Application of the simultaneous measurement system of WAXD, SAXS and transmission FTIR spectra to the study of structural changes in the cold- and melt-crystallization processes of trans-1,4-polyisoprene

Abstract

The newly developed system of simultaneous time-dependent measurements of wide-angle X-ray diffraction, small-angle X-ray scattering and transmission-type Fourier-transform infrared spectra has been applied to study the structural changes in the melt- and cold-crystallization processes of trans-1,4-polyisoprene (TPI). For the melt-isothermal crystallization process at 40 °C, the domains of relatively higher density with approximately 220 Å radius formed at first as the intermediate state, where the chain conformation was speculated to be considerably disordered. As time passed, the correlation length ξ between these domains decreased until they joined together to form the stacked lamellar structure. In these lamellae, the crystal lattices of the regular α form were created. When the isothermal crystallization was investigated at 30 °C, the intermediate-phase regularization caused the α- and β-crystalline forms to mix. In the cold-crystallization process or the heating process that started from the melt-quenched glass below −100 °C, TPI was found to crystallize at first to the β-form at approximately −55 °C, which transformed to the α-form at 50 °C via the amorphous phase as observed above. Simultaneous time-dependent measurements of WAXSD, SAXS and Fourier-transform infrared (FTIR) spectra have been performed to study the structural changes in the melt- and cold-crystallization processes of trans-1,4-polyisoprene (TPI). In the melt-isothermal crystallization process, the domains of relatively higher density were formed at first as the intermediate state, which approached each other to form the stacked lamellar structure. In the cold-crystallization process from melt-quenched glass, TPI crystallized to the β-form at −55 °C, which transformed to the α-form at 50 °C via the amorphous phase.