Poly(N,N-dimethylacrylamide-co-allyl methacrylate) (DMA-co-AMA) copolymers were prepared by the copolymerization of NN-dimethylacrylamide with allyl methacrylate (AMA). The methacryloyl group of AMA reacted preferentially, and this resulted in pendant allyl groups along the copolymer chains. Aqueous solutions of these DMA-co-AMA copolymers were thermoresponsive and showed liquid-liquid phase transitions at temperatures that depended on the AMA content. Hydrogel microspheres were prepared from these thermally phase-separated liquid microdroplets by the free-radical crosslinking of the pendant allyl groups. The morphologies of the resulting thermoresponsive microspheres as a function of the reaction temperature and the amount of the initiator were examined. (c) 2005 Wiley Periodicals, Inc.