Surface modification of silicone via colloidal deposition of amphiphilic block copolymers

Abstract

We report here on a method to functionalize silicone surfaces, which is based on the deposition of silicone-containing amphiphilic block copolymers from a colloidal water-ethanol dispersion. Using cross-linked silicones (Sylgard 184) as substrates, copolymers composed of two poly(glycerol monomethacrylate) (PGMMA) terminal blocks and a central poly(dimethylsiloxane) (PDMS) block can be effectively deposited when the PDMS content is ≥46 wt%. (≥65 mol%); the deposition provides smooth and stable surfaces, which significantly affected the protein adsorption behaviour of the substrate, suggesting a possible application in biomaterial coating. In air, the block copolymer surface films underwent a reorganization, which differs from the classical hydrophobic recovery of silicones and may be related to a disordered folding of lamellar structures. This led to a predominant surface coverage by thin, possibly monomolecular layers, which displayed a non-restructuring polar surface. However, as a consequence of the reorganization also larger aggregates were produced, albeit in relatively small numbers; these aggregates underwent a progressive hydrophobization (in this case a hydrophobic recovery) and probably dominated the contact angle behaviour of the material. In summary, the colloidal deposition of amphiphilic silicone-based block copolymers successfully modifies the surface properties of silicone substrates; however, attention must paid to reorganization phenomena in order to maximize the stability of the coating.