Yuju Che

Novel complex gel beads composed of hydrolyzed polyacrylamide and chitosan: an effective adsorbent for the removal of heavy metal from aqueous solution.

A novel kind of complex gel beads containing HPAM (hydrolyzed polyacrylamide) and chitosan components (HPAM-chitosan gel beads) was prepared and applied in the removal of Cu(2+), Pb(2+), and Hg(2+) ions from aqueous solutions. These gel beads exhibited a good performance for heavy metal removal. Moreover, the average diameter of these gel beads was about 1mm, which could be appropriate for use in column system. The removal order was Pb(2+)>Cu(2+)>Hg(2+) under the same conditions. The effects of different experimental parameters, such as adsorbent dosage, initial pH, temperature, and initial metal concentration, on the adsorption capacities were studied. The Freundlich model gave a better fit to the experimental data than the Langmuir model in adsorption isotherm study. Desorption study indicated that the gel beads were easy to be regenerated.

Solution properties of hydrophobically modified acrylamide-based polysulfobetaines in the presence of surfactants

Polymer–surfactant interactions in aqueous solutions of a acrylamide-based, hydrophobically modified polysulfobetaine (ADS) containing 3-[N-(2-methacryloxylethyl)-N,N-dimethylammonio]-propane sulfonate and stearyl methylacrylate, with sodium dodedyl sulfate (SDS), N-dodecyl-N,N,N-trimethylammonium bromide (DTAB), and Triton X-100 were studied using surface tension, rheology, Rayleigh light scattering, and dynamic laser light scattering techniques. The purpose of this study was to highlight the influences of the surfactant structure and the nature of the surfactant head group on the polymer–surfactant interactions. The results show that the interaction and association between ADS and surfactants are distinctly varied depending on surfactant type and surfactant concentration. SDS produced the strongest interactions with ADS, while DTAB and Triton X-100 interact with ADS to a lesser degree, which is attributed to surfactant structure and the nature of the surfactant head group. For SDS and DTAB, there are two driving forces for the complexation of the polymer and surfactants, resulting from the electrostatic interaction and the hydrophobic association. However, for the nonionic surfactant Triton X-100, only hydrophobic association predominated in the interaction between ADS and the surfactant. The mechanism and reconstruction of the polymer–surfactant complexes have been evaluated and discussed.

Aggregation Behavior of Copolymer Containing Sulfobetaine Structure in Aqueous Solution

Copolymers containing sulfobetaine (P(AM/DMAPS)) were synthesized by aqueous copolymerization of acrylamide with 3-[N-(2-methacroyloylethyl)-N,N- dimethylammonio]-propane sulfonate. Aggregation and disaggregation of P(AM/ DMAPS) copolymer in aqueous solution as a function of copolymer concentration, added salts, and temperature were studied by dynamic laser light scattering. P(AM/DMAPS) copolymers exist as a mixture of individual chains and interchain aggregation in deionized water. At low copolymer concentrations (below 1.0 g L−1), the intrachain aggregation is dominant. With increasing copolymer concentration, the interchain aggregation is enhanced. The addition of a small amount of salts (CNaCl < 0.1 mol L−1; CMgCl2/CaCl2 < 0.05 mol L−1) leads to the disaggregation of the intra- and interchain aggregation. Further addition of salts results in the enhancement of interchain aggregation. The influence of various cations (Na+, Ca2+, Mg2+) on the aggregation behavior increases in the order Na+ < Ca2+ < Mg2+. The increase of temperature from 25°C to 60°C facilitates the breakup of intrachain aggregation and the enhancement of interchain aggregation.

