화학공학소재연구정보센터
Polymer, Vol.90, 242-248, 2016
Controlling polylactide stereocomplex (sc-PLA) self-assembly: From microspheres to nanoparticles
Linear and star-shaped polymers have been synthesized by the controlled ring-opening (ROP) polymerization of L-and D-lactide using 1-methyl-2-hydroxymethyl-3-butylimidazolium tetrafluoroborate and dipentaerythritol as initiators, respectively. To introduce carboxylic end-groups onto the star-shaped polylactides, the reaction of -OH end-groups with succinic anhydride was employed. Afterwards, the starting and modified polylactides were used for the preparation of star-shaped and star-shaped/linear stereocomplexes in 1,4-dioxane and tetrahydrofuran (THF). In these solvents, the stereocomplexes spontaneously precipitated. Star-shaped stereocomplexes with hydroxyl end-groups formed microspheres with diameters ranging from 1 to 4 mm (depending on the initial concentration of sc-PLA components) following precipitation from THF. However, the combined effect of the nature of the end-groups and PLA architecture causes the formation of uniform stereocomplex nanoparticles (similar to 400 nm) in 1,4-dioxane from the combination of star-shaped PLA functionalized with carboxylic end-groups and linear PLA with ionic liquid end-groups. Microscopic analysis showed that nanometre-sized grains of stereocomplexes (similar to 30 nm) aggregated to form larger stereocomplex nanoparticles. It was observed that the combination of three factors, i.e., the end-group interactions, architecture of the enantiomeric components, and basicity of the solvent in which the stereocomplexes are prepared, influences the properties and morphology of the final stereocomplex-based materials. (C) 2016 Elsevier Ltd. All rights reserved.