Morphological Studies of Solution‐Crystallized Thermoplastic Elastomers with Polyethylene Endblocks and a Random‐Copolymer Midblock. Issue 21 (22nd September 2021)

• Record Type: Journal Article
• Authors: Yan, Jiaqi; Lee, Byeongdu; Smith, Steven D.; Spontak, Richard J.
• Is Part Of: Macromolecular rapid communications. Volume 42:Issue 21(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-09-22
• Subjects: block copolymers -- directed self‐assembly -- polymer morphology -- solution crystallization -- thermoplastic elastomers; Macromolecules -- Periodicals; Polymers -- Periodicals; Chemistry -- Periodicals; 547.705
• DOI: 10.1002/marc.202100442
• Languages: English
• ISSNs: 1022-1336

Abstract

Abstract: 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. Abstract : Thermoplastic elastomers possessing polyethylene endblocks and a random‐copolymer midblock composed of styrene and ethylene‐ co ‐butylene undergo concurrent self‐assembly and crystallization from solution. The transmission electron microscopy image displayed here reveals an aggregate possessing unstained crystals, whereas the small‐angle (top) and wide‐angle (bottom) X‐ray scattering profiles indicate the solution concentrations at which self‐assembly and crystallization, respectively, are first observed.