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Morphological Studies of Solution‐Crystallized Thermoplastic Elastomers with Polyethylene Endblocks and a Random‐Copolymer Midblock
Author(s) -
Yan Jiaqi,
Lee Byeongdu,
Smith Steven D.,
Spontak Richard J.
Publication year - 2021
Publication title -
macromolecular rapid communications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.348
H-Index - 154
eISSN - 1521-3927
pISSN - 1022-1336
DOI - 10.1002/marc.202100442
Subject(s) - copolymer , materials science , thermoplastic elastomer , crystallinity , crystallization , elastomer , polyethylene , polymer chemistry , composite material , chemical engineering , polymer , engineering
Styrenic thermoplastic elastomers (TPEs) in the form of triblock copolymers possessing glassy endblocks and a rubbery midblock account for the largest global market of TPEs worldwide, and typically rely on microphase separation of the endblocks and the subsequent formation of rigid microdomains to ensure satisfactory network stabilization. In this study, the morphological characteristics of a relatively new family of crystallizable TPEs that instead consist of polyethylene endblocks and a random‐copolymer midblock composed of styrene and (ethylene‐ co ‐butylene) moieties are investigated. Copolymer solutions prepared at logarithmic concentrations in a slightly endblock‐selective solvent are subjected to crystallization under different time and temperature conditions to ascertain if copolymer self‐assembly is directed by endblock crystallization or vice versa. According to transmission electron microscopy, semicrystalline aggregates develop at the lowest solution concentration examined (0.01 wt%), and the size and population of crystals, which dominate the copolymer morphologies, are observed to increase with increasing aging time. Real‐space results are correlated with small‐ and wide‐angle X‐ray scattering to elucidate the concurrent roles of endblock crystallization and self‐assembly of these unique TPEs in solution.