Determination of residual unsaturation in highly crosslinked, dough-moulded poly(methyl methacrylate) dental polymers by solid-state ¹³C NMR

Methyl methacrylate has been copolymerized with eight multifunctional, cross-linking comonomers in mixtures containing poly(methyl methacrylate) to give highly crosslinked polymers for trial as dental resins. These insoluble, optically opaque polymers have been characterized by solid-state ¹³C Nuclear Magnetic Resonance spectroscopy. The crosslinking comonomer could be identified from the appropriate resonances in the solid-state spectra. Unreacted methacrylate groups could be determined quantitatively from the resonance at 167 ppm due to CO adjacent to CC at concentrations down to at least 0.5% of the total CO. The final conversion of CC double bonds in the comonomer depended on the nature and length of the spacer segment between the reactive methacrylate groups.