The role of hard segment content on the molecular dynamics of poly(tetramethylene oxide)-based polyurethane copolymers

摘要

The effect of hard segment (4,4′-diphenylmethane diisocyanate-1,4- butanediol) content on the molecular dynamics of a series of PTMO-based segmented polyurethanes was investigated using broadband dielectric spectroscopy. The microphase-separated morphology and degrees of separation, extensively characterized in a previous publication, were utilized to aid in interpretation of the molecular dynamics. The soft phase segmental dynamics were observed to slow slightly, increase in breadth, and decrease in strength with increasing hard segment content: the influence of hard domains on the soft phase segmental dynamics is analogous to that of crystalline lamellae in semi-crystalline polymers. A Maxwell-Wagner-Sillars interfacial polarization process, arising from charge accumulation at hard/soft phase interfaces, was observed at higher temperatures. The strength of this process was found to be a rather sensitive indicator of the microphase mixing process.