31P NMR spectroscopy in benzoxazine model compounds and benzoxazine chemistry – main chain and end group studies

Abstract

Using 31P NMR spectroscopy after phosphorylation, different phenols are easily discriminated. Proposed phenolic model compounds from benzoxazine reaction/polymerization are phosphorylated with 2-chloro-1,3,2-dioxaphospholane directly in an NMR tube. The dimer and oligomer structure of benzoxazine is different from that of monomer, that is, the breaking of the oxazine ring upon polymerization results in the formation of Mannich bridge structure linking phenolic groups together. Different electronic environment in the phosphorus derivatives of the methylamine-based benzoxazine model dimer and oligomers allows comparison of these 31P NMR spectra with the 31P-NMR spectra of the compounds from traditional benzoxazine polymerization provides useful end group information. Phenolic functional groups in benzoxazine dimer and oligomers, e.g. phenolic end groups and phenolic groups on the backbone, are studied.