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Browsing by Author "Gargallo, L"

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Blends containing Amphiphilic polymers IV. Poly(N-1-alkyl itaconamic acids) with poly(2-vinyl pyridine) and poly(4-vinylphenol)
(JOHN WILEY & SONS INC, 2002) Urzua, M; Gargallo, L; Radic, D
The phase behavior of blends containing Poly(N-1-alkyl itaconamic acids) (PNAIA) with Poly(2-vinylpyrindine) (P2VPy) and Poly(4-vinylphenol) (P4VPh) were analyzed by Diferential Scanning Calorimetry (DSC) and Fourier Transform Infrared Spectroscopy (FTIR). Miscibility over the whole range of compositions is observed in both systems. All the blends show thermograms exhibiting distinct single glass transition temperatures (T-g), which are intermediate to those of the pure components. The Calorimetric Analysis using Gordon Taylor, Couchman, and Kwei treatments allows conclusion that interactions between the components is favorable to the miscibility. FTIR analysis of the blends suggests that the driving force for miscibility is hydrogen bonding formation. The variation of the absorptions of the carbonyl groups of PNAIA and the hydroxyl groups of P4VPh allows one to attribute the miscibility to weak acid base like interactions. (C) 2002 Wiley Periodicals, Inc.
Blends containing amphiphilic polymers. II. Poly(N-1-alkyl itaconamic acids) with poly(4-vinylpyridine) and poly(2-hydroxypropyl methacrylate)
(MARCEL DEKKER INC, 2000) Urzua, M; Gargallo, L; Radic, D
The phase behavior of blends containing poly(N-1-alkyl itaconamic acids) (PNAIA) with poly(4-vinylpyridine) (P4VPy) and poly(2-hydroxypropyl methacrylate) (PHPMA) were studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR) spectroscopy. The results are analyzed in terms of the side-chain structure and the specific interactions involved, mainly due to the strong interacting groups present in the different polymers. The behaviors of the blends are discussed in terms of the hydrophobic/hydrophilic ratio and the balance of the different kinds of interactions involved. The strength of the interaction is analyzed in terms of the Gordon-Taylor and Couchman parameters. Miscibility over the whole range of composition for both families of blends is found. The variation of the glass transition T-g with composition together with the FTIR spectra and thermogravimetric profiles show that the blends behave as one-phase material.
Comparative study of localized side group in poly(2,3 and 4 methyl cyclohexyl methacrylate)s. TSDC measurements
(ELSEVIER SCI LTD, 2005) Dominguez Espinosa, G; Sanchis, MJ; Diaz Calleja, R; Pagueguy, C; Gargallo, L; Radic, D
By means of thermal sampling techniques, the fine structure of the gamma-relaxation zone of poly(methyl cyclohexyl methacrylate)s (P2MCHMA), (P3MCHMA), (P4MCHMA) were analyzed. Results reveal that in this relaxation zone, at least two peaks are present. These peaks are attributed to the cis and trans isomers. Loss permittivity of the polymers under study in this relaxation zone has been reproduced from the partial depolarization data by using the elementary relaxation times and activation energies. Results are in relatively good agreement with the experimental data previously obtained. Molecular mechanic calculations have been carried out in order to elucidate the characteristics and molecular origin of the relaxations observed in this zone. An interpretation of the height of the peaks associated to the cis- and trans-isomer in terms of strain energy (SE) have been carried out. (c) 2005 Elsevier Ltd. All rights reserved.
