Related Experiment Video
Updated: May 26, 2026

Orientational Transition in a Liquid Crystal Triggered by the Thermodynamic Growth of Interfacial Wetting Sheets
Published on: May 15, 2017
Phase transitions in prequenched mesomorphic isotactic polypropylene during heating and annealing processes as
Junchai Zhao1, Zhigang Wang, Yanhua Niu
1School of Material Science and Engineering, Shijiazhuang Tiedao University, Shijiazhuang, Hebei, P R China.
Abstract:
Time-resolved simultaneous synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) technique was used to investigate the phase transitions in prequenched mesomorphic isotactic polypropylene (iPP) samples during heating and annealing processes, respectively. For the heating process, it is shown that the mesomorphic-to-monoclinic phase transition is relatively faster for the mesomorphic iPP sample obtained with the high quenching rate than that with the low quenching rate. For the former, the stability of α-monoclinic crystals formed during heating is relatively higher. As for the annealing process, WAXD and SAXS data illustrate that the higher the annealing temperature (T(a)), the earlier the mesomorphic-to-monoclinic phase transition occurs. Namely, T(a) controls the phase transition rate. Both heating and annealing processes show that the increase of content of α-monoclinic crystal phase is mainly at the expense of the mesomorphic phase, with the content of amorphous phase almost invariable. The isothermal crystallization kinetics for the prequenched mesomorphic iPP sample was analyzed through the Avrami equation, revealing a two-dimensional crystal growth under the diffusion-limited mechanism.
Related Concept Videos
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
Polymer Classification: Stereospecificity
Polymer Classification: Crystallinity
Crystalline domains are the regions where polymer chains are aligned in an orderly manner and held together in proximity by intermolecular forces. For example, chains in the crystalline domains of polyethylene and nylon are bound together by van der Waals...
Phase Transitions: Melting and Freezing
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution

