摘要
性能优异的聚合物电解质需要兼具较高的离子电导率和良好的机械性能.深入理解聚合物的结构和分子动力学及其与材料宏观性能之间的关系,对于从分子尺度设计高性能聚合物电解质至关重要.本文选取玻璃化转变温度低、氢键缔合基团位于链端的非晶遥爪型聚丙二醇模型体系,通过化学修饰端基合成了分子量为1000,2000和4000的两端端基均为烯丙基的聚丙二醇,并利用宽频介电谱研究了链端基团相互作用强度及分子量对聚丙二醇多尺度动力行为的影响.实验结果表明,具有两种不同端基的聚丙二醇均出现了对应链段尺度的α松弛和对应整链尺度的Normal Mode松弛.在相同温度下,端基相互作用会同时影响两个松弛过程,相互作用越强,松弛时间越长.由于端基含量随分子量减小而增加,分子量越小,缔合端基对高分子动力学的影响越明显.此外,利用高分子玻璃化熵理论研究了端基缔合强度和分子量对遥爪型高分子熔体链段动力学的影响,理论预测与实验结果定性一致.研究结果为聚合物电解质的分子设计提供了指导.
Abstract
Excellent polymer electrolytes require a combination of high ionic conductivity and mechanical strengths.An in-depth understanding of the relationship between polymers'microscopic structure and dynamics and macrosco-pic conductive and mechanical properties is essential for the molecular design of high-performance polymer electro-lytes.In the present paper,we selected low temperature of glass transition(Tg)and non-crystalline telechelic polypro-pylene glycol melts as a model system to investigate the molecular dynamics of associating polymers.Allyl-terminated polypropylene glycols having molecular weights of 1000,2000 and 4000 were synthesized by chemically modifying the end groups,and the influence of chain-end interaction strength and molecular weight on their multi-scale dyna-mics was investigated using broadband dielectric spectroscopy.The polypropylene glycols with two different end groups exhibit both the α-relaxation associated with the segmental motion and the normal mode relaxation associated with the global motion of the chain.End group interactions influence both two relaxations;stronger interactions lead to longer relaxation time at the same temperature.This effect becomes more pronounced for the lower-molecular-weight samples,because the motion has been suppressed for the denser end groups therein.The generalized entropy theory was utilized to study the glass formation of telechelic polymer melts having variable sticky interaction strength and molecular mass,and theoretical predictions were shown to be in qualitative agreement with experimental results.These dynamic details can be used in guiding the molecular design of polymer electrolytes.
国家科技期刊平台
NSTL
万方数据