Synthesis and characterization of new silicon-containing poly(arylene-1,3,4-oxadiazole)s

Investigation of Thin Films Made from Silicon-Containing Polyphenylquinoxaline-Amides

Thin films in the range of 50 nm to 10 μm thickness have been prepared from NMP solutions of silicon-containing polyphenylquinoxaline-amides which had been synthesized by the polycondensation reaction of aromatic diaminophenylquinoxalines with bis( p-chlorocarbonylphenyl)diphenylsilane. A spin-coating technique onto glass plates or onto silicon wafers was used to make the films, followed by gradual heating to remove the solvent. The resulting films were very smooth and free of pinholes when studied by atomic force microscopy (AFM). They showed a strong adhesion to silicon wafers, were thermally stable in air to above 400 °C and their dielectric constant was in the range of 3.5–3.7. Thermal treatment of the films was performed in order to induce crosslinking. Such treated films became completely insoluble in organic solvents, maintained their smoothness and strong adhesion to the silicon substrate, and did not show any Tg in DSC experiments. Their FTIR spectra in reflection mode did not show any changes compared with the untreated films, meaning on the one hand that the polymers maintain their structural integrity at high temperature and on the other hand that the number of crosslinks was very low and could not be detected by IR spectroscopy.

Silicon-Containing Polyesterimides

New silicon-containing polyesterimides have been synthesized by a solution polycondensation reaction, in a high-boiling-point solvent, of a silicon-containing diacid chloride (namely bis(p-chlorocarbonyl-phenylene)-diphenylsilane) with certain dihydroxy-compounds having preformed imide rings. All these polymers were soluble in polar amidic solvents, such as N-methylpyrrolidinone and dimethylformamide, and gave thin transparent films on casting their solutions. The polymers exhibited high thermal stability, with the initial decomposition temperature being above 400 °C for fully aromatic structures. Most of these polymers did show a glass transition: those containing only aromatic rings being in the range of 180–236 °C, while those having some ethylene units along with aromatic ones being in the range of 160–178 °C. The dielectric constants of the free-standing polymer films are in the range of 3.04–3.19. Very thin coatings, in the range of tens of nanometres, which were deposited onto silicon wafers, exhibited smooth and pinhole-free surfaces in atomic force microscopy investigations. All these characteristics are discussed and compared with those of related polyester-imides which do not contain silicon.

Photoinduced Optical Anisotropy in New Polymers containing Azobenzene Side Groups

A series of new photosensitive polymers have been synthesized by polycondensation reaction of 2,2-bis{3-amino-4-[( p-oxyhexyloxy- p'-butoxy)azobenzene]-phenylene}-hexafluoropropane or 2,2-bis{3-amino-4-[( p-oxybutyloxy- p'-phenyl)azobenzene]-phenylene}-hexafluoropropane with hexafluoroisopropylidene diphthalic anhydride or with a diacid chloride containing hexafluoroisopropylidene or dimethylsilane groups. These amorphous polymers have good solubility in organic solvents and good film-forming properties. The irradiation of polymer films with linearly polarized visible light causes a reorientation of the azobenzene groups by angular-selective E/Z photoisomerization. Thus, optical anisotropy is induced in the initially isotropic films. The photoinduced dichroism in the films was measured and the results are discussed with respect to the polymer structure.

Silicon-containing polyoxadiazoles-synthesis and perspectives

A review is presented on those polymers which contain diphenylsilylene units and 1,3,4-oxadiazole rings either in the main chain or in the pendent groups. The synthesis of silicon-containing monomers as well as of the polyoxadiazoles based on them is described. The properties of these polymers, such as solubility, film forming ability, thermal stability, electrochemical behavior and photoluminescence properties, and their potential applications are discussed.