Effects of phenolic substitution on the photooxidative degradation of polybenzoxazines

摘要

The photooxidative behavior of a number polybenzoxazines, based upon various phenols with different phenolic substitution, but with the same functionality (methylamine), upon exposure to ultraviolet (UV) radiation (lambda > 290 nm) is examined. Each of the new polybenzoxazine samples tested had a substituted benzoquinone photooxidation product develop upon irradiation to degrees which fell between a previously determined highest boundary value of BA-m polymer and lowest boundary value of P-m polymer, as was indicated by Fourier transform infrared spectroscopy. This study indicates that, depending upon their particular natures, different phenolic substituents at various points on the phenolic units can have critical influences on the degree, to which the photooxidation reaction occurs. It is apparent that the principles associated with electrophilic aromatic substitution generally apply to the present polymer systems affecting the extents of photooxidation. The specific manners in which the present ring substituents can impact upon the general photooxidation mechanism, as their influence pertains to the para-ring substituent, cleavage step to form the substituted benzoquinone oxidation product, are proposed. References: 18