Cucurbit[8]uril inducing supramolecular hydrogels by adjusting pH

Abstract

Novel pH and thermo-responsive supramolecular hydrogels consisting of cucurbit[8]uril (CB[8]) and poly(N-(4-vinylbenzyl)-4,4′-bipyridinium dichloride-co-acrylamide) (P4VBAM) were prepared by adjusting pH to alkalinity. In our supramolecular hydrogels system, the viologen units of P4VBAM and CB[8] could form a 1 : 2 CB[8]/viologen units binary complex with the addition of NaOH by host–guest interactions leading to forming a three-dimensional network and leading to the formation of hydrogels by the molecular recognition of CB[8] and viologen units. The viscosity of supramolecular hydrogels decreases with increasing shear rate, and these supramolecular hydrogel materials are viscoelastic on account of the dynamic nature of the binary complex with CB[8]. With the molar ratio of CB[8] to viologen units of copolymer increasing, the pore sizes within the xerogels decrease and the gel–sol transition temperature of hydrogels increases.