Spectroscopic Evidence of the Mechanism Involved in the Cationic Diglycidyl Ether of Bisphenol A Curing with Rare Earth Metal Triflates

Abstract

The cross-linking of diglycidyl ether of bisphenol A (DGEBA) using three rare earth triflates as initiators (lanthanum, ytterbium, and scandium) was studied by in situ Fourier transform infrared (FT-IR) spectroscopy. Cationic ring opening of epoxides can proceed through two different mechanisms: activated monomer (AM) and active chain end (ACE). Using advanced chemometric methods such as perturbation-correlation moving-window two dimensional correlation spectroscopy (PCMW2D) and multivariate curve resolution–alternating least squares (MCR-ALS) it has been possible to obtain spectroscopic evidence of the two mechanisms. Traditionally, the demonstration of different mechanism pathways requires designing specific experiments. The novelty of the present study is to find, without a specific experimental design, spectroscopic evidence of the pathway of the polymerization process and to analyze the effect of these initiators, as well as the evolution of the species that takes part in the curing process by structural techniques such as attenuated total reflection (ATR) FT-IR.