Probing Molecular Structures of Poly(dimethylsiloxane) at Buried Interfaces in Situ

Abstract

Silicone materials such as poly(dimethylsiloxane) (PDMS) are widely used in a variety of important applications such as polymer adhesives, packaging materials for microelectronics, polymer MEMS, microfluidics, biomedical implants, and marine antifouling coatings. In such applications, molecular structures of PDMS at buried interfaces will determine interfacial properties. Therefore, it is important to elucidate PDMS molecular structures at relevant buried interfaces. In this study, the interfacial structures of PDMS silicone elastomer in contact with silica and different polymer materials have been studied using sum frequency generation (SFG) vibrational spectroscopy. It was found that the PDMS methyl groups are ordered at the buried poly(ethylene terephthalate) (PET)/PDMS and fused silica/PDMS interfaces. However, these methyl groups tend to adopt different orientations at different interfaces. Using the SFG spectral fitting results, the possible ranges of tilt angles and twist angles of PDMS methyl grou...