For this study, a new epithio‐1,1‐diphenylethylene (DPE) derivative, namely, 9‐Methylene‐9H‐thioxanthene (MTAE), is synthesized, and its copolymerization reactions are investigated, showing distinctive features in living anionic copolymerization. At room temperature and hydrocarbon solvents, MTAE cannot be copolymerized with styrene (St) but can be copolymerized with 1,4‐divinylbenzene (DVB), forming a linear alternating copolymer. Based on this finding, ter‐polymerization of MTAE, DVB and St is conducted to generate a special alternating structure. Additionally, MTAE is found to exhibit fairly high reactivity in copolymerization with Isoprene (Ip) under the same conditions. An alternating sequence of alt‐MTAE/Ip containing high trans‐geometric Ip content (76% of trans‐1,4) and a di‐block sequence of alt‐MTAE/Ip‐b‐Ip are easily obtained. Its experimental reactivity ratio with Ip is investigated via the in situ 1H NMR method (rIp = 0.28), and the corresponding kinetic behaviors and sequence structure are elucidated. Finally, the origin of the effect of MTAE on the isomerism of Ip during chain propagation is investigated by density functional theory (DFT) calculations, and it is found that the bridge sulfur atom in MTAE interacts strongly with living species. This special finding provides a novel approach for the sequence regulation, precise functionalization, and stereo‐structure control in living anionic polymerization originating from monomer structure design.

A 1,1-diphenylethylene (DPE) derivative with an alkoxysilyl group (DPE-SiOEt) was synthesized. It was end-capped with poly(styryl)lithium (PSLi) and then copolymerized with styrene via living anionic polymerization (LAP) in a non-polar solvent at room temperature. The observed side coupling reaction was carefully investigated by end-capping the polymer. Changes in molecular weight support the plausibility of a mechanism involving living anionic species (PSLi or lithiated DPE-end-capped polystyrene, PSDLi) and the alkoxysilyl groups. Through a series of copolymerizations with different feed ratios, the kinetics of the side coupling reaction were also studied. The results showed that the side reactions could be controlled using an excess feed of DPE-SiOEt, a potentially useful strategy for the synthesis and application of well-defined alkoxysilyl-functionalized polymers via LAP.