Crystallization behavior and morphology of double crystalline poly(trimethylene terephthalate)/poly(ethylene oxide terephthalate) copolymers

Double crystalline poly(trimethylene terephthalate)/poly(ethylene oxide terephthalate) copolymers (PTT/PEOT), with PTT content ranging from 16.5 to 65.5 wt%, were synthesized by melt copolycondensation. The morphological transformation of samples from microphase separation to macrophase separation was investigated by gel permeation chromatography and transmission electron microscopy. Differential scanning calorimetry and in situ wide-angle X-ray diffraction suggested that all copolycondensation samples displayed double crystalline behavior. The melt-crystallization peak temperatures (Tm, c values) of PTT chains monotonously increased with increasing PTT content and were higher than that of homo-PTT when the content of PTT was above 30.6 wt%. Interestingly, Tm, c values of PEOT chains were also increased with increasing PTT content. Polarized optical microscopy revealed that all copolycondensation samples studied could form ring-banded spherulites and band spacing increased with increasing Tc values. In addition, band spacing decreased with increasing PTT content at a given Tc. Strangely, although PEOT was the main component in all copolycondensation samples, spherulitic morphology formed by the advance crystallization of PTT did not change after PEOT crystallization. Only a subtle change of quadrant tones was detected. (C) 2012 Society of Chemical Industry