Preparation and polymerization of methylenecyclobutene and 1‐methyl‐3‐methylenecyclobutene

Methylenecyclobutene (MCB) and 1‐methyl‐3‐methylenecyclobutene (MMCB) were synthesized, characterized, and polymerized by anionic and cationic initiators. Structural analyses of the polymers were carried out by infrared and NMR spectros‐copy. The cationic polymerization of MCB appeared to proceed entirely by a 1,5‐propagation mechanism to form low molecular weight polymers in low yields. Anionic polymerization of this monomer, on the other hand, proceeded primarily through a 1,2‐propagation path, again forming only low molecular weight polymeric products in low yield. In contrast to MCB, the methyl‐substituted monomer, MMCB, polymerized readily with cationic initiators to produce unusually high molecular weight polymers in high conversions. On the basis of both infrared and NMR spectroscopic analyses, it was concluded that the polymers also contained essentially only 1,5‐addition repeating units. Anionic initiators such as n ‐BuLi were unable to induce polymerization of this monomer, but polymerization by Ziegler‐Natta catalysts proceeded readily to yield polymers virtually identical in structure and molecular weight to those obtained with cationic initiators.