Abstract
It is known that the glass transition temperature (Tg) of the resin cured by alkylboranes as a living radical initiator is higher than Tg of the resin cured by typical radical initiators such as peroxides or azo compounds. We infer that higher Tg of the resin cured by living radical initiator originates in the difference of cross-linking structure of the cured resin. In this study, we tried to evaluate the cross-linking structures by solid state NMR. 13C-NMR spectra and spin-lattice relaxation times (T1 and T1ρ) were obtained. In the 13C-NMR spectra of the resin cured by peroxide, the signals of allylic carbons produced through disproportionation were observed. T1ρ value of the resin cured by alkylborane was shorter than those of resins cured by typical initiators. This implies that the resin cured by alkylborane had more ordered structure compared with resins cured by typical initiators. These results suggest the solid state NMR is effective for the analysis of cross-linking structure of thermoset resins.
