Synthesis and polymerization of vinyl esters and vinyl ethers having bulky substituents

Abstract In order to clarify the effect of bulky substituents on the stereoregulation of vinyl monomers, vinyl‐1‐adamantanecarboxylate and vinyl 1‐adamantyl ether were synthesized and polymerized by radical and cationic mechanisms, respectively. As open‐chain models of the adamantyl group, vinyl trialkylacetate (alkyl = ethyl, n‐propyl, and n‐butyl) and vinyl tri‐n‐propylcarbinyl ether were also synthesized and polymerized. The adamantly group in the vinyl ester favored syndiotactic propagation in a manner similar to the trimethylcarbinyl group. Higher homologs of tri‐n‐alkylcarbinyl group showed higher syndiotacticity but this effect was saturated in higher members of the series. The effect of the adamantyl group in vinyl ether was similar to that of the tert‐butyl group, leading to high isotacticity on cationic polymerizations in nonpolar solvents and to atactic polymers in polar solvents, but the tri‐n‐propylcarbinyl group was found unique in leading to what was assumed to be a heterotactic polymer. Polymers with the adamantyl group showed much higher softening points than polymers of the corresponding open‐chain groups.