Binuclear Schrock-Type Alkylidene-Triggered ROMP and Cyclopolymerization of 1,6-Heptadiynes:  Access to Homopolymers and ABA-Type Block Copolymers

The molybdenum-based binuclear Schrock-type initiator 1,4-{Mo(N-2,6-(2-Pr)2C6H3)[OCMe(CF3)2]2CH}2C6H4 (1) was used for the ring-opening metathesis polymerization (ROMP) of norborn-2-ene (NBE) and for the cyclopolymerization of a series of 1,6-heptadiynes, i.e., dimethyl dipropargylmalonate (M1), diethyl dipropargylmalonate (M2), di-tert-butyl dipropargylmalonate (M3), 4-(ethoxycarbonyl)-1,6-heptadiyne (M4), 4,4-bis(hydroxymethyl)-1,6-heptadiyne (M5), and 4-(hydroxymethyl)-1,6-heptadiyne (M6) to form the corresponding M n−X−M n block copolymers. The polymerization systems M1 - 1 (monomer M1 polymerized by the action of initiator 1) and M2-1 fulfilled the criteria of a class IV and class V living system, respectively. Poly-M1, poly-M2, poly-M3, and poly-M4 consisted of 40%, 50%, 58%, and 32% 1,2-(cyclopent-1-ene)vinylenes and 60%, 50%, 42%, and 68% 1,3-(cyclohex-1-ene)methylidenes, respectively. Finally, the block copolymers M2 25-b-M1 25-CH-1,4-C6H4-CH-M1 25-b-M2 25, M1 35-b-M2 35-CH-1,4-C6H4-CH-M2 35-b-M1 35, M1 25-b-NBE35-CH-1,4-C6H4CH-NBE35-b-M1 25, M2 40-b-NBE26-CH-1,4-C6H4-CH-NBE26-b-M2 40, NBE50-b-M1 35-CH-1,4-C6H4-CH-M1 35-b-NBE50, and NBE30-b-M2 25-CH-1,4-C6H4-CH-M2 25-b-NBE30 were prepared. Using AFM, films of M1 25-CH-1,4-C6H4-CH-M1 25 were found to be homogeneous, while phase separation was observed for M1 25-b-NBE35-CH-1,4-C6H4-CH-NBE35-b-M1 25.