Polymer, Vol.55, No.16, 3591-3598, 2014
Surface control of hydrophilicity and degradability with block copolymers composed of lactide and cyclic carbonate bearing methoxyethoxyl groups
Block copolymers of L-lactide (LA) and trimethylene carbonate (TMC) derivatives bearing methoxyethyl groups [poly(TMCM-MOE1OM)-block-PLLA] were employed as spin-coated films on substrates, and their hydrophilic and degradation behaviors were investigated. Changing the solvents for film preparation, film thickness, and copolymer composition ratios varied the contact angles in the range of 84.3 degrees +/- 2.8 degrees at 269 nm thickness and 18.2 degrees +/- 2.5 degrees at 15 nm thickness. These contact angles showed dynamic changes from hydrophobic to hydrophilic properties, probably due to the methoxyethoxyl groups connecting the flexible TMC moieties in the copolymer. Immersion into water or hexane affected the dynamic contact angles. X-ray photoelectron spectroscopy analyses revealed that a large amount of hydrophilic groups was segregated onto the surface, although both LA and TMC units existed. Such dynamic contact angle changes were delayed by the crystallization of polylactide. The hydrolyzed behaviors of these films were examined by quartz cell microbalance, showing a slow degradation process. (C) 2014 Elsevier Ltd. All rights reserved.