Real-Time Fiber Optic UV-Vis Spectroscopic Investigations on the Resorcinol-Formaldehyde Gelation Reaction

Abstract

Resorcinol-Formaldehyde (RF) based aerogels are an important class of organic aerogels formed by polycondensation reaction mostly in basic medium followed by drying, which was first reported by Pekala.1 They are the most common precursor for the preparation of carbon aerogels and find potential applications in adsorbents, catalysis, energy storage, thermal insulation and furthermore. Their properties such as density, porosity, microstructure and thermal conductivity can be tuned and altered by changing different parameters such as initial pH, molar ratios of R/W, R/C and R/F, catalysts, drying method and others.2,3 To understand the reaction mechanism and the hereby received fine tuning of the properties of the RF aerogels, it is necessary to understand the kinetics of the reactions. There are limited numbers of studies available in the literature on the kinetic investigation of sol-gel reaction between resorcinol and formaldehyde using different techniques DLS, SAXS, SEM, TEM, NMR, IR & beside others.4,5 However, the investigation of reaction kinetics using UV-Vis spectroscopy6 is very limited over the years. Here, we aimed to monitor the RF reaction using an in-line UV-Vis spectroscopy with fiber optic probe at different gelation temperatures to follow in-situ the absorbance changes with respect to the two absorbance maxima at around 340 and 500 nm. This type of investigation enables the researchers and industrialists to understand and optimize the process of RF aerogel synthesis in laboratory scale and is transferable to large scale production.