Spin probe study of semi‐interpenetrating polymer networks based on polyurethane and polymethacrylate functional prepolymers

The motional transition and heterogeneity of semi‐interpenetrating networks (SIPNs) based on polyurethane (PU) with carboxylic groups and methacrylic copolymer (PM) with tertiary amine groups were studied by the electron spin resonance (ESR) spin probe method. The concentration of functional groups in both prepolymers varied from 0 to 0.45 mmol g^?1. Spin‐probed SIPNs show that the temperature‐dependent spectra are sensitive to polymer interactions imposed by functional groups. These interactions determine the free volume distribution in the matrix and temperature at which motional transition takes place. The fraction of free volume increases with functional group concentration and reaches its maximum at 0.25 mmol g^?1. Further increases in the functional group concentration reduce the free volume. The results of the networks with strong interactions are discussed in terms of the interference of the plasticizing effect of the PU component and the formation of possible cluster cross‐links, which restricts segmental motions. Copyright © 2003 Society of Chemical Industry     

Enrichment of macaroni with cellulose-derivative protein complex from whey and corn steep liquor

Macaroni was prepared from semolina fortified with 3, 6 and 9% CMC-protein (CMC — carboxymethyl cellulose) or HEC-protein (HEC — hydroxyethyl cellulose) complexes from whey and corn steep liquor to increase the protein quality and quantity. Fortification increased the protein content up to 14.2% in DM (vs. 12.1% in control) for macaroni. Water absorption, dough weakening and mixing tolerance index were decreased, while dough development time and dough stability were increased when the amount of precipitated cellulose-protein complex from whey and corn steep liquor in the blends increased. Addition of both tested cellulose-protein complexes improved cooking quality by increasing the weight and volume of cooked macaroni, but cooking losses were greater. Sensory evaluation of the colour, flavour and appearance of macaroni were improved as a result of adding cellulose-protein complex from whey. Macaroni samples prepared from dough mixtures with 6 and 9% of cellulose-protein complex from corn steep liquor were less acceptable than those prepared from 100% semolina.     

Batch cultures of Penicillium camembertii on glucose and amino acids—model for growth and ammonium production

BACKGROUND: Three groups of amino acids were previously characterized based on their ability to be assimilated as carbon source by Penicillium camembertii. To describe the diauxic growth recorded on glucose and amino acids from the second group, such as arginine, an unstructured model was previously developed, based on the sequential consumption of both carbon substrates, glucose, followed after its exhaustion, by arginine. The model was modified to describe also the behaviour recorded during growth on other amino acids. RESULTS: The growth model involved the carbon substrate consumption (Verlhust model) and the biomass on carbon substrate yield. Glucose was therefore considered during P. camembertii growth on nitrogen source amino acids (lysine—first group); and amino acid consumption was considered during growth on carbon source amino acids (glutamate—third group), with glucose being dissimilated only for energy supply. The excess nitrogen from amino acids was released as ammonium; the linking of this production to growth was found to increase with the ability of the amino acid to be assimilated as carbon source by P. camembertii. CONCLUSION: The various metabolic behaviours recorded during P. camembertii growth on amino acids, in the presence of a primary carbon source such as glucose, were proved to be satisfactorily described by the model, showing the robustness of the model. Copyright © 2007 Society of Chemical Industry     

Synthesis and characterization of phenolic and amino resins based on α, β-unsaturated aldehydes

Phenolic and amino resins on the basis of α,β-unsaturated aldehydes were synthesized in bulk or solution. Catalysts were HCl, H₃PO₄, or formic acid, and in some cases NaOH. The course of the reactions was followed by GPC and NMR while the structure of the reaction products was determined by one- and two-dimensional NMR. The course of the reactions is influenced by experimental conditions: the type of monomers, their molar ratio, the type and quantity of the catalyst, the reaction time and temperature, and the reaction medium. At the beginning of the reaction the addition of a nucleophile to an aldehyde takes place through parallel 1,2-addition to and 1,4-addition to group. Oligomers with ? OH, , and ? CHO functional groups are able to add new monomer units or to react mutually to form higher molecular weight addition and condensation products. The overall rate constants for the beginning of the reactions were between 10^?3 L/mol s for the high reactive mixtures and 10^?7 L/mol s for the less reactive mixtures. The resins were cured by heating at temperatures above 135°C with the addition of hexamethylenetetramine.     

