A comprehensive model for solid-state polymerization of poly(ethylene terephthalate) was developed from analyzing the similarities and the differences between solid-state and melt polymerization. Considering the end groups diffusion limitation and the modification of concentrations of end groups and byproducts in the amorphous phase, a system of mass transfer and balance equations suitable for the solid-state polymerization of PET were obtained, based on simplifying the reaction kinetics of melt polymerization of PET. The degradation and other side reactions neglected in the earlier models for the solid-state polymerization of PET were included in the model. This simulation gave a quantitative prediction in the effect of temperature, particle size, starting molecular weight, and ratio of end groups on the degree of polymerization of products during the solid-state polymerization of poly(ethylene terephthalate). These simulation results were in agreement with experiments.

The aim of this study was to determine the effect of the ester carbon chain length of curing agents modified by epoxidized oleic esters on the toughness of cured epoxy resins. An amine-terminated prepolymer (i.e., curing agent G) was synthesized from a bisphenol A type liquid epoxy resin and triethylene tetramine. The toughening curing agents (G1 and G2) were prepared by reactions of epoxidized oleic methyl ester and epoxidized oleic capryl ester, respectively, with curing agent G. Fourier transform infrared spectrometry was used to characterize the chemical structure of the curing agents. The effects of the carbon chain length of the oleic ester group in the curing agents on the toughness and other performances of the curing epoxy resins were investigated by analysis of the Izod impact strength, tensile strength, elongation at break, thermal properties, and morphology of the fracture surfaces of the samples. The results denote that the toughness of the cured epoxy resins increased with the introduction of oleic esters into the curing agents without a loss of mechanical properties and that the toughness and thermal stability of the materials increased with increasing ester carbon chain length. The toughness enhancement was attributed to the flexibility of the end carbon chains and ester carbon chains of the oleic esters in the toughening curing agents.

The reaction of catechin and rutin with Ru(NH 3 ) 5 L 3+ (L ) N-methylpyrazinium (pzCH 3 + ), pyrazine (pz), and isonicotinamide (isn)) complexes underwent a two-electron oxidation on the catechol ring (B ring) with the formation of quinone products. The kinetics of the oxidation, carried out at [H + ] ) 0.01-1.0 M and pH ) 4.0-7.6, suggested that the reaction process involves the rate determining one-electron oxidation of the flavonoids in the form of H 2 X (k 0 ), HX -(k 1 ), and X 2-(k 2 ) by Ru(NH 3 ) 5 L 3+ complexes to form the corresponding semiquinone radicals, followed by the rapid scavenge of the radicals by the Ru(III) complexes. The specific rate constants (k 0 , k 1 , and k 2 ) were measured and the results together with the application of the Marcus theory were used to estimate the selfexchange parameters for the one-electron couples of the flavonoids, H 2 X/H 2 X +• , HX -/HX • , and X 2-/X -• .

ABSTRACT:Copoly(p-hydroxybenzoate/bisphenol A terephthalate) is a new type of wholly aromatic copolyester which has an obvious character of the thermotropic liquid crystal. In this paper, we characterized the copolyester by high resolution nuclear magnetic resonance (NMR) spectroscopy (including two-dimensional technique, 2D NMR), and discussed NMR spectra of the copolyesters having various monomer compositions. The combined use of homonuclear and heteronuclear two-dimensional NMR provided unambiguous spectral assignment for the eopolyester. It was found that the 13 C NMR spectra of carbonyl group in the copolyester chain were not so simple as in the monomeric aromatic ester and they gave the useful information of the chain sequences. There are good relationships between the carboxyl group resonance peaks and the triad of the monomer residues.

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