(354f) Nacre-Like Composite Materials Produced Via Magnetically-Controlled Sol-Gel Phase Separation

Naturally occurring materials and structures have been always inspired scientists, who tried to either replicate or mimic them. Examples include gutta-percha, wood, opals, bones and nacre.

The latter has gained considerable interest in the last few years. Naturally occurring nacre is made of thin hexagonal platelets of aragonite, having a size of 10-20 mm and a thickness of 0.5 mm held together by a bio-polymer. This peculiar structure confers it excellent mechanical properties.

In this work we have prepared a new ceramic-polymer composite material inspired by the structure of nacre. This material is made from a monolithic skeleton of silica platelets in a size range of 20-30 mm and a thickness of ~1mm reinforced by a polyetheramines based polymer. The silica platelets have been produced via a modification of the magnetically controlled phase separation in sol-gel process previously developed in our laboratories [1]. In this process polymer-magnetite nanoparticles produced via miniemulsion polymerization have been dispersed in an acidic solution where PEG and the silicon precursor TMOS have been previously dispersed. The obtained solution was then transferred to a mold and placed between the poles of an electromagnet. As shown in the literature, the application of a rotating magnetic field leads to the formation of two dimensional sheet-like structures. In our case we decided to rotate the sample inside a uniaxial magnetic field to mimic a rotating field. Once the monolith was formed it was functionalized with(3-aminopropyl)-triethoxysilane in order to promote the attachment of the polymer to the surface during the impregnation step.

The obtained structures have been analyzed with SEM microscopy and mechanical compression test before and after the polymer impregnation step. We have shown that the radial velocity plays an important role in the formation of the platelets structure and of the initial anisotropic mechanical properties of the materials. The impregnation step enhances these properties by making the material more stable.

Literature:

1. Furlan M. and Lattuada M., 2012, “Fabrication of Anisotropic Porous Silica Monoliths by means of Magnetically-Controlled Phase Separation in Sol-Gel processes” Langmuir, 28 (34), 12655–12662