离子交联型聚合物的离子聚集形态研究进展

Advances in Study of Ionic-aggregate Morphology of Ionomers

系统评述了离子含量、抗衡离子、离子基团、基体近程链结构(柔顺性、介电常数、基团空间位阻、支化、共价交联)、中和度、离子沿主链分布结构、环境条件(温度、溶剂、水分)及制备历史(熔融压制、溶液铸膜、再沉淀、高温退火)等对离子交联型聚合物(以下简称离聚物)的离子聚集形态(参与聚集离子比例、离子簇的形状、尺寸、聚集数、数密度、分布及内部配位结构)的影响。在此基础上,指出离子簇内部是否存在原子的有序排列、离聚物低温差示扫描量热(DSC)吸热峰的起源、现有离子跃迁理论的缺陷及基体远程链结构—分子量对离子簇形态的效应为当前亟待解决的离子聚集形态方面的四个基本问题。尤其对于离子跃迁理论的扩展与完善提出了建议:不仅要考虑离子相互作用强度这一结构因素,亦须涵盖离子簇聚集数(离子簇近围的链段紧密堆砌程度)及离子簇数密度(离子交联密度)这两个形态因素,如此才能合理诠释或预测离聚物的结构-性能关系。

In this article, effects of ion content, counterion, ionic group, short-range chain-structure （flexibility, permittivity, group steric-hindrance, branching, covalent cross-linking, etc. ） of the matrix polymer, degree of neutralization, ionic-group distribution along the backbone chain, ambient conditions （temperature, solvent, water, etc. ）, and preparation history （melt pressing, solution casting, re-precipitation, high-temperature annealing, etc. ） on the ionaggregation morphology （fraction of aggregated ionic-groups, shape, size, aggregation number, number density, distribution-in-matrix and internal coordination structure of ionic aggregates） have systematically been reviewed for ionomers. On the basis of this, it has been pointed out that four basic issues on ion-aggregation morphology are urgent to be resolved, i. e. , whether there exists an ordered arrangement of atoms inside the ionic aggregates, origin of the low temperature differential scanning calorimetry （DSC） endothermic peak of ionomers, disadvantages of the currently-held ion hopping theory, and effect of molecular weight, an important index to long-range chain-structure of the matrix polymer, on the ionic aggregate morphology. Particularly, it has been suggested that, to extend and perfect the ion hopping theory, we accommodate two morphological factors, ionic-aggregate aggregation number （i. e. , extent of chain-segment close packing in the coronas of ionic aggregates） and number density （i. e. , ionic cross-linking density）, in addition to the pre existing structural factor, strength of ionic interactions, thereby to reasonably explain or predict the structure-property relationships of ionomers.