Molecular Structures of Surfaces and Interfaces of Poly(dimethylsiloxane) Incorporated with Silicone Oils Containing Phenyl Functionality

Poly(dimethylsiloxane) (PDMS) materials have been widely researched and applied as fouling-release coatings. Incorporation of silicone oils into PDMS has been shown to improve the antifouling properties of PDMS materials. In this research, we applied sum frequency generation (SFG) vibrational spectroscopy to study PDMS materials incorporated with various silicone oils containing phenyl groups in air, water, and protein solutions. It was found that the surface structures of various silicone oils varied, which results in different surface structures of PDMS with different oils incorporated. Such different PDMS surfaces interact with water molecules differently, leading to different surface hydrations. A model protein, fibrinogen, was used to study molecular interactions between oil-incorporated PDMS and biological molecules, testing the antifouling and fouling-release performance of different PDMS materials. It was found that fibrinogen has different adsorption behaviors on different PDMS surfaces, while adsorbed fibrinogen adopts bent structures. This study demonstrated that SFG can be used to deduce molecular information on silicone oil, PDMS, water, and fibrinogen on surfaces/at interfaces in situ in real-time. The different silicone oils incorporated into PDMS changed the PDMS surfaces, leading to varied interactions with water and biological media, influencing the antifouling and fouling-release activities. In most cases, the presence of silicone oils could enhance the surface hydration. However, the presence of phenyl groups could reduce the level of surface hydration. Nevertheless, our studies demonstrated that incorporation of silicone oils into PDMS led to better antifouling or fouling-release properties.