Inter- and intra-molecular ionic interactions of polyampholyte: Carboxymethyl-2-diethylaminoethylcellulose

Carboxymethyl-2-diethylaminoethylcellulose (CM-DEAE cellulose) was prepared by etherification of carboxymethylcellulose with diethylaminoethyl chloride in a NaOH solution. The behaviour of CM-DEAE cellulose in aqueous solution was studied by viscosity and GPC measurements. The degree of substitution (DS) and existing states of DEAE substituents were examined by the use of proton NMR, and those of the CM substituents were observed with FT-IR. The results reveal that the reduced viscosity and apparent molecular size of CM-DEAE cellulose vary with the concentration of sodium chloride and changes in pH and DS. These phenomena can be explained in terms of inter- and intra-molecular ionic interactions.     

Use of inverse gas chromatography to quantify interactions in amine cured epoxy resins

Flory–Huggins interaction parameters, λ, were determined for a series of probes in an amine cured epoxy resin matrix (433–493 K) and its precursors (324–363 K) by inverse gas chromatography (IGC). Hildebrand–Scatchard theory was combined with Flory–Huggins theory in order to estimate infinte dilution solubility parameters (δ₂) for the matrix and its precursors at 298 K. It was shown that the value of the solubility parameter for the cured resin matrix lies between those of its precursors. Compared to the majority of published work, an unusual aspect of this application of IGC is that solubility parameters have been determined when the stationery phases are (i) small molecules and (ii) a highly crosslinked polymer. Moreover, all possible attempts have been made to ensure equilibrium conditions between probe and stationary phase, and compensation for asymmetry of peak profile has been applied in determining δ₂. The solubility parameters estimated by IGC are in good agreement with those calculated by other methods.     

Viscoelasticity of oxidized starch/low methoxy pectin mixtures in the presence of glucose syrup

The structural properties of mixtures of pectin, oxidized starch and glucose syrup were investigated using small deformation dynamic oscillation. In the absence of added calcium, preparations of low methoxy pectin with glucose syrup formed viscous solutions, which remained crystal-free at subzero temperatures. Samples of oxidized starch and glucose syrup, on the other hand, exhibited solid-like behaviour because of the crystalline nature of the amylose-like helices. Mixtures of the two polysaccharides with the co-solute clearly showed phase inversion from liquid to solid-like behaviour with increasing amounts of starch in the formulation. The transformation was reflected in the textural properties of samples, which varied from thick solutions to firm gels. The viscoelasticity of the system was modified further by the introduction of high methoxy pectin. Preparations of high methoxy pectin and glucose syrup formed rubbery gels whose amorphous nature underwent a glass transition during cooling.     

Thermal degradation of cinnamoylated poly(vinyl alcohol)

Thermogravimetry and pyrolysis in combination with gas chromatography and infrared spectroscopy were the experimental techniques applied to the thermal degradation of cinnamoylated poly(vinyl alcohol) samples, constituted from vinyl alcohol-vinyl cinnamate photocrosslinkable copolymers. The thermal decomposition products include gases, liquids and solids. The gases are formed from saturated and unsaturated volatile hydrocarbons C₁? C₄, carbon monoxide and carbon dioxide. The liquid fraction includes aromatic hydrocarbons and some oxygenated organic compounds. The solid product identified in the greatest amount was cinnamic acid. The content in the thermal decomposition products varies considerably both with copolymer composition and temperature.     

Rapid analysis of polymer homologues and additives with SFE/SFC-MS coupling

A rapid and easy analysis method for polymers is presented. The method involves sample preparation by SFE, separation of the extracted compounds by SFC and simultaneous quantitative detection by FID, as well as identification of unknowns by MS. The applications illustrate how structural research work and routine polymer analysis can be done with this time saving method.     

Ultrasonic study of molecular association of poly(vinyl chloride) solution in tetrahydrofuran

Ultrasonic absorption, velocity, adiabatic compressibility, relaxation time and relaxation amplitude measurements are reported on poly(vinyl chloride) (PVC) solution in tetrahydrofuran (THF) using pulsed ultrasonic apparatus operating at 2 MHz and 313 K. Results show a linear increase of velocity. density, viscosity, absorption coefficient, relaxation time and relaxation amplitude values with the increase of PVC concentration in THF. In contrast the compressibility decreases with increasing PVC concentration. This suggests interaction between PVC and THF molecules.     

Packed-microtubes model for flowthrough chromatography of protein

A mathematical model for flowthrough (perfusion) chromatography, namely packed-microtubes (PMT) model, has been proposed for a column packed with biporous (BiP) anion exchanger in which the mesopores and flowthrough pores are created with liquid and solid porogens, respectively. The model is established based on the assumption that the BiP particle is made up of packed microtubes. Bovine serum albumin (BSA) is used as a model protein and three kinds of anion exchangers (i.e., mesoporous, macroporous and BiP resins) are used as adsorbents to determine the model parameters and to evaluate the model. Adsorption equilibrium and finite bath experiments are performed to determine the adsorption isotherms and kinetics parameters. Both the bound amounts of the protein on the surface of the mesopores and macropores are experimentally determined and taken into account in the mathematical model. With all the model parameters determined by independent experiments or calculated from available correlations, model simulations are performed and compared with the experimentally determined breakthrough profiles of the BiP column. It is found that the model predictions agree reasonably well with the experimental data obtained under various conditions and the PMT model fit experimental data better than the modified double linear driving force (LLDF) model proposed by Leitão and Rodriogues (1999. Biochemical Engineering Journal 3, 131) in which the adsorbent particle is considered to be made up of packed microparticles. The results indicate that the PMT model is more reasonable for this kind of BiP adsorbent.     

Lithium/V6O13 cells using silica nanoparticle-based composite electrolyte

The electrochemical behavior of Li/V₆O₁₃ cells is investigated at room temperature (22 °C) both in liquid electrolyte consisting of oligomeric poly(ethyleneglycol)dimethylether+lithium bis(trifluoromethylsulfonylimide) and composite electrolytes formed by blending the liquid electrolyte with silica nanoparticles (fumed silica). The addition of fumed silica yields a gel-like electrolyte that demonstrates the desirable property of suppressing lithium dendrite growth due to the rigidity and immobility of the electrolyte structure. The lithium/electrolyte interfacial resistance for composite gel electrolytes is less than that for the corresponding base-liquid electrolyte, and the charge-discharge cycle performance and electrochemical efficiency for the Li/V₆O₁₃ cell is significantly improved. The effect of fumed silica surface group on the electrochemical performance is discussed; the native hydrophilic silanol surface group appears better than fumed silica that is modified with a hydrophobic octyl surface moiety.     

Study of the physico–chemical characteristics and rheological behaviour of boehmite dispersions for dip-coating applications

Dispersions of a totally dispersible AlOOH powder have been studied. The effect of the initial composition has been studied to outline the reactions that determine the final rheological behaviour of the dispersions. The final viscosity and viscoelastic properties of the dispersions are determined by the sol–gel phenomena occurring during the ageing treatment. Gel formation is favoured by low water and high acid contents, while it is disfavoured by prolonged stirring. Gelling time from 48 h to 4 months has been observed depending on the initial composition.