Monolithic Mo oxide/polypyrrole hybrid aerogels and xerogels were successfully synthesized through sol-gel methods. The PPy formed appears to be β-substituted. A 100 fold increase in electrical conductivity was observed for the hybrids (4× 10–3 S/cm) as compared to the pristine MoO3 gels (2× 10–5 S/cm). An initial increase in Li+ intercalation capacity is also observed for the hybrid. The electrical conductivity and Li+ intercalation depend greatly on the concentration of Motrichloro alkoxide precursor and sol aging conditions. The hybrid aerogels have a density of 0.5 g/cc and a surface area of 120 m2/g. The as-formed gels are amorphous and crystallize to the orthorhombic MoO3 phase at 375°C.

In this work, intercalated material was prepared consisting of a regular interchange of organic/inorganic layers. The products were obtained by reacting 3,4-dihidroxi-fenilalanina (DL-DOPA) in a solution with V2O5.nH2O gel, which suffered an oxidative polymerization/intercalation process, forming a film with a dark blue metallic color. The films were characterized using UV\Vis transmission spectroscopy, FTLR, ESR, X-ray diffraction, dc conductivity, and cyclic voltammetry. The X-ray diffractograms indicate that the lamellar structure of the V2O5 is preserved but the inter-planar space increase from 1.18 nm to 1.38 nm. The FTIR and ESR spectra confirms that the V2O5 structure is preserved, however the presence of melanin induces the reduction of Vv ions to Viv. The increase in the inter-planar spacing is observed to increase the stability and reproducibility of the electrochemical insertion/de-insertion of Li+. This increase in stability is also observed in the electrochromic properties of the film, which are fully reproducible even after more than 60 oxidation-reduction cycles. The melanin affects also the activation energy of the dc conductivity which changes from 0.35 eV to 0.20 eV.

Low-cost preceramic polymers have been developed and used for various coating and composite applications. These siloxane-based polymers can be tailored to be precursors to ceramics or remain as polymeric materials. Polyhydridomethylsiloxane (PHMS) serves as the base polymer, and it can be cured or modified by dehydrocoupling or a combination of hydrosilylation-dehydrocoupling reactions, both catalyzed by transition metal catalysts (Pt and Ru). The base polymer filled with various powders is used primarily for thick ceramic coatings. Modified polymers are used for low-temperature paint-like applications, especially where ambient curing is desirable. Both organic and inorganic modifications of PHMS for coating applications are discussed in this article. Paints containing such polymers and fillers are being evaluated for corrosion resistance and high-temperature applications.

Interactive dispersion-type LDPE/EVA films with anticorrosive properties were produced using host-guest systems of thermally stable volatile corrosion inhibitors (VCI) dicyclohexylammonium p-nitrobenzoate and phosphate, adsorbed on NaY zeolites and diatomaceous earths. Carbon steel specimens were either directly exposed to the inhibiting systems studied or wrapped with the additivated films. Accelerated corrosion tests were carried out where the inhibitive properties of the systems being studied were determined by mass loss of the test coupons. The influence of the mineral support on the volatility of the corrosion inhibitors was evaluated by TG/DTG techniques. The obtained results may be regarded as a confirmation of the hypothesis that VCI volatility may be controlled by their deposition on determined supports. Also, both VCIs had their efficiency enhanced by zeolites, and the phosphate greatly benefited from the use of diatomaceous earth.

1H-13C and 1H- 29Si CP/MAS NMR spectroscopy has been used to characterize the structure of sol-gel derived hybrid materials prepared from 3-glycidoxypropyltrimethoxysilane (GLYMO) and tetraethylorthosilicate (TEOS) as a function of hydrolysis water ratio and organic content. 1H-13C CP/MAS NMR data indicate that the concentration of hydrolysis water (R value) has a fundamental effect on the nature of the acid-catalyzed hydrolysis and ring opening products. 1H-29Si CP/MAS NMR data suggest that for low R values, the ormosils are composed of a silica network with epoxide groups randomly dispersed throughout. At high R values, epoxide functionalities were found to coat the surfaces of dense silica particles. Salt spray analysis indicates that the corrosion resistance behavior of thin films derived from GLYMOTEOS ormosils decreases as the concentration of hydrolysis water increases and improves as the organic content in the film increases. These observations can be related to the underlying thin film structure.

