Browsing by Author "RADIC, D"

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    BLENDS OF POLY(MONOALKYLITACONATES) POLY(VINYLPYRIDINES) AND MODEL MOLECULES
    (GORDON BREACH SCI PUBL LTD, 1994) GARGALLO, L; GATICA, N; RADIC, D
    The compatibility in blends containing poly(monoalkylitaconates) (PMAI) and poly(vinylpyridines (PVPy) by several analytic techniques i.e, viscometry, UV-VIS spectrophotometry, Differential Scanning Calorimetry (DSC) Furier Transform Infrared Spectrophotometry (FTIR) was studied. Blends of PVPy with PMAI give rise to insoluble products irrespective of the starting composition, which can be attributed to interpolymer complex formation. From UV-VIS it is possible to observe miscibility behaviour between polymers. By DSC the thermograms observed are similar to those of PMAI but different from those of pure PVPy. A variation of the wavenumber of the carbonyl group of PMAI with composition is observed by FTIR, which is another argument to suspect miscibility. In order to study the effect of the molecular weight of the components on the miscibility, the analysis of blends containing PVPy and the corresponding poly(moalkylitaconates) monomer analogues was performed. Compatibility is observed in these cases but with important differences between the magnitudes of the variations relative to the polymeric blends. Miscibility is unfavoured as the molecular weight of the components increases, in good agreement with theory.
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    BLENDS OF POLY(N-VINYL-2-PYRROLIDONE) POLY(DIALKYL ITACONATES) AND POLY(METHACRYLATES)
    (GORDON BREACH SCI PUBL LTD, 1994) OPAZO, A; GARGALLO, L; RADIC, D
    Blends containing poly(N-vinyl-2-pyrrolidone) (PVP) and poly(dialkyl itaconates) (PDI) and poly(methacrylates) (PMA) with different side chain structures were prepared. polymer blends of various compositions were studied by Differential Scanning Calorimetry (DSC) and Thermomechanical Analysis (TMA). The effect of the substitution on the lateral chain is also analyzed. One Tg value, over the whole range of compositions is observed for the majority of the blends reflecting compatibility. Inmiscible polymer blends are also observed which is apparently dependent on the structure of the side chain.
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    BLENDS OF POLY(VINYLPYRROLIDONE)/ POLY(MONOITACONATES) .1. INTERPOLYMER COMPLEX-FORMATION
    (1992) RADIC, D; OPAZO, A; GUERRERO, X; GARGALLO, L
    Blends containing poly(vinylpyrrolidone) (PVP) of three different molecular weights and poly(monoitaconates) (PMI) with different side chain structures were prepared. Polymer blends of various compositions were analyzed by Differential Scanning Calorimetry (D.S.C.). The calorimetric study was performed on films prepared from methanol and dimethylformamide (DMF). One Tg value is observed for the majority of the samples over a wide range of composition, but in all cases a minimum in the Tg-composition diagram is observed which is attributed to an interpolymer complex formation. The analysis of these systems in solution by using turbidimetry and viscometry techniques for PMMI/PVP confirms the results obtained in the solid state.
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    CALORIMETRIC STUDY OF SOME POLY(MONO-NORMAL-ALKYL ITACONATES)
    (1991) DIAZCALLEJA, R; RIBESGREUS, A; GARGALLO, L; RADIC, D
    A calorimetric study of poly(mono-n-alkyl itaconates) containing 8, 10, 12 and 14 carbon atoms in the side chain was performed. No glass transition temperature (T(g)) was observed in the temperature range 213-263 K, but a melting process was observed for the dodecyl and tetradecyl derivatives, which was attributed to crystalline order in the long side chains.
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    COMPLEXATION OF POLY(MONOBENZYL ITACONATE) AND POLY(N-VINYL-2-PYRROLIDONE) IN DILUTE-SOLUTION
    (1989) PEREZDORADO, A; PIEROLA, IF; BASELGA, J; GARGALLO, L; RADIC, D
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    COMPLEXATION OF POLY(MONOBENZYL ITACONATE) AND POLY(N-VINYL-2-PYRROLIDONE) IN DILUTE-SOLUTION .2. INFLUENCE OF VARIABLES INVOLVED IN SAMPLE PREPARATION
    (1990) PEREZDORADO, A; PIEROLA, IF; BASELGA, J; GARGALLO, L; RADIC, D
    Upon mixing dilute solutions of poly(monobenzyl itaconate)c) (PMBI) and poly(N-vinyl-2-pyrrolidone) (PVP) in methanol, a soluble interpolymer complex is formed whose properties depend on the method employed to prepared the sample. It was found that the local concentration of the polyacid is the controlling factor. Depending on that concentration, a metastable polymer complex is formed which turns to equilibrium upon sonication. Cooling or heating and aging time have a minor effect. The turbidity of the polymer complex depends on the polyacid concentration to the power-nu (at constant polybase/polyacid ratio). For the metastable complex, nu-almost-equal-to 2, typical of weak polymer complexes. Changes in turbidity are accompanied by a decrease in nu. In the equilibrium state, nu almost-equal-to 1,5 a value being more typical of strong complexes.
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    CONDUCTIVITY CONTRIBUTION TO DIELECTRIC LOSS OF POLY(MONOCYCLOPENTYL ITACONATE)
    (HUTHIG & WEPF VERLAG, 1994) SANCHIS, MJ; CALLEIA, RD; GARGALLO, L; RADIC, D
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    CONFORMATIONAL CHARACTERISTICS OF POLY(VINYLPYRROLIDONE) - SOLVENT-DEPENDENCE OF THE CHAIN DIMENSIONS
    (HUTHIG & WEPF VERLAG, 1993) TARAZONA, MP; SAIZ, E; GARGALLO, L; RADIC, D
    Conformational energies as function of rotational angles over two consecutive skeletal bonds for both meso and racemic diads of poly(N-vinyl-2-pyrrolidone) have been computed. The results of these calculations were used to formulate a statistical model that was then employed to calculate the unperturbed dimensions of this polymer. The conformational energies are sensitive to the Coulombic interactions, which are governed by the dielectric constant of the solvent, and to the size of the solvent molecules. Consequently, the calculated values of the polymeric chain dimensions are strongly dependent on the nature of the solvent, as it was experimentally found before.
