General Features for Polyacrylates

Analysis of the decay of TREPR signals can be complicated and has been the subject of many previous investigations. Qualitatively, we can say the following 

FIGURE 14.8 TREPR data obtained during 248 nm laser flash photolysis of atactic PMMA in five different solvents at ambient temperature. Delay time is 0.6 is for all spectra, and the sweep width is 150 G. (A) 1.61 g in 20 mL dichloromethane. (B) 1.53 g in 20 mL chloroform. (C) 1.04 gin 20 mL acetonitrile. (D) 1.20gin20mLTHF. (E) 1.49 gin 25 mL dioxane. Note the changes in width and shape for the alternating broad and sharp packets of lines. 

The decay time constants for the polymeric radicals clearly vary from solvent to solvent, ranging over an order of magnitude from about 2 ps in tetrahydrofuran (THF) to 200 ns in methylene chloride. A similar solvent dependence of NMR Ti values has been reported by Spyros et al. They studied poly(naphthyl methacrylate) using the inversion recovery technique and found that the spin-lattice relaxation time of 

---