Spin-on glasses, generated by the condensation of an organic-inorganic hybrid silsesquioxane (SSQ), have great potential as low dielectric-constant semiconductor interconnection materials. After curing and condensation SSQ materials consist of an amorphous, inorganic, –Si–O-Sibridging network with organic, non-bridging –Si–R side groups. Relative dielectric constants in the range 2.5–3.3 are obtained for SSQ materials, depending on the curing conditions, and compare with 4.0 for conventionally-used fused silica. The non-bridging side groups significantly disrupt the SSQ network—occupying more than 25% of the Si bonds—and lead to materials that are considerably less stiff, hard and tough than fused silica. Perhaps more importantly, SSQ materials have thermal expansion coefficients greater than that of the intended Si substrate and therefore finish curing in a state of residual tension, leading to a susceptibility to stress-corrosion cracking. In this paper the development of thermomechanical properties during curing of SSQ spin-on glasses is considered and related to the driving force for film cracking deriving from the residual tension. Various crack suppression schemes involving mechanisms both intrinsic and extrinsic to the base SSQ are discussed.

Suspensions of silica (20 nim) in propoxyethanol were used to make porous silica coatings. A silane coupling agent, glycidoxypropyltrimethoxysilane (GPS), was added as a binder to increase coating durability and prevent cracking. GPS addition prevented crack formation but only when added in large amounts (GPS to silica weight ratio 0.5 to 1) such that porosity was filled by a GPS-based siloxane polymer. Attempts to enhance the fracture toughness of porous coatings through UV curing and glycol additions failed to lead to improvements in the critical cracking thickness (CCT). However, addition of triethylenetetramine resulted in a 3-fold increase in the CCT. Wear resistance increased for both the UV-cured and amine-cured coatings.

We investigated sol-gel derived silica based hard coatings on modified polyester substrates. The silica network was modified by incorporating an organic component and adding transition metal oxides. These modifications resulted in tailored thermal, optical and mechanical properties of the coatings. Various low temperature densification techniques were studied including appropriate sol-preparation procedure, enhanced solvent evaporation, ultraviolet (UV) irradiation, and low-temperature (below 150°C) heating. Oxygen plasma etching was applied to improve the adhesion of the sol-gel coatings on the plastic surface. Nanoindentation analysis revealed that the sol-gel coatings have a surface hardness up to 2.5±0.27 GPa, approximately an order of magnitude higher than that of the plastic surface.

The sol-gel process has been applied for the synthesis of inorganic-organic powder materials. For this purpose, low reactivity and, for reasons of comparison, nanoscaled sol-gel precursors and nanoscaled silica filler were used to synthesize a low molecular weight inorganic-organic composite which was meltable between 85°C and 100°C and curable at temperatures of 150°C - 200°C. The powders were used for electrostatic coating of aluminum sheets. The resulting coatings of the unfilled system exhibited excellent mechanical properties, e. g. a high abrasion resistance (weight losses between 6 mg and 10 mg per 1000 cycles by taber abrader test (ASTM D1044)) and high values for hardness (universal hardness (DIN 55676): 150 N/mm2). The hardness of the materials was increased up to 210 N/mm2 by the addition of silica, while the abrasion resistance remained unaffected.

The tear strengths of in-situ filled poly(dimethylsiloxane) (PDMS) networks were investigated using “trouser-tear” tests. The filled PDMS networks were prepared by the simultaneous curing and in-situ precipitation technique, the silica reinforcing phase being obtained by the hydrolysis and condensation of tetraethoxysilane present in excess of that required for the chain end-linking process. Transmission electron micrographs showed well-dispersed and unagglomerated silica particles, and thermogravimetric analysis indicated that the silica particles gave some improvements in thermal stability. In the tearing tests, “stick-slip” tearing was observed at higher rates, especially for the filled networks. The tear strengths were found to increase with increase in the amount of silica incorporated, with the largest increases occurring at the low silica contents.

