Re-entrant volume phase transition of hydrogel membrane of microcapsule

Abstract

Reentrant volume phase transition of hydrogel wall membrane of microcapsules (MC) was first observed using MC suspensions consisting of poly(L-lysine-alt-terephthalic acid) wall and aqueous inner and outer solutions with different pHs. To analyze the dynamics of the reentrant phase transition, we extended the theory for the swelling and the shrinking dynamics of the microcapsule gel (Langmuir 2003, 19, 4051-4054). In the theory, the microcapsule size and the force constant for the driving force which give rise to the size relaxation were chosen as the thermodynamic variables. The time course of the cross-sectional area of the microcapsules fitted well to the theoretical equations, and the time constants determined as the fitting parameters were discussed in terms of the force constant relaxation and the size relaxation.3