An Autonomous Phase Transition−Complexation/Decomplexation Polymer System with a Molecular Recognition Property

We describe a novel polymer that exhibits a coordination of molecular recognition and actuation functionalities within itself. This coordination induces an autonomous polymer shrinking/swelling phase transition, accompanied by the complexation/decomplexation of a guest molecule. The artificial polymer exhibited autonomous behavior induced by molecular recognition, which is a unique function of the living body. We used β-cyclodextrin (CD) as the molecular recognition moiety, and poly( N -isopropylacrylamide) (NIPAM) as the actuation moiety in the polymer. Both these components affect each other: complexation between CD and its guest molecule 8-anilino-1-naphthalenesulfonic acid ammonium salt (ANS) induces a phase transition in the NIPAM chain. Meanwhile, the phase transition in the NIPAM chain affects CD/ANS complex formation. Coordination of these two phenomena induces an autonomous polymer shrinking/swelling behavior with CD/ANS complexation/decomplexation. We successfully observed this behavior using UV−vis and fluorescence spectroscopy.