Comparative study of poly(2,3 and 4 methyl cyclohexyl methacrylate)s. Dielectric relaxation spectroscopy (DRS)
(ELSEVIER SCI LTD, 2005) Dominguez Espinosa, G; Sanchis, MJ; Diaz Calleja, R; Pagueguy, C; Gargallo, L; Radic, D
The relaxation properties of poly(methyl cyclohexyl methacrylate)s (P2MCHMA), (P3MCHMA), (P4MCHMA) were analyzed. Dielectric spectroscopy (DS) techniques were used for this purpose. These polymers exhibit prominent alpha peaks, associated to the dynamic glass transitions, and then poorly defined beta-relaxations and two other relaxation zones labelled as gamma and delta-relaxation in order of decreasing temperatures. The alpha relaxation processes were analyzed by means of the free volume theory, using the Vogel-Fulcher-Tammann-Hesse (VFTH) equation and in terms of the Havriliak-Negami (HN) empirical equation. Previously to these analyses, conductive contributions to the loss permittivity were subtracted. The apparent activation energies for the secondary processes under study have been calculated by means of Arrhenius. Comparison with previous relaxation results of poly(cyclohexyl methacrylate) (PCHMA), i.e. the polymer without substituents in the cyclohexyl ring, has been also carried out. In this way, changes in the glass transition absorptions as well as in the secondary processes have been discussed. (c) 2005 Elsevier Ltd. All rights reserved.
Compatibilization of poly(ethylene oxide)/poly(styrene) blends: Effect of the molecular weight of the compatibilizer
(TAYLOR & FRANCIS INC, 2001) Opazo, A; Villar, V; Rios, H; Gargallo, L; Radic, D
The effect of the molecular weight and concentration of the compatibilizer maleic acid-alt-styrene copolymer (MAaS) on the compatibility behavior of incompatible poly(ethylene oxide)/poly(styrene) (PEO/PS) blends was studied by differential scanning calorimetry (DSC) and polarized light microscopy (PLM). PEO with (M) over bar (w)=100,000 (PEO100) and PS with (M) over bar (w) = 225,000 (PS225) were used for this study. DSC measurements showed two T-g values that were shifted relative to those of the pure components. This result should be indicative that MAaS acts as a compatibilizer for the blend. Diminishing of the spherulitic growth rate G was observed as the content and molecular weight of MAaS increased in the blend. This result was confirmed by morphological analysis, by which it was possible to observe that the amorphous component diminished its droplike domains. Contact angle measurements suggest that the wettability of PEO drops on a PS/MAaS surface are larger in the system containing MAaS as the compatibilizer.
Deconvolution of the relaxations associated with local and segmental motions in poly(methacrylate)s containing dichlorinated benzyl moieties in the ester residue
(AMER INST PHYSICS, 2005) Dominguez Espinosa, G; Diaz Calleja, R; Riande, E; Gargallo, L; Radic, D
The relaxation behavior of poly(2,3-dichlorobenzyl methacrylate) is studied by broadband dielectric spectroscopy in the frequency range of 10(-1)-10(9) Hz and temperature interval of 303-423 K. The isotherms representing the dielectric loss of the glassy polymer in the frequency domain present a single absorption, called beta process. At temperatures close to T-g, the dynamical alpha relaxation already overlaps with the beta process, the degree of overlapping increasing with temperature. The deconvolution of the alpha and beta relaxations is facilitated using the retardation spectra calculated from the isotherms utilizing linear programming regularization parameter techniques. The temperature dependence of the beta relaxation presents a crossover associated with a change in activation energy of the local processes. The distance between the alpha and beta peaks, expressed as log(f(max;beta)/f(max;alpha)) where f(max) is the frequency at the peak maximum, follows Arrhenius behavior in the temperature range of 310-384 K. Above 384 K, the distance between the peaks remains nearly constant and, as a result, the alpha onset temperature exhibited for many polymers is not reached in this system. The fraction of relaxation carried out through the alpha process, without beta assistance, is larger than 60% in the temperature range of 310-384 K where the so-called Williams ansatz holds. (c) 2005 American Institute of Physics.
