Hybrid optical films of TiO2‐triethoxysilane‐capped polythiourethane (TCPTU) with high refractive indices have been prepared via an in situ sol‐gel method. The high refractive index triethoxysilane‐capped polythiourethane (TCPTU) was synthesized by polyaddition of the triethoxysilane‐modified trimercaptothioethylamine (TMTEA) and 2,2′‐dimercaptoethylsulfide (MES) with 2,4‐tolylene diisocyanate (TDI). The titania content in the hybrid films can be adjusted from 0 to 80 wt.‐% by the feed ratio of titania precursor [Ti(OBu)4] to polymer (TCPTU). Both FTIR and DSC analyses indicate that there is chemical bonding between the titania domain and the polymer chain. TGA results suggest that the titania of high content was successfully incorporated into polymer matrices and this series of hybrid films have good thermal properties. AFM measurements indicate that in the hybrid films the titania domains are of nanosize scale and the domain size averagely decreases from 60–80 nm to 5–20 nm with increasing content of titania, and the variation of surface roughness for the hybrid films has the same trend. These may be relative to the content of TCPTU and the interaction between titania and polymer (TCPTU). The refractive indices of the hybrid films at 632.8 nm increased from 1 632 to 1 879 as the titania content varied from 0 to 80 wt.‐%.
Summary: In this work, silver nanoparticles were embedded in electrospun organic/inorganic composite nanofibers consisting of PAN and TiO2 through photocatalytic reduction of the silver ions in silver nitrate solutions under UV irradiation. The morphology and diameter of PAN/TiO2 composite nanofibers could be controlled by varying the initial contents of TiO2 in the spinning solution. From TEM images and UV‐Vis spectra, it has been confirmed that monodisperse silver nanoparticles with a diameter of ≈2 nm were deposited selectively upon the titania of the as prepared composite nanofibers. The amount of Ag nanoparticles embedded on composite nanofibers was greatly influenced by the amount of TiO2 in composite nanofibers, reflecting the role of titania as the inorganic stabilizer and photocatalyst.
Morphology of silver nanoparticles embedded on PAN/TiO2 composite nanofibers. 相似文献
A method of manufacturing free‐standing, micrometer‐scale honeycomb polyetherimide films is reported for the first time. Films are manufactured with a dip‐coating technique under water‐assisted self‐assembly. It is shown that the addition of poly(organosilane/siloxane)s and poly(ethylene glycol) allows the formation of regular honeycomb patterns. The films demonstrated the high thermal stability inherent for polyetherimide. The wetting properties of films are reported. The presence of nanopores was revealed with SEM imaging of the films. The makeup of the films allows their use as asymmetric membranes for reverse osmosis and ultrafiltration.
Summary: Organic‐inorganic nanocomposite hybrid coatings were prepared through a dual‐cure process involving cationic photopolymerization of a hyperbranched epoxy functionalized resin and subsequent condensation of an alkoxysilane inorganic precursor. All the formulations investigated gave rise to photocured films characterized by high gel content values. An increase in glass transition temperature and an increase in storage modulus above Tg in the rubbery plateau is observed with increasing TEOS content in the photocurable formulation. The important role of GPTS on reducing the inorganic domain size and avoiding macroscopic phase separation was demonstrated by TEM analyses.
TEM obtained for one of the cured films in the presence of GPTS. 相似文献
Hybrid organic/inorganic acrylic nanostructured films were prepared by a UV/thermal dual‐curing process. The role of a fluorinated hydroxyl acrylate monomer (AF) as coupling agent was investigated. Increased Tg values and modulus of the dual‐cured films were achieved by increasing the TEOS inorganic precursor. The coupling agent deeply modified the surface properties of the cured films: the formation of hybrid films characterized by high hydrophobicity together with an increase on surface hardness was achieved. TEM analysis clearly evidenced the reducing of the nanosize dimensions of the inorganic silica domains by increasing the coupling agent content in the photocurable formulation.
Summary: We report herein calixarene derivatives, which could adapt to various fields of application, as novel pore generators for making nanoporous materials. The pore structure of nanoporous materials exhibits disordered pores with small mesopore diameter (2–3 nm), which is similar to the micelle‐like assembled structure of the calixarene compounds. The electro‐optical properties such as dielectric constants and refractive indexes of these porous thin films can easily be manipulated. The calixarene‐templated nanoporous films could find a variety of potential applications, such as low‐dielectric constant (k) materials and high‐surface area materials for catalysis and biotechnology.
