Shengfang Li

Removal of Cationic Dyes from Aqueous Solution by Hydrophobically Modified Poly(acrylic Acid) Hydrogels

Hydrophobically modified poly(acrylic acid) hydrogels were synthesized using acrylic acid (AA), methyl methacrylate (MMA), ethyl methacrylate (EMA) and butyl methacrylate (BMA) as copolymer monomers. These hydrogels were carried out for removal cationic dyes from aqueous solution. It was found that the adsorption of cationic dye depended on the length of the side chain, hydrophobic monomer (MMA, EMA and BMA) content and pH of the solution. Increasing the hydrophobic monomer content led to an increase in the adsorption of cationic dyes on the hydrogels. The adsorption kinetics and isotherms of hydrogels were in good agreement with pseudo–second-order equation and the Langmuir equation, respectively. The cationic dyes adsorption of hydrogels involved a mechanism that combined swelling and electrostatic and hydrophobic interaction.

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.

Synthesis and characterization of a new reactive hyperbranched polyphosphate ester, and its modification on benzoxazine-bisoxazoline resins

A new reactive hyperbranched polyphosphate ester (HPPE) was synthesized by one step reaction. The structure of HPPE was characterized by 1H NMR, FTIR, and inherent viscosity. High performance flame retardant modified benzoxazine-bisoxazoline resins were obtained by the additional reaction with HPPE. Differential scanning calorimetry showed that there was an obvious shift in the exothermic peak of BPH5 (mass ratio of Ba-1,3-PBO and HPPE was 95:5) from 225 to 202 °C, comparing with that of BPH0 (pure benzoxazine-bisoxazoline resins). It meant that the curing reaction could be catalyzed and accelerated by HPPE. The impact strength experiments illustrated that the maximum impact strength of modified resins may reach 19.2 kJ/m2. The char yield at 700 °C of BPH5, BPH15, and BPH30 were 3.34, 4.47, and 7.75%, respectively. The benzoxazine-bisoxazoline resins modified by HPPE showed good flame retardancy.