Ionomer solution to film solidification dependence upon solvent type and its impact upon morphology and ion transport
Ionomer solution to film solidification dependence upon solvent type and its impact upon morphology and ion transport
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离聚物溶液到薄膜的固化取决于溶剂类型及其对形态和离子传输的影响
DOI：
10.1016/j.eurpolymj.2017.10.011
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发表时间：
2017
影响因子：
6
通讯作者：
C. Cornelius
中科院分区：
文献类型：
--
作者：
Donghui Wang;Yanfang Fan;Mingqiang Zhang;R. Moore;C. Cornelius
在溶液铸造、溶剂蒸发和凝固过程中，离聚体链和溶剂分子的相互作用影响链缠结、官能团的空间排列、微观结构的发展、形态和物理性质。这些概念是用固定离子交换容量为1.0，估计溶解度参数为21.8 (J/cm3)1/2的聚（t-丁基苯乙烯-b-乙烯-alt-丙烯-b-磺化苯乙烯-b-乙烯-alt-丙烯-b-t-丁基苯乙烯）来研究的。用等体积的环己烷：庚烷混合物（C:H）、氯仿（CHCl3）和四氢呋喃（THF）溶液铸膜。利用透射电子显微镜（TEM）、小角x射线散射（SAXS）、傅里叶变换红外光谱（FT-IR）和电化学阻抗谱对后续膜结构进行了评估。商业供应的薄膜具有随机分布的磺化结构域，其初始质子电导率为11.8 mS/cm。由C:H溶液铸造而成的薄膜具有随机分布的磺化结构域。当使用THF溶液浇铸时，这种随机形态变得更加有序，具有片状形态。由chcl3制备的薄膜具有介于随机和有序之间的形态。膜形态差异归因于较差的溶剂体系抑制链溶剂化。溶液铸膜的质子电导率在随机形态下为1.0 mS/cm，在片状结构下为15.3 mS/cm。将离子- thf溶液浇铸温度提高到40°C，薄膜的电导率提高了103% （31.2 mS/cm）。这导致水分吸收从29 wt%变化到80 wt%。将THF溶液浇铸的薄膜从干燥状态循环到潮湿状态，发现片状形态可以保持其导电性，但商业膜的导电性从11.8 mS/cm下降到0.98 mS/cm。发现离聚体薄膜的性质取决于溶剂质量和加工工艺。
Ionomer chain and solvent molecule interactions during solution-casting, solvent evaporation, and solidification impacts chain entanglements, spatial arrangement of functional groups, microstructure development, morphology, and physical properties. These concepts were investigated using poly(t-butylstyrene-b-ethylene-alt-propylene-b-sulfonatedstyrene-b-ethylene-alt-propylene-b-t-butylstyrene) with a fixed ion-exchange capacity of 1.0, and estimated solubility parameter of 21.8 (J/cm3)1/2. Films were solution-cast using an equal volume cyclohexane:heptane mixture (C:H), chloroform (CHCl3), and tetrahydrofuran (THF). Subsequent film structures were evaluated using transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), FT-IR, and electrochemical impedance spectroscopy. A commercially supplied film had sulfonated domains randomly distributed throughout it, and its initial proton conductivity was 11.8 mS/cm. A film created by solution-casting from C:H had a morphology containing randomly distributed sulfonated domains. This random morphology became more ordered with a lamella-like morphology when solution-cast using THF. The film produced from CHCl3had a morphology that was between random and ordered. Film morphology differences were attributed to a poorer solvent system that inhibited chain solvation. The solution-cast film’s proton conductivity was 1.0 mS/cm for a random morphology, and 15.3 mS/cm with a lamella-like structure. Increasing the ionomer-THF solution-casting temperature to 40 °C produced a film with a 103% increase in conductivity (31.2 mS/cm). This led to a water uptake change from 29 wt% to 80 wt%. Cycling a THF solution-cast film from its dry to a wet state revealed that a lamella-like morphology would maintain its conductivity, but the commercial film’s conductivity decreased from 11.8 mS/cm to 0.98 mS/cm. Ionomer film properties were found to be dependent upon solvent quality and processing.