Summary: Solutions containing chitosan of different molecular weights and several acidic monomers were prepared under various aging conditions. Hybrid chitosan/acrylic resin emulsions were prepared from these solutions by emulsion polymerization. The viscosities of the hybrid chitosan/acrylic resin emulsions were influenced significantly by the molecular weight of chitosan, the acidic monomer used, and the aging conditions. DSC and FT‐IR spectroscopy of the hybrid chitosan/acrylic resin films indicated that chitosan was well distributed in the films. The water absorption and formaldehyde adsorption abilities of the acrylic resin films prepared with chitosan were higher than the corresponding films prepared without chitosan, and they increased with increasing molecular weight of the chitosan. The morphology of these films, studied by TEM, revealed that the distribution of chitosan in the hybrid chitosan/acrylic resin emulsion was dependent on the molecular weight of chitosan, the acidic monomer used, and the aging conditions.
Epoxy/BaTiO3 hybrid materials are prepared as good candidates for organic capacitors. The hybrid system is cured by using camphorquinone and a iodonium salt through a free‐radical promoted cationic polymerization using a long‐wavelength tungsten halogen lamp. The cured films are fully characterized. Morphological characterization shows a well‐dispersed inorganic phase within the organic matrix. Electrical characterization demonstrates a linear increase of the dielectric constant with increasing filler content, while low dielectric loss values are obtained.
The fabrication and characterization of a hybrid polymer p‐n junction‐type thin film via electropolymerization of NPs and a precursor polymer is described. Blends of TiO2 NPs, CdSe NCs, Cbz‐COOH, and PVK were utilized to enable electrochemical deposition on ITO glass substrates. Spectroscopic, microscopic, and wetting measurements confirmed thin film fabrication. CV yielded a CPN nanocomposite with electropolymerized (i.e., crosslinked) carbazole units embedding CdSe NCs. Absorption and emission measurements confirmed a charge transfer mechanism between the crosslinked carbazole and the NCs resulting in a p‐n junction‐type thin film on ITO; with the observed quenching of CdSe NC emission. Several possible applications of such thin films are also discussed.
Transparent polyimide (PI) and chemically modified graphene nanocomposite films are prepared from solutions of pyromellitic dianhydride (PMDA)/4,4′‐oxydianiline (ODA) poly(amic acid) with various amounts (0.2–0.8 wt%) of graphene carboxylic acid (GCA) in DMAc. The GCA is synthesized by modifying chemically oxidized graphene (COG) with many carboxylic acid groups (–COOH) and is well‐dispersed in DMAc, the organic solvent most frequently used for PI synthesis. The GCA sheets in the PI/GCA composite films are well‐dispersed and aligned two‐dimensionally in the direction parallel to the PI films, which enhances the mechanical properties of the nanocomposite films.
Three series of composite films based on polyimide and MWNTs were prepared by conversion of pyromellitic dianhydride and 4,4′‐oxydianiline in the presence of the nanotubes, followed by thermal imidization. Carboxy‐ and amino‐functionalized as well as unmodified nanotubes were used. It was demonstrated that just 0.5 wt.‐% of nanotubes increased the tensile properties of the composite films distinctly. Surprisingly, a significant influence of the functional groups on the mechanical performance of the composite films could not be demonstrated. However, it was shown that functional groups may reduce the conductivity of the films. Furthermore, the influence of ultrasonication is discussed.
A difunctional methacrylate oligomer was mixed with a variable amount of a MAPTMS precursor in the presence of both a radical and a cationic photoinitiator. The simultaneous photolysis of both photosensitive molecules upon UV irradiation allowed the single‐step generation of a type‐II polymethacrylate/polysiloxane nanocomposite film. Methacrylate and methoxysilyl conversions during irradiation were efficiently monitored by FTIR spectroscopy. The inorganic structure of the resulting silica‐based hybrid films was characterized using 29Si solid‐state NMR. Finally, the reinforcement ability of the resulting hybrid films was also assessed by using a unique range of characterization techniques: DMA, scratch test, and nanoindentation.
Novel nanocomposites based on conductive Ag nanoparticles and a self‐assembled polystyrene‐block‐polybutadiene‐block‐polystyrene (SBS) block copolymer were investigated. Good confinement of the nanoparticles into polystyrene microphase was achieved by the addition of DT as surfactant. The polymeric matrix kept its hexagonal order packed cylindrical structure up to 7 wt.‐% content of Ag nanoparticles. An electrostatic force microscopy (EFM) analysis of well‐dispersed metal‐organic hybrid Ag/SBS films was used to characterize the electric behavior of the conductive nanocomposites.
