A simple method was developed to directly deposit silver nanoparticles on the surface of silica spheres. The photochemical reduction was carried out by ultraviolet irradiation in air atmosphere at room temperature. The [Ag(NH3)2]+was reduced to silver atoms upon ultraviolet irradiation. Silver atoms subsequently deposited on the surface of silica spheres and agglomerated into silver nanoparticles. Silica spheres with silver nanoparticles of different size and density can be simply controlled by adjusting the UV-light irradiation time. The silver nanoparticles deposited on silica spheres were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, and field emission scanning electron microscopy.

Polyimide/silica/silver hybrid films were prepared via the combination of sol-gel method and in situ single-stage self-metallization technique. The structure of polyimide films in the thermal curing process and the influence of silica content on the transfer and aggregation of silver particles to the surface of hybrid films were investigated. Films were characterized by transmission electron microscopy, dynamic mechanical thermal analysis Fourier transform infrared spectroscopy, ultraviolet visible spectroscopy and mechanical measurements. The results indicated that there was no degradation of polyimide matrix after the formation of silica and silver particles. Silica acted as the nucleus for the silver particles. With increasing the content of silica, more and more silver particles keep in the hybrid films instead of transferring onto the surface of the hybrid films, and the reflections of hybrid films decreased gradually.

Polyimide/γ-Fe2O3 nanocomposite films with superparamagnetic behavior have been prepared by thermal curing of the magnetite (Fe3O4) nanoparticles-containing poly(amic acid) (PAA) derived from pyromellitic dianhydride (PMDA) and 4,4’-oxydianiline (4,4’-ODA) in N,N-dimethylacetamide (DMAc). To improve the dispersion of the doped nanoparticles, the amine-functionalized Fe3O4 nanoparticles reacted with the PMDA dianhydride in DMAc firstly, and then polymerization was carried out by adding 4,4’-ODA and then PMDA to form the PAA-grafted magnetic particles. Thermal treatment of the Fe3O4-doped precursor film converted the PAA into its final polyimide form with concomitant transformation of Fe3O4 into γ-Fe2O3, yielding a polyimide film with superparamagnetic behavior. The distribution of nanoparticles in the polymer matrix was investigated by transmission electron microscopy and field emission scanning electron microscopy. The nanoparticles and composite films were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, magnetic and mechanical measurement.

Polyimide/silica/silver hybrid films were prepared by the sol-gel method combined with in situ single-stage self-metallization technique. The structure of polyimide films in the thermal curing process and the influence of silica content on the migration and aggregation of silver particles to the surface of hybrid films were investigated. The hybrid films were characterized by transmission electron microscopy, dynamic mechanical thermal analysis, Fourier transform infrared spectroscopy, ultraviolet visible spectroscopy and mechanical measurements. The results indicated that there was no degradation of the polyimide matrix after the formation of silica and silver particles. Silica acted as the nucleus for the silver particles. With increasing silica content, more and more silver particles were kept in the hybrid films instead of being migrated onto the surface of the hybrid films and the reflections of hybrid films decreased gradually.

Polyurethane(PU) films have been hydroxylated by ozone and chemical reduction,and then grafted with 2-bromoisobutyryl bromide as the initiator for the atom transfer radical polymerization(ATRP) of 2-(dimethylamino)ethyl methacrylate(DMAEMA).The elemental composition and chemical structure of the films were characterized by water contact angle measurements,X-ray photoelectron spectroscopy (XPS) and attenuated total reflection-Fourier transform infrared(ATR-FTIR) spectroscopy.The molecular weight and polydispersities(PDI) of the polymer chains were determined by gel permeation chromatography(GPC).The results showed that the PU film had the most effective hydrophilic surface after treatment with ozone for 23 min,with the molecular weight and PDI of the resulting polyDMAEMA being 4.85×104 and 2.095,respectively.

Mono-disperse γ-Methacryloxypropyltrimethoxysilane(MPS) modified silica nanoparticles have been prepared by an in situ one-step process in which the preparation and modification steps were carried out concurrently.FTIR,XPS,TGA and TEM were used to characterize the chemical structure and morphology of the silica nanoparticles.The results indicated that the nanoparticles were monodisperse with an MPS organic shell having an external diameter of 75 nm and a surface density of about 3.45 μmol/m2.

Silver quantum dots (QDs) embedded silica/PAAc hybrid nanoparticles were prepared by copolymerization of acrylic acid (AAc) onto γ-Methacryloxypropyltrimethoxysilane (MPS) modified silica nanoparticles followed by reduction of the immobilized Ag+ ions to metallic Ag. The prepared hybrid nanoparticles were characterized using X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The hybrid nanoparticles dispersed well in aqueous media and showed effective bactericidal activities. The results suggest that the hybrid nanoparticles have potential application as a water-soluble agent in many fields.

A new route to porous polyimide (PI) films with pore sizes in the nanometer regime was developed. A polyamic acid (PAA)/polyurethane (PU) blend with PU as the disperse phase was first prepared via in situ polymerization of pyromellitic dianhydride and 4,4-oxydianiline in PU solutions. Porous PI films were obtained from PAA/PU films by thermolysis of PU at 360°C and imidization of PAA at 300°C, respectively. Fourier transform infrared spectroscopy and thermal gravimetric analysis were used to detect the imidization and thermolysis processes of PAA/PU blends under thermal treatment. The microporous structure of the PI films was observed by transmission electron microscopy. It was found that the size and content of pores increased with an increase in the PU mass fraction in the PAA/PU blend up to 20%. Because of the existence of nanopores, the dielectric constant of PI films decreased by a wide margin and was less than 2.0 at a PU mass fraction of 20%. It implies that this is an effective means to reduce the dielectric constant of PI, but it also causes the decrease of tensile strength and the rise of water absorption.

