Differential Solubility of Poly(ethylene-terephthalate) Fibre vs. Temperature 2. Calorimetric Study of the Non-dissolved Fractions

The differential solubility of two poly(ethyleneterphthalate) (PET) fibres was determined in one thermally treated substrate and in another thermally untreated. In both cases, mixtures of phenol/tetrachloroethane with the appropriate composition were used. The non-dissolved fractions of the untreated PET fibre display a molecular mass and a crystallinity which increase on increase of the temperature of the differential solubility test. In the case of the thermally treated substrate, both the molecular mass and the crystallinity of the residual fraction remain constant on increase of the test temperature. This revised version was published online in July 2006 with corrections to the Cover Date.     

Host-guest interaction between swelling clay minerals and poorly water-soluble drugs. 1: Complex formation between a swelling clay mineral and griseofulvin

The formation of a complex between a swelling clay mineral and griseofulvin (GF), a poorly water-soluble drug, was examined. A strong host-guest interaction between the neutral drug molecules and the clay mineral was observed not only in the solid state but also in aqueous dispersion. The powder X-ray diffraction patterns revealed the disappearance of a crystalline phase of GF through host-guest interaction for samples having low GF contents. The complex formation was confirmed to be due to monolayer adsorption on the basis of quantitative thermochemical analyses. The strong interaction between GF and the clay was also detected when the complex powder was dispersed in an aqueous medium on the basis of the intensity changes of from free GF solution in CD and fluorescence spectra as compared with those observed for the free GF solution.     

Spectroscopic Investigation of Sublimated Products of Ultradisperse Polytetrafluoroethylene

The structure of fractions isolated by thermal sublimation of ultradisperse polytetrafluoroethylene (UPTFE) powder has been studied by IR spectroscopy. At 50°C–160°C, fractions of highly amorphous fragments are condensed on a cold receiver; the fragments are constructed from branched chains with terminal olefin groups. Fractions isolated at 300°C and higher are close in structure to PTFE and are highly crystalline. It is assumed that sample amorphism is due to the irregular distribution of the fractions of fragments with terminal olefin and lateral fluoromethyl groups in the structures.Original Russian Text Copyright © 2004 by L. N. Ignatieva, A. K. Tsvetnikov, O. N. Gorbenko, T. A. Kaidalova, and V. M. Buznik__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 830–836, September–October, 2004.     

Effects of crystallinity, {001}/{101} ratio,and Au decoration on the photocatalytic activity of anatase TiO2 crystals

Anatase TiO₂ nanocrystals and sub-microcrystals with truncated octahedral bipyramidal morphologies were prepared by direct calcination of TiOF₂ precursors. The as-prepared TiO₂ samples were thoroughly characterized by X-ray diffraction, Raman spectroscopy, field-emission scanning electron microscopy, N₂ adsorption-desorption isotherms, X-ray photoelectron spectroscopy, and UV-visible diffuse spectroscopy. It was found that the crystallinity, grain size, and {001}/{101} ratio of the samples can be increased by raising the calcination temperature from 500 to 800 °C. The higher crystallinity and {001}/{101} facet ratio resulted in an increase in both aqueous and gas-phase photocatalytic activities, by inhibiting the recombination and separation of electrons and holes. After selecting two TiO₂ samples with high crystallinity and {001}/{101} ratio, Au nanoparticles were decorated on their surfaces, and the photocatalytic activity of the resulting samples under visible light illumination was studied. It was found that the visible light-induced photocatalytic activity increased by 2.6 and 4.8 times, respectively, upon Au decoration of the samples prepared by calcination of TiOF₂ at 700 and 800 °C.     

Novel cellulose derivatives. IV. Preparation and thermal analysis of waxy esters of cellulose

Cellulose esters with linear aliphatic acyl substituents ranging in size from C₁₂ (lauric acid) to C₂₀ (eicosanoic acid) were prepared in homogeneous solution (DMAc/LiCl) using a novel synthetic method based on the use of a mixed p-toluenesulfonic/carboxylic acid anhydride. The resulting waxy cellulose esters had a high degree of substitution (DS), between 2.8 and 2.9, and showed little degradation. Thermal analysis of these cellulose derivatives by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) revealed a series of transitions that represented motion by both ester substituents and cellulosic main chain. Broad crystallization and melting transitions attributed to side-chain crystallinity were observed in the range between −19 and +55°C; these side-chain T_m and T_c transition temperatures increased by 10°C per carbon atom of the ester substituent. The T_g of these derivatives increased linearly with increasing substituent size from 94°C for C₁₂ (cellulose laurate) to 134°C for C₂₀ (cellulose eicosanoate). Evidence of “main-chain” crystallization was not observed for these samples, except in the case of peracetylated C₁₂ and C₁₄ esters, which had T_m values of 96°C and 107°C, respectively. © 1996 John Wiley & Sons, Inc.     

