Friedel—Crafts Acylation on Porous Divinyl Benzene Polymer Particles: A Reaction Kinetic Process Studied by Mid- and Near-Infrared Spectroscopy

Abstract

Porous poly(para-divinylbenzene) and poly(meta-divinylbenzene) particles were synthesized from para-divinylbenzene and meta-divinylbenzene monomers with toluene and 2-ethylhexanoic acid as porogens. The residual vinyl groups in the particles were thereafter reacted with lauroyl chloride by using the Friedel–Crafts reaction. The conversion of vinyl groups was followed by analyzing polymer particles taken from the reaction mixture at different time intervals. Infrared spectroscopy in both the mid- and near-infrared region was used as the analytical technique. The intensity changes in the overtone absorption at 1628 nm due to the vinyl bonds were used as the basis for the quantification of the reaction. Spectra of the particles in the mid-IR region provide understanding of the changes taking place in the polymer matrix during the acylation reaction. The results indicated that the reaction took place at a faster rate in the polymer particles synthesized from para-DVB monomer compared with the poly(meta-DVB) particles. The polymer particles synthesized with toluene as porogen react faster than the polymer particles prepared with 2-ethylhexanoic acid as the porogen. The analysis also indicated that the acylation takes place at the early stages of the reaction and the product formed transforms into more stable products at the latter stages. On the basis of the infrared analysis, mechanisms for the formation of the different products are proposed.