Poly N-isopropyl Acrylamide Polymer Synthesis And Characterization,

The synthesis of Poly(N-isopropylacrylamide) was studied in various conditions such as in various solvents,initiators and different polymerization temperatures and time. Poly(N-isopropylacrylamide-co-methylacrylate) ,Poly(N-isopropylacrylamideco-ethylacrylate),Poly(N-isopropylacrylamide-co-butylacrylate),Poly(Nisopropylacrylamide-co-arylic acid) and Poly(N-isopropylacrylamide-co-acryamide) were synthesized by using solution free radical polymerization technique.The segmental structures obtained, monomer抯 compositions in copolymers were characterized using infrared spectroscopy and DSC technology. The study also focused on the influence of copolymers?chain structure, different pH value, and concentrations of NaCI electrolyte solution on thermo-sensitive behaviors of these polymers. Starting at a far higher temperature of samples?lower critical solution temperature (LCST), the swelling ratios of both homo- and copotymers were measured by lowering swelling temperature gradually under an equilibrium state. It is the first time in this study that a concept of a lower critical gel formation temperature (LCGFT) for these polymers was proposed. The results indicated, that although LCGFT possesses the similar significance comparing with LCST, it is more valuable in practical applications.Finally, the deliver and release rule of neutral red which was loaded into the Poly(N-isopropylacrylamide) and Poly(N-isopropylacrylamide-comethylacrylate) was studied in phosphate buffer pH=7.O by the method of gradiently controlling temperature. The results suggested that the Poly(N-isopropylacrylamide) possesses the potential to control the dilivery of small molecule via temperature variation.