PHASE-SEPARATION IN CRYSTALLIZABLE MULTIBLOCK POLY(ETHER-ESTER) COPOLYMERS WITH POLY(TETRAMETHYLENE ISOPHTHALATE) HARD SEGMENTS

The process of isothermal crystallization and phase separation in poly (tetramethylene isophthalate) (PTMI) and multiblock copolymers of PTMI with poly(tetramethylene oxide) (PTMO) is examined by differential sc anning calorimetry. Morphology development is studied from the superco oled liquid to the completion of crystallization for compositions rang ing from 30 to 100 wt% PTMI over a wide range of isothermal crystalliz ation temperatures. A model is suggested whereby phase separation in t he copolymers proceeds in a manner similar to crystallization of the h omopolymer, implying phase-mixed non-crystalline regions with inhomoge neous mobilities. The experimentally observed multiple endotherm behav iour in the PTMI/PTMO copolymers is a characteristic of the hard segme nt, and is also observed in the PTMI homopolymer.