Preparation and Characterization of Urea-formaldehyde Resin/reactive Montmorillonite Composites

The urea-formaldehyde resin/reactive montmorillonite composites were prepared by in situ polymerization. The reactive montmorillonite was prepared firstly by being ion exchanged with organic molecules and secondly by being grafted with silane coupling agent, which could be demonstrated by X-ray diffraction（XRD） and thermogravimetric analysis（TGA）. Scanning electron microscopy（SEM） revealed that the morphology of the urea-formaldehyde resin/reactive montmorillonite composites were ellipsoid or columnar particles. Energy dispersive spectrometry（EDS） confirmed that the reactive montmorillonite was encapsulated by urea-formaldehyde resin. Differential scanning calorimetry（DSC） indicated that curing process of the ureaformaldehyde resin/reactive montmorillonite composites consumed more energy than pure urea-formaldehyde resin. Thermogravimetric analysis（TGA） showed that the thermal stability of the urea-formaldehyde resin/reactive montmorillonite composites improved compared to pure urea-formaldehyde resin. Furthermore, the reactive montmorillonites reduced the formaldehyde emission of the composites and increased the water resistance. Finally, the mechanism to prepare the urea-formaldehyde resin/reactive montmorillonite composites was proposed.

Thermally Stable and Organo-soluble Polyamides Containing Triazine Rings and Ether Linkages in the Main Chain: Synthesis and Characterization

In order to synthesize new polyamide（PA） 5 and copolyamides（Co PA） 7a-7d, a new-type of dicarboxylic acid containing triazine ring was successfully synthesized from 2,4-dichloro-6-methoxy-s-triazine 1 and 4-aminobenzoic acid. New polyamide 5 containing triazine moiety was prepared from 4,4＇-（6-methoxy-1,3,5-triazine-2,4-diyl）bis（azanediyl）dibenzoic acid 3 and 4,4′-diaminodiphenylether by direct polycondensation reaction. Then new series thermally stable copolyamides 7a-7d with high solubility in common organic solvents were synthesized from the direct polycondensation reaction of diacid 3 as a first monomer, aliphatic-aromatic diacids 6a-6d as second diacids and 4,4′-diaminodiphenylether. All of the above polymers were fully characterized by 1H-NMR and FTIR spectroscopy, elemental analysis（CHN）, inherent viscosity, solubility tests, gel permeation chromatography（GPC）, differential scanning calorimetry（DSC） and thermogravimetric analysis（TGA）. The resulted Co PAs 7a-7d have shown good inherent viscosities, solubility and thermal properties.

The origins of the broadband photoluminescence from carbon nitrides and applications to white light emitting

Carbon nitrides synthesized by thermal polycondensation of melamine at 700 ~C exhibit photoluminescence （PL） ranging from 400 to 650 nm. This broad PL is attributed to band to band transitions and bandtail transitions of lone pair （LP） states of intra-tri-s-triazine and inter-tri-s-triazine nitrogens. The proposed PL mechanism is further confirmed by diffusion reflectance spectroscopy, as well as time-resolved and temperature-dependent PL. This intense fluorescence is stable at different pH and resistant to UV exposure, suggesting that this inexpensive broadband luminescent material could be significant for white- light-emitting （WLE） applications. Thus, quasi-WLE films and membranes with designed patterns are fabricated by embedding the carbon nitrides into polymethyl methacrylate. Moreover, even broader PL （400 to 740 nm） is acquired in com- posite films composed of carbon nitrides, further suggesting that the carbon nitrides are robust candidates for WLE.