Radiation-Induced Polymerization Of 3-Hexylthiophene In Oxygen-Free And Oxygen-Saturated Dichloromethane Solvent

As alternative radiolytic approach, the synthesis of P3HT was made possible thanks to the oxidation of 3HT monomers by chloromethyl and dichloromethyl radicals or by their corresponding peroxyl radicals in situ produced by dichloromethane solvent radiolysis. Under two different experimental conditions, in oxygen-free solution and in oxygen-saturated solution, two different polymers, "P3HT(N2)" and "P3HT(O2)" respectively, were successfully synthesized. Both produced materials were discerned by several analytical and spectroscopic techniques. UV-Vis absorption spectroscopy results showed that the radiolytic yield of 3HT oxidation in dichloromethane solvent is higher under O-2 atmosphere. Indeed, a dose of 75 kGy was needed to polymerize 10 mM in 3HT under N-2 atmosphere, meanwhile a dose of 35 kGy was sufficient to polymerize the same amount of 3HT under O-2. The average molecular weight of P3HT(O2) was found higher than that of P3HTN, as revealed by SEC chromatography analysis. Also, P3HT(O2) exhibits better thermal stability than P3HT(N2). ATR-FTIR spectroscopy revealed the specific presence into P3HT(O2) polymers of some functional groups such as carbonyl, hydroxyl and carboxyl moieties, which clearly explains the difference between the morphological structures of P3HT(N2) and P3HT(O2) as highlighted by cryo-TEM, SEM and AFM microscopies. Finally, both radio-synthesized P3HT(N2) and P3HT(O2) polymers were found characterized by remarkably significant conductive, electronic and optical properties.