Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, 27695, USA.
Advanced Photon Source, Argonne National Laboratory, Argonne, IL, 60439, USA.
Macromol Rapid Commun. 2021 Nov;42(21):e2100442. doi: 10.1002/marc.202100442. Epub 2021 Sep 22.
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.
苯乙烯类热塑性弹性体（TPEs）以具有玻璃状末端嵌段和橡胶状中间嵌段的三嵌段共聚物的形式存在，占据了全球 TPE 市场的最大份额，通常依赖于末端嵌段的微相分离和随后形成的刚性微区来确保令人满意的网络稳定。在这项研究中，研究了一种相对较新的结晶 TPE 家族的形态特征，它由聚乙烯末端嵌段和由苯乙烯和（乙烯-丁烯）部分组成的无规共聚物中间嵌段组成。在略有末端嵌段选择性的溶剂中以对数浓度制备的共聚物溶液在不同的时间和温度条件下进行结晶，以确定共聚物自组装是由末端嵌段结晶还是相反来指导。根据透射电子显微镜，在研究的最低溶液浓度（0.01wt%）下，形成半结晶聚集体，并且观察到控制共聚物形态的晶体的尺寸和数量随着老化时间的增加而增加。实空间结果与小角和广角 X 射线散射相关联，以阐明这些独特 TPE 在溶液中末端嵌段结晶和自组装的并发作用。