Ionic polymers with tunable liquid‐crystalline properties

Side‐chain polyesters were synthesized from N‐octyl‐, N‐dodecyl‐ or N‐hexadecyl‐diethanolamine and succinic acid anhydride. These polyesters were then transformed into polyester hydrochlorides by protonation of the amino groups using different amounts of HCl (20–100 mol%). Above 60 mol% the reaction is not quantitative and a degree of protonation of up to 88% is obtained. The structures of the synthesized polyesters and their hydrochlorides were determined by ¹H nuclear magnetic resonance spectroscopy. The thermal properties of the synthesized polyesters and their hydrochlorides were also studied using differential scanning calorimetry in relation to the side‐chain length and the degree of polyester protonation. The polyester with octyl side chains and its hydrochlorides were amorphous liquids at room temperature, while the polyester and polyester hydrochlorides with hexadecyl side chains formed a smectic crystalline phase, S_mB, or its tilted analogues. The polyester with a dodecyl side chain was also an amorphous liquid at room temperature, while its hydrochlorides with various degrees of protonation were smectic liquid crystals, as determined by X‐ray diffraction. By simply varying the degree of protonation the liquid crystal isotropization temperature was increased from 32 °C to 82 °C. Copyright © 2011 Society of Chemical Industry     

A simple procedure to eliminate known poles from a time series

An extremely simple procedure is presented for eliminating known or previously computed poles from a time series and for obtaining a `deflated' time series which contains only the remaining poles. Time-series deflation can be used in combination with any numerical algorithm used to compute poles. As an important example, it is demonstrated how the time-series deflation technique combined with Prony's method can produce more accurate results than the use of Prony's method alone     

Effect of cobalt doping on the dielectric response of Ba0.95Pb0.05TiO3 ceramics

Dielectric response of Ba_0.95Pb_0.05TiO₃ ceramics doped with 0.1 and 1 wt.% of Co₂O₃, synthesized by conventional high-temperature method, was studied in wide temperature and frequency range. The temperature dependences of the real and the imaginary parts of dielectric permittivity of the ceramics were compared with those of BaTiO₃ and Ba_0.95Pb_0.05TiO_3. The addition of Co³⁺ ions results in a broadening of dielectric anomalies related to the transition to paraelectric cubic phase, and the structural transition between the tetragonal and the orthorhombic phases. At low temperatures (125–200 K) the dielectric absorption of Co-doped Ba_0.95Pb_0.05TiO₃ ceramics was found to exhibit relaxor-like properties. The dielectric response has been found to contain the contributions characteristic of fluctuations of the polar nanoregion boundaries and reorientations of the dipole moments between allowed directions in the nanoregions in the rhombohedral and the orthorhombic phases. The behavior speaks in favor of ordering of polar defects in the host lattice of Ba_0.95Pb_0.05TiO₃ in a form polar nanoregions_.     

Effect of processing on the quality of edible argan oil

Sensory quality of edible oil is essential to get the consumer acceptance. Modifications during processing can alter edible oil sensory quality. The storage stability and sensory quality of argan oil prepared from (1) mechanically pressed unroasted kernels, (2) mechanically pressed roasted kernels, (3) hand-pressed roasted kernels, and (4) hand-pressed roasted kernels coming from goat-digested fruits was studied at room temperature and under accelerated conditions (60 °C). The roasting process had a positive effect on storage stability of the resulting oils, while argan oil prepared from mechanically pressed roasted kernels provides the optimum storage stability. Oil from hand-pressed roasted kernels originating from goat-digested fruits was not suitable for human consumption because of the unpleasant taste and odoûr. Only oil from mechanically pressed roasted kernels did not produce negative sensory attributes like fusty or Roquefort cheese.