Intelligent Polymer Materials Based On Responsive Guest Molecules

Intelligent polymer hydrogel is a hydrophilic polymer material with a functional network structure.Many interesting functions of polymer network structure have been realized by introducing stimuli responsive supramolecular actions,such as biological tissues,drug delivery,and electronic devices.Cyclodextrin,as a host molecule with a hydrophobic cavity structure,can rely on different stimulus response mechanisms to recognize guest molecules,and form host-guest interactions with different guest molecules.Based on the thixotropic host-guest interaction between cyclodextrin and guest molecules,a network system combining host-guest coordination with metal ions or hydrogen bonding can be constructed,and some specific functional hydrogels can be designed.In this paper,the host-guest interactions between photo-isomerized azobenzene and p H-responsive benzimidazole with cyclodextrin were used as response triggering switches,which is used to prepare multiple supramolecular hydrogels.And the molecular structure,chain Segment motion and material properties are characterized.The specific research results are as follows:1.The host-guest cross-linkiner(?-CD-Azo)is prepared by complexing acryl-functionalized?-cyclodextrin(?-CDAAm)and acryl-functionalized azobenzene(Azo AAm).Using acrylamide(AAm)as the network monomer,PAAM/sodium alginate hydrogel was prepared by mixing sodium alginate(Alg)with?-CD-Azo.The metal ion coordination(Alg-Ca²⁺)formed by complexing calcium ion(Ca²⁺)with Alg,which is used as the second network of the gel.The rheological and mechanical relaxation experiments show that the modulus and relaxation behavior of the network reflect the orthogonality between the host-guest action and the metal coordination action.2.Based on the orthogonality of?-CD-Azo host-guest interaction and Alg-Ca²⁺metal ion coordination interaction cross-linking,PAAM hydrogel was prepared.The metal complexation formed by Alg and Ca²⁺can realize the shape memory of the hydrogel,and the shape recovery can be completed under the complex competition of ethylenediaminetetraacetic acid(EDTA).Based on the individual controllability of the two supramolecular effects,a series of shape-memory hydrogels devices with light adaptation are constructed through the dissociation and combination of light-controlled host-guest interactions.3.Poly-?-cyclodextrin and acryloyl functionalized benzimidazole(Bz IAAm)were used to prepare supramolecular cross-linkinger through complexation of the host-guest interaction,and copolymerized with AAm to obtain host-guest cross-linked hydrogel.Tests in mechanical experiments indicate that there is p H responsiveness between the host-guest complexing of Bz IAAm and?-CD.And through the synergistic effect of the hydrogen bonding,the host-guest interaction and the ionic binding of benzimidazole cations in the PAAM gel system,adhesion behavior of the hydrogel material is completed.These results of this article indicate that the functional supramolecular hydrogel with stimulus response was successfully constructed by combining the host-guest interaction with different stimulus response mechanisms and metal ion coordination and hydrogen bonding.Using the specificity and dynamic reversibility,the function of supramolecular hydrogels is directionally regulated,which provides a strategy for the design of controllable functions of smart polymer hydrogels.