Dielectric relaxation behaviour of poly(cyclobutyl methacrylate)s
(WILEY, 2002) Diaz Calleja, R; Garcia Bernabe, A; Sanchez Martinez, E; Hormazabal, A; Gargallo, L; Radic, D
Dielectric behaviour of two poly(methacrylate)s with cyclobutyl groups in the side-chains has been studied. This investigation was performed by determining the dielectric permittivity and loss in terms of frequency and temperature for poly(cyclobutyl. methacrylate) (PCBuM) and poly(cyclobutylmethyl methacrylate) (PCBuMM). Dynamic dielectric measurements show sub-glass relaxations, probably due to motions in the lateral chain, including the cyclobutyl ring. The effect of the insertion of a flexible spacer group into the side-chain is also analyzed. The alpha relaxations were analyzed in terms of the Havriliak-Negami equation and the free volume theory tested according to the Vogel-Fulcher-Tamman-Hesse equation. The conductive and interfacial phenomena were studied by hopping and MacDonald-Coelho models. (C) 2002 Society of Chemical Industry.
Dielectric relaxational behavior of poly(diitaconate)s containing cyclic rings in the side chain
(WILEY, 2003) Diaz Calleja, R; Garcia Bernabe, A; Sanchez Martinez, E; Sanchis, MJ; Hormazabal, EA; Gargallo, L; Radic, D
Dielectric relaxations of several poly(diitaconate)s with cyclobutyl, cycloheptyl, and cyclooctyl groups in the side chain were investigated. The study was performed by determining the dielectric permittivity and loss, depending on the frequency and temperature. Dynamic dielectric measurements indicated several relaxations according to the chemical structure of the polymers. The dielectric behavior of these polymers was compared with those of poly(dicyclohexyl itaconate), previously reported. The a relaxations were analyzed with the Havriliak-Negami equation. Significant differences in the subglass relaxations were observed. A tentative explanation of the molecular origin of each absorption was proposed in terms of the number of carbon atoms of the ring and their conformational versatility. Strong conductive processes were observed in these polymers at low frequencies and high temperatures. (C) 2003 Wiley Periodicals, Inc.
Dielectric relaxations of poly(2-norbornyl methacrylate) and poly(3-methyl-2-norbornyl methacrylate)
(ELSEVIER SCI LTD, 2001) Diaz Calleja, R; Garcia Bernabe, A; Pagueguy, C; Gargallo, L; Radic, D
Dielectric behaviour of poly(2-norbornyl methacrylate) (P2NBM) and poly(3-methyl-2-norbornyl methacrylate) (P3M2NBM) was studied. The effect of the methyl substituent on the norbornyl ring is to decrease the temperature of the dynamic glass transition about 50 K. Moreover, weak secondary relaxations are observed in the two polymers under study. The secondary process of P3M2NBM has been conveniently analysed in terms of the empirical Fuoss-Kirkwood (F-K) equation. (C) 2001 Elsevier Science Ltd. All rights reserved.
Dynamic mechanical and dielectric relaxational behavior of poly(cyclohexylalkyl methacrylate)s
(AMER CHEMICAL SOC, 2001) Calleja, RD; Garcia Bernabe, A; Sanchez Martinez, E; Hormazabal, A; Gargallo, L; Gonzalez Nilo, F; Radic, D
The dynamic mechanical and dielectric behavior of three poly(cyclohexylalkyl methaerylate)s with different spacer groups has been studied. The study was performed by determining the components of the complex relaxation modulus E* and the complex dielectric permittivity epsilon*. Results are discussed in terms of the effect of the side chain structure and the insertion of flexible spacer groups. Molecular dynamic calculations for the repeating unit of the polymers under study are analyzed. Close to room temperature the interconversion between axial and equatorial conformations is not observed whitin the total time of 5 ns. The analysis was then performed from 1000 to 1500 K, and the results were extrapolated to lower temperatures. By this way the fraction of axial and equatorial conformations was calculated. The free energy change against the number of carbon atoms in the side chain is in excellent agreement with the experimental data. This means that the gamma relaxation associated with the chair-to-chair conformational change in the cyclohexyl group is also influenced by the length of the spacer group. The molecular dynamics approach allows to observe the relative incidence of the two conformations of the cyclohexyl group which can be related to the motions responsible for the gamma relaxation.