The effects of the CTA concentration on polymerization kinetics, polymer microstructure, particle morphology, and adhesive performance of waterborne hybrid PSAs prepared by simultaneous free‐radical and addition miniemulsion polymerizations are studied. The development of the microstructure is shown to differ from waterborne acrylic PSAs obtained by free‐radical polymerization because of the contribution of the addition reaction, which in turn causes marked differences in the adhesive performance of the final films. A computer simulation is developed to obtain detailed information about the microstructure of PU/acrylic hybrids and to correlate the microstructure with the final adhesive properties.
Ultra‐thin fibers, consisting of blends of a PPE derivative and polystyrene, with average diameters ranging from 430 to 1 200 nm, were produced by electrospinning. The electrospinnability was significantly improved by adding pyridinium formate to the spinning solution. FT‐IR spectroscopy was used to confirm the composition of the electrospun fibers and their morphology was probed by SEM. The optical properties of the as‐prepared solutions, pristine and annealed fibers, and corresponding spin‐coated and solution‐cast films were investigated by UV‐vis spectroscopy. A comparison of the PL emission spectra revealed aggregation of PPE molecules in the electrospun materials but the extent of aggregation can be reduced if the materials are annealed above the glass transition temperature.
Iron‐oxide nanoparticles were functionalized with epoxy groups and were dispersed into a dicyclo‐aliphatic epoxy resin to obtain organic‐inorganic hybrid coatings via cationic ring‐opening photopolymerization. TEM investigations confirmed that the filler has a size‐distribution range between 5 to 20 nm, without the formation of aggregates. The influence of the presence of Fe2O3 on the rate of polymerization was investigated by real time FT‐IR spectroscopy. Increasing the iron‐oxide nanofiller in the photocurable resin induced an increase in the Tg values. By controlling the phase separation it was possible to obtain transparent iron‐oxide nanostructured coatings, characterized by improved hardness.
Air and 5 wt.‐% BSA solution are used as a model system to generate protein‐coated microbubbles, which are significantly smaller in diameter than the processing needle apertures. The effects of processing parameters (applied voltage and flow rate) on the bubble size distribution and stability are studied. The optimal processing conditions are also explored in terms of heating of the solutions and prepared structures. Both individual microbubbles and porous films were successfully prepared using this method which has significant potential for the preparation of microbubbles for drug delivery systems, porous coatings, thin films, scaffolds and ultrasound contrast agents. The versatile nature of the method implies that many macromolecules and other active agents can be used.
Summary: A new method to synthesize polyimide (PI)/silica nanohybrids has been presented. It uses silicic acid oligomer as the silica precursor, which was obtained by extracting with tetrahydrofuran (THF) from PH‐adjusted water glass. The films of PI/silica nanohybrids remained transparent even at high silica content due to the formation of nanometer‐scaled SiO2 particles at the addition of γ‐aminopropyltriethoxysilane (APTES). In comparison with pure PI, PI/silica hybrids showed improved thermal stability and mechanical properties, and lower linear coefficients of thermal expansion (CTEs). The glass transition temperatures of the hybrids were increased with increasing content of silica or APTES as a result of the increasing limitation to the movements of the PI backbone.
Transparent light‐emitting hybrid materials are produced by UV curing of acrylic resins containing silica precursors and photoluminescent [Cu4I4L4] clusters. Acrylic double‐bond conversion is followed by means of FT‐IR spectroscopy, and optical measurements are performed on cured films showing a high transparency of the films up to a content of 30 wt% TEOS and a bright luminescence with a maximum of emission centered at 565 nm (yellow‐orange). This study shows the possibility to obtain new advanced materials in which functional properties such as photoluminescence and scratch resistance are successfully conjugated in a hybrid film that maintains high transparency.
A processing method based on stretching of molten polymer nanocomposites was applied to prepare dichroic films. First, dodecanethiol‐capped gold particles were embedded in low density polyethylene. The resulting isotropic films were stretched in the melt under uniaxial loading using an elongational rheometer. The melt elongation technique resulted in reproducible characteristics of the optical properties and can be directly transferred to an industrial scale. The organic coating of the metal particles plays an important role in the generation of the dichroism. A reactive surface (adsorbed perfluorophenyl azide) led to strongly agglomerated particles which obviously did not lead to dichroic films.
