Polymer electrolyte membranes for the direct methanol fuel cell: A review

The direct methanol fuel cell (DMFC) has the potential to replace lithium‐ion rechargeable batteries in portable electronic devices, but currently experiences significant power density and efficiency losses due to high methanol crossover through polymer electrolyte membranes (PEMs). Numerous publications document the synthesis and characterization of new PEMs for the DMFC. This article reviews this research, transport phenomena in PEMs, and experimental techniques used to evaluate new PEMs for the DMFC. Although many PEMs do not show significant improvements over Nafion®, the benchmark PEM in DMFCs, experimental results show that several new PEMs exhibit lower methanol crossover at similar proton conductivities and/or higher DMFC power densities. These results and recommendations for future research are discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Parts B: Polym Phys 44: 2201–2225, 2006     

水溶性聚酯的结构和性能

由对苯二甲酸二甲酯、间苯二甲酸、间苯二甲酸二甲酯５－磺酸钠与乙二醇等共缩聚合成的ＰＥＴ型水溶性聚酯（ＷＳＰ）是一种新型的水溶性聚合物，在化纤、纺织、涂料、粘合剂、电子、油墨等领域有着广泛的应用前景．化纤领域超细纤维新材料的研究、开发和生产，迫切需要一...     

壳聚糖固体聚合物电池用膜

壳聚糖是甲壳素脱乙酰基的产物，具有良好的成膜性、生物相容性、环保以及价格低廉等特点。作为一种碱性高分子膜材料，近年来已成为聚电解质研究领域中的研究热点。本文综述了壳聚糖固体聚合物电池用膜的研究现状，其改性工艺主要包括共混、化学改性、质子酸掺杂、无机盐掺杂等方法，比较了各种工艺处理后壳聚糖固体聚合物电解质膜的性能差异，并就壳聚糖固体聚合物电解质膜中离子传导机理中有待解决的问题进行探讨，并提出了进一步改进壳聚糖固体聚合物电解质膜性能的研究思路。     

聚电解质溶液中2.6-ANS探针的荧光谱研究

本文合成了2.6—ANS荧光探针分子,并在含有不同外加盐的NaPSS溶液中测定了探针的荧光发射光谱。结果表明:探针的荧光强度随Cs增大而增大,而探针光谱的最大发射波长和半波宽度随Cs增大而减小。当Cs达到一定值时,荧光谱参数与Cs关系曲线出现转折点,此时聚离了链以“类胶束”状态存在。     

Formation and Physicochemical Features of Hybrid Threadlike Micelles in Aqueous Solution

We investigate the construction of long, stable hybrid threadlike micelles consisting of polyelectrolytes and oppositely charged surfactants in aqueous solution and examine the physicochemical features such as their structure and viscoelastic behavior in aqueous solution. The most important point for their construction is the careful control of interactions, especially electrostatic interactions, caused between the surfactants and polyelectrolytes. Incorporated polyelectrolytes are fully extended in these hybrid threadlike micelles irrespective of the molecular weight of the polymer. The viscoelastic behavior of the hybrid threadlike micellar solution is similar to that of ordinary threadlike micellar systems consisting of low‐molecular‐weight substances. However, the inclusion of polymers in the micelles causes differences in their mechanical properties.     

Negatively charged hyperbranched polyether-based polyelectrolytes

The preparation of carboxylated hyperbranched polyglycerols of narrow polydispersity was achieved by modification (78–90%) of the hydroxyl end groups via Michael addition of acrylonitrile, followed by hydrolysis. High conversion could only be achieved for low molecular weight starting materials (520 and 1,030 g mol⁻¹). The solution properties of the resulting materials were investigated by dynamic light scattering (DLS), showing the formation of large aggregates with size depending on the pH value. After deposition on a negatively charged mica surface, the structures observed by atomic force microscope (AFM) show the coexistence of aggregates and single macromolecules. Most interesting, in the case of the lower molecular weight sample (PG 520 g mol⁻¹), extended and ordered terrace structures were formed, which are unprecedented for hyperbranched polymers and are of interest for surface modification in general.     

Highly hydrophobically modified polyelectrolytes: Field variables to control emulsion type

Highly hydrophobically modified (with n-dodecylamide chain) linear poly(acrylic acid)s (HHMPAAH) and poly(sodium acrylate)s (HHMPAANa) with various degrees of grafting (τ) were synthesized and used as emulsifiers of the n-dodecane/water system. The type of emulsion, oil in water (O/W) or water in oil (W/O), was investigated as a function of the polymer chemical structure (τ, salt or acid form of the copolymer) and aqueous phase electrolyte concentration (NaNO₃). Increasing τ and/or salt concentration was found to favor the formation of inverse emulsions. Direct liquid–liquid dispersions are more likely to form with poly(sodium acrylate)s than with poly(acrylic acid)s. Hence, field variables such as τ, pH and ionic strength are relevant parameters to control emulsion type. Moreover, a balanced polyelectrolyte neither soluble in oil nor in water was synthesized for the first time. With this original emulsifier, the dispersion type was found to change from O/W to W/O with polymer salting out. The work provides convenient model system for fundamental studies of polymer conformation at liquid–liquid interfaces. Received: 31 March 1998 Accepted: 30 April 1998     

Theoretical study on the structure and property relationship of the cationic conjugated polyelectrolytes

A theoretical study using density functional theory was performed to understand the structure/property relationship of the cationic conjugated polyelectrolytes, poly[9,9-bis-(6′-N,N,N-trimethylammonium) hexyl] fluorene-alt-4,7-(2,1,3-benzothiadiazole)] (PFBT-X, where X = Br). The torsion angle between the fluorene and benzothiadiazole units in the PFBT monomer was found to substantially affect the structural and electronic properties of the cationic PFBT monomer. The changes of geometrical parameter, HOMO and LUMO energy levels, and band gap, as well as the absorption maximum are discussed in terms of the torsion in the PFBT monomer structure. For comparison, its neutral analogue, the monomer of poly(9,9-di-n-octylfluorene-alt-benzothiadiazole) (F8BT) was also studied. The length of conjugation backbone was also examined.     

功能性超薄有序分子沉积膜的制备及其结构研究

1991年G.Decher等首次探讨了阴阳离子与聚电解质交替沉积制备有机超薄膜的方法。我们在完善成膜技术和发展成膜基质的基础上,详细研究了其成膜过程与膜的结构,并定义这种新的自组装超薄有序膜为分子沉积膜——MD膜。MD膜是利用阴阳离子的静电吸附反应特性,通过相反离子体系的交替分子沉积制备的层状有序自组装多层超薄膜。需要指出的是,分子沉积既是有机超薄膜的制备技术,本身又是一种自组装超薄有序膜。MD膜制备工艺简单,热稳定性和长期稳定性好,不受基体形状与面积限制。     

Effect of chemical modification of ion-exchange membrane MA-40 on its electrochemical characteristics

Transport characteristics of commercial heterogeneous anion-exchange membranes MA-40 and MA-41 are studied, together with those of membrane MA-40M fabricated by treating the MA-40 surfaces with a strong polyelectrolyte complex. It is demonstrated that, after modification, the electrical conductivity of MA-40M in an NaOH solution increases. At overlimiting currents, the water dissociation rate on this membrane decreases as compared with the initial membrane. At the same time, no noticeable change in the rate of transport of counter-ions (ions Cl^-) through the membrane at a fixed potential drop is discovered at under-and overlimiting currents. The MA-40M membrane behavior is explained by the conversion of secondary and tertiary functional ammonium groups in the near-surface membrane layers approximately 80 μm thick into quaternary groups during the treatment by the polyelectrolyte.