Unusual Thermal Properties of Polylactides and Polylactide Stereocomplexes Containing Polylactide-Functionalized Multi-Walled Carbon Nanotubes

• Published in: Macromolecules 2012-11, Vol.45 (21), p.8714-8721
• Main Authors: Brzeziński, M, Bogusławska, M, Ilčíková, M, Mosnáček, J, Biela, T
• Format: Article
• Language: English
• Subjects: Applied sciences; Composites; Exact sciences and technology; Forms of application and semi-finished materials; Polymer industry, paints, wood; Technology of polymers
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma301554q

A novel and simple method for the preparation of linear, high-molar-mass, thermally stable polylactide stereocomplexes (sc-PLA) with multiwalled carbon nanotubes (MWCNTs) covalently attached to enantiomeric PLA chains is presented. The MWCNTs modified with organic spacers terminated with −OH groups were used as initiators for the ring-opening polymerization (ROP) of enantiomeric l- and d-lactides. The weight percentage of MWCNTs in the final stereocomplexes was approximately 1 wt %. The nascent (as-polymerized) polymer samples obtained by the ROP in bulk at 130 °C exhibited unusually high melting temperatures (≥190 °C) as well as enthalpies of fusion close to that estimated for polylactides with 100% crystallinity. PLA stereocomplexes were prepared from equimolar mixtures of l-PLA and d-PLA that also contained MWCNT-g-PLA, either by precipitation from solution or, for the first time, as a thin film via the slow evaporation of solvent. Crystallization in the form of stereocomplexes after melting was, unusually, completely reversible, without formation of any homochiral crystallites. Shish-kebab morphologies for the thin-film stereocomplexes containing 1 wt % of MWCNT-g-PLA were observed by atomic force microscopy.