ABSTRACT
Soluble hydroxyl-containing polyimides have recently been studied as thermally stable polymers for photoresist applications [1-3], non-linear optics [4] and as a hardener [5]. On the other hand, fluorinated polyimides have attracted attention for applications in gas separation [6], pervaporation [7] and sensors [8, 9]. A polymer with both glassy and crystalline domains exhibits low vapor permeability and, thus, is not a good candidate for surface acoustics wave (SAW) coatings. Therefore, polymer coatings with low glass transition temperature (Tg) are prefer-
able for SAW devices. Polysiloxanes are chemically stable and have very low Tg. imparting optimum viscoelastic properties for rapid vapor sorption; however, they are rarely used in chemical sensor systems [8, 9]. In addition to having favorable permeation properties, the polymer must be soluble in a volatile solvent and exhibit stable, well-formed coating. In a previous paper, we found that the rigid imide segments restricted the motions of the polysiloxane chains, and the flexible polysiloxane segments enhanced the stability of imide segments [10]. Furthermore, the hydroxyl group in the soluble polyimide can be phosphorylated with diphenylphosphoryl chloride [11].
