INTEMA   05428
INSTITUTO DE INVESTIGACIONES EN CIENCIA Y TECNOLOGIA DE MATERIALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Self-assembly of nanoparticles and block copolymers in cross-linked polymers employing polymerization-induced phase separation
Autor/es:
ROBERTO J. J. WILLIAMS; AGUSTINA B. LEONARDI; HERNÁN E. ROMEO; ILEANA A. ZUCCHI; CRISTINA E. HOPPE
Lugar:
Madrid
Reunión:
Conferencia; 4th International Colloids Conference: Surface Design & Engineering; 2014
Resumen:
Different types of modifiers like linear polymers, block copolymers (BCP), liquid crystals (LC) or nanoparticles (NP) stabilized by organic ligands can be dissolved in a reactive solvent constituted by the precursors of a cross-linked polymer. Phase separation takes place during polymerization mainly due to the significant decrease of the entropic contribution to the free energy of mixing. By an adequate selection of the starting formulation and reaction conditions, the segregated phase self-assembles forming ordered arrays. Ternary blends including polystyrene (PS) and an LC in epoxy precursors enabled to confine the LC in the segregated PS phase leading to thermally reversible light scattering films. Blends of PS, gold NP and epoxy precursors led to the segregation of NP in PS domains and their self-assembly as bcc (body centered cubic) colloidal crystals. Hierarchical aggregates of gold NP on different length scales were in situ generated at the surface of an organic-inorganic hybrid coating during the process of film formation by polycondensation and solvent evaporation. The initial 2-nm gold NP self assembled as 20-nm bcc colloidal crystals that were aggregated into compact microparticles. Fractal arrays of these microparticles were formed at the film surface. A large variety of nanostructured architectures can be accessed during polymerization of BCP / epoxy blends. Using different types and concentrations of PS -b-PEO (polyethylene oxide) block copolymers, it was possible to generate dispersions of spherical micelles, wormlike micelles or domains of hexagonally-packed cylinders in the transparent cured materials. For a blend containing 20 wt% of a PS-b-PMMA (polymethyl methacrylate), the system evolved from a dispersion of spherical micelles to bcc structures, chains of spherical micelles, cylindrical micelles and hexagonally-packed cylinders. By selecting the cure cycle it was possible to trap some of these morphologies in the final material and change its transparency and dynamic mechanical properties.