The Experts below are selected from a list of 3648 Experts worldwide ranked by ideXlab platform

Lewis J. Fetters - One of the best experts on this subject based on the ideXlab platform.

  • thermoreversible cylinder sphere transition of polystyrene block polyisoprene diblock copolymers in Dioctyl Phthalate solutions
    Macromolecules, 1996
    Co-Authors: Shinichi Sakurai, Takeji Hashimoto, Lewis J. Fetters
    Abstract:

    We present experimental results of a thermoreversible morphological transition between spheres and cylinders for polystyrene-block-polyisoprene diblock copolymers (SI) in Dioctyl Phthalate solutions. Morphologies were characterized using small-angle X-ray scattering (SAXS), and spherical and cylindrical states were found above and below the order−order transition (OOT) temperature, TOOT, respectively. TOOT increased with an increase of polymer concentration for the range covered in this study (higher than 70 wt % polymer concentration). The concentration dependence of TOOT was found to be given by the relationship of (χeffrC)OOT/φprC = A + B/TOOT, where (χeffrC)OOT denotes the critical value of the product of χeff and rC at the cylinder−sphere OOT, χeff is the effective interaction parameter between styrene and isoprene segments in the presence of solvent, rC is the reduced degree of polymerization of an entire block copolymer, and φp is the volume fraction of the block copolymer in the solution. A and B ...

  • Thermoreversible Cylinder−Sphere Transition of Polystyrene-block-polyisoprene Diblock Copolymers in Dioctyl Phthalate Solutions
    Macromolecules, 1996
    Co-Authors: Shinichi Sakurai, Takeji Hashimoto, Lewis J. Fetters
    Abstract:

    We present experimental results of a thermoreversible morphological transition between spheres and cylinders for polystyrene-block-polyisoprene diblock copolymers (SI) in Dioctyl Phthalate solutions. Morphologies were characterized using small-angle X-ray scattering (SAXS), and spherical and cylindrical states were found above and below the order−order transition (OOT) temperature, TOOT, respectively. TOOT increased with an increase of polymer concentration for the range covered in this study (higher than 70 wt % polymer concentration). The concentration dependence of TOOT was found to be given by the relationship of (χeffrC)OOT/φprC = A + B/TOOT, where (χeffrC)OOT denotes the critical value of the product of χeff and rC at the cylinder−sphere OOT, χeff is the effective interaction parameter between styrene and isoprene segments in the presence of solvent, rC is the reduced degree of polymerization of an entire block copolymer, and φp is the volume fraction of the block copolymer in the solution. A and B ...

Zhaobo Wang - One of the best experts on this subject based on the ideXlab platform.

Guarionex Morales - One of the best experts on this subject based on the ideXlab platform.

  • Time-Resolved Small-Angle X-ray Scattering Studies of Spinodal Decomposition Kinetics in a Semidilute Polystyrene−Dioctyl Phthalate Solution
    Macromolecules, 1996
    Co-Authors: Yonglin Xie, Karl F. Ludwig, Rama Bansil, Patrick D. Gallagher, And Čestmír Koňák, Guarionex Morales
    Abstract:

    Synchrotron-based time-resolved small-angle X-ray scattering was used to measure the early-stage spinodal decomposition kinetics in a highly viscous semidilute solution of polystyrene in Dioctyl Phthalate. Although strong nonlinearities in the kinetics were observed, a linear theory analysis could fit the evolution of the structure factor at short times and low wavenumbers. Nonlinearities become significant earlier at higher wavenumbers, which is consistent with recent computer simulation studies. From the linear theory analysis, the exponential relaxation rate of the structure factor R(q) was found to be linear in q 2 in the low-wavenumber region of the experiments, in agreement with mean-field theory for spinodal decomposition in polymer solutions. The wavenumber-dependent Onsager transport coefficient A(q), which is the Fourier transform of the nonlocal mobility in a polymer system, was determined to scale as q -4 . This q dependence, which is stronger than that predicted by existing theory, may be related to entanglement effects.

