Trapping of Radicals in a Network

In densely crosslinked dimethacrylates, radicals with lifetimes of several days have been observed and the lifetimes were found to depend on crosslink density Extremely long lifetimes at room temperature have been observed with photopoly-merized di(meth)acrylates In the case of photopolymerized HDDA and HEBDM, the lifetimes exceeded 5 months at room temperature and under vacuum, even in the presence of large amormts of unreacted monomer and pendent double bonds. 

In poly(TEGDA) on the other hand, much shorter lifetimes were observed. Within one night, the three-line spectrum was converted into a single-line spectrum, which 

The formation of such radicals would certainly increase the mobility of the radical sites as compared with acrylate groups and thereby reduce their lifetime. 

Knowledge of structure and reactivity of trapped radicals is especially important for the design of thermal postcuring schedules as used with the manufacturing of lenses. This knowledge may also provide a starting point for the study of long term behavior. 

---