Synthetic hydrogels (10): anomalous transport behaviour in crown ether-containing hydrogel membranes

The physical immobilisation of a range of crown ethers within hydrogel memb ranes of a range of water contents has been examined. The efficiency of the immobilisation process increases with increasing size of the crown and dec reasing water content (and thus mean pore radius) of the hydrogels. Success ful occlusion was achieved with dicyclohexano-18-crown-6 in a poly(2-hydrox yethyl methacrylate) membrane containing 10% ethyleneglycol dimethacrylate crosslinking agent. Of various ions examined with this modified membrane, K + was subject to the greatest modulation of its transport behaviour; this b eing characterised by a substantial initial induction period followed by a steady state rate that never attained the value achieved with unmodified me mbranes of a similar water content. This behaviour is quite novel in compar ison with ionophore modulated transport in hydrophobic membranes but bears some resemblance to that of gas permeation in glassy polymers. (C) 2000 Els evier Science Ltd. All rights reserved.