The Experts below are selected from a list of 9693 Experts worldwide ranked by ideXlab platform

Iwao Teraoka - One of the best experts on this subject based on the ideXlab platform.

  • Scale-up study of high osmotic pressure chromatography for separation of poly(epsilon-caprolactone).
    Journal of chromatography. A, 2003
    Co-Authors: Dean Lee, Iwao Teraoka
    Abstract:

    Methods to prepare fractions of poly(epsilon-caprolactone) with a narrow molecular mass distribution in large quantities have been examined using high osmotic pressure chromatography under the Theta Condition. Effects of column dimension and coupling columns in series on the separation resolution were studied. We found that use of a thicker column can improve the resolution if adverse effects of viscous fingering are avoided. We also demonstrated that coupling the columns results in a better separation if the second column does not adsorb high-molecular-mass components purified in the first column.

  • Scale-up study of high osmotic pressure chromatography for separation of poly(ε-caprolactone)
    Journal of Chromatography A, 2003
    Co-Authors: Dean Lee, Iwao Teraoka
    Abstract:

    Methods to prepare fractions of poly(e-caprolactone) with a narrow molecular mass distribution in large quantities have been examined using high osmotic pressure chromatography under the Theta Condition. Effects of column dimension and coupling columns in series on the separation resolution were studied. We found that use of a thicker column can improve the resolution if adverse effects of viscous fingering are avoided. We also demonstrated that coupling the columns results in a better separation if the second column does not adsorb high-molecular-mass components purified in the first column.

  • Mean-field Gaussian chain theory for semidilute Theta chains in a slit
    The Journal of Chemical Physics, 2001
    Co-Authors: Iwao Teraoka, Peter Cifra
    Abstract:

    Mean-field Gaussian chain theory for nondilute polymer solutions is being applied to polymer chains in the Theta Condition confined to a slit in a wide range of concentrations. Various existing lattice chain theories were used to obtain the effective potential for the Gaussian chain. Calculation results for the monomer density profile, the partition coefficient, and the chain dimension across the slit at various concentrations were computed and compared with the results obtained in the lattice Monte Carlo simulations. The need for a higher concentration to flatten the density profile and to cause the weak-to-strong penetration transition, compared with athermal chains, was confirmed. At the monomer–monomer interaction widely used as the Theta Condition on the cubic lattice, the chain cluster theory by Freed and the random mixing approximation by Huggins provide a better agreement with the simulation results than the Flory model and the Guggenheim model do. The agreement is, however, not as good as the one for athermal chains.

Dean Lee - One of the best experts on this subject based on the ideXlab platform.

  • Scale-up study of high osmotic pressure chromatography for separation of poly(epsilon-caprolactone).
    Journal of chromatography. A, 2003
    Co-Authors: Dean Lee, Iwao Teraoka
    Abstract:

    Methods to prepare fractions of poly(epsilon-caprolactone) with a narrow molecular mass distribution in large quantities have been examined using high osmotic pressure chromatography under the Theta Condition. Effects of column dimension and coupling columns in series on the separation resolution were studied. We found that use of a thicker column can improve the resolution if adverse effects of viscous fingering are avoided. We also demonstrated that coupling the columns results in a better separation if the second column does not adsorb high-molecular-mass components purified in the first column.

  • Scale-up study of high osmotic pressure chromatography for separation of poly(ε-caprolactone)
    Journal of Chromatography A, 2003
    Co-Authors: Dean Lee, Iwao Teraoka
    Abstract:

    Methods to prepare fractions of poly(e-caprolactone) with a narrow molecular mass distribution in large quantities have been examined using high osmotic pressure chromatography under the Theta Condition. Effects of column dimension and coupling columns in series on the separation resolution were studied. We found that use of a thicker column can improve the resolution if adverse effects of viscous fingering are avoided. We also demonstrated that coupling the columns results in a better separation if the second column does not adsorb high-molecular-mass components purified in the first column.

Susan J. Muller - One of the best experts on this subject based on the ideXlab platform.

