Reiner Kasemann

Development of optical waveguides by sol-gel techniques for laser patterning

ORMOCERs with high optical performance and chemical stability are synthesized via the sol-gel process. Methacrylate group substituated silanes are copolymerized with methacrylic acid which acts as a chemical link between Zr as second inorganic network former. Chemical stable complex formation is proved by IR analysis and 13c NMR investigations. This material is laser patternable by the addition of a suitable photoinitiator and is characterized by high dielectric strength and low optical loss for applications in optics and non-linear optics.

X(2)-active sol-gel inorganic-organic nanocomposites

Various compositions of inorganic-organic composites (ormocers and nanocomposites) have been synthesized and used as matrices for NLO push-pull molecules. It has been shown that dielectric properties and electrical conductivity during the sol-gel transition (curing parallel to corona poling) are the most important factors for obtaining high (Chi) (2) efficiencies. With low conductivity systems, (Chi) (2) values up to 9.7 pm/v have been obtained.

A new type of a sol-gel-derived inorganic-organic nanocomposite

A new type of sol-gel-based transparent inorganic-organic nano composites has been developed by increasing the inorganic phase dimension to values just below the point, where scattering can be neglected. For this purpose, nanosized boehmite particles {le} < 50 nm are homogeneously incorporated in a sol based on tetraethoxysilane and an epoxysilane. The nanoscale boehmite particles act as catalysts for the polymerization of the epoxy silane to polyethylene oxide, as proved by {sup 13}C NMR, and are linked to the matrix by Si-O-Al bridges, as proven by {sup 27}Al-NMR spectroscopy. The synthesized sols can be applied by standard coating techniques on transparent polymers and are cured thermally. The mechanical properties (scratch resistance, hardness) have been substantially improved compared to systems with molecular dimensions of the inorganic phase. The effect is attributed to the special structure of flexibly suspended nano-scale boehmite particles in an inorganic-organic network by a tailored interface.

Fine structure in the χ(2) signals of inorganic‐organic nanocomposites

Thin films of organically modified ceramics with nonlinear‐optical‐active chromophores produced in a sol‐gel process exhibit Maker fringe signals which are superimposed by a periodic fine structure. The fine structure is shown to be due to Fabry–Perot resonances of the second‐harmonic light which are stronger as compared to the amplitude corresponding to the regular Fresnel surface reflectivity by one to two orders of magnitude. The effect which is also observed on unpoled samples is tentatively ascribed to an accumulation and partial spontaneous orientation of the chromophores at the film surfaces.

Sol-gel synthesis of a diepoxy-crosslinked ormocer adhesive for Cu/polyimide sealing systems

Sol-gel-derived Omocer adhesives starting from methyl-vinyl silanes, diphenyl silanes and tetraethoxy silanes with tailored strain dissipation properties have been synthesized and tailored as hot-melt sealing adhesives for Cu to polyimide. In order to establish an appropriate strain dissipation mechanism within the brittle Ormocer systems used as starting materials, an organic polymer chain based crosslinking reaction, linking amino groupings bonded to silanes together with difunctional epoxides was investigated. For controlling the process, spectroscopic data were used and correlated to peel strength. The system shows a peel strength of 10 N/cm, good dielectric properties and a high heat stability.

Fluorine modification of ORMOCER (ORganically MOdified CERamics)-coating materials

Fluorine modified ORMOCER (ORganically Modified CERamics) coating materials have been synthesized from 3-methacryloxy-propyltrimethoxysilane, zirconium-n-propoxide, methacrylic acid and various amounts of 1H,1H,2H,2H-perfluorooctyltriethoxysilane. The ≈ 5 μm thick films showed a good adhesion to glass surfaces and good abrasion resistance. Evaluation of contact angle measurements has shown that these transparent materials exhibit a low surface free energy similar to perfluorinated polymers.

Synthesis of high performance Cu/polyimide adhesives based on inorganic-organic composite materials

Sealing of Cu to polyimide in a hot melt process is difficult due to the very different surface properties of Cu and polyimide. Silicone-based systems are widely used due to their heat resistance, but their sealing strength is still rather low. A new hot melt system has been developed by using silane-based oligomers with polar groups (-OH and -NH2) to provide good adhesion and aromatic epoxy units to tailor the stress dissipation ability of the system during the peel test. The system is cured by heat, shows a peel strength of 10 N/cm and is stalbe up to 180 °C. The synthesis principles and the general properties of the system as well as the sealing performance are described.

Anorganisch-organische Nanokomposite als abriebbeständige Korrosionsschutzschichten

Uber den Sol-gel Prozes wurden neuartige anorganisch-organische Nanokomposite hergestellt. Durch kontrollierte Synthesebedingungen lassen sich flussige Phasen erzeugen, die als Beschichtungsmaterialien verwendet werden konnen. Die transparenten Schichten zeigen z.B. auf Aluminiumoberflachen gegenuber Polymerbeschichtungen wesentlich bessere Kratz- und Abriebfestigkeiten und wirken gleichzeitig als effektiver Korrosionsschutz.