Dynamic mechanical and dielectric relaxations in poly(di-n-chloroalkylitaconates)
(ELSEVIER SCI LTD, 2004) Sanchis, MJ; Diaz Calleja, R; Pelissou, O; Gargallo, L; Radic, D
Dielectric and viscoelastic relaxation measurements have been carried out on poly(2-chloroethyl diitaconate) (PDCEI) and poly(3-chloropropyl diitaconate) (PDCPI) between 123 K and temperatures about 293 K above the glass transition temperatures.
Dynamic mechanical and dielectric relaxations in poly(dibenzyl itaconate) and poly(diethylphenyl itaconate)
(ELSEVIER SCI LTD, 2000) Calleja, RD; Martinez Pina, F; Gargallo, L; Radic, D
Dynamic mechanical and dielectric behaviour of poly(dibenzyl itaconate), and poly(diethylphenyl itaconate) were studied. The study was performed by determining the components of the complex relaxation modulus E* and the complex dielectric permittivity epsilon*. The results are compared with those previously reported for poly(benzyl methacrylate), poly(monobenzyl itaconate) and poly(monoethylphenyl itaconate). The results are discussed in terms of the effect of flexible spacer groups and of the different steric hindrance between mono and disubstituted polymers. (C) 1999 Elsevier Science Ltd. All rights reserved.
Dynamic mechanical and dielectric relaxations in poly(pentachlorophenyl methacrylate)
(WILEY-V C H VERLAG GMBH, 1998) Calleja, RD; Jaime's, C; Sanchis, MJ; San Roman, J; Gargallo, L; Radic, D
In the present work, a comparative study of the dynamic mechanical and dielectric properties of two related polymers, poly(pentachlorophenyl methacrylate) (PPCPM) and poly(phenyl methacrylate) (PPhM), was carried out. In both polymers a similar relaxational behaviour was observed. Dielectric relaxation measurements give an improved resolution as compared with that obtained from dynamic mechanical techniques for a given process. The polymers show a secondary loss peak at approximately room temperature and a prominent peak overlapped with the conductivity electrode polarization contributions at temperatures above the glass transition temperature, studied by dielectric relaxation measurements. The activation energy associated with the relaxation process at low temperature is about 77 kJ.mol(-1) (which is similar to that observed in poly(alkyl methacrylates)) whose origin is attributed to the hindered partial rotation of the carboxymethyl group. An improved method of separating dipolar contributions from the non-dipolar ones was used to characterize the high temperature relaxation process and to obtain information from the diffusion coefficient of the conducting species.
Dynamic mechanical and dielectric relaxations of poly(difluorobenzyl methacrylates)
(WILEY-BLACKWELL, 2000) Diaz Calleja, R; Sanchis, MJ; Saiz, E; Martinez Pina, F; Miranda, R; Gargallo, L; Radic, D; Riande, E
This work reports the mechanical and dielectric relaxation spectra of three difluorinated phenyl isomers of poly(benzyl methacrylate), specifically, poly(2,4-difluorobenzyl methacrylate), poly(2,5-difluorobenzyl methacrylate) and poly(2,6-difluorobenzyl methacrylate). The strength of the dielectric glass-rubber relaxation of the 2,6 difluorinated phenyl isomer is, respectively, nearly three and two times larger than the strengths of the 2,5 and 2,4 isomers. The 2,4 isomer presents a mechanical ct peak the intensity of which is nearly two times that of the other two isomers. Both the mechanical and dielectric relaxation spectra display a subglass process, called gamma relaxation, centered in the vicinity of -50 degrees C at 1 Hz and, in some cases, a subglass beta absorption is detected at higher temperature partially masked by the glass-rubber relaxation. The mean-square dipole moments per repeating unit, [mu 2]/x, measured at 25 degrees C in benzene solutions, are 2.5 D-2, 1.9 D-2, and 5.0 D-2 for poly(2,4-difluorobenzyl methacrylate), poly(2,5-difluorobenzyl methacrylate) and poly(2,6-difluorobenzyl methacrylate), respectively. These results, in conjunction with Onsager type equations, permit to conclude that auto and cross-correlation contributions to the dipolar correlation coefficient may have the same time-dependence. On the other hand, dipole intermolecular interactions, rather than differences in the flexibility of the chains, seem to be responsible for the relatively high calorimetric glass-transition temperature of the 2,6 diphenyl isomer, which is, respectively, nearly 36 degrees C and 32 degrees C above the T-g's of the 2,4 and 2,5 isomers. Molecular Mechanics calculations give a good account of the differences observed in the polarity of the polymers. (C) 2000 John Wiley & Sons, Inc.
