Wide range control in the elastic properties of PDMS polymer by ion beam (H+) irradiation

Abstract The effects of ion irradiation on the elastic and surface properties, nanostructure and the chemical changes of the widely used polydimethylsiloxane (PDMS) polymer were investigated as a function of the ion fluence, induced by high-energy ionizing radiation (2.0 MeV proton beam). The polymer was irradiated with different fluences of protons and then the chemical changes, the elastic modulus and surface roughness were investigated by infrared spectroscopy (ATR-FTIR) and Atomic Force Microscopy (AFM). The FT-IR measurements showed very significant chemical changes in the material upon proton irradiation, such as detachment of methyl side groups first, then the starting of the main chain scissions, until the major silicatization of the PDMS by the formation of an inorganic silica like final product (SiO x ). The AFM force curves were obtained by performing contact-mode point-spectroscopy. Their evaluation showed, that the surface elastic properties of PDMS can be controlled in the range of 240 MPa to 49 GPa (Young's modulus) with ion fluencies between 1.68 × 10 13 ions/cm 2 to 1.25 × 10 16 ions/cm 2 , respectively. Compared to the 3–4 MPa of the reference material this indicates a more than four orders of magnitude increase in the elastic modulus of the material. The accompanying changes in the nanostructure of the polymer were characterized with AFM topography measurements and are also discussed in detail.