Riguang Jin

Preparation of highly reflective and conductive metallized polyimide films through surface modification: processing, morphology and properties

Silvered polyimide films have been prepared by potassium hydroxide hydroxylation of polyimide film surfaces and incorporation of silver ions through subsequent ion exchange. Thermal curing not only recycloimidized the poly(amic acid) into polyimide, but also reduced silver ions into silver atoms and near-atomic silver clusters, which diffused and aggregated to give reflective and conductive surfaces without need of the addition of reducing agents. Films were characterized by X-ray photoelectron spectrometer, transmission electron microscopy, scanning electron microscopy and tapping mode atomic force microscopy. The thickness of the silvered layers and the reflectivity and conductivity of the silvered films can be controlled. By this method, the double-sided silvered polyimide films with excellent reflective (reflectivity > 97%) and conductive surfaces (surface resistivity = 0.02 Ω cm−2) could be easily fabricated. Their essential mechanical properties could be maintained, and the silver–polymer adhesion was outstanding.

Synthesis and characterization of stimuli-responsive poly(acrylic acid) grafted silica nanoparticles

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.

Controllable embedding of silver nanoparticles on silica nanospheres using poly(acrylic acid) as a soft template

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.