Polytrimethylolpropane Tri-methacrylate TRIM

Hjerthei and co-workers [97] used C-CP-MAS- C-NMR to determine the double bonds in TRIM and compared results to the results obtained hy standard bromine addition methods. They also examined the possibility of utihsing different relaxation parameters obtained by NMR measurements to study the mobility of unreacted units. 

A detailed analysis of the cross-polarisation behaviour showed that quantitative results can be obtained. The amount of unreacted units, typically 0-15%, was found to depend on the polymerisation parameters. Conditions favouring mobility, i.e., higher temperatures or increased solvent quality, resulted in lower content of residual double bonds. Bromine addition values are 2-3% higher than the NMR data. The reactivity toward bromine further indicates that the mobility is reasonably high. This has also been confirmed by measurements of the rotating-frame relaxation time constant, Tj ( C) Most likely, Tjp is dominated by spin-lattice processes i.e., it can be interpreted in terms of molecular dynamics. The values obtained for C=0 and C =CH2 in unreacted units are about twice that of C=0 in reacted units, indicating increased mobility. The reactivity of the remaining double bonds in a radical polymerisation with a chiral monomer was also demonstrated. 

The % fraction of unreacted methacrylate groups in TRIM, depend on polymerisation temperature and range from 8.4% at 60 C to 2.7% at 90 C. 

CP-MAS-NMR has also been used in studies on polytetramethylene glycol dimethacrylate [94]. 

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