MISCIBILITY OF ASSOCIATED POLYMER BLEND SOLUTIONS .1. ONE-END-AMINATED POLYSTYRENE ONE-END-CARBOXYLATED POLY(ETHYLENE GLYCOL) BLENDS IN TOLUENE

The effects of polymer associations on miscibility are investigated for polymer blend solutions of one-end-aminated polystyrene (APS) and one-end-carboxylated poly(ethylene glycol) (CPEG), which are able to associate with each other by means of the functional groups at the end of the respective polymer chains. Cloud points are measured for their toluene solutions, where the strength of association and the segment interaction vary with the total polymer concentration. The following conclusions are deduced from the experimental results and a Flory-Huggins type theory for associated polymer blend solutions developed here. (1) The introduction of an amino group onto the polystyrene (PS) chain end gives substantially no effect on miscibility with poly(ethylene glycol) (PEG), whereas the carboxyl group introduced onto PEG reduces the miscibility of PS and PEG. Blend solutions of APS/CPEG exhibit higher miscibility than those of PS/CPEG. (2) The theory can interpret these experimental results well, showing that the strength of association between carboxyl groups is stronger than that between carboxyl and amino groups. (3) The strength of association between amino and carboxyl groups is not so strong as to show two peaks in the phase diagram of solvent fraction against polymer composition, which is theoretically expected for a strongly associated system.