High energy (MeV) ion fluence dependent nano scale free volume defects studies of PMMA films

A systematic study on the dependence of the free volume at nanoscale in carbon ions irradiated polymethylmethacrylate polymer samples was carried out by means of positron annihilation lifetime spectroscopy and Doppler broadening spectroscopy (DBS). An investigation about the evolution of cross-linking in the polymeric chains after ion irradiation was carried out from the calculated values of hole radius, free volume and fractional free volume using Tao-Eldrup Model. The role of rise in temperature on the growth of free volume was observed at higher fluences. The results were supported by variations in the S parameter of DBS study. The structural analyses were carried out using XRD to investigate for the modification in the structural nature, degree of crystallinity and average crystallite size of the polymer after ion irradiation. Additional information on the modifications of optical and chemical properties was extracted by means of UV–visible and FTIR spectroscopy respectively.