The temperature sensitive copolymer of microsize hydrogels consist of N-isopropylacrylamide (NIPAM) and 2-acrylamido-2 methylpropanesulphonic acid (AMPS) have been synthesized by soap free emulsion polymerization method in presence of polyethylene glycol (PEG) as macroinitiator and N, N´-methylenebisacrylamide (NMBA) as cross-linker. In this work, Dynamic Light Scattering (DLS), Transmission Electron Microscope (TEM) and Atomic Force Microscope (AFM) technique were used to characterize copolymer microgels. The particle sizes observed by TEM were spherical with diameter around 103nm to 133.1nm. While DLS measurement shows narrow particle size distribution with hydrodynamic diameter from 343.6nm to 528 nm at temperature 25oC and 132.5nm to 414.4nm at temperature 50oC depending on AMPS content in microgels samples. The swelling ratio (α) and temperature sensitive properties of microgels were decreased with increasing AMPS content in feed composition. The volume phase transition of microgels in aqueous solution was investigated by mean of DLS. The transition temperature was determined from the first derivative curve of the hydrodynamic diameter with respect to temperature and practically found to be continuous. The volume change in the particles associated with temperature dependent hydrodynamic diameter of microgel particles. Further, the swelling data obtained from DLS measurements are analyzed using theoretical model Flory and Rehner. The description of volume fraction (Ø)as a function of temperature by the Flory- Rehner is applicable to 2mol% AMPS content microgel sample only.
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