This proposal looks to study the electron spin relaxation using high field ALC measurements in two polymers, which differ only by the non-metal (i.e S or Se) in the polymer chain. The measurements will be made at temperatures between 10K to 300K. The key objectives are to discover if the electron spin relaxation increases with mass in a polymeric system, thus indicating generality across all molecular semiconductors; to compare the results with the indirect estimates of the spin relaxation at different temperatures made in the literature and to prove without doubt whether polaron motion is present in polymeric systems.