Abstract: Cationic copolymerization of trioxane and trimethylolpropane (TMP) formal or its ester derivatives yields acetal copolymers having pendant functional groups. The TMP formal or ester derivatives of TMP formal may therefore include functional groups selected from hydroxyl or ester moieties which are protected and thus survive the copolymerization with trioxane. These groups may then be present as functional reactive sites for the subsequent synthesis of block copolymers and/or to chemically bind modifiers to the acetal copolymer backbone, for example.