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

The surface property of vessels (matrices) for gelation affected the deswel ling process of thermosensitive poly(N-iso-propylacrylamide) (NIPAAm) gels. Cracks were frequently observed on the gel surface in the process of deswe lling. 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 a cceleration for deswelling was observed in the case of the gel prepared on hydrophilic glass. The probability of cracking and the deswelling rate incr eased with increasing hydrophobicity of the matrix surface. The storage mod uli (E') of the swollen gels (22 degreesC) prepared on glass and PTFE as th e matrices were 50 and 18 kPa, respectively. The deswelling time for gels p repared in PTFE matrix decreased from 400 (gels prepared on glass) to 50 mi n without cracking. The hydrophobic matrix was suitable for preparation of the fast-responsive poly(NIPAAm) gel. (C) 2001 Elsevier Science B.V. All ri ghts reserved.