  • Study of mixed solvent quality in a polystyrene–dioctyl phthalate–polystyrene system
    Journal of Polymer Science Part B: Polymer Physics, 1996
    Co-Authors: Michael J. Solomon, Susan J. Muller
    Abstract:

    Polymer solvent interactions in the ternary system high molecular weight polystyrene (HMPS), low molecular weight polystyrene (LMPS), and dioctyl phthalate (DOP) have been characterized by means of intrinsic viscometry (IV), dynamic light scattering (DLS), and static light scattering (SLS). Excluded volume exponents have been extracted from the scaling of intrinsic viscosity and translational diffusivity with polymer molecular weight for a mixed solvent of 13 wt % LMPS/87 wt % DOP. The value of the excluded volume exponent, v = 0.45, indicates that HMPS in the mixed solvent DOP/LMPS has apparently assumed a reduced conformation relative to the Theta Condition. However, SLS measures of the second virial coefficient (A 2 ) confirm that DOP is a Theta solvent at our experimental temperature of 22°C and indicate that the addition of LMPS increases A 2 . SLS also suggests that neither solvent component is strongly preferentially adsorped into the HMPS coil. Our system then is a mixture of a Theta solvent and a good solvent that exhibits poor solvent scaling behavior. We believe this to be the first demonstration of such behavior in a system that does not exhibit appreciable preferential adsorption. We conclude by examining our observations in the context of current descriptions of mixed solvent thermodynamics.

  • study of mixed solvent quality in a polystyrene dioctyl phthalate polystyrene system
    Journal of Polymer Science Part B, 1996
    Co-Authors: Michael J. Solomon, Susan J. Muller
    Abstract:

    Polymer solvent interactions in the ternary system high molecular weight polystyrene (HMPS), low molecular weight polystyrene (LMPS), and dioctyl phthalate (DOP) have been characterized by means of intrinsic viscometry (IV), dynamic light scattering (DLS), and static light scattering (SLS). Excluded volume exponents have been extracted from the scaling of intrinsic viscosity and translational diffusivity with polymer molecular weight for a mixed solvent of 13 wt % LMPS/87 wt % DOP. The value of the excluded volume exponent, v = 0.45, indicates that HMPS in the mixed solvent DOP/LMPS has apparently assumed a reduced conformation relative to the Theta Condition. However, SLS measures of the second virial coefficient (A 2 ) confirm that DOP is a Theta solvent at our experimental temperature of 22°C and indicate that the addition of LMPS increases A 2 . SLS also suggests that neither solvent component is strongly preferentially adsorped into the HMPS coil. Our system then is a mixture of a Theta solvent and a good solvent that exhibits poor solvent scaling behavior. We believe this to be the first demonstration of such behavior in a system that does not exhibit appreciable preferential adsorption. We conclude by examining our observations in the context of current descriptions of mixed solvent thermodynamics.

Yo Nakamura - One of the best experts on this subject based on the ideXlab platform.

  • Hydrodynamic factors for linear and star polymers on lattice under the Theta Condition
    Polymer, 2004
    Co-Authors: Kazuhito Shida, Kaoru Ohno, Yoshiyuki Kawazoe, Yo Nakamura
    Abstract:

    Abstract Monte Carlo calculations were made to evaluate the intrinsic viscosity [η] and hydrodynamic radius RH along with the mean square radius of gyration 〈S2〉 for linear and star polymers with the arm number f=3, 4, 6, and 8 on a simple cubic lattice. For the hydrodynamic calculation, Zimm's method based on the rigid-body approximation was used. The ensemble averages were taken according to the Boltzman factor with the contacting energy between segments, which was chosen to be 0.275 for the Theta Condition, multiplied by the number of contacts among the chain. The ratios gη≡[η]star/[η]linear and gH≡(RH)star/(RH)linear calculated agreed with experimental data for Theta solvent systems within 3.5 and 2.5%, respectively, where the subscripts describe the structure of polymer chain. The hydrodynamic factors Φ and ρ defined by [η]M/(6〈S2〉)3/2 and 〈S2〉1/2/RH, respectively, with the molecular weight M obtained from the simulation for linear and star polymers with f=4 and 6 were also close to experimental values. It was concluded that most of the error of analytical theories, which fail to predict hydrodynamic properties for star polymers, comes from the preaveraging approximation of the Oseen tensor.

