To develop novel biomedical soft materials with degradability, amphiphilic poly(L-lactide)-grafted dextrans (Dex-g-PLLAs) of relatively high sugar unit contents were synthesized with the trimethylsilyl protection method. The characteristic properties of solution-cast films prepared from the obtained Dex-g-PLLAs were investigated. The water absorption and degradation rate of the Dex-g-PLLA films increased with increasing sugar unit content. The morphology of the bulk phase and top surface of the Dex-g-PLLA films was evaluated with transmission electron microscopy and atomic force microscopy, respectively. The bulk phase of the Dex-g-PLLA films with a sugar unit content of 16-25 wt % was found by transmission electron microscopy to form a lamellar type of phase-separated structure composed of approximately 80-100-nm-wide nanodomains because of their amphiphilic and branched structures. The hydrophobic top surface for a Dex-g-PLLA film with a sugar unit content of 25 wt % covered with PLLA segments was confirmed by atomic force microscopy phase images to be easily converted to a wettable top surface covered with hydrophilic dextran aggregates showing an 8-10-nm-wide honeycomb pattern by means of annealing in water. (c) 2006 Wiley Periodicals, Inc.