Thermally responsive random copolymers of di(ethylene glycol) methyl ether methacrylate (M(EO)(2)MA) and oligo(ethylene glycol) methyl ether methaerylate (OEOMA) (M-n similar to 300 or 475) with varied compositions were successfully synthesized via activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP) in miniemulsion at 65 degrees C. The copolymeriza bons were controlled, generating well-defined copolymers with relatively narrow molecular weight distribution (M-w/M-n similar to 1.3-1.5) Because of the relatively high reaction temperature (65 degrees C), OEOMA was confined into oil phase, although OEOM A was miscible with water in all proportions at room temperature. The compositional study proved that the composition of the copolymers reflected the comonomer feed ratio. The cloud point of the resulting copolymer increased proportionally with the OEOMA molar content. Microgels of P(M(EO)(2)MA-co-OEOMA) were also prepared by addition of ethylene glycol dimethacrylate (EGDMA) cross-linker. Similar to their linear analogues, the phase transition temperature of the copolymer microgels can be tuned by changing OEOMA content in the microgels.