Influence of the fine structure on the response of polymer chains to perturbation fields
(AMER CHEMICAL SOC, 2006) Dominguez Espinosa, G; Diaz Calleja, R; Riande, E; Gargallo, L; Radic, D
The relaxation behavior of poly(3-methylbenzyl methacrylate), poly(3-fluorobenzyl methacrylate), and poly(3-chlorobenzyl methacrylate) was thoroughly studied by broadband dielectric spectroscopy with the aim of investigating the influence of slight differences in chemical structure on the response of polymers to electric perturbation fields. Retardation spectra calculated from dielectric isotherms utilizing linear programming regularization parameter techniques were used to facilitate the deconvolution of strongly overlapped absorptions. Above the glass transition temperature, the spectra of the two halogenated polymers present a secondary gamma process well separated from a prominent peak resulting from the overlapping of the alpha and beta relaxations. The spectra of poly(3-methylbenzyl methacrylate) exhibit at long times a well-developed alpha absorption followed in decreasing order of time by two weak absorptions, named beta and gamma, whose intensities increase with temperature. The temperature dependence of the distance of the a peak from the beta and gamma peaks, expressed in terms of log(f(max,beta)/f(max,alpha)) and log(f(max,gamma)/f(max,alpha)), respectively, is studied. The Williams ansatz and the extended ansatz give a fairly good account of the relaxation behavior of the polymers. The stretch exponent associated with the a relaxation increases with temperature from ca. 0.2 at low temperatures to the vicinity of 0.5 at high temperatures. At low temperatures, the alpha relaxation is described by a Vogel-type equation, but at high temperature the beta and alpha processes are roughly described by the same Arrhenius equation. In the whole temperature range, the activation energy they relaxation is significantly lower than that of the beta absorption. The mechanisms involved in the development of the secondary relaxations are qualitatively discussed.
Maleic acid-alt-styrene copolymer as compatibilizer for poly(ethylene oxide)-poly(styrene) blends
(MARCEL DEKKER INC, 2000) Villar, V; Opazo, A; Gargallo, L; Rios, H; Radic, D
Maleic acid-alt-styrene (MAaS) copolymer with number-average molecular weight (M) over bar (n) = 2500 was used as a compatibilizer in blends of poly(ethylene oxide) (PEO) and poly(styrene) (PS). PEO with weight-average molecular weight (M) over bar (w) = 10(5) (PEO100) and two PS samples with (M) over bar (w) = 9 x 10(4) and 4 x 10(5), respectively (PS90 and PS400, respectively) were used. A depression of the melting temperature T-m of PEO in blends containing MAaS relative to pure PEO and PEO/PS blends was observed. The melting enthalpy DeltaH(m) for the PEO/PS blends containing MAaS was lower than those of pure PEO and PEO/PS blends without compatibilizer. The crystallization kinetics of PEO and the blends were studied by differential scanning calorimetry (DSC) at different crystalization temperatures T-c. Flory-Huggins interaction parameters chi (12) for the blends were estimated. Their values are in good agreement with those obtained for similar systems and suggest that the free energy of mixing DeltaG(mix) should be negative. Polarized optical microscopy shows differences in the macroscopic homogeneity of the blends containing compatibilizer that could be attributed to a compatibilization process.
