Allylidene Monomers: Anionically Polymerizable 1,1-Disubstituted 1,3-Diene Derivatives

The anionic polymerizations of a series of allylidene monomers, 1,3-butadiene derivatives with substituents on the 1,1-position such as dimethyl (DMBd), cyclohexane ring (AC6), cycloheptane ring (AC7), 2,2,5,5-tetramethylcyclopentane ring (ATMC5), and bornane (ABn), proceeded quantitatively either in benzene at 40 degrees C with sec-BuLi for 17-24 h or in THF with sec-BuLi at 0 or 30 degrees C for 48-168 h. The obtained polymers from allylidene monomers possessing ring structures had predictable molecular weights based on the molar ratios between the monomer and the initiators and narrow molecular weight distributions (M-w/M-n < 1.09). Based on H-1, C-13, DEPT135, and HMQC NMR spectroscopy results, the microstructures of the resultant polymers were found to be strongly dependent on the bulkiness of the substituent. Allylidene monomers with less bulky substituents such as DMBd, AC6, and AC7 resulted in polymers wherein the 1,4-trans microstructure was predominant. In contrast, under the same polymerization conditions, ATMC5 and ABn monomers exclusively resulted in polymers with the 3,4-microstructure. The polymers exhibited a wide range of glass transition temperatures (-40 to 194 degrees C), which depended on the bulkiness of the monomer used.