Pristine poly(3-hexylthiophene) (P3HT) samples were irradiated by 100 MeV silver (Ag8+) ion at fluences ranging from 10(10) to 10(12) ions cm(-2). The modification in the structure of P3HT is explained in the light of a comparative study of samples before and after irradiation by using various techniques such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), residual gas analysis (RGA) and dc conductivity. Significant changes in FT-IR spectra and surface morphologies of irradiated samples have been observed at the ion fluence of 10(12) ions cm(-2). Changes in FTIR spectra, conductivity and surface morphology of the irradiated samples are further explained by RGA investigations. The obtained micropatterned polymers can be applied as microstructures with defined conductivity for sensor applications. (C) 2011 Elsevier B.V. All rights reserved.