6°C. Similarly, the mechanical strength of the synthesized terpolymer is greatly enhanced due to the incorporation of CHO. These improvements in mechanical and thermal properties are of importance for the practical application of PPC.

Synthesis and characterization of poly(aryl ether ketone) ionomers with sulfonic acid groups on pendant aliphatic chains for proton-exchange membrane fuel cells

Co-reporter:Z.P. Guan, M. Xiao, S.J. Wang, Y.Z. Meng

European Polymer Journal 2010 Volume 46(Issue 1) pp:81-91

Publication Date(Web):January 2010

DOI:10.1016/j.eurpolymj.2009.08.021

A series of parent poly(aryl ether ketone)s bearing different content of unsaturated pendant propenyl groups were synthesized via nucleophilic substitution polymerization from 3,3′-diallyl-4,4′-dihydroxybiphenyl, 9,9′-bis(4-hydroxyphenyl) fluorene and 4,4′-difluorobenzophenone. The polymers with pendant aliphatic sulfonic acid groups were further synthesized by free radical thiol-ene coupling reactions between 3-mercapto-1-propanesulfonic sodium and the parent propenyl functional copolymers. The resulting sulfonated polymers with high inherent viscosity (1.83–4.69 dL/g) were soluble in polar organic solvents and can form flexible and transparent membranes by casting from their solutions. The copolymers with different ion exchange capacity could be conveniently synthesized by varying the monomers ratios. Transmission electron microscopy (TEM) was used to examine the microstructures of the membrane and the results revealed that significant hydrophilic/hydrophobic microphase separation with spherical, uniform-sized (5–10 nm) and well-dispersed hydrophilic domains was afforded. The proton conductivities of the as-prepared membranes and the state-of-the-art Nafion 117 membrane in fully hydrated state were investigated. The results revealed that the proton conductivity of the synthesized membranes increased more remarkably than that of Nafion 117 membrane with increasing temperature. The membrane with 1.69 mequiv/g of IEC had a conductivity of 2.5 × 10−2 Scm−1 at 100 °C. The membranes also possessed excellent mechanical properties, good thermal, oxidative, hydrolytic and dimensional stabilities.

Novel application of thermally expanded graphite as the support of catalysts for direct synthesis of DMC from CH3OH and CO2

Co-reporter:J. Bian, M. Xiao, S.J. Wang, Y.X. Lu, Y.Z. Meng

Journal of Colloid and Interface Science 2009 Volume 334(Issue 1) pp:50-57

Publication Date(Web):1 June 2009

DOI:10.1016/j.jcis.2009.03.009

Novel Cu–Ni bimetallic catalysts supported on thermally expanded graphite (TEG) were prepared as an example to show the particular characteristics of TEG as a carbon support material. The structures of TEG and the synthesized Cu–Ni/TEG catalysts were characterized using BET, FTIR, TG, SEM, TEM, XRD and TPR techniques. The catalytic activities of the prepared catalysts were investigated by performing micro-reaction in the direct synthesis of dimethyl carbonate (DMC) from CH3OH and CO2. The experimental results indicated that the prepared Cu–Ni/TEG catalysts exhibited highly catalytic activity. Under the optimal catalytic conditions at 100 °C and under 1.2 MPa, the highest conversion of CH3OH of 4.97% and high selectivity of DMC of 89.3% can be achieved. The highly catalytic activity of Cu–Ni/TEG in DMC synthesis can be attributed to the synergetic effects of metal Cu, Ni and Cu–Ni alloy in the activation of CH3OH and CO2 and the particular characteristics of TEG as a carbon support material.Novel TEG supported Cu–Ni bimetallic catalyst was synthesized and utilized in the direct synthesis of DMC to illustrate the superior properties of TEG as a catalyst support.

