Characterization of silica-polymer aerogel composites by small-angle neutron scattering and transmission electron microscopy

In this work a new type of silica-biopolymer aerogel composite containing c hitosan has been studied with small-angle neutron scattering (SANS) and tra nsmission electron microscopy (TEM). A new small-particle mass-fractal mode l scattering function, derived from the Teixeira mass-fractal scattering fu nction, was used to fit the SANS data. As the content of chitosan was incre ased, the fractal dimension was decreased from 2.9 to 2.5, and the cut-off- length increased from 3.2 to 6.0 = This indicates that chitosan helps form a more open aerogel structure. It supports a structural model in which ther e are primary particles that connect with each other closely to form cluste rs, and these clusters serve as a secondary structural unit to form the chi tosan-reinforced aerogel network. It also indicates that chitosan reinforce s the inter-particle connections. This picture is consistent with the TEM m easurements, which reveal that there are 1.5 mn wide entities with long dim ensions in the 3-10 am range. (C) 2001 Elsevier Science B.V. All rights res erved.