  • time resolved small angle x ray scattering studies of spinodal decomposition kinetics in a semidilute polystyrene Dioctyl Phthalate solution
    Macromolecules, 1996
    Co-Authors: Yonglin Xie, Karl F. Ludwig, Rama Bansil, Patrick D. Gallagher, And Cestmir Koňak, Guarionex Morales
    Abstract:

    Synchrotron-based time-resolved small-angle X-ray scattering was used to measure the early-stage spinodal decomposition kinetics in a highly viscous semidilute solution of polystyrene in Dioctyl Phthalate. Although strong nonlinearities in the kinetics were observed, a linear theory analysis could fit the evolution of the structure factor at short times and low wavenumbers. Nonlinearities become significant earlier at higher wavenumbers, which is consistent with recent computer simulation studies. From the linear theory analysis, the exponential relaxation rate of the structure factor R(q) was found to be linear in q 2 in the low-wavenumber region of the experiments, in agreement with mean-field theory for spinodal decomposition in polymer solutions. The wavenumber-dependent Onsager transport coefficient A(q), which is the Fourier transform of the nonlocal mobility in a polymer system, was determined to scale as q -4 . This q dependence, which is stronger than that predicted by existing theory, may be related to entanglement effects.

Shinichi Sakurai - One of the best experts on this subject based on the ideXlab platform.

  • thermoreversible cylinder sphere transition of polystyrene block polyisoprene diblock copolymers in Dioctyl Phthalate solutions
    Macromolecules, 1996
    Co-Authors: Shinichi Sakurai, Takeji Hashimoto, Lewis J. Fetters
    Abstract:

    We present experimental results of a thermoreversible morphological transition between spheres and cylinders for polystyrene-block-polyisoprene diblock copolymers (SI) in Dioctyl Phthalate solutions. Morphologies were characterized using small-angle X-ray scattering (SAXS), and spherical and cylindrical states were found above and below the order−order transition (OOT) temperature, TOOT, respectively. TOOT increased with an increase of polymer concentration for the range covered in this study (higher than 70 wt % polymer concentration). The concentration dependence of TOOT was found to be given by the relationship of (χeffrC)OOT/φprC = A + B/TOOT, where (χeffrC)OOT denotes the critical value of the product of χeff and rC at the cylinder−sphere OOT, χeff is the effective interaction parameter between styrene and isoprene segments in the presence of solvent, rC is the reduced degree of polymerization of an entire block copolymer, and φp is the volume fraction of the block copolymer in the solution. A and B ...

  • Thermoreversible Cylinder−Sphere Transition of Polystyrene-block-polyisoprene Diblock Copolymers in Dioctyl Phthalate Solutions
    Macromolecules, 1996
    Co-Authors: Shinichi Sakurai, Takeji Hashimoto, Lewis J. Fetters
    Abstract:

    We present experimental results of a thermoreversible morphological transition between spheres and cylinders for polystyrene-block-polyisoprene diblock copolymers (SI) in Dioctyl Phthalate solutions. Morphologies were characterized using small-angle X-ray scattering (SAXS), and spherical and cylindrical states were found above and below the order−order transition (OOT) temperature, TOOT, respectively. TOOT increased with an increase of polymer concentration for the range covered in this study (higher than 70 wt % polymer concentration). The concentration dependence of TOOT was found to be given by the relationship of (χeffrC)OOT/φprC = A + B/TOOT, where (χeffrC)OOT denotes the critical value of the product of χeff and rC at the cylinder−sphere OOT, χeff is the effective interaction parameter between styrene and isoprene segments in the presence of solvent, rC is the reduced degree of polymerization of an entire block copolymer, and φp is the volume fraction of the block copolymer in the solution. A and B ...

Stephen J. Lombardo - One of the best experts on this subject based on the ideXlab platform.

