The process disclosed herein is the bromination of polymers of propargyl methacrylate and the brominated products produced thereby. Propargyl methacrylate has a terminal acetylenic group which upon bromination gives anethylenic dibromo derivative which is hydrolytically stable. In comparison the derivative obtained upon dibromination of a polymer of allyl methacrylate gives dibromopropyl methacrylate repeating units whereas the dibromonation of propargyl methacrylate gives dibromoallyl methacrylate repeating units. In view of the ethylenic group in the dibromoallyl radical, the bromine atoms are very resistant to hydrolysis whereas the bromine in the dibromopropyl radical is much more susceptible to hydrolysis. Moreover, the bromination of a terminal acetylenic group proceeds with much greater facility and more thoroughly under milder conditions than is the case when the acetylenic group is a non-terminal acetylenic such as 2-butyn-1-yl acrylate or methacrylate.