Carbanionic Copolymerization-Induced Crystallization

Novel semicrystalline copolymers were successfully synthesized by alternating carbanionic copolymerization in this work. During alternating carbanionic copolymerization of 9-methylene-9H-thioxanthene (MTAE) and 2,3-dimethylbuta-1,3-diene (DMBD), insoluble polymers were observed and carefully characterized with wide-angle X-ray scattering (WAXS), wide-angle X-ray diffraction (WAXD), and polarizing microscopy (POM). All results confirmed that novel semicrystalline alternating copolymers were obtained, and the corresponding degree of crystallinity (XC) was greater than 60%. To investigate how the MTAE-alt-DMBD copolymers underwent crystallization, alternating copolymers of MTAE/isoprene (Ip), 1,1-diphenylethylene (DPE, without bridging plane structure)/DMBD, 9,9-dimethyl-10-methylene-9,10-dihydroanthracene (MMAE, with bridging planar structure)/Ip, and MMAE/DMBD were synthesized. All copolymers are alternating copolymers and have a higher trans structure content of the dienes in the chain (greater than 62%), but only MMAE-alt-DMBD exhibited crystalline properties. This suggests that the bridging plane structure of MTAE and MMAE and the appropriate diene steric hindrance play a crucial role in the crystallization process. Probably because of the bridging plane structure of MTAE or MMAE and the steric hindrance of DMBD, the structural units formed a compact and ordered regular arrangement during the copolymerization process. Novel crystalline copolymers and the behavior of carbanionic copolymerization-induced crystallization (CCPIC) were first revealed in this study. It is also believed that this will open a new field involving syntheses of crystalline polymers and bring new vitality to the study of living anionic polymerization.