Interdiffusion in polystyrene crosslinked by keV ion irradiation

Abstract

Mass transport properties of polymers are deeply influenced by the presence of crosslinks between chains, induced by high‐energy ion irradiation.Diffusion coefficients in polystyrene, measured after irradiation with 300‐keV protons in the fluence range 1012–1014 ions/cm2, show strong variation up to two orders of magnitude. Diffusion process has been studied in deuterated/hydrogenated polystyrene bilayer by using the forward recoil analysis technique with 2.0‐MeV He beam. The adopted experimental procedure allows us to detect diffusion coefficients in the range 5×10−13–10−15 cm2/s. Two molecular weights have been chosen for the hydrogenated polystyrene (7500 and 575 000 amu), in both experiments the molecular weight of deuterated polystyrene has been maintained constant (27 000 amu). Combining diffusion, molecular weight distribution, and solubility measurements performed in the same irradiation conditions, we have tested that diffusion process is slowed down when branching of chains or formation of a large unsoluble fraction occurs in the original polymer structure.