  • Effects of supercritical extraction on the plasticization of poly(vinyl butyral) and Dioctyl Phthalate films
    The Journal of Supercritical Fluids, 2004
    Co-Authors: Rajesh V. Shende, Melissa Kline, Stephen J. Lombardo
    Abstract:

    Abstract Supercritical extraction of organic phases from films containing poly(vinyl butyral) (PVB) binder and Dioctyl Phthalate (DOP) plasticizer was performed with CO 2 and C 2 H 4 at 35–75 °C and 10–40 MPa for cycle times of 3 h. For films containing 60:40 wt.% PVB:DOP, extraction efficiencies near 50% were observed with either fluid at 75 °C and 40 MPa, which suggests nearly complete removal of the plasticizer. The degree of plasticization of the PVB+DOP films before and after supercritical extraction was characterized by using differential scanning calorimetry. For films containing 60:40 wt.% PVB:DOP, no thermal transitions were observed from −15 to 110 °C before supercritical extraction, whereas multiple thermal transitions were seen after supercritical extraction. The glass transition temperatures, T g , of the films after extraction were between 24 and 45 °C, as compared to the T g ∼72.5 °C for the as-received PVB.

  • Supercritical extraction of binder containing poly(vinyl butyral) and Dioctyl Phthalate from barium titanate–platinum multilayer ceramic capacitors
    Journal of Materials Science: Materials in Electronics, 2001
    Co-Authors: Rajesh V. Shende, Daniel S. Krueger, Stephen J. Lombardo
    Abstract:

    Supercritical extraction using carbon dioxide was examined for the removal of binder from multilayer ceramic capacitors. The binder contained poly(vinyl butyral) (PVB) and Dioctyl Phthalate (DOP), and the dielectric and metal electrode materials were barium titanate and platinum, respectively. At 40 MPa of carbon dioxide at 95 °C, approximately 55 wt % of the binder could be removed, and this was mainly the Dioctyl Phthalate component. The use of entrainers such as 2-propanol, methyl isobutyl ketone, and n-hexane was seen to have negligible effect on the degree of binder removal. The dielectric constant, loss tangent, and breakdown voltage of devices processed by supercritical extraction were similar as compared to devices processed by thermal oxidation alone. Although it was not possible to extract all of the binder with supercritical carbon dioxide, removal of the DOP fraction increases the pore space in the body by a factor of two. Transport model calculations indicate this partial removal of binder mitigates the buildup of pressure in the subsequent thermal processing step and can reduce the processing time for thermal removal of the remaining binder by a factor of 25.

  • supercritical extraction of binder containing poly vinyl butyral and Dioctyl Phthalate from barium titanate platinum multilayer ceramic capacitors
    Journal of Materials Science: Materials in Electronics, 2001
    Co-Authors: Rajesh V. Shende, Daniel S. Krueger, Stephen J. Lombardo
    Abstract:

    Supercritical extraction using carbon dioxide was examined for the removal of binder from multilayer ceramic capacitors. The binder contained poly(vinyl butyral) (PVB) and Dioctyl Phthalate (DOP), and the dielectric and metal electrode materials were barium titanate and platinum, respectively. At 40 MPa of carbon dioxide at 95 °C, approximately 55 wt % of the binder could be removed, and this was mainly the Dioctyl Phthalate component. The use of entrainers such as 2-propanol, methyl isobutyl ketone, and n-hexane was seen to have negligible effect on the degree of binder removal. The dielectric constant, loss tangent, and breakdown voltage of devices processed by supercritical extraction were similar as compared to devices processed by thermal oxidation alone. Although it was not possible to extract all of the binder with supercritical carbon dioxide, removal of the DOP fraction increases the pore space in the body by a factor of two. Transport model calculations indicate this partial removal of binder mitigates the buildup of pressure in the subsequent thermal processing step and can reduce the processing time for thermal removal of the remaining binder by a factor of 25.