Browsing by Author "Opazo, A"

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    Blends of poly(2-hydroxyethyl methacrylate) (styrene-co-dialkyl itaconates) and poly(N-vinyl-2-pyrrolidone) (styrene-co-dialkyl itaconates)
    (1996) Opazo, A; Gargallo, L; Radic, D
    Blends containing poly(N-vinyl-2-pyrrolidone) (PVP) and poly(hydroxyethyl methacrylate) (PHEMA) with (styrene-co-dimethyl itaconate) (Sty-co-DMI) and(styrene-co-diethylitaconate) (Sty-co-DEI) copolymers of three different compositions were studied. One Tg value over the whole range of compositions is observed for the majority of the blends, what is indicative of compatibility. The Gordon-Taylor k(GT) and the Couchman k(C) parameters were determined for all the blends in order to compare the strength of the interactions. The effect of the side chain structure of the copolymer on the miscibility of these blends is analyzed.
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    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.
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    Conformational transition in (maleic anhydride mono-n-octyl itaconate) copolymer
    (1996) Gargallo, L; Opazo, A; Radic, D
    The dependence of intrinsic viscosity [eta] on temperature for fractions of poly(maleic anhydride-co-mono-n-octylitaconate) [p(MA-co-MOI)] was studied. A discontinuity in [eta] as function of temperature similar to that of poly(mono-n-octylitaconate) (PMOI) is found which has been attributed to a conformational transition of the polymer chain. This conformational transition can be removed by the addition of poly(dimethylsiloxane) (PDMS). The effect is interpreted in terms of interpolymer complexation.
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    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.
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    Morphology and thermal properties of two polymethacrylates modified by a polymer liquid crystal
    (WILEY-BLACKWELL, 2004) Brostow, W; Gargallo, L; Hormazabal, A; Jaklewicz, M; Menard, KP; Opazo, A; Radic, D
    We have studied blends of a polymer liquid crystal (PLC) with poly(cyclohexylethyl methacrylate) (PCHEMA) or poly(cyclohexylpropyl methacrylate) (PCHPMA). The PLC is PET/0.6PHB where PET = poly(ethylene terephthalate), PHB = p-hydroxybenzoic acid and 0.6 is the mole fraction of the latter in the copolymer. The microstructure was studied by scanning electron microscopy (SEM). PCHEMA + PLC (20 wt% of the latter, blend E) has a fine texture with LC islands evenly distributed in the matrix and good adhesion between the phases resulting from their partial miscibility. The PCHPMA + PLC (20 wt% of the latter, blend P) shows only limited compatibility. The SEM results are confirmed by values of the glass transition temperatures T-g determined via thermal mechanical analysis. The T-g value of the blend E is shifted towards the T-g of PLC; T-g of blend P is practically equal to that of PCHPMA. The linear isobaric expansivity alpha(L) values for both blends are lower than the respective values for pure PCHPMA and PCHEMA. Thermal stabilities of the blends determined by thermogravimetry are also better than those of pure polymethacrylates. The temperature of 50% weight degradation for blend E is higher than that for pure PCHEMA by more-than 60K (C) 2004 Society of Chemical Industry.
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    Poly(N-1-alkylitaconamic acids) poly(N-vinyl-2-pyrrolidone) blends
    (1998) Urzua, M; Opazo, A; Gargallo, L; Radic, D
    Blends containing poly(N-1-alkylitaconamic acids) (PNAIA) and poly(N-vinyl-2-pyrrolidone) (PVP) of two different weight average molecular weights, were studied by differential scanning calorimetry (DSC), Thermogravimetric analysis (TGA), and infrared spectroscopy (FTIR). The phase behaviour of the blends is analyzed in terms of the side chain structure and the specific interactions involved, mainly due to the free carboxylic group and the amide groups in PNAIA and the carbonyl group of PVP. The strength of the interaction was analyzed in terms of the Gordon-Taylor parameters.
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    Synthesis and characterization of functionalized vinyl copolymers -: II.: Structure-monomer reactivity relationship in copolymers containing 4-vinylpyridine moieties
    (2006) Gatica, N; Fernández, N; Opazo, A; Radic, D
    Copolymers containing 4-vinylpyridine as common monomer with tert-butyl acrylate and acrylic acid of different comonomer compositions were synthesized and characterized. Copolymer composition was determined by elemental analysis, from which monomer reactivity ratios (MRR, r) were estimated using straight line intersection procedures such as Fineman-Ross and Kelen-Tudos methods and a nonlinear one, the Reactivity Ratios Error in Variables Model. In this case, the values of MRR are r(4VPy) = 0.046 and r(tBA) = 0.054 (for 4VPy-co-tBA), and r(4VPy) = 0.0 and r(AA) = 0.610 (for 4VPy-co-AA). A copolymer tending to the alternation and another containing isolated units of one of the monomers between small blocks of the another one were obtained, depending on the chemical nature of the comonomers. The different proposed comonomer distributions are analyzed in terms of the obtained MRR values and compared with related systems. The MRR are connected with structural properties of the monomers such as polarity, aromaticity and electron delocalization.
