N-Isopropylacrylamide (NIPA)/N-tert-butylacrylamide (NTBA) submicron-sized copolymer gel particles of various compositions were prepared by precipitation polymerization and the swelling behaviors of the gels were studied with different compositions and temperature using photon correlation spectroscopy (PCS). The experimental data showed that the volume transition temperature (T-v) of the gels varied with the amount of monomers having different hydrophobicity added.