Dual Stimuli-Responsive Supramolecular Hydrogel Based on Hybrid Inclusion Complex (HIC)

A novel dual-responsive supramolecular hydrogel composed of an azobenzene (AZO) end- functionalized block copolymer PDMA-b-PNIPAM (AZO-(PDMA-b-PNIPAM)) and β-cyclodextrin-mod- ified CdS quantum dot (β-CD@QD) has been demonstrated. Based on the host-guest inclusion complexa- tion of AZO of the block copolymers and CD cavities on β-CD@QD, they form a hybrid inclusion complex (HIC). The HIC contains a QD as the core and the block copolymer as the shell with the PNIPAM block as the outer layer. Dynamic light scattering (DLS) and UV-vis spectroscopy investigation proved the HIC structure in diluted solution. Hydrogel formed easily upon heating the aqueous solution of HIC at a concentrationaslowas7wt%;asaresultofPNIPAM,aggregationoccurredabovetheLCST.Theinclusion complex and the domains of the collapsed PNIPAM chains serve as two distinct cross-links and render the hydrogel excellent dual sensitivity to competitive hosts/guests substitution and to temperature variation. Furthermore, rheology results quantitatively exhibit the hydrogel formation mechanism and the sol-to-gel reversibility following the two external stimuli.