Synthesis and characterization of temperature and pH responsive Poly(N-isopropylacrylamide) copolymer

Temperature responsive poly(N-isopropylacrylamide) (PNIPAM) exhibits a lower critical solution temperature (LCST) of approximately 32 °C in aqueous solution, below which the polymer is water soluble and above which it becomes water insoluble. The LCST of PNIPAM copolymer increases responding to hydrophilic block acrylic acid (AA). The copolymer is pH and temperature responsive. The duel responsive copolymer, poly(N-isopropylacrylamide-co-acrylic acid), was synthesized via solution polymerization and characterized by IR, GPC. Subsequently, the composition of copolymer was assayed by titration. The lower critical solution temperature (LCST) of the copolymer reached a higher temperature not only with the ratio of AA segments increase, but also with the pH increase. As the ratio of AA segments is higher, LCST significantly increased upon increasing pH values. Therefore, the LCST of the copolymer will change by changing the ratio of AA segments and pH value, which has application in drug delivery.