Synthesis And Study Of Stimulus Responsive Supramolecular Polymers Containing Cyclodextrin

Supramolecular polymers are a very special kind of polymer whose building units are connected by highly directional and reversible non-covalent bonds.As a natural product,cyclodextrin has the advantages of easy availability of raw materials,low cost,low toxicity,and good biocompatibility.It can be complexed with a variety of functional guest,so it is widely used in host-guest identification systems.Supramolecular polymers based on cyclodextrins are often responsive to a variety of stimuli and have potential applications in materials,environmental protection,biomedicine,etc.In recent years,it has also received much attention from scholars at home and abroad.In this paper,a series of stimuli-responsive supramolecular polymers based on cyclodextrins are designed and constructed.The main contents are generalized as follows:In chapter 2,we demonstrate a simple and effective way to construct a dual-modality hydrogel whose stiffness can be modulated by photo-switching the weak host-guest physical crosslinking points to strong chemical crosslinking points.2:1 host-guest complexation of coumarin with?-CD was prepared and used to form a supramolecular polymer hydrogel via free radical copolymerization.In this state,the main crosslinking in the hydrogel was physical crosslinks.The hydrogel was stiffened upon irradiation of 365 nm light,as the coumarin dimerization was occurred in?-CD,coming with crosslinks changing from partial physical crosslinks supplied by host-guest interactions to COU-COU covalent interactions.In contrast,when irradiated by 254 nm light,COU-COU covalent bond decoupled.The hydrogel turned back to a soft physical crosslinking state.The storage modulus of our material could increase to 2.3 MPa after exposed at 365nm light.In addition,it also could conduct self-healing properties and the self-healing rate of the material could be controlled by UV light.In chapter 3,a polymer hydrogel based on SP-Azo functionalized PAM,which was crosslinked by noncovalent hydrophobic interactions was reported.The polymer hydrogel was thermo-and light-responsive.Temperature was a factor that not only controlled the color change but also the viscosity of hydrogel.With heating at 60 ~?,polymer hydrogel lost most of the intrinsic viscosity and turned to red for the isomerization of spiropyran.The change could be reversibly recovered to original state as cooled down to 20 ~?.Different from temperature,light irradiation specifically regulated hydrogel color upon 365 nm and 440 nm light,while no significant influence on viscosity.The gel could be transited to sol by addition of?-CD,which included hydrophobic groups to increase the solubility of polymer in aqueous solution.The hydrogel could be regained after UV irradiation at?=365 nm,and after irradiation at?=440 nm,the hydrogel changed into a clear sol again.And treating sol with a competitive guest,the?-CD cavity was occupied to release the pendant groups,resulting in the regain of hydrogel.