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

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Title: Controlling polylactide stereocomplex (sc-PLA) self-assembly: From microspheres to nanoparticles.
Authors: Michalski, Adam1, Makowski, Tomasz2, Biedroń, Tadeusz1, Brzeziński, Marek1 mbrzezin@cbmm.lodz.pl, Biela, Tadeusz1 tadek@cbmm.lodz.pl
Source: Polymer. May2016, Vol. 90, p242-248. 7p.
Subjects: Polylactic acid, Molecular self-assembly, Star-branched polymers, Stereochemistry, Nanoparticles, Linear polymers, Ring-opening polymerization, Imidazoles
Abstract: 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. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
Description
Abstract: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. [ABSTRACT FROM AUTHOR]
ISSN:00323861
DOI:10.1016/j.polymer.2016.03.049