The Construction Of Stimuli-responsive Supramolecular System Base On Ethyl Cellulose/Chitosan

Polysaccharide as one of the most natural macromolecules is widely used in the food, chemical and biomedical industry with its good renewability, biodegradability and biocompatibility. The common polysaccharides include cellulose, chitosan, starch and so on. Among them, cellulose and cellulose derivatives, which possess low cost and favorable mechanical properties, are applied as dispersant, humectant and adhesive in many traditional industries. Additionally, the functional modification of cellulose as well as cellulose derivatives, such as grafting, oxidation and coupling, can expand their applications to drug delivery and catalyst carriers. Meanwhile, with its nontoxicity and excellent biocompatibility, chitosan has various applications in the commodity industry, biological tissue engineering, bio-pharmaceuticals and others. In this thesis, living ring-opening polymerization (ROP), click reaction and Schiff s base reaction were utilized to modify ethyl cellulose and chitosan. Furthermore, host-guest interaction, hydrophobic interaction and dynamic chemical bonds were involved during the construction of supramolecular system based on ethyl cellulose or chitosan.Specifically, based upon ethyl cellulose (EC), a UV/visible light controlled supramolecular system were constructed, which combined the host-guest interaction of β-cyclodextrin (β-CD) and trans-azobenzene (tAzo) groups. First, macroinitiator EC was used to initiate the polymerization of ε-caprolactone (ε-CL) to form the biodegradable comb copolymer EC-g-PCL, then β-CD was linked to the PCL side chains via click reaction. Thus, the hydrophobic chain (EC-g-PCL-β-CD) was obtained. Meanwhile, hydrophilic chain (PEG-/Azo) was prepared via N,N’-dicyclohexylcarbodiimide coupling reaction. The obtained supramolecular system (EC-g-PCL-β-CD/PEG-/Azo) self-assembled into micelles in water with hydrophobic chain (EC-g-PCL-β-CD) as core and hydrophilic chain (PEG-/Azo) as shell. Furthermore, the morphologies and the UV-visible light stimuli-responsiveness of the micelles were explored in detail.In addition, a novel self-healing hydrogel system based on chitosan combining dynamic covalent Schiff-base linkage and hydrophobic interaction has been designed and constructed. Pluronic-F127modified with4-formylbenzoic acid was used as the macromolecular crosslinker. The dynamic hydrogel showed good self-healing ability and unique thermo-responsiveness, making it an outstanding choice as carrier for drug-controlled release and repair material.