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A novel photosensitive carbon nanotube (CNT) paste based on an acrylated single‐walled carbon nanotube (ac‐SWNT), a cross‐linking agent, and a photoinitiator has been prepared. Unlike the conventional photosensitive CNT pastes reported to date, our photosensitive paste system does not use a polymeric binder for the photopolymerization following UV exposure because the ac‐SWNT itself has cross‐linkable groups. Therefore, the subsequent firing process can be performed at relatively low temperatures and the residue of the organic vehicle in the SWNT pattern is minimized after firing. The ac‐SWNT was synthesized from the reaction between carboxylated SWNT (ca‐SWNT) and methacryloyl chloride in the presence of base, and its structure was characterized by Fourier transform infrared, Raman, and X‐ray photoelectron spectroscopy. After UV exposure and development with N,N‐dimethyl formamide a pattern with a resolution of 8 µm was obtained from the photosensitive CNT paste, which was then fired at 300 °C to give a clear SWNT pattern. When the photosensitive CNT paste was used for the fabrication of a cathode emitter for field emission displays, the CNT pattern emitted electrons under an applied electrical field with emission characteristics comparable with those obtained with screen‐printing from conventional CNT pastes. Therefore, such a photosensitive paste for fabricating SWNT patterns can be used in the production of field‐emission displays and in future device integration requiring carbon nanotubes, because it provides large‐area patterning of SWNT with high stability and uniformity.

Poly(methyl-co-cyclosiloxane bearing silsesquioxane)s (P(M-co-CSSQs)) were prepared. Using poly(e-caprolactone) (PCL) as a template, PCL / P(M-co-CSSQ) nanohybrid films were fabricated. The electrical, morphological, and mechanical properties of the PCL / P(M-co-CSSQ) films were investigated. The dielectric constant of a cured PCL / P(M-co-CSSQ) film at 420℃ scaled down from 2.55 to 2.05 and refractive index from 1.41 to 1.33 when 20 vol. % of the PCL was admixed with the polymer matrix. The elastic modulus and hardness of the cured PCL / P(Mco- CSSQ) (2:8, vol./vol.) film were 2.50 and 0.32 GPa, respectively, showing dependency on the PCL content.

Summary: Dielectric cyclosiloxane bearing polysilsesquioxanes (CS-PSSQs) were prepared by acid catalyzed polymerization using 2,4,6,8-tetramethyl-2,4,6,8-tetra(trimethoxysilylethyl)cyclotetrasiloxane. The molecular weight, and content of the functional end-groups of the CS-PSSQs were found to be dependent on the process parameters, such as the molar ratio of water and catalyst to the &bond;OCH3 group of the silane monomer, the amount of solvent, and the poly(ɛ-caprolactone) (PCL) content, etc. Based on these CS-PSSQ prepolymers, nanoporous organic/inorganic hybrid thin films were fabricated by spin-coating mixtures of these prepolymers with star-shaped PCL on the silicon substrate, and subsequently heating them at 150 and 250 °C for 1 minute each and then at 420 °C for 1 hour. A dielectric constant as low as 2.28 was achieved for the nanoporous PCL/CS-PSSQ (3:7 v/v) film, along with low moisture absorption in ambient and water conditions, primarily due to the presence of hydrophobic moieties such as ethylene and methyl groups of the polymer and nano-sized hydrophobic pores inside the matrix, resulting in the film having stable dielectric properties. Moreover, the PCL/CS-PSSQ (3:7 v/v) nanohybrid film revealed a nanoporous structure containing ca. 1.52 nm of average-sized mesopores, as measured by the N2 adsorption method. The CS-PSSQ-only film showed high mechanical strengths having an elastic modulus and hardness of 6.64 and 0.88 GPa, respectively, for the 7 500 Å thick film and 2.41 and 0.38 GPa, respectively, for the PCL/CS-PSSQ (3:7 v/v) film. In addition, the crack velocity of the CS-PSSQ-only film was found to be ca. 10⁻¹¹ m · s⁻¹ in ambient conditions and an aqueous environment, probably due to the enhanced hydrophobicity and mechanical toughness of the incorporated methyl group, siloxane unit and ethylene moieties in the polymer matrix.

Several kinds of homogeneous organic–inorganic hybrid polymer thin films were designed with improved mechanical properties and low dielectric constants (<3.0). Novel soluble siloxane–silsesquioxane hybrid polymers were synthesized with cyclic and/or cage silane monomers, which had triorganosiloxy (R3Si1/2), diorganosiloxane (R2SiO2/2), and organosilsesquioxane (RSiO3/2) moieties with ethylene bridges at the molecular level, by the hydrolysis and condensation of 2,4,6,8-tetramethyl-2,4,6,8-tetra(trimethoxysilylethyl)cyclotetrasiloxane (a cyclic monomer). The electrical properties of these films, including the dielectric constant (~2.51), leakage current (6.4 × 10⁻¹¹ A/cm² at 0.5 MV/cm), and breakdown voltage (~5.4 MV/cm) were fairly good. Moreover, the mechanical properties of the hybrid films, including the hardness (~7 GPa), modulus (~1.2 GPa), and crack-free thickness (<2 μm), were excellent in comparison with those of previous spin-on-glass materials with low dielectric constants. The excellent mechanical properties were proposed to be due to the high contents of Si&bond;OH groups (>30%) and the existence of ethylene bridge and siloxane moieties in the hybrid polymer precursors. In addition, the mechanical properties of the hybrid films were affected by the contents of the cagelike structures. The more cagelike structures a hybrid film contained, the worse its mechanical properties were. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 626–634, 2003

Poly(methyl-co-trifluoropropyl)silsesquioxanes (P(M-co-TFP)SSQs) were prepared using methyltrimethoxysilane (MTMS) and trifluoropropyltrimethoxysilane (TFPTMS). The molecular weight, microstructure of the copolymers and properties of their thin films have been changed by adjusting reaction parameters such as the molar ratio of water to silane, the molar ratio of catalyst to silane, reaction time, solvent content, and temperature. The refractive index of the copolymer thin film decreased from 1.404 to ca. 1.348 as curing temperature was increased to 420 °C. The dielectric constant of the film decreased with an increase of the molecular weight of the copolymer, and the lowest dielectric constant obtained was ca. 2.2. Hardness and elastic modulus of the thin films were 0.7 and 5 GPa, respectively. Crack velocity was measured to be 10⁻¹¹ m/s at the film thickness of around 0.9 μm under aqueous environment.

Mesoporous dimethylsiloxane-incorporated silica materials are synthesized which exhibit high surface areas, regular mesopores, thick walls, high hydrophobicity and high mechanical strength.