TRESR study of the photo-induced electron transfer in P3DDT/maleic anhydride blend in THF solution under UV flash photolysis

Abstract Photo-induced electron transfer (PET) between a poly(3-dodecylthiophene) (P3DDT) and maleic anhydride (MA) in their blend in liquid solution of tetrahydrofuran was observed by the time-resolved electron spin resonance (TRESR) under UV flash photolysis at 308 nm. The observed spectra were identified as free-radical signals of positive polarons on polymer chains and MA anion radicals. Their emissive chemical induced dynamic electron polarization (CIDEP) originated mainly from excited triplet states (triplet mechanism of CIDEP). Analysis of radical spectra integral intensity distribution shows at the influence of radical pair mechanism (RPM) of CIDEP with the positive sign of the exchange interaction constant ( J  > 0). The last is attributed to Coulombic interaction between geminately formed polarons and MA anion radicals. The spin relaxation times of radicals were determined by fitting the time evolution of the TRESR signal at near-resonance positions of the field using the Bloch equations and direct Fourier transform analysis.