Weixiao Cao

Synthesis of diazoresin and its photocrosslinking reaction

Diazoresins with different specific viscosities were prepared from diphenylamine-4-diazonium salt and paraformaldehyde in concentrated sulphuric acid with different ratios of CH2O/−N2+X-. In order to obtain a diazoresin with a specific viscosity in a given time at 0–5°C, more than a stoichiometric ratio was necessary. The photocrosslinking reaction of the diazoresins with various binder resins in solid film was investigated. The results show that the photocrosslinking reaction took place only in a system composed of diazoresin and binder resin containing −OH side-chain groups. The photodecomposition of diphenylamine-4-diazonium salt and its diazoresin in alcohol was studied. It was demonstrated that the diphenylamine aryl cation formed on decomposition is the dominant intermediate. The photocrosslinking mechanism between diazoresin and binder resin is discussed in a preliminary way.

Fabrication of Covalently Attached Ultrathin Films Based on Dendrimers via H‐Bonding Attraction and Subsequent UV Irradiation

Multilayed ultrathin films were obtained from phenolic shell-modified PAMAM dendrimers (G3.0) and diazo resin (DR) as building blocks via hydrogen bonding attraction using the nature of the linkage between layers converted from H-bonding to covalent, which increased the stability of the film dramatically.

Fabrication of a Covalently Attached Multilayer Film via In‐Situ Reaction

A covalently linked ultrathin multilayer film was fabricated from 2-nitro-N-methyl-diphenylamine-4-diazonium-formaldehyde resin (NDR) and phenol-formaldehyde resin (PR) in methanol-in-situ. The UV-vis, XRD, AFM and FTIR show that this multilayer is of high regularity, smoothness and stability.

Synthesis and characterization of 3-methoxydiphenylamine-4-diazonium salt and its diazoresin

3-Methoxydiphenylamine-4-diazonium salt (MDDS) and its diazoresin were synthesized. The photo- and thermal decomposition of salt and the resins were investigated. The results show that MDDS exhibits excellent thermostability as well as high photosensitivity. A series of diazoresins with different organic counteranions, which dissolve in common solvents and usually were chosen to manufacture the negative presensitized plate, were also synthesized The kinetics of the photo- and thermal decomposition of MDDS in ethanol is reported.

Self-assembly of single-walled carbon nanotube based on diazoresin

Abstract The self-assembly film of single-walled carbon nanotube (SWCNT) based on diazoresin (DR) were prepared on CaF 2 , mica substrates and Pt tip. After oxidation, the ends of SWCNT were opened and turned into carboxylic group, which can react with diazonium group via Coulombic attraction. The film formed was photosensitive. After UV irradiation, the ionic bond between carboxylic group and diazonium group would turn into covalent bond following the decomposition of the diazonium group. The self-assembly layer and the bond conversion between the layers of the film have been verified with infrared (IR) spectroscopy, UV-Vis spectroscopy and transmission electron microscope (TEM).

