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Interplay of crystallization and liquid-liquid phase separation in polyolefin blends: A thermal history dependence study |
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| Authors: | Katsumi Shimizu Howard Wang Go Matsuba Hongdoo Kim Charles C Han |
| Affiliation: | a Advanced Protein Crystallography Research Group, RIKEN Harima Institute, 1-1-1 Kouto, Sayo-chou, Sayo-gun, Hyogo 679-5148, Japan b Department of Mechanical Engineering, Binghamton University, SUNY, Binghamton, NY 13902, United States c Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan d CAS Key Laboratory of Engineering Plastics, Joint Laboratory of Polymer Science and Materials, Institute of Chemistry, The Chinese Academy of Sciences, Beijing 100080, PR China e Department of Chemistry, Kyung Hee University, Kyungkido 449-701, South Korea f Department of Physics, George Washington University, Washington DC, United States g State Key Laboratory of Polymer Physics and Chemistry, Joint Laboratory of Polymer Science and Materials, Institute of Chemistry, The Chinese Academy of Sciences, Beijing 100080, PR China |
| Abstract: | The kinetic interplay between crystallization and liquid-liquid phase separation (LLPS) in random copolymer blends of poly(ethylene-ran-hexene) (PEH) and poly(ethylene-ran-butene) (PEB) has been studied using optical microscopy. Morphologies of blends gone through three different thermal histories are compared: (1) single-quench (SQ), a homogeneous melt quickly cooled to isothermal crystallization temperatures (Tcry), (2) double-quench (DQ), a homogeneous melt quickly cooled to an intermediate temperature (Tlps) between binodal and equilibrium melting temperature (Tm0) and stored for a period of time and then cooled to Tcry, and (3) cyclic-quench (CQ), a homogeneous melt quickly cooled to Tlps and stored for a period of time, then gone through four cycles of crystallization and remelting. Comparing DQ morphologies to SQ ones, both crystal growth rate and nucleation density in the former are affected by prior LLPS. A scaling argument has been provided to partially account for the observed phenomena. In CQ, characteristic lengths of secondary features induced by crystallization depend strongly on the overall PEH composition, whereas are insensitive to temperature cycling. The contrast of large domains becomes more prominent upon cyclic crystallization and remelting. On the other hand, primary LLPS domains coarsen with CQ while loosing the contrast. |
| Keywords: | Polyolefins Crystallization Phase separation |
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