Trimethylsilyl hydroxypropyl cellulose (TMS-HPC) was synthesized from hydroxypropyl cellulose and hexamethyldisilazane in dimethyl formamide. The structure of TMS-HPC was characterized by infrared spectroscopy, H-1 NMR and C-13 NMR. The obtained TMS-HPC achieved solubility in a variety of organic solvents, such as chloroform, acetone, and xylene so that the lyotropic liquid crystal mesophase can be formed in concentrated acetone. The critical concentration (C*) in acetone confirmed by PLM photographs is approximately 36%. The relationship between the structure and solubility was analyzed using XRD. With the partial protection technique of the hydroxyl group via the TMS group and the solubility of TMS-HPC in organic solvents and the easy deprotection of TMS groups, a new amphiphilic biodegradable graft poly(E-caprolactone) (PCL) with water-soluble HPC as a backbone was obtained by homogeneous graft copolymerization. The structure of the graft copolymer (HPC-g-PCL) obtained was confirmed by H-1 NMR. (c) 2006 Elsevier B.V. All rights reserved.