Novel Features of 9‐Methylene‐9H‐thioxanthene (MTAE) in Living Anionic Polymerization

Abstract

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.

Carbanionic Copolymerization-Induced Crystallization

“…To explore the relationship between the crystallization behavior of MTAE- alt -DMBD and its polymer chain structure, our previous work on MTAE- alt -Ip was repeated, namely, the composition of the conjugated diene in the copolymer was tuned to Ip (see Scheme ). Setting the feed ratio of MTAE/Ip/Li as 20:20:1 (see Run 5 in Table ), the specific aggregation process and analytical method were the same as those in the previous work . In the whole polymerization reaction, the solution system was in a uniform and transparent state, and the product was soluble in benzene.…”

“…Setting the feed ratio of MTAE/Ip/ Li as 20:20:1 (see Run 5 in Table 1), the specific aggregation process and analytical method were the same as those in the previous work. 28 In the whole polymerization reaction, the solution system was in a uniform and transparent state, and the product was soluble in benzene. The corresponding M n and PDI of Run 5 were characterized by SEC as 6.7 kg mol −1 and 1.17, respectively (see Figure 1b).…”

“…Significantly, high stereoselectivity was found in copolymerization with Ip, and a 75% trans-1,4 microstructure of the Ip unit was reached in the alternating structure, which was attributed to strong S−Li interactions occurring during chain propagation. 28 Interestingly, when we used MTAE containing a bridging sulfur atom as a comonomer for alternating copolymerization with 2,3-dimethylbuta-1,3-diene (DMBD), a crystalline copolymer was prepared. This is the first report of a crystalline polymer with an alternating sequence of nonpolar monomers prepared by living anionic copolymerization under mild conditions.…”

“…In response to this problem, a new epithio -DPE derivative, 9-methylene-9 H -thioxanthene (MTAE), was synthesized in our previous work, and high reactivity (corresponding r Ip = 0.28) was exhibited in anionic copolymerization with Ip in benzene at room temperature. Significantly, high stereoselectivity was found in copolymerization with Ip, and a 75% trans -1,4 microstructure of the Ip unit was reached in the alternating structure, which was attributed to strong S–Li interactions occurring during chain propagation …”