Surface modification of polydimethylsiloxane elastomer for stable hydrophilicity, optical transparency and film lubrication

Abstract

The surface of polydimethylsiloxane (PDMS) elastomer was hydrophilized by poly(acrylic acid) (PAAc) using Surface Initiated Atomic Transfer Radical Polymerization (Si-ATRP). The ATRP initiator chosen was ((Chloromethyl) phenylethyl) trichlorosilane, which was immobilized on the surface of the PDMS through a simple but innovative method of drop coating, in contrast to the commonly used vapor deposition and solution-immersion methods. Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) and X-ray Photoelectron Spectroscopy (XPS) were employed to examine surface properties of modified PDMS and confirmed presence of the PAAc chains covalently bonded to the PDMS surface. Physical properties and topography of the modified sample were characterized by water contact angle measurement and Atomic Force Microscopy. It is shown that the drop-coating of the silane initiator for ATRP modification with PAAc can result in good surface hydrophilization while causing minimum damage to the PDMS preserving its desired optical transparency. The resultant hydrophilic PDMS is stable in air and has film lubrication behavior in aqueous conditions and may be used in the development of advanced microfluidic devices and sensors where both surface hydrophilicity and bulk transparency are desired.