| In aqueous solution, due to the phase separation between the hydrophobic monomers and hydrophilic polymer, it's difficult to hydrophobic modified hydrophilic cellulose ether derivative--hydroxyethyl cellulose (HEC) by using the hydrophobic monomers. Only a little hydrophobic group could be grafted on the HEC due to the heterogeneous reaction. In this thesis, the silylation of HEC was prepared firstly. Then the degradable hydrophobic modified HEC was prepared in organic solvent by using caprolactone and lactide as hydrophobic monomers.At first, Silylation of hydroxyethyl cellulose was synthesized using hexametyyldisilazane(HMDS) as silylation agent. The structure of product was characterized by IR spectrum and NMR spectrum. The effect of reaction temperature, reaction time and co-solvent on silylation yield was investigated. And then, the thermal stability and solubility of silylating hydroxyethyl cellulose were studied. Because the hydroxyl groups in HEC were partially substituted by trimethylsily groups, the product could be dissolved in many kind of common organic solvents, such as toluene, tetrahydrofuran(THF) and so on.Further, with the TMS protection for the partial hydroxyl groups of HEC groups, the novel HEC grafted polycaprolactone (PCL) and HEC grafted Polylactide (PLA) were successfully prepared by homogenous ring-opening graft polymerization and deprotection procedure. The structure of product was characterized by IR spectrum and NMR spectrum. And then the rheology and surface tension of HEC-g-PCL was studied. The effect of different amounts of hydrophobic monomers on viscosity of copolymer was investigated. The results indicated that hydrophobic modified HEC displayed excellent rheological thicken behavior. The surface tension of copolymer is complicated. Fluorescence spectrum indicated that the hydrophobic groups of copolymer formed many hydrophobic microdomains in aqueous solution. Further more, Micellization and surface tension of HEC-g-PLA was also investigated.
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