Molecular simulation and experimental analysis of heterogeneous systems based on biodegradable polymerspolymer blends and nanocomposites/modelización molecular y análisis experimental de sistemas he

Résumé

The research leading to this thesis is framed within the area of Materials Science, specifically in the Biopolymers field. The present work has been performed in the group ¿Science and Engineering of Polymeric Biomaterials¿ at the School of Engineering of Bilbao, UPV/EHU.The analysis of miscibility state between different pairs of polymers such as polylactide/poly(vinyl phenol), polylactide/poly(styrene-co-vinyl phenol) and poly(para-dioxanone)/poly(vinyl phenol) blends was conducted. Theoretical and experimental results on the study of phase behavior in polymer blends were described and analyzed using Molecular modeling and experimental methods.New strategies have been proposed to improve the dispersion and crystallization behaviour of poly(L-lactide) in presence of CNTs. Non-covalent functionalization of nanocomposites based on polylactide and CNTs was performed, using three compatibilizers; pyrene, anthracene and imidazolium end-functionalized poly(L-lactic acid). One of the previous systems, PLLA/py-end-PLLA/CNTs, was chosen for a more in depth characterization study of the morphology, thermal and mechanical properties. In this context, experimental and molecular modeling results are introduced for the formation of a supramolecular system among poly(ethylene oxide-co-L lactide), LiCl and CNTs.The citotoxicity evaluation in PLLA/py-end-PLLA/MWCNT nanocomposites was carried out. A strong evidence of a good bioacceptance of the pyrene-end-PLLA/MWCNTs nanocomposites was demonstrated in tests with human bone narrow stromal cells drawn to osteogenic differentiation. The presence of MWCNTs, at the analyzed concentration range, indicates no adverse effects on cell adhesion or cell population size.Finally, a study on CNTs was performed as specific nucleating agents for the formation of stereocomplex crystals in enantiomeric polylactide blends of high molecular weight. The presence of previously synthesized pyrene-end-functionalized poly(lactic acid) compatibilizer was analyzed. The main objective of this part of the investigation was the improvement of the CNT dispersion in a PLA matrix and the enhancement of the formation of stereocomplex crystals by blending pyrene end-functionalized PLLA chains with PDLA.In conclusion, the present thesis exposes several methodologies and approaches (blends and nanocomposites), to improve the properties of biodegradable polylactides.