Conformational Change Analysis of Poly(ethylene 2,5-furandicarboxylate)\nand Poly(ethylene terephthalate) under Uniaxial Stretching

Abstract

Changes\nin the local conformations of poly­(ethylene 2,5-furandicarboxylate)\n(PEF) and poly­(ethylene terephthalate) (PET) after crystallization\nfrom the amorphous state were studied and compared by infrared analysis.\nBoth strain-induced crystallization (SIC) under uniaxial loading (D-PEF\nand D-PET) and crystallization under static conditions (TC-PEF and\nTC-PET) were used to determine the effect of mechanical stretching.\nIt appears that, although the crystalline systems are the same, the\ninner organization of the amorphous phases is influenced by stretching.\nIn addition to the increased incidence of the more extended aliphatic\nchain conformation (<i>trans</i>), stretching appears to\nreduce the number of activated hydrogen bonds between segments, which\nare more constrained in PEF than in PET. The effect of stretching\non the β-relaxation, which is related to local motions of carbonyl\ngroups, showed that PEF carbonyl groups of amorphous regions are freed\nby the stretching. We conclude that the different chain architectures\nof the polyesters induce different sensitivities of the amorphous\nphase to the drawing process.