Cationic copolymerization of a functional aldehyde, methyl glyoxylate (GM), with a seven-membered cyclic acetal, 1,3-dioxepane (DXP), leads to polyacetals containing ester side groups that may be used for functionalization. Partial replacement of the ester groups in GM-DXP copolymers with amide groups by reaction with alpha-amino-omega-methoxypoly(oxyethylene) (Jeffamine) led to graft copolymers, and the remaining ester groups could easily be hydrolyzed to carboxylate groups. The resulting water-soluble graft copolymers, containing poly(oxyethylene) side chains and carboxylate groups along the main chain, belong to the class of double hydrophilic copolymers that are recently studied as modifiers of the processes occurring at the interface between crystal surfaces and surrounding solution.