Acceleration of deswelling for poly(N-isopropylacrylamide) gel prepared on the hydrophobic surface of the matrix

The surface property of vessels (matrices) for gelation affected the deswelling process of thermosensitive poly(N-isopropylacrylamide) (NIPAAm) gels. Cracks were frequently observed on the gel surface in the process of deswelling. The outbreak of cracks caused a change of the deswelling rates. The deswelling rate was accelerated in the case of the gel prepared in a matrix made of hydrophobic polytetrafluoroethylene (PTFE) or silicone, while no acceleration for deswelling was observed in the case of the gel prepared on hydrophilic glass. The probability of cracking and the deswelling rate increased with increasing hydrophobicity of the matrix surface. The storage moduli (E′) of the swollen gels (22°C) prepared on glass and PTFE as the matrices were 50 and 18 kPa, respectively. The deswelling time for gels prepared in PTFE matrix decreased from 400 (gels prepared on glass) to 50 min without cracking. The hydrophobic matrix was suitable for preparation of the fast-responsive poly(NIPAAm) gel.