prepared from 3,3-di(prop-2-ynyl)oxetane and phenylacetylene was representatively polymerized in the presence of BF3 catalyst. A cationic random copolymerization of one of 1,3-dihydrospiro[indene-2,3′-oxetane] derivatives with 3-ethyl-3-(phenoxymethyl)oxetane and radical random copolymerization of diethyl 5-(4-vinylphenyl)-1H-indene-2,2(3H)-dicarboxylate with styrene have also been demonstrated.