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    Synthesis and characterization of functionalized vinyl copolymers I. Structure-monomer reactivity relationship in copolymers containing N-vinyl-2-pyrrolidone moieties
    (SOC CHILENA QUIMICA, 2005) Gatica, N; Fernandez, N; Opazo, A; Radic, D
    Copolymers containing N-vinyl-2-pyrrolidone as a common monomer with acrylic acid, 4-methyl styrene and vinyltrichlorosilane of different comonomer compositions were synthesized and characterized. Copolymer composition was determined by elemental analysis, from which monomer reactivity ratios (MRR, r) were estimated using straight line intersection procedures, such as Fineman-Ross and Kelen-Tudos methods, and a nonlinear one, the Reactivity Ratios Error in Variables Model. In this case, the values of MRR are r(VP) = 0.1 and r(AA) = 1.1 (for VP-co-AA), r(VP) = 0.8 and r(4MS) = 14.6 (for VP-co-4MS), and r(VP) = 0.0 and r(VTCS) = 0.3 (for VP-co-VTCS).
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    Synthesis and characterization of functionalized vinyl copolymers.: Electronegativity and comonomer reactivity in radical copolymerization
    (2003) Gatica, N; Fernández, N; Opazo, A; Alegría, S; Gargallo, L; Radic, D
    Vinylsilane monomers (vinyltrimethoxysilane (VTMOS) and vinyltriethoxysilane (VTEOS)), methyl methacrylate (MMA), tert-butyl acrylate (tBA) and N-vinyl-2-pyrrolidone (VP) were used in the synthesis of functionalized vinyl copolymers. By using these monomers, VTMOS-co-MMA, tBA-co-VP and VTEOS-co-VP, with various compositions, were synthesized. The copolymers were characterized by viscometry, H-1-NMR, FTIR and elemental analysis. The monomer reactivity ratios were estimated by the Fineman-Ross and Kelen-Tudos linear procedures. These parameters were also estimated by using a computer program based on a non-linear minimization procedure known as Reactivity Ratios Error in Variables Model. Random copolymers and others containing blocks of one of the monomer units were obtained, depending on the chemical nature of the comonomers. The estimated comonomer sequence and distribution are discussed in terms of structural properties of the monomers such as molecular volume of the side groups, electronegativity of the substituents and steric hindrance. Analysis by comparison with other copolymers with analogous structures was also performed. (C) 2003 Society of Chemical Industry.
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    Synthesis and characterization of polyarylureas. I. Potentially semiconducting polymers
    (WILEY-BLACKWELL, 2001) Diaz, FR; Godoy, A; Moreno, J; Bernede, JC; Sanchez, CO; Opazo, A; Gargallo, L
    Polyarylureas were synthesized from the reaction between phosgene with aromatic diamines. Depending on the pH, the polyarylureas presented different colors when the solvent used was pyridine. The polyarylureas were characterized by IR spectroscopy, elemental analysis, and X-ray photoelectron spectroscopy (XPS). To study the thermal stability of the polymers, a thermal degradation was performed between 35 and 700 degreesC. The polyarylureas decomposed above 350 degreesC. Without doping, polyarylureas are considered as semiconductors [sigma = 10(-9) (Omega cm)(-) (1)]; after doping with I-2, their electrical conductivity increases by several orders of magnitude. (C) 2001 John Wiley & Sons, Inc.
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    Thermal stability of aromatic poly(monoitaconates)
    (GORDON BREACH SCI PUBL LTD, 1996) Radic, D; Tagle, LH; Opazo, A; Gargallo, L
    Thermogravimetric analysis of poly(mono-benzyl itaconate), (PMBzI) poly(mono-ethylphenyl itaconate) (PMEPI) and poly(mono-n-propyl itaconate) (PMPPI), were performed by dynamic thermogravimetry. The thermal stability of these polymers depends on the side chain structure. The kinetic analysis of the degradation data shows that the thermal decomposition of these polymers follows a 0.5 kinetic order in all the cases.
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    Thermal studies of poly(esters) containing silicon or germanium
    (SOCIEDAD CHILENA DE QUIMICA, 2001) Tagle, LH; Diaz, FR; Opazo, A
    The thermal properties of poly(esters) containing silicon or germanium in the main chain and derived from the diphenols bis(4-hydroxyphenyl)-diphenylsilane and bis(4-hydroxyphenyl)-diphenylgermane and isophthaloyl or terephthaloyl acid dichlorides were studied by differential scanning calorimetry and dynamic thermogravimetry. Poly(esters) derived from terephthalic acid showed higher Tg and thermal stability values than those derived from isophthalic acid. Poly(esters) containing Ge showed higher Tg values but lower thermal decomposition temperatures when compared with the analogous with Si.