Maleic anhydride-co-stearyl methacrylate copolymers. Synthesis, characterization, and some aspects of the solution behavior
(MARCEL DEKKER INC, 1998) Leiva, A; Gargallo, L; Radic, D
Maleic anhydride-stearyl methacrylate copolymer was synthesized by radical polymerization. The copolymer was fractionated and characterized by dynamic and static light scattering (DLS and SLS) experiments in different concentration regimes. Seven fractions of low polydispersity index(< 1.18) were studied. A typical behavior corresponding to good and theta (theta) solvents, according to the classical theories for polymers in solution, was found in the dilute regime. The results indicate in a semiquantitative way that this copolymer shows a normal behavior in the dilute regime. The rigidity parameters sigma and C-infinity show flexibility of the polymer chain, due to the incorporation of the maleic anhydride (MA) units, when the copolymer is compared with those corresponding to other poly(methacrylates) previously reported. In the semidilute regime and depending on the solvent nature, aggregation of the copolymer was detected. The aggregation was analyzed in terms of the values of the autocorrelation function determined by dynamic light scattering.
Mechanical and dielectric properties of bulky side chain poly(methacrylates). Analysis of the low frequency phenomena .1. Poly(5-indanyl methacrylate)
(SOC PLASTICS ENG INC, 1997) Calleja, RD; Jaimes, C; SanchisSanchez, MJ; MartinezPina, F; Gargallo, L; Radic, D
This paper composes the dynamic mechanical and dielectric relaxation properties for Poly (5-indanyl methacrylate) (P51M), a polymer with a bulky side chain. Measurements were carried out from about -100 degrees C to near 250 degrees C. A secondary loss peak was observed in dielectric measurements at room temperature (20 degrees C at 0.1 Hz.), whereas nothing was resolved in the mechanical spectrum, A prominent alpha relaxation associated with the glass transition was also observed near 107 degrees C at 0.1 Hz. in the dielectric and the mechanical spectra. Dipolar dielectric loss overlapped with conductivity at high temperatures and low frequencies. A new method to split the conductive, interfacial, and dipolar contributions to the spectrum is proposed.
Modification of the air-water interface by a chitosan adsorption process. Effect on an amphiphilic polymer monolayer
(WILEY, 2004) Gargallo, L; Leiva, A; Urzua, M; Alegria, L; Miranda, B; Radic, D
Monolayer formation by poly[(maleic anhydride)-alt-(stearyl methacrylate)] (MA-alt-StM) on aqueous subphases, with and without chitosan, was studied by the Langmuir technique. Chitosan (CS) modified considerably the shape of the MA-alt-StM isotherms on water. To explain this behavior, the surface activity properties of chitosan at the air-solution interface were studied. The variations of the interfacial tension, gamma(int), with chitosan concentration and temperature, were also determined. The results were discussed in terms of the modification of the air-water interface owing to the presence of chitosan in the subphase and the surface activity. It was found that the standard free energy of adsorption, DeltaG(ads)(0),values were dependent on the degree of acetylation (DA) over the DA range being studied. (C) 2004 Society of Chemical Industry.
Monomer reactivity in functionalized vinyl copolymers: A theoretical approach
(MARCEL DEKKER INC, 2004) Gatica, N; Gargallo, L; Radic, D
This work studies how the variation of the inter-atomic distance affects the total energy in addition reactions of several vinyl radicals on vinyl monomers. Based on the energetic profiles obtained, the corresponding activation eneigies were evaluated and correlated with the relative reactivity of the monomers forming the vinyl copolymers poly(2-vinylpyridine-co-N-vinyl-2-pyrrolidone), poly(4-vinylpyridine-co-N-vinyl-2-pyrrolidone), poly(vinyltrimethylsilane-co-N-vinyl-2-pyrrolidone) and poly(vinylcyclohexane-co-N-vinyl-2-pyrrolidone), previously characterized with an estimation of their monomer reactivity ratios (MRR). The results are discussed as a theoretical support to a work developed in the general framework of the synthesis and characterization of functionalized vinyl copolymers.

Browsing by Author "Gargallo, L"

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