Colored charge-transfer complexes from N,N-dimethyl-p-toluidine

Yellow mixtures form on adding essentially colorless N,N-dimethyl-p-toluidine (DMPT) to colorless methacrylate monomers containing phthalate, isophthalate, or terephthalate diester groups. The color-causing interactions between the amines and monomers were investigated using ultraviolet spectroscopy. Equations were derived from predicting interactions between formulation ingredients and DMPT that would lead to undesired color.