Hongjie Xu

Preparation and properties of organo‐soluble polyimides based on 4,4′‐diamino‐3,3‐dimethyldiphenylmethane and conventional dianhydrides

4,4′-Diamino-3,3′-dimethyldiphenylmethane was used to prepare polyimides in an attempt to achieve good organo-solubility and light color. Polyimides based on this diamine and three conventional aromatic dianhydrides were prepared by solution polycondensation followed by chemical imidization. They possess good solubility in aprotonic polar organic solvents such as N-methyl 2-pyrrolidone, N,N-dimethyl acetamide, and m-cresol. Polyimide from 4,4′-diamino-3,3′-dimethyldiphenylmethane and diphenylether-3,3′,4,4′-tetracarboxylic acid dianhydride is even soluble in common solvents such as tetrahydrofuran and chloroform. Polyimides exhibit high transmittance at wavelengths above 400 nm. The glass transition temperature of polyimide from 4,4′-diamino-3,3′-dimethyldiphenylmethane and pyromellitic dianhydride is 370°C, while that from 4,4′-diamino-3,3′-dimethyldiphenylmethane and diphenylether-3,3′,4,4′-tetracarboxylic acid dianhydride is about 260°C. The initial thermal decomposition temperatures of these polyimides are 520–540°C.

Preparation of soluble polyimide–silver nanocomposites by a convenient ultraviolet irradiation technique

Abstract The soluble polyimide (PI)–silver nanocomposites were synthesized successfully by a novel convenient ultraviolet irradiation technique. Two precursors (AgAc, AgNO 3 ) were used as the sources of the silver particles. Transmission electron microcopy showed that two types of silver particles with diameters of 6–10 and 15–20xa0nm, respectively, were homogeneously dispersed in the PI matrix. X-ray diffraction results were well corresponding to the size of the smaller silver particles, and the larger silver particles may be the aggregates of the smaller ones. The absorption peaks due to the surface plasmon resonance of the silver particles in the two PI–silver nanocomposites was observed at 420–430xa0nm in the ultraviolet–visible (UV–VIS) absorption spectra.

Preparation and properties of high‐pretilt‐angle polyimides based on an alicyclic dianhydride and long alkyloxy side‐group‐containing diamines

A series of polyimides were prepared by a solution polycondensation reaction between 3-carboxylmethylcyclopentane-1,2,4-tricarboxylic dianhydride and 4-alkyloxybenzene-1,3-diamines in N-methyl-2-pyrrolidone and chemical imidization with triethylamine and acetic anhydride. These polyimides possess great organo-solubility, high optical transparency, and high pretilt angles. They are soluble not only in strong polar aprotic organic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, m-cresol, and 1,4-butyrolactone but also in common low-boiling-point solvents such as chloroform and tetrahydrofuran, and some are even soluble in acetone. They exhibit high transparency at wavelengths greater than 320 nm. They can generate pretilt angles greater than 5°, and some can even achieve pretilt angles greater than 10°. The pretilt angle of a polyimide increases with the increasing length of the alkyloxy side group. The polyimides possess glass-transition temperatures between 180 and 230 °C and thermal decomposition temperatures (onset temperatures) of about 435 °C.

CELL CULTURING ON NANOGROOVED POLYSTYRENE PETRI DISH INDUCED BY ULTRAVIOLET LASER IRRADIATION

Nanogrooved surface of polystyrene (PS) petri dishes was induced by an ultraviolet laser irradiation (ULI) method. After laser treatment, the water contact angle was decreased significantly from 72° to 38°. The influence of the surface modification on the growth of the human tongue squamous cells carcinomas (HTSCC) was investigated. The laser-irradiated PS surface showed enhanced attachment and growth in HTSCC cell culture test. Moreover, cell orientation was successfully controlled by selectively treating the PS surface.

A novel solid-liquid route for the preparation of Cu3Se2 and Ag2Se nanocrystals

Abstract Cu 3 Se 2 and Ag 2 Se nanocrystals have been synthesized with Se as the precursor in aqueous solutions under photo-irradiation at room temperature. The obtained products were analyzed through X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The results showed that the tetragonal phase of Cu 3 Se 2 with nearly spherical grains and the orthorhombic phase of Ag 2 Se with nanoscale dendrite were formed. The experiments also confirmed that photo-irradiation and Na 2 SO 3 played important roles in the formation of Cu 3 Se 2 and Ag 2 Se nanocrystals. The formation mechanism of Cu 3 Se 2 and Ag 2 Se nanocrystals was investigated in detail.

A study on mineralization behavior of amino-terminated hyperbranched polybenzimidazole membranes

Amino-bearing polymers, coated with apatite or similar minerals, have attracted significant attention for their potential in medical applications. In this study, an amino-terminated hyperbranched polybenzimidazole (HBPBI) membrane was used as a substrate for apatite growth. The membrane was soaked in solutions of CaCl2, Na2HPO4 and SBF to yield an apatite coating. The structure and morphology of the layers were characterized by FTIR-ATR, XRD and FESEM. The results indicate that the high densities of amino, imide and imidazole groups on the amino-terminated HBPBI membrane provide active sites for the growth of apatite.

Preparation and properties of novel fluorinated polyimides based on 2,2', 6,6'-tetrafluorobenzidine

Fluorinated polyimides were prepared from 2,2′,6,6′-tetrafluorobenzidine and four conventional dianhydride monomers by a solution polycondensation reaction followed by a chemical imidization. Polyimide based on 2,2′,6,6′-tetrafluorobenzidine and hexafluoroisopropylidene bis(3,4-phthalic anhydride) (6FDA) is soluble in organic solvents such as NMP, DMA, DMF, THF, chloroform, and acetone while those based on 2,2′,6,6′-tetrafluorobenzidine and pyromellitic dianhydride (PMDA), benzophenone-3,3′,4,4′-tetracarboxylic acid dianhydride (BTDA), diphenylether-3,3′,4,4′-tetracarboxylic acid dianhydride (ETDA) are not. Polyimide from 2,2′,6,6′-tetrafluorobenzidine and 6FDA possesses high optical transparency at 350–700 nm and has a in-plane refractive index of 1.558 at 632.8 nm. All polyimides exhibit glass transition temperatures above 350°C. They also possess very high thermal stability.