  • Solution Properties of Polymacromonomers Consisting of Polystyrene
    Molecular Interactions and Time-Space Organization in Macromolecular Systems, 1999
    Co-Authors: Ken Terao, Yo Nakamura, Takashi Norisuye
    Abstract:

    Analyses are made of z-average radii of gyration Z l/2 and intrinsic viscosities [η] for two series of polymacromonomer samples consisting only of polystyrene (PS) and having fixed side chain lengths of 15 and 33 styrene monomer units in cyclohexane at 34.5°C (the Theta point) and in toluene at 15°C, on the basis of the wormlike chain with or without excluded volume. The current theories for this model are shown to be capable of consistently explaining the main-chain length dependences of Z and [η] for the two polymacromonomers in the Theta and good solvents. The chain stiffness is an increasing function of side chain length and higher in the good solvent than in the Theta solvent. Thus, the semiflexibility of polymacromonomers under the Theta Condition arises from the high segment density near the main chain and monomer-monomer repulsions in good solvents further stiffen the polymer backbone.

Michael J. Solomon - One of the best experts on this subject based on the ideXlab platform.

  • Study of mixed solvent quality in a polystyrene–dioctyl phthalate–polystyrene system
    Journal of Polymer Science Part B: Polymer Physics, 1996
    Co-Authors: Michael J. Solomon, Susan J. Muller
    Abstract:

    Polymer solvent interactions in the ternary system high molecular weight polystyrene (HMPS), low molecular weight polystyrene (LMPS), and dioctyl phthalate (DOP) have been characterized by means of intrinsic viscometry (IV), dynamic light scattering (DLS), and static light scattering (SLS). Excluded volume exponents have been extracted from the scaling of intrinsic viscosity and translational diffusivity with polymer molecular weight for a mixed solvent of 13 wt % LMPS/87 wt % DOP. The value of the excluded volume exponent, v = 0.45, indicates that HMPS in the mixed solvent DOP/LMPS has apparently assumed a reduced conformation relative to the Theta Condition. However, SLS measures of the second virial coefficient (A 2 ) confirm that DOP is a Theta solvent at our experimental temperature of 22°C and indicate that the addition of LMPS increases A 2 . SLS also suggests that neither solvent component is strongly preferentially adsorped into the HMPS coil. Our system then is a mixture of a Theta solvent and a good solvent that exhibits poor solvent scaling behavior. We believe this to be the first demonstration of such behavior in a system that does not exhibit appreciable preferential adsorption. We conclude by examining our observations in the context of current descriptions of mixed solvent thermodynamics.

  • study of mixed solvent quality in a polystyrene dioctyl phthalate polystyrene system
    Journal of Polymer Science Part B, 1996
    Co-Authors: Michael J. Solomon, Susan J. Muller
    Abstract:

    Polymer solvent interactions in the ternary system high molecular weight polystyrene (HMPS), low molecular weight polystyrene (LMPS), and dioctyl phthalate (DOP) have been characterized by means of intrinsic viscometry (IV), dynamic light scattering (DLS), and static light scattering (SLS). Excluded volume exponents have been extracted from the scaling of intrinsic viscosity and translational diffusivity with polymer molecular weight for a mixed solvent of 13 wt % LMPS/87 wt % DOP. The value of the excluded volume exponent, v = 0.45, indicates that HMPS in the mixed solvent DOP/LMPS has apparently assumed a reduced conformation relative to the Theta Condition. However, SLS measures of the second virial coefficient (A 2 ) confirm that DOP is a Theta solvent at our experimental temperature of 22°C and indicate that the addition of LMPS increases A 2 . SLS also suggests that neither solvent component is strongly preferentially adsorped into the HMPS coil. Our system then is a mixture of a Theta solvent and a good solvent that exhibits poor solvent scaling behavior. We believe this to be the first demonstration of such behavior in a system that does not exhibit appreciable preferential adsorption. We conclude by examining our observations in the context of current descriptions of mixed solvent thermodynamics.