An attempt to modify N-isopropylacrylamide hydrogels exhibiting a thermoshrinking volume phase transition of the lower critical solution temperature type in aqueous solution has been made in this work via the adjustment of crosslinking density and/or the introduction of acidic monomers within the gel structure by copolymerization with acrylic acid or methacrylic acid. The increase in crosslinking density twas resulted in the decrease in water content and the increase in phase transition temperature of the resulting NIPAAm gels. The introduction of acidic monomers within the gel network has also been found to cause the overall increase in water content and the sensitive change in the phase transition temperature. While in a lower pH region (pH<4) the decrease in water content of gels and the more favorable thermosensitive phase transition behavior were observed, at pH>5 the considerable decrease in thermosensitivity and the abrupt increase in both water content and degree of volume swelling were observed, as confirmed by the DSC measurements.

LCST를 갖는 N-isopropylacrylamide (NIPAAm)수화겔을 가교도의 조절 빛 acrylic acid(AAc), methacrylic acid(MAAc)와의 공중합에 의하어 개질하였다. 가교밀도의 증가가 함수율의 감소와 전이온도의 상승을 가져옴이 확인되었다. 이온화기를 가진 산성 단량체를 겔 구조속에 도입하므로써 전반적인 함수율의 증가와 열민감성의 변화를 확인하였다. pH 4이하의 영역에서는 겔의 함수율 감소와 열민감성 수축의 정도가 커졌으며 전이온도가 낮아지는 현상이 관측되었으나, 보다 높은 pH 영역에서는 열응답성이 상당히 떨어지고 전이온도가 높아지는 경향을 띠었는데 이들 현상은 DSC를 이용한 전이열 측정의 결과로부터 확인되었다.

Keywords: responsive hydrogel; N-isopropylamide; ohase transition behavior