Strengths have been measured for silica gels prepared with poly(ethylene oxide) (PEO) and poly(vinyl acetate) (PVAc). The modulus of rupture was determined using standard three-point bending in a mechanical tester. The samples were prepared by mixing tetraethylorthosilicate with the polymers dissolved in water (PEO) or water/ethanol(PVAc). Molecular weights between 200 and 3400 were used for PEO. Substitutions of the polymer for silica represented between 5 and 25% on a weight basis. In these systems, the interactions between the polymer and the silica network are largely through hydrogen bonding, between ether oxygens in PEO and silanols and between hydroxyls in PVAc and silanols. The extent of the bonding increases with increasing aging time, as indicated by an almost linear increase in the modulus of rupture. The increase for PEO was greater than for PVAc. Among PEO samples, the strengths were higher for higher molecular weights at the same weight fraction.

The properties of nano-structured plastics are determined by complex relationships between the type and size of the nano-reinforcement, the interface and chemical interaction between the nano-reinforcement and the polymeric chain, along with macroscopic processing and microstructural effects. In this paper we investigated the thermal and viscoelastic property enhancement on crosslinked epoxy using two types of nano-reinforcement, namely organoion exchange clay and polymerizable polyhedral oligomeric silsesquioxane (POSS) macromers. Glass transitions of these nano-composites were studied using differential scanning calorimetry. Small strain stress relaxation under uniaxial deformation was examined to provide insights into the timedependent viscoelastic behavior of these nano-composites. Since the size of POSS macromer is comparable to the distance between molecular junctions, hence as we increase the amount of POSS macromers, the glass transition temperature, Tg, as observed by DSC increase. However for epoxy network reinforced with clay, we did not observe any effect on the Tg due to the presence of clay reinforcements. In small strain stress relaxation experiments, both types of reinforcement provided some enhancement in creep resistance, namely the characteristic relaxation time as determined using a stretched exponential relaxation function increased with the addition of reinforcements. However, due to different reinforcement mechanisms, enhancement in the instantaneous modulus was observed for clay-reinforced epoxies, while the instantaneous modulus was not effected in POSS-epoxy nano-composites.

Novel micro-composites from Polyvinyl chloride (PVC) and silica were prepared using sol-gel technique. Different catalysts were used for the in-situ generation of silica network from tetraethylorthosilicate (TEOS) in the PVC matrix. Thin transparent films containing various proportions of silica in PVC were cast by the solvent elution technique. Mechanical properties of these films were studied. The results showed an increase in the value of Young's modulus and strain at rupture by the addition of small amount of silica in PVC. However, the stress at yields point and stress at rupture decreased with the addition of silica contents. Scanning electron microscopy (SEM-EDAX) studies were also performed on these samples.

Two types of polymer-silica nanocomposites have been prepared by undergoing free radical polymerization of 2-hydroxyethyl methacrylate (HEMA) either in the presence of HEMA-functionalized SiO2 nanoparticles (Type 1) or during the simultaneous in situ growing of the silica phase through the acid-catalyzed sol-gel polymerization of tetraethoxysilane (TEOS) (Type 2). Relationships between synthesis, morphology and mechanical properties are discussed mainly on the basis of solid state 29Si nuclear magnetic resonance spectroscopy (NMR), transmission electron microscopy (TEM), small angle X-ray scattering (SAXS), and dynamic mechanical analysis (DMA).

In order to link the fundamental research field of polymer crystallization with the technical important field of composite materials polymer-layered silicate nanocomposites from polyethylene (PE) are prepared and their morphology and properties are investigated. The effect of an external confinement introduced by highly anisotropic silicate layers of organically modified clay minerals on crystal growth and nanocomposite properties has been studied. The prepared nanocomposites of organically modified clay minerals and PE exhibit not only a homogeneous distribution of individual silicate layers but also of tactoids. The isothermal crystallization rate of PE in the corresponding nanocomposite at 120 °C is increased in the composite material due to the action of the silicate layers. A significant effect on crystal phase has not been observed so far but from X-ray experiments, however the crystal size seems to be influenced. The thermal stability of the nanocomposites is significantly enhanced and the decomposition mechanism has been changed due to the presence of the layered silicates within the host polymer acting as a barrier for the diffusion of small molecules like oxygen. Due to the none permanent attachment of the polymer chains to the silicate surface the thermal-mechanical properties are only moderately enhanced at low temperature while the glass transition temperature remains unaffected.

