Ice Segregation-Induced Self-Assembly of Liquid Crystalline Silver Nanofibers into Poly(vinyl alcohol) Biocompatible Hydrogels

HERNÁN E. ROMEO; CRISTINA E. HOPPE; IVAN PARDIÑAS BLANCO; ARTURO LÓPEZ QUINTELA; ROBERTO J. J. WILLIAMS; YANINA MINABERRY; MATÍAS JOBBÁGY

Lyon

Simposio; II International Symposium "Frontiers in Polymer Science"; 2011

Anisotropic metal nanoparticles (NPs) are finding applications in diverse fields as photonics, catalysis, sensors, etc.1, because of their enhanced fluorescence, non-linear optical properties, near infrared optical resonances and orientation-dependent plasmon excitations.2,3 The use of processing techniques that allow simultaneous ordering and dispersion of these NPs into the final materials are highly desirable for the design of novel nanostructured materials. In particular, the use of anisotropic NPs which exhibit liquid crystalline behavior could represent a useful and promising strategy to produce the ordering of these nano-objects at the supramolecular level, for instance, into biocompatible polymer matrices, which could lead to novel composite materials with potential advanced functional properties in biomedical fields.      Biocompatible cryogenic processes, based on freezing of hydrogels and subsequent freeze-drying, have been widely used for scaffold preparation. During the freezing of colloidal aqueous suspensions most solutes are segregated from the ice phase, giving rise to a macroporous structure characterized by “fences” of matter enclosing ice. This method, named ISISA (ice segregation-induced self-assembly), allows controlling the macroporosity of the final device by tuning suitable freezing conditions.4      In this way, the combination of unidirectional freeezing with the use of anisotropic NPs (exhibiting liquid crystalline phase behavior) and biocompatible hydrogels could produce simultaneous formation of macropores in the final material along with the ordering of the NPs. Hence, application of ISISA to these systems could find interesting applications in biosensing and other biomedical-related fields.      In this study liquid crystalline silver nanofibers (Ag-NFs) dispersed in poly(vinyl alcohol) (PVA) solutions are organized employing the ISISA method. The influence of processing parameters on the morphology and porosity of the final materials is analyzed; the influence of Ag-NFs and PVA concentrations on the properties of the composites (mechanical, electrical, optical and biological) is also established.   References: 1- B. Lim and S. E. Skrabalak Angew. Chem. Int. Ed. 2009, 48, 60. 2-M. A. Firestone, M. L. Dietz, S. Seifert, S. Trasobares, D. J. Miller, N. J. Zaluzec Small 2005, 1, 754. 3-B. J. Wiley, S. Hyuk Im, Z. Li, J. McLellan, A. Siekkinen, Y. Xia J. Phys. Chem. B 2006, 110, 15666. 4-M. C. Gutiérrez, Z. Y. García-Carvajal, M. Jobbágy, F. Rubio, L. Yuste, F. Rojo, M. L. Ferrer, F. del Monte Adv. Funct. Mater. 2007, 17, 3505