Biodegradable poly(alkylene succinate) blends: Thermal behavior and miscibility study

New binary blends composed of poly(ethylene succinate) and poly(propylene succinate) or poly(ethylene succinate) and poly(butylene succinate) were prepared. Both PESu/PPSu and PESu/PBSu systems belong to semicrystalline/semicrystalline pairs. The miscibility and crystallization behavior was investigated using differential scanning calorimetry (DSC), wide angle X‐ray diffraction (WAXD), and polarizing light microscopy (PLM). Blends of PESu and PPSu exhibited a single composition dependent glass transition temperature over the entire range of composition, indicating that the system is miscible. The melting point depression of the high melting temperature component, PESu, was analyzed according to the Nishi‐Wang equation. A negative polymer–polymer interaction parameter was obtained, indicating that the blends are thermodynamically miscible in the melt. The two components crystallized sequentially when the blends were cooled rapidly to a low temperature. DSC traces of PESu/PBSu blends after quenching showed two distinct composition dependent glass transition temperatures between those of the neat polymers, showing that the polymers are partially miscible. The amorphous PESu/PBSu blends in the intermediate compositions showed three cold‐crystallization peaks, indicating the influence of mixing. The crystallization rates of PBSu were reduced and those of PESu were increased. WAXD showed reduced crystallinity and peak broadening in the patterns of the blends of intermediate compositions, while no spherulites could be detected by PLM. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 584–597, 2006     

Barrier property enhancement of polyamide 6 by blending with a polyhydroxyamino‐ether resin

In this work, the transport properties of the system formed by polyamide 6 (PA6) and polyhydroxyamino‐ether resin (PHAE) have been studied after characterizing the miscibility behavior. A single glass transition has been observed using differential scanning calorimetry that usually means total miscibility, but measurements by solid‐state cross‐polarization magic angle spinning NMR have shown that this system is only partially miscible, in good agreement with phase behavior reported before. Both carbon dioxide and water vapor transport properties of PA6/PHAE blends have been measured. For both penetrants, permeability coefficient shows an interesting negative deviation from the additive value, even the barrier character to carbon dioxide of pure PHAE is maintained up to 60 % in PA6 composition. Besides, PHAE reduces the plasticization effect of water in PA6. These improvements are very interesting for the PA 6 due to its wide use in packaging applications. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1625–1634, 2009     

Glass transition temperatures in binary polymer blends

Knowledge of the glass transition temperatures (T_gs) as function of composition reflects miscibility (or lack of it) and is decisive for virtually all properties of polymer‐based materials. In this article, we analyze single blend‐average and effective T_gs of miscible polymer blends in full concentration ranges. Shortcomings of the extant equations are discussed to support the need for an alternative. Focusing on the deviation from a linear relationship, defined as ΔT_g = T_g ? φ₁T_g,1 ? φ₂T_g,2 (where φ_i and T_g,i are, respectively, the weight fraction and the T_g of the i‐th component), a recently proposed equation for the blend T_g as a function of composition is tested extensively. This equation is simple; a quadratic polynomial centered around 2φ₁ ? 1 = 0 is defined to represent deviations from linearity, and up to three parameters are used. The number of parameters needed to describe the experimental data, along with their magnitude and sign, provide a measure of the system complexity. For most binary polymer systems tested, the results obtained with the new equation are better than those attained from existing T_g equations. The key parameter of the equation a₀ is related to parameters commonly used to represent intersegmental interactions and miscibility in binary polymer blends. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 80–95, 2008     

Investigation at the chain segmental level of the miscibility of poly(vinyl chloride)/atactic poly(methyl methacrylate) blends

We employed high‐resolution ¹³C cross‐polarization/magic‐angle‐spinning/dipolar‐decoupling NMR spectroscopy to investigate the miscibility and phase behavior of poly(vinyl chloride) (PVC)/poly(methyl methacrylate) (PMMA) blends. The spin–lattice relaxation times of protons in both the laboratory and rotating frames [T₁(H) and T_1ρ(H), respectively] were indirectly measured through ¹³C resonances. The T₁(H) results indicate that the blends are homogeneous, at least on a scale of 200–300 Å, confirming the miscibility of the system from a differential scanning calorimetry study in terms of the replacement of the glass‐transition‐temperature feature. The single decay and composition‐dependent T_1ρ(H) values for each blend further demonstrate that the spin diffusion among all protons in the blends averages out the whole relaxation process; therefore, the blends are homogeneous on a scale of 18–20 Å. The microcrystallinity of PVC disappears upon blending with PMMA, indicating intimate mixing of the two polymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2390–2396, 2001     

Small-angle neutron scattering study on the miscibility and concentration fluctuation of hydrogen-bonded polymer blends

