Key Elements on Surface Properties of Polyimide Copolymers
Several sorts of block polyimide based copolymers, namely poly(imide-co-siloxane) (PIS) block copolymers containing siloxane blocks in their polymer backbone have been investigated. In comparison with pure polyimides the PIS block copolymers possess some improvements, for example, enhanced solubility, low moisture sorption, and their surface reaches the higher degree of hydrophobicity already at low content of polysiloxane (PSI) in PIS copolymer. This kind of the block copolymers are used as high-performance adhesives and coatings. The surface as well as adhesive properties of PIS block copolymers depends on the content and length of siloxane blocks. The surface properties of PIS block copolymers are strongly influenced by enrichment of the surface with siloxane-based segments. Micro phase separation of PIS block copolymers occurs due to the dissimilarity between the chemical structures of siloxane and imide blocks even at relatively low lengths of the blocks. The surface analysis of PIS block copolymers using various methods of investigation ,for example, contact angle measurements, scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS), was performed, and the strength of the adhesive joint to more polar polymer was studied. The surface and adhesive properties are discussed in view of the varied composition of PIS block copolymers.