Dynamic light scattering studies of resorcinol formaldehyde gels as precursors of organic aerogels

Patricia M. Cotts; Rick Pekala

doi:10.1117/12.44167

1 June 1991 Dynamic light scattering studies of resorcinol formaldehyde gels as precursors of organic aerogels

Patricia M. Cotts, Rick Pekala

Proceedings Volume 1430, Photon Correlation Spectroscopy: Multicomponent Systems; (1991) https://doi.org/10.1117/12.44167
Event: Optics, Electro-Optics, and Laser Applications in Science and Engineering, 1991, Los Angeles, CA, United States

Abstract

Aerogels are exceptionally light foams formed by extraction of the solvent from a gel under supercritical conditions where surface tension forces are greatly reduced. This results in very little shrinkage of the gels when dried. The dried aerogels have extremely high surface area and have applications as catalyst supports and thermal and acoustic insulators. While most studies have used aerogels formed from silicon dioxide, the authors focused on organic aerogels obtained by the reaction of resorcinol and formaldehyde (RF). The kinetics of the gel formation have been studied using dynamic light scattering. These studies encompass three areas:(1) initial reaction of RF into branched 'clusters' as a function of resorcinol/catalyst (Na2CO3) ratio; (2) aggregation of the clusters into linear chains to form the gel network; and (3) the modulus of the completely gelled sample. The initial particle size increases linearly with R/C ratio as was observed by TEM on dried samples. The scattering intensity increases exponentially as the gel is formed as is observed for polymer gels formed by spinodal decomposition. The cooperative diffusion coefficient (which is directly related to the gel modulus) scales with concentration to a power of approximately unity, which is larger than the 3/4 usually observed for polymer networks.

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Patricia M. Cotts and Rick Pekala "Dynamic light scattering studies of resorcinol formaldehyde gels as precursors of organic aerogels", Proc. SPIE 1430, Photon Correlation Spectroscopy: Multicomponent Systems, (1 June 1991); https://doi.org/10.1117/12.44167

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KEYWORDS

Dynamic light scattering

Correlation function

Particles

Diffusion

Polymers

Transmission electron microscopy

Scattering

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