Synthesis of High-Molecular Weight Biobased Epoxy Resins: Determination of the Course of the Process by MALDI-TOF Mass Spectrometry

Abstract

The presented research shows the results of matrix-assisted laser desorption/ionization mass spectrometry, which was used as a means of monitoring the synthesis of novel high-molecular weight epoxy resins. The products were obtained by the reaction of epoxidized soybean oil (ESBO) and bisphenol A (BPA), using a modern and pro-ecological modification of the well-known method of the synthesis of epoxy resins, called “the epoxy fusion process”. On the basis of the obtained spectrograms, the manner in which substrates reacted with each other during the conducted synthesis was determined. Initially, after the reaction of the oxirane group of ESBO with the hydroxyl group of BPA, subsequent reactions occurred, involving other molecules of bisphenol and the remaining oxirane rings of epoxidized vegetable oil or the reaction of a free phenolic group with the following macromolecule of modified oil. It was found that the final product of the polyaddition (ESBO_BPA), obtained by the epoxy fusion process conducted in bulk, consists of macromolecules with various structure. First, smaller oligomers such as 1ESBO + 1BPA and ESBO + 2BPA were formed, and as the reaction proceeded, they rapidly reacted with each other forming larger macromolecules: 2ESBO + 2BPA, ESBO + 3BPA, 2ESBO + 3BPA, 3ESBO + 3BPA, and 3ESBO + 4BPA. On the basis of the course of the ESBO_BPA polyaddition process in the registered m/z range, it was found that 1ESBO + 1BPA tends to react with other substrates from the reacting mixture to create a linear product. Bisphenol A is a rigid element, which connects the elastic alkyl chains of epoxidized soybean oil in the obtained macromolecule.