Browsing by Author "Rios, H"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    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.
  • Thumbnail Image
    Item
    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.
  • Thumbnail Image
    Item
    Surface characterization and study of Langmuir films of poly(4-vinylpyridine) quaternized with n-alkylbromide
    (JOHN WILEY & SONS LTD, 2001) Gargallo, L; Miranda, B; Rios, H; Gonzalez Nilo, F; Radic, D
    The surface behaviour of poly(4-vinylpyridine)s (P4VP) quaternized with four different alkyl chains (pentyl, hexyl, octyl and decy bromide) were studied. Surface pressure-area isotherms (pi -A) at the air-water interface were determined. Depending on the length of the side-chains, the pi -A isotherms show a plateau region. An extensive plateau is observed for n >6. The plateau pressures are similar for n = 8 and n = 10. The monolayers are stable and exhibit hysteresis phenomena. Brewster angle microscopy (BAM) is used to monitor the monolayer topography of the polymer on water subphase. To obtain information about the surface energy (SE) and the degree of hydrophobicity of these systems, we have estimated the critical surface tension, gamma (c), and the dispersion force and polar contributions to SE, gamma (D) and gamma (P), respectively, by measurements of the contact angle (CA) of water and bromobenzene on the polymer surface. The results obtained are depend on the length of the alkyl lateral chain of the functionalized polymers. (C) 2001 Society of Chemical Industry.