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)(2)C6H3)[OCMe(CF3)(2)](2)-CH}(2)C6H4 (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., ditnethyl dipropargylmalonate (M1), diethyl dipropargylmalonate (M2), di-tert-butyl dipropargyltnalonate (M3), 4-(ethoxycarbonyl)-1,6-heptadiyne (M4), 4,4-bis(hydroxymethyl)-1,6-heptadiyne (M5), and 4-(hydroxytnethyl)-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 M1(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-C6H4-CH-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).