Thomas Köpnick

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.

Synthesis and study of new silicon-containing polyoxadiazoles

A series of new poly-1,3,4-oxadiazoles has been synthesized by polycondensation reaction of hydrazine sulfate with a mixture of a dicarboxylic acid containing unsaturated bonds and a dicarboxylic acid containing silicon, by using methanesulfonic acid/phosphorus pentoxide as a reaction medium. These polymers were highly thermostable but they were only soluble in strong inorganic acids such as sulfuric or methanesulfonic ones. An alternative way was followed by using the corresponding dihydrazides containing unsaturated bonds and the corresponding diacid chloride containing silicon that reacted in N-methylpyrrolidinone (NMP) to give soluble silicon-containing unsaturated polyhydrazides, which were cyclodehydrated either by thermal or chemical treatment to give the corresponding polyoxadiazoles. Very thin coatings of polyhydrazides and polyoxadiazoles were deposited onto silicon wafers and they showed a very smooth surface, free of pinholes, when studied by atomic force microscopy (AFM). Some polyoxadiazole films showed strong blue photoluminescence.

New Silicon-Containing Poly(Imide-Amide)s

New aromatic silicon-containing poly(imide-amide)s have been synthesized by solution polycondensation of various aromatic diamines having ether bridges between phenylene rings with a diacid chloride containing silicon. These polymers are easily soluble in polar amidic solvents such as N-methyl-pyrrolidinone or dimethylformamide and can be cast into thin flexible films or coatings from such solutions. They show high thermal stability, with an initial decomposition temperature above 410°C and a glass transition temperature in the range of 251-285°C. Very thin polymer films deposited by the spincoating technique onto silicon wafers showed a smooth, pinhole-free surface in atomic force microscopy investigations.

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.

Comparison of Properties of Silicon-containing Poly(amide-imide)s

New silicon-containing poly(amide-imide)s have been synthesized by direct polycondensation of various aromatic diamines with a dicarboxylic acid containing the dimethylsilylene group and preformed imide cycles. These polymers are easily soluble in polar amidic solvents such as N-methylpyrrolidinone (NMP) or dimethylformamide (DMF) and can be cast into thin flexible films or coatings from such solutions. They show high thermal stability, with initial decomposition temperature being above 400°C and glass transition temperature in the range of 220-270°C. Very thin polymer films deposited by spin-coating technique onto silicon wafers showed a smooth, pinhole-free surface in atomic force microscopy investigations.

Aromatic Polyazomethines Containing Phenylquinoxaline Rings

New aromatic polyazomethines have been synthesized by polycondensation of terephthalic dialdehyde with aromatic diamines containing preformed phenylquinoxaline rings. These polymers are easily soluble in polar aprotic solvents such as N-methylpyrrolidinone and dimethylacetamide, and even in less polar liquids like tetrahydrofurane and can be cast into thin flexible films or coatings from such solutions. They show high thermal stability with the initial decomposition temperature being above 500 °C and glass transition temperatures in the range 240–292 °C. The very thin polymer coatings deposited by a spin-coating technique onto silicon wafers show a very smooth, pinhole-free surface in atomic force microscopy investigations. The free-standing films of 20–30 μm thickness show a low dielectric constant, which is in the range 3.25–3.56, which is promising for a future application as high-performance dielectrics.

Study of thin films made from aromatic polyamides with silicon and phenylquinoxaline rings in the main chain

Abstract Aromatic polyamides containing silicon and phenylquinoxaline rings in the main chain have been prepared by polycondensation reaction of a silicon-containing diacid chloride, namely bis(p-chlorocarbonylphenyl)-diphenylsilane, with various aromatic diamines having preformed phenylquinoxaline units. These polymers were easily soluble in polar aprotic solvents, such as N-methylpyrrolidinone (NMP) and dimethylformamide (DMF), and in tetrahydrofurane. They showed high thermal stability with decomposition temperature being above 450°C and glass transition temperature in the range of 253–304°C. Polymer solutions in NMP were processed into thin films having the thickness of tens of nanometer to 10 μm, by spin-coating onto glass plates or silicon wafers. The films had strong adhesion to substrates and exhibited very smooth surfaces, free of pinholes, in atomic force microscopy (AFM) studies. The free-standing films had dielectric constant in the range of 3.48–3.69. Thermal treatment of the films up to 350°C rendered them completely insoluble in organic solvents, while maintaining their smoothness and strong adhesion to the silicon substrate, and with no Tg in DSC experiments. Their FTIR spectra did not show any changes compared to the untreated films, meaning that polymers maintain their structural integrity at high temperature.

Photo-optical and electrochemical behavior of novel heterocyclic copoly(naphthylimide-amide)s

This study is concerned with the synthesis and properties of new soluble quinoxaline-containing copoly(naphthylimide-amide)s having different flexible units such as ether, hexafluoroisopropylidene or diphenylsilane, in which the six-membered imide cycle is directly connected to the amide unit through a N-N bond. The polymers were successfully synthesized through the Yamazaki-Higashi polycondensation reaction of a mixture 1:1 of naphthalene-N,N’-bis(imido-amine) and 4,4′-{1,4-phenylene-bis[(3-phenyl-2,7-quinoxalinediyl)oxy]}dianiline or 4,4′-{oxy-bis[4,1-phenylene(3-phenyl-2,7-quinoxalinediyl)oxy]}dianiline with 4,4′-hexafluoroisopropylidene-bis(benzoic) acid, 4,4′-diphenylsilane-bis(benzoic) acid or with 4,4′-oxy-bis(benzoic) acid. These poly(imide-amide)s exhibited good solubility in common aprotic solvents, and the resulting polymer solutions were processed into amorphous thin films with homogeneous and neat surfaces. Their thermal characterization indicated a moderate to high thermal stability and no glass transition. The photoluminescence study of polymers both in solution and film state showed their ability for blue light color emission. The HOMO and LUMO energy levels were calculated by using cyclic voltammetry and UV–vis spectroscopy data, showing good electron injection and transport characteristics.