Photodegradation of Alternating p-tert-Butylstyrenyl- and exo-Norbornyl-CO Copolymers Studied by Multiple-Frequency Time-Resolved Electron Paramagnetic Resonance Spectroscopy

The photodegradation of two alternating R-CO copolymers (R= p-tert-butylstyrenyl and exo-norbornyl) was studied using time-resolved EPR spectroscopy at two different frequencies, X-band (9.5 GHz) and Q-band (35.1 GHz), and by product analysis. For the tert-butylstyrenyl-CO copolymer the EPR spectra displayed strong chemically induced dynamic spin polarization (CIDEP) expected fort triplet-born radical pairs from the Norrish I α-cleavage reaction. Simulation of the spectra allowed unambiguous assignment of the radicals present as early as 200 ns after the laser flash