Xianli Liu

Facile preparation of pH-sensitive poly(acrylic acid-co-acrylamide)/SiO2 hybrid hydrogels with high strength by in situ frontal polymerization

A series of poly(acrylic acid-co-acrylamide) (PAA)/SiO2 hybrid hydrogels were prepared by in situ frontal polymerization. It was found that the increase in the concentration of SiO2 nanoparticles could lead to the increase in front velocity (Vf) and the highest front temperature (Tmax). This may be attributed to the fact that SiO2 nanoparticles could increase the liquid viscosity of reaction mixture. The obtained PAA/SiO2 hybrid hydrogels were characterized by SEM and Fourier transform infrared spectroscopy spectrum and swelling measurements. The pH-sensitive swelling behaviors showed that the prepared PAA/SiO2 hybrid hydrogel had high pH sensitivity in different pH buffer solutions. Mechanical property test indicated that the PAA/SiO2 hybrid hydrogels exhibited a high compressive strength while remaining a high swelling radio (SR). The maximum of compressive strength and SR of the hybrid hydrogel may reach 42.6 kPa and 17.8, respectively, which was much higher than that of pure PAA hydrogel.

Measurement of pyrene in the gills of exposed fish using synchronous fluorescence spectroscopy

A synchronous fluorescence spectroscopy (SFS) method was developed for determination of pyrene in the gills of exposed fish. The wavelength differences (Δλ) of 50 nm was maintained between excitation and emission wavelengths and it was found to be suitable for the effective determination of pyrene in fish gills; the peak were observed at λ(ex) 334.5 nm. Linear relationships between SFS intensity and the concentration of pyrene in n-hexane solution were established. It was demonstrated that the SFS method was effective, simple, and less expensive, providing an attractive alternative for the rapid analysis of pyrene in fish gills.

Synthesis and characterization of benzoxazine monomers from rosin and their thermal polymerization

Two novel benzoxazine monomers (Bra-1 and Bra-2) from rosin were synthesized and the highly thermally stable polybenzoxazines were obtained by the thermal cure of the corresponding benzoxazine monomers. The chemical structure of the monomers was confirmed by FTIR and 1H NMR spectra. FTIR and DSC showed that the monomers were thermally initiated and polymerized via ring-opening polymerization. Thermogravimetric analysis (TGA) indicated that the incorporation of rigid bulky hydrogenated phenanthrene ring and imide structure could enhance the char yield and thermal stability of polybenzoxazines.

Comparison of two bisbenzoxazines containing carboxylic groups and their thermal polymerization

Two bisbenzoxazine monomers containing carboxylic groups (named as BBA for based on bisphenol-A and BPA for based on phenolphthalein) were synthesized and their structure and properties were compared with each other. The chemical structures of these bisbenzoxazine monomers containing carboxylic groups were confirmed by Fourier transform infrared (FTIR), 1H NMR, and differential scanning calorimetry (DSC). FTIR spectrum and DSC showed that both of the bisbenzoxazine monomers were thermal initiated and polymerized via ring-opening polymerization. Thermogravimetric analysis indicated that the incorporation of carboxylic groups could catalyze the benzoxazine ring-opening reaction and the polybenzoxazine from BPA showed higher char yield and thermal stability than that from BBA.