Polyimide/silica (PI/SiO2) nanocomposite films with 10 wt % of silica content were prepared by sol-gel process under the conditions with and without additional water. The presence of additional water has great effect on the silica particle size and thus on the properties of the prepared PI/SiO2 films. The results indicated that with additional water, the silica particles formed before the imidization of poly(amic acid) (PAA) and aggregated with the increasing of temperature and degree of the proceeding imidization process. For the nonaqueous process, the hydrolysis condensation reaction of tetraethoxysilane (TEOS) did not occur until the imidization of PAA took place, and no silica particles were found in the unimidized PAA films. The hydrolysis-condensation reaction of TEOS was initiated simultaneously by the trace water released from the imidization reaction, the self-catalysis mechanism of the approach provide a means of achieving uniformly dispersed silica particles formed in the PI matrix with particle size in the range of 30-70 nm. (c) 2007 Wiley Periodicals, Inc.

Silver nanoparticles embedded on silica nanospheres were prepared by using ion-exchangeable poly(acrylic acid) (PAAc) grafted on the silica surface as a soft template followed by chemical reduction. The prepared hybrid nanospheres were characterized using x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet–visible (UV–vis) absorption spectroscopy, and bactericidal activity measurements. The results suggest that mono-dispersed Ag nanoparticles with controllable diameters can be obtained on the surface of silica nanospheres by varying the concentration of the silver nitrate and the pH value of the suspension, and the hybrid nanospheres have excellent bactericidal activity and potential applications as bactericidal agents in biomedical fields.

Silica-poly(acrylic acid) (PAAc) core–shell nanoparticles (NPs) were successfully prepared via graft copolymerization of acrylic acid (AAc) onto vinyl-bond-modified silica NPs. Transmission electron microscopy (TEM) results indicated that the obtained micropheres have a core–shell morphology. Fourier transform infrared (FTIR) analysis and x-ray photoelectron spectroscopy (XPS) measurements confirmed that the surface of the nanoparticles was polymer-rich, consistent with the core–shell morphology. The influence of the synthetic conditions, such as reaction time and AAc concentration on the graft yield of PAAc grafted on the silica NPs was investigated. Dynamic light scattering (DLS) analysis showed that the silica-PAAc core–shell nanoparticles possessed excellent response to pH and ion strength. Because of their pH-responsive behavior and small feature size, nanostructure devices designed from the smart silica nanoparticles have potential applications including sensors and membranes.

By reactive extrusion in twin screw extruder, EPDM-g-MAH was prepared and then blended with PPO and PA6. The effect of the content of MAH in EPDM-g-MAH and the content of EPDM-g-MAH on the mechanical properties and morphology of PPO/PA6 alloy was studied. The results indicate that with the increase of the content of MAH in EPDM-g-MAH, the compatibility of EPDM and PPO/PA6 is improved, and the best performance of the blends is obtained when the content of MAH in EPDM-g-MAH varied from 1% to 2%. With the increase content of EPDM-g-MAH, the impact strength of the blends increases, but its tensile strength decreases.

A new route to porous polyimide films which leads to pore sizes in the nanometer regime. was developed. The polyimide.-foams were prepared from,blending PAA and PU via in situ polymerization( the latter being the disperse phase) by the thermolysis of PU and imidization of PAA, so porous polyimide(PI). films were prepared. The results of IR, TGA and TEM measurement shows that the optimal thermolysis temperature of PU is 360 degrees C, upon a thermal treatment the PU undergoes decomposition, leaving strip nanopores in PI matrix, and the size of pores increases with increasing PU,content. Because of the existence of nanopores, the dielectric constant of PI decreased by a wide margin and was less than 2.0 at PU mass fraction 20%, thus proving that this is an effective means to reduce the dielectric constant of PI, but it cause the decrease of tensile strength and the rise of water absorption.

Reflective and surface conductive flexible polyimide (PI) films were prepared by the incorporation of silver(l) acetate and 1,1,1-trifluoro-2,4-pentanedione into a dimethylacetamide solution of several poly(amic acid)s which were prepared from dianhydrides and diamines. Thermal curing of the silver(I)-containing poly(amino acid)s precursor led to cycloirniclization of the PI with silver(l) reduction and formation of a reflective and conductive silvered surface at about 13 wt % silver. Effects on silver particles migration and aggregation were discussed in this article. The results indicated that the PI structures with flexible chains and groups easily fabricate the silvered films, with both reflective and conductive characteristics. With the forced air condition, the evaporation rate of the solvent and water increases, which facilitates the migration of silver particles to give reflective and conductive silvered surfaces. Films were characterized by transmission electron microscopy, scanning electron microscopy, and tapping-mode atomic force microscopy. Electrical conductivity, reflectivity, and dynamic mechanical thermal analysis were performed on the metallized films. (c) 2006 Wiley Periodicals, Inc.

A method to generate nanoporous polyimide films with low dielectric constants was proposed. The preparation consisted of two steps. Firstly, a polyimide/silica hybrid film was prepared via sol–gel process. Secondly, the hybrid film was treated with hydrofluoric acid to remove the dispersed silica particles, leaving pores with diameters between 20 and 120 nm, depending on the size of silica particles. Both hybrid and porous films were subjected to a variety of characterizations including transmission electron microscopy observation, dielectric constant measurement and tensile strength measurement.