腰接基对对苯二甲酸-双(4-甲氧基苯酯)液晶性的 影响

合成了一系列不同腰接取代基的刚性对苯二甲酸-双(4-甲氧基苯酯)小分子液晶化合物,研究了不同腰接取代基液晶性的影响。研究发现,如果在对苯二甲酸-双(4-甲氧基苯酯)的腰部引入不同结构的取代基,将不同程度地降低其熔点和液晶清亮点,合适的取代基则有利于液晶相的生成。     

Anomalous Melting of Poly(Phenylene Oxide)

Slow evaporation of toluene from poly(2,6-dimethyl-1,4-phenylene oxide), PPO, at 23°C produced crystals which melt between 185 and 265°C and have a crystallinityof 0.58. About 8 wt% of the crystals appear to melt temperatures below 220°C. The lattertemperature marks the end of the glass transition interval for this polymer.This revised version was published online in November 2005 with corrections to the Cover Date.     

Properties and treatments of pulps from recycled paper. Part II. Surface properties and crystallinity of fibers and fines

Surface properties of bleached kraft pulps were evaluated before and after recycling, and after a series of chemical treatments designed to improve and/or modify the pulp characteristics. The surface free energy characteristics of the pulps were determined using the Wilhelmy technique, and ESCA and ATR-FTIR methods were used to evaluate the chemical composition of the surfaces of the pulp fibers. In general rather small changes were noted at the fiber surfaces with recycling and chemical treatment. Recycling tended to increase the acid component and decrease the base component of the surface free energy of the pulps. This could result from exposure of carboxyl groups from hemicelluloses and/or from oxidized layers from the bleaching process. ESCA analyses also indicated increased carboxyl concentration at the surfaces of the recycled fibers. Although treatment with aqueous bases and organic solvents tended to increase the hydroxyl content on the surface of recycled pulps, the chemical treatments were not beneficial to pulp quality. AFM and SEM of fiber and fine surfaces of kraft pulps revealed that the fines fraction was altered to a much greater extent with recycling. Although recycled fibers appeared to have improved wettability, these small changes in the surface characteristics do not appear to play the dominant role in the characteristics of recycled pulps. Recycling did not change the crystallinity of whole pulps, but it increased the crystallinity of the fines fraction. The increase in the crystallinity of the fines fraction and the reduction in the water retention value (WRV) and the bulk carboxyl content (xylan) of the recycled pulps, as noted in Part I of this paper, appear to play the predominant role in determining the characteristics of recycled pulps. It appears that the loss of the hemicelluloses in the bulk of the fiber with recycling is much more important for internal fibrillation than the apparent small increase of hemicelluloses at the surface of recycled fibers.     

Hydrolytic degradation of polyester–polyether block copolymer based on polycaprolactone/poly(ethylene glycol)/polylactide

Polyester–polyether block copolymers based on polycaprolactone/poly(ethylene glycol)/polylactide (PCEL) with various compositions were synthesized by direct copolymerization of ϵ‐caprolactone, L ‐lactide and PEG (6000) in the presence of stannous octoate at 130 °C for 56 hr. The degradation behavior of the copolymers was investigated in a pH 7.4 phosphate buffer solution at 37 ±1 °C. Various techniques such as weight, gel permeation chromatography, ¹H nuclear magnetic resonance, differential scanning calorimetry and X‐ray diffractometry were used to monitor the changes in water absorption, weight loss, molar mass, molar mass distribution, thermal properties and compositions. The results show that the hydrophilicity of copolymer was enhanced with increasing poly(ethylene oxide) content, which led to the PEG sequences fast release and an increase in weight loss of the copolymer. Bimodal chromatograms were detected in the degradation, which were attributed to the degradation mechanism of the partial crystalline polymer proceeding predominantly in amorphous zones. Copyright © 2000 John Wiley & Sons, Ltd.     

Structure and properties of blend membranes prepared from cellulose and alginate in NaOH/urea aqueous solution

Regenerated cellulose (RC)/alginic acid (AL) blend membranes were satisfactorily prepared from 6 wt % NaOH/4 wt % urea aqueous solution by coagulating with 5 wt % CaCl₂ aqueous solution, and then treated with 3 wt % HCl. Morphology, crystallinity, mechanical properties, and thermal stability of the membranes were investigated by scanning electron microscopy (SEM), IR and UV spectroscopes, X‐ray diffraction, tensile tests, and thermogravimetric analysis (TGA). The RC/AL blends were miscible in all weight ratios of cellulose to alginate. The membranes have homogeneous mesh structures, and the mesh sizes of the blend membranes (200–2000 nm) significantly increased with increasing alginate content. The crystalline state of the AL membrane prepared from 6 wt % NaOH/4 wt % urea aqueous solution was broken completely, and the crystallinity of the blend membranes decreased with an increase of AL. Comparing with AL membranes, the tensile strength and breaking elongation of the blend membranes were obviously improved in dry and wet states. Therefore, the RC/AL blends offer a promising way of alginate as separate and functional materials used in the wet state. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 451–458, 2001