Controlling polylactide stereocomplex (sc-PLA) self-assembly: From microspheres to nanoparticles

• Published in: Polymer (Guilford) 2016-05, Vol.90, p.242-248
• Main Authors: Michalski, Adam, Makowski, Tomasz, Biedroń, Tadeusz, Brzeziński, Marek, Biela, Tadeusz
• Format: Article
• Language: English
• Subjects: Architecture; End-group functionalization; Microspheres; Nanoparticles; Polylactide; Polylactides; Polymerization; Self assembly; Solvents; Stereocomplexes
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2016.03.049

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 μm (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 (∼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 (∼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. [Display omitted] •Investigation of combination of end-group interactions and stereocomplexation in sc-PLA.•The morphology of sc-PLA depends on the components end group structure and architecture.•Influence of concentration of sc-PLA components on particles size was observed.•sc-PLA materials exhibit hierarchical structure.