Thermal concentration fluctuation in the blends of deuterated poly(ethylene oxide) (dPEO) and poly(vinyl acetate-co-vinyl alcohol) [P(VAc-VOH)] with various VOH contents f_OH were examined by small angle neutron scattering techniques at a fixed blend composition, dPEO/P(VAc-VOH) = 20/80 which is close to the critical composition. Blends at the highest f_OH (=0.35) showed a non-Lorentzian scattering profile: specifically the scattering intensities at the low q (angle) region were suppressed compared to those expected from the random phase approximation (RPA) theory. However, for the blends at lower f_OH (≤0.28), the profiles could be represented by the RPA. Using the RPA we determined effective values of the Flory-Huggins interaction parameter χ_eff as a function of f_OH (=0–0.28). The χ_eff showed the minimum around f_OH = 0.1–0.18 meaning the highest miscibility of the blend at these f_OH. On the basis of the random copolymer theory, we evaluated the three interaction parameters χ_Ac–EO, χ_EO–OH, and χ_Ac–OH separately from the χ_eff(f_OH) and found the order of magnitude; χ_Ac–EO < 0 < χ_EO–OH < χ_Ac–OH. The largest positive χ_Ac–OH showing intrachain interaction in the P(VAc-VOH) copolymer was concluded to be the origin of the enhanced miscibility at around f_OH = 0.1–0.18. On the basis of the Coleman and Painter's theory, the effects of hydrogen bonding on these three χ_A-B were discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2556–2565, 2008     

Thermodynamic interactions in blends of poly(4-tert-butyl styrene) and polyisoprene by small-angle neutron scattering

The thermodynamic interactions between poly(4-tert-butyl styrene) [P(4tBS)] and 1,4-polyisoprene (PI; both hydrogenous) were obtained as functions of the temperature, PI molecular weight, and blend composition through the examination of miscible ternary blends of these two components with a common miscible labeled polymer [90% 1,2-deuterated polybutadiene (dPBD)] with small-angle neutron scattering. The thermodynamic interaction parameters between P(4tBS) and dPBD and between P(4tBS) and PI increased with increasing temperature and were consistent with lower critical solution temperature behavior. Although the binary blends of P(4tBS) and dPBD exhibited phase separation at elevated temperatures, the thermodynamic interaction parameters between P(4tBS) and PI remained large and negative and independent of the PI molecular weight. Finally, the thermodynamic interactions for PI and P(4tBS) depended strongly on the ratio of PI to P(4tBS) and were also sensitive to the amount of dPBD present in the ternary blend. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3204–3217, 2004     

Level‐set based numerical simulation of a migrating and dissolving liquid drop in a cylindrical cavity

In the present paper the dissolution of a binary liquid drop having a miscibility gap and migrating due to thermo‐solutal capillary convection in a cylindrical cavity is studied numerically. The interest in studying this problem is twofold. From a side, in the absence of gravity, capillary migration is one of the main physical mechanisms to set into motion dispersed liquid phases and from the other side, phase equilibria of multi‐component liquid systems, ubiquitous in applications, often exhibit a miscibility gap. The drop capillary migration is due to an imposed temperature gradient between the cavity top and bottom walls. The drop dissolution is due to the fact that initial composition and volume values, and thermal boundary conditions are only compatible with a final single phase equilibrium state. In order to study the drop migration along the cavity and the coupling with dissolution, a previously developed planar two‐dimensional code is extended to treat axis‐symmetric geometries. The code is based on a finite volume formulation. A level‐set technique is used for describing the dynamics of the interface separating the different phases and for mollifying the interface discontinuities between them. The level‐set related tools of redistancing and off‐interface extension are used to enhance code resolution in the critical interface region. Migration speeds and volume variations are determined for different drop radii. Copyright © 2004 John Wiley & Sons, Ltd.     

Miscible blends of zinc-neutralized sulfonated polystyrene and poly(2,6-dimethyl 1,4-phenylene oxide)

Zinc-neutralized sulfonated polystyrene ionomers (ZnSPS) and poly(2,6-dimethyl 1,4-phenylene oxide) homopolymer (PXE) form miscible blends up to at least 7.8 mol % sulfonation, as measured by thermal and mechanical criteria. The addition of an equal weight of PXE raises the glass transition temperature of ZnSPS by 40–50°C. However, this miscibility is not achieved by eradicating the microdomain structure present in ZnSPS, even though the PXE coils are considerably larger than the spacings between ionic aggregates. Small-angle x-ray scattering indicates that while the average interaggregate spacing is roughly the same in ZnSPS and its 50/50 blend with PXE at a given sulfonation level, the extent of phase separation is reduced upon PXE addition, indicating that more ionic groups are dispersed in the matrix. Factors influencing miscibility in the ZnSPS/PXE materials and related blends are discussed.