Browsing by Author "Villar, V"

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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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    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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    Thermodynamics of hydrogen bonding in polycomplexes of poly(4-vinylpyridine) with maleic acid-alt-ethylene copolymer
    (ELSEVIER SCIENCE BV, 2003) Villar, V; Irusta, L; Fernandez Berridi, MJ; Iruin, JJ; Iriarte, M; Gargallo, L; Radic, D
    Hydrogen bonding formation in a polymer complex between poly(4-vinylpyridine) (P4VPy) and maleic acid-alt-ethylene (MA-alt-E) copolymer has been studied. Fourier transform infrared spectroscopic (FT-IR) studies have evidenced that the carboxylic groups of MA-alt-E interact with the pyridine ring of P4VPy. The existence of hydrogen bonding interactions in these systems is shown by the appearance of new bands at 1640 and 1503 cm(-1) and a broadening of the -C=C- band of the pyridinic ring. The thermodynamic analysis of the hydrogen bonding was performed through the estimation of the enthalpy of mixing in the polycomplex formation process. DeltaH(M) was determined by means of an association model developed by Painter and co-workers and by flow calorimetric direct measurements. These results showed a high negative value for the enthalpy of mixing, which is consistent with the blend miscibility given that DeltaH(M) is the main contribution to the change of the free energy of mixing, AGM. (C) 2003 Elsevier Science B.V. All rights reserved.