Guoxiang Cheng

Properties of polyelectrolyte complex films of chitosan and gelatin

A series of chitosan–gelatin complexes was prepared by varying the ratio of constituents. Differential scanning calorimetry was used to determine the amount of the different states of water. The interaction between chitosan and gelatin was checked by IR and X-ray analysis and was related to mechanical strength. The results indicate that the water take-up of a chitosan–gelatin complex is depressed by strong interactions within networks. Chitosan can improve the tensile strength of complex films, and even with high water content these can keep appropriate tensile strength and higher elongation. © 1999 Society of Chemical Industry

Synthesis and characteristics of tyrosine imprinted beads via suspension polymerization

Tyrosine imprinted polymer beads for solid-phase extraction (SPE) purposes were prepared by suspension polymerization, using trimethylolpropane trimethacrylate as cross-linker, and 2-vinylpyridine and 2-acrylamido-2-methylpropanesulfonic acid as bifunctional monomers in an aqueous system. The SPE evaluation showed that, except for the good regenerating properties, the imprinted polymers prepared by suspension polymerization exhibited a considerable binding specificity to tyrosine, and had similar adsorbing and molecule separating properties as those prepared by seed swelling and suspension polymerization, although the size distribution was slightly wider. The suspension polymerization technique is less time-consuming, simpler and easier to carry out.

Effects of fiber volume fraction, hot pressing parameters and alloying elements on tensile strength of carbon fiber reinforced copper matrix composite prepared by continuous three-step electrodeposition

Abstract Carbon fiber reinforced copper matrix composites have been produced by continuous three-step electrodeposition plus hot pressing technique. Iron or nickel element was added to copper matrix to improve interfacial bonding of the composite. The effects of fiber volume fraction and hot pressing parameters (temperature, pressure and time) on the tensile strength of the composite were investigated. Emphasis was placed on the influence of alloying elements on the tensile strength of the composite. The composite was found to exhibit the highest strength at an optimum V f , hot pressing parameter temperature, pressure, or time by keeping other parameters constant. This optimum value was related to the alloying element incorporated in the copper matrix. It is observed that incorporation of alloying elements does not change the general trends, but changes the mechanism governing the decreasing trends of the tensile strength of the composites as the hot pressing temperature exceeds the optimum value. Further, the alloying elements affect the highest strength values ( σ max ). C/Cu(Ni) composite with the medium interfacial bonding strength exhibits the highest σ max . It is concluded from our experiments that a diffusion bonding is preferable since the fiber–matrix interaction can be easily controlled and the fiber degradation is limited during hot pressing process.

The dynamic swelling behaviour of chitosan-based hydrogels

A comparative study of the swelling behaviour of crosslinked chitosan (cr-CS) and its semi-interpenetrating polymer network (IPN) with poly(oxypropylene glycol) (cr-CS/PE semi-IPN) was carried out by DSC, NMR and positron annihilation lifetime spectroscopy (:PALS). The results reveal that cr-CS/PE semi-IPN containing hydrophobic moieties has more free volume for water at a definite water content and restricts its mobility less. NMR and PALS data indicate that water clusters coexist with water molecules hydrogen-bonded to the network at the beginning of swelling

Preparation and characterization of gelatin gel with a gradient structure

Gelatin gel with a gradient structure was produced by a vapour crosslinking procedure. The crosslinking degree at various depths (distance from plate surface) and its gradient are dependent on the crosslinking time and vapour temperature. The experimental data indicate that the gelatin gel with a gradient structure does not follow a second-order swelling kinetics. The dissolution rate can also be regulated by crosslinking time and vapour temperature. © 2000 Society of Chemical Industry

Adsorption and Regeneration Properties of Tyrosine-imprinted Polymeric Beads

Tyrosine-imprinted polymeric beads with diameters in the range 120–140 mm were prepared in an aqueous system by seed swelling and suspension polymerization using trimethylolpropane trimethacrylate (TRIM) as the crosslinking agent and acrylamide (AM), 2-vinylpyridine (VP) and/or 2-acrylamido-2-methylpropane sulphonic acid (AMPS), respectively, as functional monomers (FMs). The molecular recognition properties, dynamic adsorption behaviours and regeneration capabilities of the molecularly imprinted beads (MIBs) were investigated via a solid-phase extraction method. The functional monomers were found to be indispensable for preparing MIBs with highly specific molecular recognition properties. Irrespective of the choice of FM, when the FM/TRIM molar ratio was 4:15 the MIBs prepared exhibited the most desirable properties for the purposes of this study. When only one FM was used, it was found that AMPS provided the best solution as far as all the adsorption, recognition and regeneration capabilities of the MIBs were concerned. However, MIBs with the best molecular recognition and adsorption properties, and with only a slight sacrifice in their regeneration properties, were prepared using AMPS and VP as bifunctional monomers. For such MIBs, the initial separation factor, α, and static distribution coefficient, KD, were 2.01 and 2.15 ml/g, respectively.