Living Ring-Opening Metathesis Polymerizations of 3,4-Disubstituted Cyclobutenes and Synthesis of Polybutadienes with Protic Functionalities

The compounds bis(phenylmethyl) cis -cyclobutene-3,4-dicarboxylate ( 1 ) and cis -3,4-bis(2-oxa-3-phenylpropyl)cyclobutene ( 2 ) were polymerized by ring-opening metathesis polymerizations using Mo(CHC(CH 3 ) 2 R 1 )(NC 6 H 3 -2,6-diisopropyl)(OR 2 ) 2 (R 1 = Ph, R 2 = C(CH 3 ) 3, I; R 1 = CH 3, R 2 = C(CF 3 ) 2 CH 3, II ) as the initiator. For I as initiator, no chain termination or chain transfer processes were observed during the lifetime of the polymerization, showing that the polymerizations of 1 and 2 by I are living. Block copolymers containing 1 and 2 and diethyl cis -cyclobutene-3,4-dicarboxylate ( 5 ) were synthesized. The double bonds of the poly- 2 and poly- 3 ranged from 70% trans to 92% cis depending on the initiator and monomer used. Poly- 1 and poly- 2 were treated with iodotrimethylsilane and converted to the acid-functionalized and alcohol-functionalized poly- 4 and poly- 6, respectively. Block copolymers were treated with iodotrimethylsilane and converted to materials with blocks bearing protic functionalities and blocks bearing polar aprotic groups.