Thermo-Sensitivity of N-Isopropylacrylamide Copolymers Containing Hydrophobic Units

Random copolymers of N-isopropylacrylamide(NIPAM) with four types of acrylate,namely,methyl methacrylate(MMA),ethyl acrylate(EA),butyl acrylate(BA) and butyl methacrylate(BMA),were prepared respectively through solution free radical polymerization.Thermo-sensitivity of aqueous solutions of the copolymers obtained was investigated by turbidity fest and dynamic light scattering measurement.It is found that the structure and content of acrylic comonomer strongly affect the LCST of the copolymers,i.e.,the larger the carbon number in the ester moiety of the acrylate the lower the LCST,and the alkyl group located at the ester moiety is more effective in lowering the LCST than the alkyl at the α position of the acrylate.Conclusively,water soluble thermo-sensitive copolymer with a lowered and designed LCST can be obtained by random copolymerization of NIPAM with a selected acrylate.