Regulation from gradient to near periodic sequence during anionic copolymerization of styrene and dimethyl-[4-(1-phenyl-vinyl)phenyl]silane (DPE-SiH)

Abstract

A facile strategy for achieving sequence-controlled polymers with a sufficient molecular diversity is of great importance. The periodic and gradient copolymers of styrene (St) and dimethyl-[4-(1-phenylvinyl)phenyl]silane (DPE-SiH) obtained through the living anionic copolymerization (LACOP) under the variable feed ratios (St:DPE-SiH = 0.5–4) in a nonpolar solvent without additives were well studied in our prior work (Zhang et al., 2019) [34]. Herein, a further study on the critical feed ratio of St (S) and DPE-SiH (D) at 3:1 is performed during the LACOP, where a peculiar interest lies whether a novel sequence will emerge between the periodic and gradient sequence with the additives of t-BuOK and THF. As the whole chain propagation process is monitored using in situ1H NMR spectroscopy, the copolymerization kinetics, i.e., the reactivity ratio (r), apparent rate parameters (Kapp.), and the copolymer microstructures are investigated. Both t-BuOK and THF favors the incorporation of St into LACOP, as the trends rSt = 0.1 (gradient sequence without additives) < rSt = 0.22–0.29 (near periodic sequence for t-BuOK) < rSt = 0.7–0.76 (near periodic sequence for THF). The near periodic sequences exhibit different periodicities distributed as “DSSDSS” for the t-BuOK and “DSSSDSSS” for the THF in the major. The strategy achieves the sequence regulation from statistically gradient to near periodic copolymers. Furthermore, we observe that the near periodic copolymers exhibit the similar Tg values but over the gradient copolymers.