Roles of polymer-solvent complexes in conformational ordering of polymer molecules dispersed in gels

On gelation of crystallizable stereoregular polystyrenes (isotactic IFS and syndiotactic SPS), highly ordered skeletal conformations of particular types characteristic of the respective polymer are formed. The conformational orderliness is evaluated in the absolute scale through quantitative analysis of infrared absorption bands due to the respective ordered conformation. The kinetic and/or thermodynamic behaviors of gelation process and the accompanied conformational ordering are strongly influenced by solvent. Solvent effect on the aggregation state formed in SPS gels has been investigated by means of small angle neutron scattering and discussed in relation to the gelation rate. In some solvents, two different ordering processes, gelation and crystallization, proceed in a competitive way. On the basis of these experimental facts, the roles of specific polymer-solvent interactions in gels are considered from the viewpoint of molecular-level structure.