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    DIELECTRIC AND VISCOELASTIC RELAXATION OF POLY(2-CHLOROETHYL METHACRYLATE) AND POLY(3-CHLOROPROPYL METHACRYLATE)
    (ELSEVIER SCI LTD, 1994) PELISSOU, O; CALLEJA, RD; GARGALLO, L; RADIC, D
    Dielectric and viscoelastic relaxation measurements have been performed on poly(2-chloroethyl methacrylate) and poly(3-chloropropyl methacrylate) between -140-degrees-C and the glass transition temperatures. The splitting of the dipolar relaxations from those of conductive origin in the dielectric spectra was performed.
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    DIELECTRIC AND VISCOELASTIC RELAXATIONS IN POLY(DICYCLOHEXYL ITACONATE)
    (1992) DIAZCALLEJA, R; GARGALLO, L; RADIC, D
    The relaxation spectrum of poly(dicyclohexyl itaconate) (PDCHI) was studied by dynamic mechanical, DC dielectric and thermally stimulated current measurements. Four relaxations, alpha, beta, gamma and delta, were obtained. The only method by which all four peaks were observed is that of dynamic dielectric measurements because of the broad range of frequencies employed. The beta, gamma and delta-relaxations were characterized by the activation energy in a relaxation map. A tentative explanation of the molecular origin of each absorption is proposed. In the case of thc alpha-relaxation we have used two transformations, one from the permittivity to polarizability and thc second from compliance to deformability in order to make evident the existence of this relaxation.
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    DIELECTRIC AND VISCOMETRIC BEHAVIOR OF POLY(DIBENZYL ITACONATE) AS A FUNCTION OF TEMPERATURE
    (1988) GARGALLO, L; YAZDANIPEDRAM, M; RADIC, D; HERNANDEZFUENTES, I; HORTA, A
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    DIELECTRIC RELAXATIONS IN POLY(MONOCYCLOHEXYL ITACONATE)
    (JOHN WILEY & SONS INC, 1992) DIAZCALLEJA, R; GARGALLO, L; RADIC, D
    A study of the dielectric relaxation spectrum of poly (monocyclohexyl itaconate) (PMCHI) is performed by means of two experimental techniques: first, at variable frequency in the audio zone and, second, by thermally stimulated depolarization currents. Because of the high conductivity of the samples, there is a hidden dielectric relaxation that can be detected by using the macroscopic dynamic polarizability alpha* defined in terms of the dielectric complex permittivity epsilon* by means of the equation-alpha* = (epsilon* - 1)/(epsilon* + 2). The transformation performed through this equation is discussed in order to obtain the dielectric relaxations in the zone of high temperatures and low frequencies of the spectrum.
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    DIELECTRIC RELAXATIONS IN POLY(THIOCARBONATES)
    (JOHN WILEY & SONS INC, 1994) CALLEJA, RD; GARGALLO, L; RADIC, D
    The dielectric absorptions observed on six poly (thiocarbonates) (PTC) containing different substituents in the interphenylic carbon atom are subjected to a study. The a relaxation process associated with the glass transition temperature, which appears at the highest temperature studied, is overlapped with a strong conductive component. Between 80 and 100-degrees-C dielectric activity (beta) is observed, which is related to structural relaxation phenomena. Polymers with double substitution on the interphenylic carbon atom show a gamma relaxation with an activation energy of ca. 11 kcal mol-1 while those where the carbon atom is linked to a cyclohexyl group show higher activation energies and their respective characteristics. A cryogenic absorption around -120-degrees-C, for at least three polymers with an activation energy of about 5 kcal mol-1, is detected. (C) 1994 John Wiley & Sons, Inc.
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    DIELECTRIC RELAXATIONS IN POLY[2,2-PROPANE-BIS-(4-PHENYL THIOCARBONATE)]
    (1992) MARTINEZ, ES; DIAZCALLEJA, R; RIBAS, SM; GARGALLO, L; RADIC, D
    The dielectric relaxation properties of poly[2,2-propane-bis-(4-phenyl thiocarbonate)] (PTC) have been studied. The existence of crystallinity, which can be eliminated by quenching, is detected. The degree of crystallinity of polymer samples was determined by differential scanning calorimetry in order to investigate the effect of this factor on the dielectric behaviour of this polymer. The thermal degradation of the samples was studied by thermogravimetry. The degradation of the polymer begins before the glass transition temperature T(g). The dielectric spectrum is complex showing several relaxation phenomena. With increasing temperature a gamma-relaxation can be observed at - 100-degrees-C (5 kHz). The activation energy obtained from an Arrhenius plot (ln f vs T-1) is 6 kcal mol-1. At 160-degrees-C the alpha-relaxation which is associated with the glass transition temperature T(g) is detected. The dielectric behaviour of this poly(thiocarbonate) is compared with the corresponding poly(carbonate).
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    DIELECTRIC-RELAXATION BEHAVIOR OF POLY(CYCLOHEXYLMETHYL METHACRYLATE) AND POLY(BENZYL METHACRYLATE)
    (1989) RIBESGREUS, A; DIAZCALLEJA, R; GARGALLO, L; RADIC, D