A copolymer suitable for use in forming a solid polymer electrolyte film comprising a first monomer represented by Formula (1): wherein n is 2 to 1,000; m is 2 to 1,000; x and y are individually 1 to 100; p is 0 to 10; and q is 1 to 10, R1 is an alkyl group having 1 to 10 carbon atoms, and A is an alkyl acryloyl group an acryloyl group, alkyl acryloyl group, methacryloyl group, alkyl methacryloyl group, a vinyl group, an allyl group, a styryl group, or a combination of two or more thereof; and a second monomer chosen from a hydroxyl-substituted alkyl acrylate, a hydroxyl-substituted alkyl methacrylate, or a combination of two or more thereof. The copolymer may be used to form a solid polymer electrolyte composition comprising (i) the copolymer, (ii) a plasticizer, and (iii) a salt. The solid polymer electrolyte may be used to form a solid polymer electrolyte film, which may be suitable for use in electrochemical devices.