The copolymers disclosed herein are of propargyl acrylate and methacrylate. Polymerization of propargyl acrylate and methacrylate in free radical systems generally results in crosslinked or gelled products since the free radicals will activate polymerization through the acetylenic as well as through the acrylic unsaturation. Therefore the copolymers are advantageously prepared byanionic polymerization. The comonomers are those which are copolymerizable with acrylates and methacrylates inanionic polymerizations. The comonomers are styrene, its homologs and derivatives, and monounsaturated acrylates and methacrylates. The copolymers are particularly valuable for post-treatment and post-reactions, such as bromination, decaboronation, thermal and radical crosslinking, Mannich reaction with an aldehyde and ammonia or amono- or disubstituted amine, or reactions with nitrileoxides, aldehydes, ketones, epoxides, sodamide, etc, The copolymers can be tailored to give ultimate properties according to the type and the proportion of comonomers and the proportion of acetylenic groups as Well as the typeof postreactant or post-treatment.