말단 아민기를 갖는 폴리(N-이소프로필아크릴아미드) 및 알긴산 나트륨-g-폴리(N-이소프로필아크릴아미드)의 합성과 열응답 특성

Abstract

열응답성 고분자인 폴리(N-이소프로필아크릴아미드) (PNIPAAm) 말단에 아민기를 갖는 PNIPAAm-<TEX>$NH_2$</TEX> 및 이들 알긴산 나트륨에 그래프팅시킨 공중합체를 합성하고 이들의 여러 가지 특성들을 분석하였다. PNIPAAm-<TEX>$NH_2$</TEX>를 합성하기 위하여 N-이소프로필아크릴아미드를 라디칼 중합할 때 2-aminoethanethiol hydrochloride (AESH)를 연쇄이동제로 사용하였다. AESH 농도를 높이면 PNIPAAm-NH2의 분자량이 작아지며 PNIPAAm-<TEX>$NH_2$</TEX> 수용액의 하한임계용액온도(LCST)가 낮아졌다. N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide 및 N-hydroxysuccinimide를 사용하여 PNIPAAm-<TEX>$NH_2$</TEX>를 graft-onto 방법으로 알긴산 나트륨에 그래프팅시킨 alginate-g-PNIPAAm 공중합체 역시 온도에 따라 팽윤-수축 거동을 하였으며, PNIPAAm-<TEX>$NH_2$</TEX>보다 약간 높은 온도에서 LCST를 나타내었고, 그래프트된 PNIPAAm의 양이 많아질수록 팽윤비가 커졌다. Amino group-terminated poly(N-isopropylacrylamide) (PNIPAAm-<TEX>$NH_2$</TEX>) was synthesized via a radical polymerization of N-isopropylacrylamide (NIPAAm) using 2-aminoethanethiol hydrochloride (AESH) as a chain transfer agent. The molecular weight of the PNIPAAm-<TEX>$NH_2$</TEX> was controlled by changing the concentration of AESH. The LCST of the aqueous solution of PNIPAAm-<TEX>$NH_2$</TEX> increased slightly with increasing the AESH concentration. Alginate-g-PNIPAAm copolymer was synthesized by grafting PNIPAAm-<TEX>$NH_2$</TEX> onto sodium alginate using N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide and N-hydroxysuccinimide. The formation of the grafted copolymers was confirmed by FTIR spectroscopy, solubility in water, and SEM-EDS. Alginate-g-PNIPAAm also exhibited swelling-deswelling behavior. However, it showed a LCST at a slightly increased temperature compared to PNIPAAm. The swelling ratio of the alginate-g-PNIPAAm hydrogel increased with the increase of the grafted PNIPAAm content.