Physically cross-linked pH-responsive chitosan-based hydrogels with enhanced mechanical performance for controlled drug delivery

A novel physically cross-linked pH-responsive hydrogel with enhanced mechanical performance (PCAD) was prepared from chitosan (CS), acrylic acid (AA) and (2-dimethylamino) ethyl methacrylate (DMAEMA) via in situ free radical polymerization for controlled drug delivery. The successful fabrication of the hydrogels was verified by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) measurements. Scanning electron microscopy (SEM) and mechanical analyses demonstrated that the morphological and mechanical behaviors of the resultant hydrogels were strongly affected by the content of AA and DMAEMA. Moreover, the swelling properties of these hydrogels were systematically investigated, and the results indicated that they exhibited strong pH sensitivity. The drug delivery applications of such fabricated hydrogels were further evaluated, from which Bovine serum albumin (BSA) and 5-fluorouracil (5-Fu) were chosen as the model drugs for in vitro release. The results showed that the amount of 5-Fu and BSA released can be tuned by changing the composition of the hydrogel and the pH of the medium. Toxicity assays confirmed that the blank hydrogels had negligible toxicity to normal cells, whereas the 5-Fu-loaded hydrogels remained high in cytotoxicity for LO2 and HepG-2 cancer cells. As seen from the results, PCAD hydrogels seem to have a potential application in drug-delivery systems controlled by the external pH value for cancer therapy.

Effect of pH on Gelation Behavior of Hydrolyzed Polyacrylamide and O-carboxymethyl Chitosan Mixed System

The effect of pH on gelation behavior of hydrolyzed polyacrylamide (HPAM) and O-carboxymethyl chitosan (CMCH) were investigated by rheological measurements. The steady state shear experiments showed that the variation of apparent viscosity of each system had a similar tendency in the process. In basic environment, with the decrease of pH value, the apparent viscosity increased markedly, and in an acidic environment, the apparent viscosity decreased with the decrease of pH value. The results from oscillation experiments indicated the storage modulus (G′) was higher than the lose modulus (G″) in the whole frequency investigated when pH was nearby 7, which indicated that gel formed in this condition. The critical angular frequency (ω*) could also be affected by pH, which implied that the viscoelastic property of the sample was influenced by pH. All results implied that there was a sol-gel transition when pH was nearby 7 for all HPAM and CMCH systems investigated.

Hydrazinolyzed cellulose-g-polymethyl acrylate as adsorbent for efficient removal of Cd(II) and Pb(II) ions from aqueous solution

Hydrazinolyzed cellulose-graft-polymethyl acrylate (Cell-g-PMA-HZ), an efficient adsorbent for removal of Cd(II) and Pb(II) from aqueous solution, has been prepared by ceric salt-initiated graft polymerization of methyl acrylate from microcrystalline cellulose surface and subsequent hydrazinolysis. The influences of initial pH, contact time, and temperature on adsorption capacity of Cell-g-PMA-HZ as well as adsorption equilibrium, kinetic and thermodynamic properties were examined in detail. As for Cd(II) adsorption, kinetic adsorption can be explained by pseudo-second-order, while adsorption isotherm fits well with Langmuir isotherm model, from which maximum equilibrium adsorption capacity can be derived as 235.85 mg g-1 at 28 °C. Further thermodynamic investigation indicated that adsorption of Cd(II) by adsorbent Cell-g-PMA-HZ is endothermic and spontaneous under studied conditions. On the other hand, isotherm of Pb(II) adsorption fits well with Freundlich isotherm model and is more likely to be a physical-adsorption-dominated process. Consecutive adsorption-desorption experiments showed that Cell-g-PMA-HZ is reusable with satisfactory adsorption capacity.

Dilational Rheological Properties of Fluorocarbon Modified Poly(acrylamide)s at the Air/Water Surface

A series of fluorocarbon modified poly(acrylamide)s containing low amounts (0.1–1.5 mol%) of fluorocarbon (CF3(CF2)5–) are synthesized by copolymerization of acrylamide with 2-(perfluorohexyl) ethyl acrylate). The dynamic surface tension results show that the efficiency and effectiveness of the copolymers to lower surface tension increase with increasing the fluorocarbon content. The results of surface dilational viscoelasticity show that with the increase of the fluorocarbon content, the dilational viscoelasticity increases at the low concentration (<0.5 wt%), but firstly increases and then decrease at high concentration (>0.5 wt%). Furthermore, temperature has effect on the dilational viscoelasticity of the adsorbed layer in different extents.