High-density, spatially addressable arrays of DNA probes offer a high-throughput approach to DNA sequence analysis that is likely to have a major impact on biological and genetic research. These arrays are comprised of short strands of immobilized DNA (“probe”) sequences prepared synthetically on a planar glass support. Samples of unknown, fluorescentlylabeled strands of “target' DNA can be analyzed by sequence-specific binding (“hybridization”) to the arrays in order to extract detailed sequence information. The detection sensitivity of these arrays is dependent on quantity and density of immobilized probe molecules on the surface, as well as the thermodynamics of nucleic acid hybridization. In this report, substrates with a porous, “3-dimensional” surface layer were investigated as a means of increasing the number of available probes, and therefore the amount of detectable bound target per unit area. Two methods for creating porous silica layers were investigated - a “subtractive” method and an “additive” method. For the systems investigated, the additive method, sol-gel processing, offered the most promising route for high density DNA arrays.

Hydrated silica rich Si-OH and Si-0- groups serve in a body environment as sites for nucleation of apatite, and are known as an essential chemical species for bioactive materials. Organic polymers having surface modified with the hydrated silica will show bioactivity: bone tissues grow toward the apatite layer and bond to materials. Thus MOPS-M (3-methacryloxypropyltrimethoxysilane) was grafted under emulsion polymerization procedure to high density polyethylene (HDPE), poly (vinyl chloride) (PVC) and polyamide (PA) substrates to examine in vitro deposition of apatite (bioactivity) after soaking in a simulated body fluid (Kokubo solution). Bioactivity was confirmed for the grafted PVC and PA substrates and discussed in terms of contact angle and relative amount of grafted silane molecules.

In an effort to lower the percolation threshold of carbon black-filled polymer composites, various polymer microstructures were examined. Composites prepared with a polyvinyl acetate (PVAc) latex and a poly(vinyl acetate – ethylene) water-dispersible powder showed a significantly lowered percolation threshold relative to an equivalently prepared composite that used a polyvinyl alcohol (PVA) solution to form the matrix phase. The percolation threshold of the dispersion-based composites occurred at 5 vol.% carbon black, while the equivalent solutionbased composite produced a threshold at 14 vol.%. By excluding the carbon black from regions occupied by polymeric particles, the dispersion-based composites lead to preferential aggregation of carbon black, as evidenced by SEM, and a lowered percolation threshold.

The organometallic complexes of transition metal M = Cu(I), Ag(I), Au(I) with d10 electronic configuration have interesting optical, electronic and magnetic properties. It is possible to prepare the high functional organometallic polymer materials by coordinating π-conjugated organic molecules with d10 metals. According to the experimental structures, the model polymers [M-C-C(N)]n are built up and quantum chemistry methods are used to calculate their properties. It is indicated from theoretical analysis that the organometallic polymers would have comparable conductivity when interactions exist between metals and π electrons of different chains.

Hybrid materials as inorganic-organic nanostructured composites require tailored surface chemistry in order to obtain a homogeneous distribution of the nanoparticles in the matrix. For this reason, nanoparticles with organic functions have been synthesized, first, to provide the desired ζ-potential at a given pH value, second, to avoid irreversible agglomeration due to the spacing effect, and third, to provide the appropriate surface chemistry. I could be shown that using this approach, it is possible to switch the ζ-potential of SiO2 nanoparticles from a negative to a positive potential at neutral and to bind DNA fragments to the particles for an effective transfection into cells. Other examples show that nanoparticles (TiO2, SiC2) coated with epoxy and methacryloxy groupings can be used as coating sol for the fabrication of thin films with green densities up to 67 % by volume only by photochemical crosslinking of the polymerizable groupings. Using this approach, interference layers have been fabricated on transparent plastics. In soft matrices, these particles permit to establish appropriate ζ-potentials and in electric fields by electrophoresis, it was possible to up-concentrate them to form gradient index optics. The investigations show that surface chemistry-tailored nanoparticles are a useful tool for the fabrication of nanocomposite hybrids.