Resorcinol-formaldehyde (RF) gels have been studied extensively, subsequently finding many uses. However, despite significant research efforts, there is still no accepted model describing the formation of these structures, which limits our ability to tailor the material for its application. This work combines an experimental and simulation approach to better understand the gel growth process, and how the resulting structure depends on the growth conditions. The experimentally investigated areas include the influence of the sodium carbonate catalyst concentration, processing temperature, as well as solvent exchange and drying methods. Textural properties of the dried xerogels were obtained using nitrogen adsorption analysis, resulting in values of accessible BET surface area, average pore size, and micropore and total pore volumes. The data obtained suggest that, with increasing resorcinol/catalyst (R/C) ratio, the surface area decreases while the average pore width increases. This is most likely caused by the formation of a larger number of smaller clusters at lower R/C values, and fewer larger clusters at higher R/C ratios. These experimental data form the basis of a model for the growth and gelation of RF clusters that employs a kinetic Monte Carlo method in two-dimensions. Our simulated structures were characterised by their fractal properties, which influences transport properties, and simulated gas adsorption isotherms provided direct means of comparison to experiment. Trends in how the properties of the simulated gels vary with growth conditions agree with the experiment, which offers the hope of developing design tools for future xerogel applications.

Prediction and control of organic xerogel microstructure: Experiments and modelling

256th National Meeting (2018)

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