Abstract: A block copolymer containing one or more polyoxyethylene blocks and one or more polyoxy(higher alkylene) blocks, wherein at least some of the blocks are linked together by an oxymethylene group, can be prepared by reacting one or more dihydroxy terminated polymers selected from poly(ethylene glycol), poly(higher alkylene glycol), and block copolymers thereof in solution with a dihalomethane in the presence of a base. Such copolymers can be used as surfactants and surface modifiers. The reaction can be conducted at ambient temperature, and does not require the addition of heat.