In effort to address challenges in the efficient synthesis of highly functional block copolypeptides, we report use of a combination of functional monomer polymerization and postpolymerization modification to obtain new double hydrophilic block copolypeptides with desirable properties. We prepared copolymers that contain discrete hydrophilic, nonionic poly(L-methionine sulfoxide) and Ca2+ ion binding poly(L-phosphonohomoalanine) segments. The facile and selective postpolymerization conversion of inexpensive, readily prepared poly(L-methionine) segments into nonionic, hydrophilic poly(L-methionine sulfoxide) segments reduces the need for use of combinations of protecting groups. The complex copolypeptides prepared using this strategy were able to promote formation of CaCO3 microspheres with tunable polymorphism. (C) 2016 Wiley Periodicals, Inc.