가교도가 다른 열민감성 Poly(N-isopropylacrylamide) 수화겔의 팽윤 및 수축 거동

Abstract

Poly(N-isopropylacrylamide)(PNIPAAm) hydrogels were synthesized via radical polymerization of N-isopropylacrylamide in aqueous medium using ammonium persulfate and N,N'-methylenebisacrylamide (MBA) as an initiator and a crosslinking agent, respectively. PNIPAAm hydrogels exhibited a critical gel transition temperature (CGTT) at 32~34 oC. Swelling and deswelling behaviors of the hydrogels with different crosslinking densities were analyzed by measuring swelling ratio below and above CGTT. The swelling ratio of the hydrogel below CGTT decreased with increasing MBA concentration, while that above CGTT increased. As MBA concentration increased, the micropore size decreased, however, the number of micropore increased slightly in the freeze-dried hydrogels swollen in water at 25 oC (below CGTT) before drying. The micropore became smaller and denser in the deswollen state. The swelling ratio of the hydrogels decreased slightly with the repeated swelling and deswelling treatment.