Development of a Molecular Recognition Separation Membrane Using Cyclodextrin Complexation Controlled by Thermosensitive Polymer Chains

A molecular recognition polymer membrane that uses a thermosensitive polymer with a host receptor has been developed. The membrane exhibits a high selectivity, in which β-cyclodextrin (CD) moieties recognize a specific guest molecule, and poly( N -isopropylacrylamide) [P(NIPAM)] controls the molecular recognition ability. A pendant CD monomer was introduced into the linear P(NIPAM) chain, and this resulted in a faster volume change from the increased diffusivity of water over the normal cross-linked gel. The copolymer was fixed onto the pore surface of a porous polyethylene substrate using plasma-graft polymerization. The temperature dependence of the binding constant of 8-anilino-1-naphthalenesulfonic acid ammonium salt showed a drastic decrease at temperatures above the lower critical solution temperature of the copolymer chains. The defining mechanism of the inclusion properties is the steric hindrance of the host−guest interaction, which depends on the thermosensitive volume change of the grafted chains. This membrane shows temperature-controlled molecular recognition and can be applied as a novel affinity separation system.