Yifeng Zhang

A glucose biosensor based on microporous polyacrylonitrile synthesized by single rare-earth catalyst

A glucose biosensor was constructed by electrochemical adsorption of glucose oxidase (GOD) in microporous polyacrylonitrile (PAN), which was synthesized by single rare-earth catalyst-Y(OAr)(3.) The biosensor shows a fast response, good operational stability and reproducibility. The influences of molecular weight of polymer, pH, operating potential and temperature on the biosensor response were explored by amperometric method. The apparent activation energy and optimum pH of enzyme-catalyzed reaction are 35.9 kJ mol(-1) and 6.2, respectively.

Random copolymerization of ∈-caprolactone and trimethylene carbonate with rare earth catalysts

Random copolymerization of trimethylene carbonate (TMC) with ϵ-caprolactone (CL) catalyzed by rare earth chloride-epoxide or rare earth isopropoxide has been investigated for the first time. It was found that in the presence of epoxide, rare earth chlorides have high activities for the copolymerization, giving high-molecular-weight random copolymer P(CL-co-TMC) with a narrow molecular weight distribution. Light rare earth chloride-propylene oxide systems are more effective for the copolymerization than heavy rare earth chloride-propylene oxide systems. For the rare earth chloride-epoxide catalyst system, epoxide is the requisite component, and its amount affects the catalytic activity; while rare earth isopropoxide can catalyze the copolymerization alone. The preparative conditions of the copolymer with NdCl3-5PO system were studied. The reactivity ratios of CL and TMC copolymerization with NdCl3-5PO determined by Fineman-Ross method are 1.60 for rTMC and 0.72 for rCL, respectively. The copolymers were characterized by 1H- and 13C-NMR, GPC, and DSC. The mechanism study shows that the rare earth alkoxide is the active species that initiates the ring opening copolymerization of CL and TMC with acyl-oxygen bond cleavages of the monomers.

Preferential separation of ethanol from aqueous solution through hydrophilic polymer membranes

The pervaporation behaviors of aqueous ethanol mixtures through the poly(ethylene oxide) (PEO)/chitosan (CS) blend membrane were investigated. The results show that both CS and PEO/CS membrane preferentially permeate ethanol at a lower alcohol concentration in feed, and the selectivity of CS membrane toward alcohol can be greatly improved by introducing hydrophilic polymer PEO into CS. The PEO/CS blend membrane gave a separation factor of 4.4 and a flux of 0.9 kg m−2 h for 8 wt % of ethanol in the feed at 20°C. At the same time, the reason introducing PEO can improve alcohol-permselectivity of CS membrane is explained on the basis of experimental data. Blending with PEO made the structure of CS chain looser, which resulted in ethanol molecules passing through easily, on the other hand, strengthened the ability of forming water clusters that inhibit the permeation of water molecules. From the experimental results, although the PEO/CS blend membrane was not a usable membrane with high selectivity to alcohol, a new method to prepare alcohol-permselective membranes appears to be developed by modifying hydrophilic polymers.

Synthesis of Functional Resins from Poly(Chloromethyl thiirane) and Their Sorption Properties for Noble Metal

ABSTRACT Three new kinds of functional resins bearing polythioether backbone and primary amino group (CA), or dithiocarbamate (CDTC) or Shiff base (CSB) in side chain, were synthesized from poly(chloromethyl thiirane). The sorption capacities of CA resins for noble metals were 5–8 mmol Au(III)/g resin and 7–9 mmol Ag+/g resin. CDTC resins could absorb 9–11 mmol Ag+ per gram resin, but little Au(III). CSB had similar properies as CDTC. These resins all exhibited low capacities, no more than 2 mmol/g resin, for Hg2+, Pb2+, Ni2+, Fe3+, Zn2+, and Cu2+. Thus, Au(III) and Ag+ can be separated successfully from the above common ions. The resins were easily regenerated and reused without an obvious decrease in the sorption capacity for Ag+.