Molecular recognition of alcohol by volume phase transition of cross-linked poly(2-methacryloyloxyethyl phosphorylcholine) gel

Abstract

The swelling behavior of a cross-linked poly(2-methacryloyloxyethyl phosphorylcholine (MPC)) gel in various water/alcohol mixtures was investigated. When the poly(MPC) gel was immersed in various water/alcohol mixtures, a change in the gel volume was observed depending not only on the composition of the alcohol in the mixture but also on the chemical structure of the alcohol. In water/monohydric alcohol mixtures, the poly(MPC) gel had an irregular swelling behavior with a change in the composition of the alcohol, showing the so-called reentrant volume phase transition. These volume phase transition strongly depended on a hydrophobic group, i.e. the polarity of the alcohol. On the other hand, polyhydric alcohol (diol or triol) did not affect the swelling of the poly(MPC) gel even when the composition of the alcohol was changed.These results suggest that water molecules hydrated on the poly(MPC) chains were withdrawn by hydration of the alcohol molecules and the volume of the poly(MPC) gel decreased. That is in good agreement with the hydration ability of the alcohol and its polarity. Thus, the poly(MPC) gel could recognize a difference in the polarity among the alcohol molecules.