Synthesis and characterization of diphenylamine diazonium salts and diazoresins

3-Methoxydiphenylamine-4-diazonium salts (MDP-4-DS), 2-sulfodiphenylamine-4-diazonium salts (SDP-4-DS), N-methyldiphenylamine-4-diazonium salts (NMDP-4-DS), N-methyldiphenylamine-2-diazonium salts (NMDP-2-DS), carbazole-3-diazonium salts (C-3-DS), N-ethylcarbazole-3-diazonium salts (NEC-3-DS) (all of them with various counterions) and the corresponding diazoresins were synthesized. The photochemical and thermal decomposition properties of the salts and resins were studied. The results show that among the diazonium salts and resins studied, the MDP-4-DS and its resin exhibit the highest thermostability as well as high photosensitivity. The influence of the counterion on the properties of the diazonium salt and the diazoresin was also investigated. N-Methoxydiphenylamin-4-diazoniumsalz (MDP-4-DS), 2-Sulfodiphenylamin-4-diazoniumsalz (SDP-4-DS), N-Methyldiphenylamin-4-diazoniumsalz (NMDP-4-DS), N-Methyldiphenylamin-2-diazoniumsalz (NMDP-2-DS), Carbazol-3-diazoniumsalz (C-3-DS), N-Ethylcarbazol-3-diazoniumsalz (NEC-3-DS) (jeweils mit verschiedenen Gegenionen) und die entsprechenden Diazoharze wurden synthetisiert. Die photochemischen und die thermischen Zersetzungseigenschaften der Salze und Harze wurden untersucht. Von den untersuchten Diazoniumsalzen und Harzen zeigen MDP-4-DS und das entsprechende Harz die hochste Thermostabilitat und Photosensitivitat. Der Einflus des Gegenions auf die Eigenschaften der Diazoniumsalze und ihrer Harze wurde ebenfalls untersucht.

Photo-induced DNA cleavage in self-assembly multilayer films

Electrostatic self-assembly multilayer films have been successfully fabricated from a C60–ethylenediamine adduct (C60–EDA), and DNA. Under visible light irradiation, the DNA is cleaved and the films are destroyed. The photo-induced reaction follows a direct electron-transfer mechanism. A high oxygen concentration in the solution enhances the reaction, while separation of C60–EDA and DNA retards the reaction dramatically.

Fabrication of ultrathin films based on chitosan and bovine serum albumin and their stability studied with the radio-labeled method

Chitosan (CS)/bovine serum albumin (BSA) ultrathin films were fabricated on the modified quartz wafer through the layer-by-layer deposition technique. The effects of the experimental conditions, such as pH, molecular weight (MW), ionic strength and the coexistence of the additional polyanions on the fabrication and the stability of assembly films were investigated with a radio-labeled method. The results show that the amount of adsorbed BSA is proportional to the number of assembly cycle except the first two cycles and CS/BSA films fabricated in CS acetic acid aqueous solution (aq. AcOH) at pH 5.2 are more favorable compared with at pH 1.0. When two different MW CS were used (M η≈1.2×105, M η≈1.0×106), the lower MW CS adsorbs more BSA, but the films formed are less stable. The same trend is observed, i.e. the amount of adsorbed BSA in deionized water is higher but the films fabricated are less stable than in phosphate-buffered saline (PBS). The adsorption of BSA in the presence of poly(sodium styrene-sulfonate) (PSS) decreases severely due to existence of the strong interaction between BSA and PSS, which has been confirmed by the fluorescence spectrometry. The morphology of CS/BSA assembly films was visualized with atomic force microscopy (AFM) and shows that some aggregates of BSA occur and are eluted first in 1% sodium dodecyl sulfate (SDS) aqueous solution.

Interaction of sodium dodecyl sulfate with polyelectrolyte complex from diazoresin and poly(sodium styrene sulfonate) in aqueous solution

Polyelectrolyte complex diazoresin-poly(sodium styrene sulfonate) (DR-PSS) from diazoresin (DR) as cationic polyelectrolyte and poly(sodium styrene sulfonate) (PSS) as anionic polyelectrolyte does not dissolve in water or organic solvent because of its electrostatic crosslinking structure. It was found that the complex dissolves considerably in aqueous solution of sodium dodecyl sulfate (SDS) and confirmed that the DR-PSS-SDS system possesses extraordinary thermostability as well as high photosensitivity and can be used directly to produce a photoimaging coating.

Micropatterns constructed from Au nanoparticles

Covalently linked Au-NPs micropatterns have been successfully fabricated from the self-assembly film composed of 4-mercaptophenol-capped Au nanoparticles (Au-NPs) and -N2+ containing polymers of nitro-diazoresin (NDR) by selective exposure to UV light and development in sodium dodecyl sulfate (SDS) aqueous solution. The resultant well-defined micropatterns were characterized with AFM and XPS.