Temperature-induced phase transition of poly(N,N-dimethylaminoethyl methacrylate-co-alkyl acrylamide)

Abstract

[Part A] Novel semi-interpenetrating polymer networks (IPNs) constructed with sodium alginate (SA) and poly (N,N-dimethylaminoethyl methacrylate (DMAEMA)-co-acrylamide (AAm)) have been prepared in an attempt to provide temperature-sensitive polymer systems. The role of SA is to provide a crosslinked network and that of poly DMAEMA-co-AAm is to provide temperature-sensitivity to the polymer network. Firstly, poly DMAEMA-co-AAm were prepared to demonstrate a temperature-induced phase transition. Poly DMAEMA has a lower critical solution temperature (LCST) around 50 ℃ in water. With copolymerization of DMAEMA with AAm, the LCST shift to the lower temperature was observed, probably due to the formation of hydrogen bonds between amide and N,N-dimethylamino groups. FT-IR studies clearly showed the formation of hydrogen bonds which protect N,N-dimethylamino groups from exposure to water and result in a hydrophobic contribution to the LCST. Two types of polymer gels were prepared. The one is a crosslinked gel composed of poly DMAEMA-co-AAm. The other is a composite gel composed of SA and poly DMAEMA-co-AAm which have semi-IPNs structure. Although both polymer systems exhibited the temperature-sensitivity, more rapid and significant temperature-sensitivity was observed in the case of composite gels, which exhibited significant temperature-sensitive release pattern in response to pulsatile temperature change. [Part B] Polymer gels composed of N,N-dimethylaminoethyl methacrylate (DMAEMA) and acrylamide (AAm) (or ethylacrylamide (EAAm)) were prepared to observe temperature-sensitive swelling behavior. The temperature dependence of equilibrium swelling of poly (DMAEMA-co-AAm) aqueous solution as a function of chemical composition. However, poly (DMAEMA-co-AAm) gel did not show the similar trend to poly (DMAEMA-co-AAm) gel. In the case of poly (DMAEMA-co-AAm), the hydrogen bond, which played an important role in controlling the LCST, was maintained with formation of the gel ...