Carbon nanotubes supported Cu–Ni bimetallic catalysts and their properties for the direct synthesis of dimethyl carbonate from methanol and carbon dioxide

Co-reporter:Jun Bian, Min Xiao, Shuan-Jin Wang, Yi-Xin Lu, Yue-Zhong Meng

Applied Surface Science 2009 Volume 255(Issue 16) pp:7188-7196

Publication Date(Web):30 May 2009

DOI:10.1016/j.apsusc.2009.03.057

Abstract

Multi-walled carbon nanotubes (MWCNTs) supported Cu–Ni bimetallic catalysts for the direct synthesis of dimethyl carbonate (DMC) from CH₃OH and CO₂ were synthesized and investigated. The supporting materials and the synthesized catalysts were fully characterized using FTIR, scanning electron microscopy (SEM), transmission electron microscopy (TEM), temperature-programmed reduction (TPR), X-ray diffraction (XRD) and X-ray photoelectron spectrum (XPS) techniques. The catalytic activities were investigated by performing micro-reactions. The experimental results showed that the metal phase and Cu–Ni alloy phase in the catalyst were partially formed during the calcination and activation step. Active metal particles were dispersed homogeneously on the surface of the MWCNTs. Cu–Ni/MWCNTs catalysts were efficient for the direct synthesis of DMC. The highest conversion of CH₃OH was higher than 4.3% and the selectivity of DMC was higher than 85.0% under the optimal catalytic conditions of 120 °C and around 1.2 MPa. The high catalytic activity of Cu–Ni/MWCNTs in DMC synthesis can be attributed to the synergetic effects of metal Cu, Ni and Cu–Ni alloy in the activation of CH₃OH and CO₂, the unique structure of MWCNTs and the interaction between the metal particles and the supports.

The silica-doped sulfonated poly(fluorenyl ether ketone)s membrane using hydroxypropyl methyl cellulose as dispersant for high temperature proton exchange membrane fuel cells

Co-reporter:Y.F. Zhang, S.J. Wang, M. Xiao, S.G. Bian, Y.Z. Meng

International Journal of Hydrogen Energy 2009 Volume 34(Issue 10) pp:4379-4386

Publication Date(Web):May 2009

DOI:10.1016/j.ijhydene.2008.12.092

The sulfonated poly(fluorenyl ether ketone)s (SPFEK) membranes doped with SiO2 and dispersed by hydroxypropyl methyl cellulose (HPMC) were prepared and investigated for polymer electrolyte membrane fuel cells (PEMFCs) used at high temperature and low relative humidity (RH). The above membrane was prepared by solution dispersion of SPFEK and SiO2 using HPMC as dispersant. The physio-chemical properties of the hybrid membrane were studied by means of scanning electron microscope (SEM), ion-exchange capacity (IEC), proton conductivity, and single cell performance tests. The hybrid membranes dispersed by HPMC were well dispersed when compared with common organic/inorganic hybrid membranes. The hybrid membranes showed superior characteristics as a proton exchange membrane (PEM) for PEMFC application, such as high ionic exchange content (IEC) of 1.51 equiv/g, high temperature operation properties, and the satisfactory ability of anti-H2 crossover. The single cell performances of the hybrid membranes were examined in a 5 cm2 commercial single cell at both 80 °C and 120 °C under different relative humidity (RH) conditions. The hybrid membrane dispersed by HPMC gave the best performance of 260 mW/cm2 under conditions of 0.4 V, 120 °C, 50% RH and ambient pressure. The results demonstrated HPMC being an efficient dispersant for the organic/inorganic hybrid membrane used for PEM fuel cell.

Highly effective direct synthesis of DMC from CH3OH and CO2 using novel Cu–Ni/C bimetallic composite catalysts

Co-reporter:Jun Bian, Min Xiao, Shuan Jin Wang, Yi Xin Lu, Yue Zhong Meng

Chinese Chemical Letters 2009 Volume 20(Issue 3) pp:352-355

Publication Date(Web):March 2009

DOI:10.1016/j.cclet.2008.11.034

Novel Cu–Ni/C has been prepared and utilized as an efficient catalyst system in direct synthesis of DMC from CH3OH and CO2.

Thermal degradation behavior of Copoly(propylene carbonate ε-caprolactone) investigated using TG/FTIR and Py-GC/MS methodologies

Co-reporter:Wenhan Luo, Min Xiao, Shuanjin Wang, Shan Ren, Yuezhong Meng

Polymer Testing (April 2017) Volume 58() pp:13-20

Publication Date(Web):April 2017

DOI:10.1016/j.polymertesting.2016.12.004

Electrostatic shield effect: an effective way to suppress dissolution of polysulfide anions in lithium–sulfur battery