Blends of PDMS and random copolymers of dimethylsiloxane and methylphenylsiloxane: Phase separation in the quiescent state and under shear

Hinrichs, Axel; Wolf, Bernhard

doi:10.1002/(sici)1521-3935(19990201)200:2<368::aid-macp368>3.0.co;2-r

Cited by 15 publications

(5 citation statements)

References 10 publications

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“…[10] These results are within experimental error identical. Phase equilibrium experiments were carried out by adding the precipitant dropwise to the homogeneous solution of cellulose in the thermodynamically favorable solvent at the equilibrium temperature under vigorous stirring up to the required over-all composition.…”

Section: Phase Diagramssupporting

confidence: 66%

Fractionation of unsubstituted cellulose from solutions in either Ni-tren or (N,N-dimethylacetamide + LiCl)

Loske

Lutz

Striouk

et al. 2000

Macromol. Chem. Phys.

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Starting from solutions of unsubstituted cellulose (Avicel PH101, Mw = 30.1 kg/mol and Mw/Mn = 3 or Solucell 500, Mw = 230 kg/mol, Mw/Mn = 2.8) in either Ni‐tren (0.8 M aqueous solution of the dihydroxotris(2‐aminoethly)amine nickel(II) complex) or in a mixed solvent DMAc+LiCl (consisting of N,N‐dimethylacetamide plus lithium chloride) it was investigated whether the segregation of a second phase caused by the addition of suitable precipitants leads to polymer fractionation. With Ni‐tren the long chains accumulate in the precipitate formed upon the addition of sulfuric acid; as the pH falls below ≈ 9, the solution is free of cellulose. Nevertheless this route option for fractionation must be ruled out because of a pronounced chain scission taking place in that solvent. For (DMAc + LiCl) the best low molecular weight precipitant that could be found was acetone; it allows the fractionation of the lower molecular weight Avicel but fails for Solucell as a result of the high viscosities of its solutions in the presence of acetone. It was therefore investigated whether that deficiency could be overcome by the use of high molecular precipitants. In these experiments poly‐(methyl methacrylate), incompatible with cellulose, was used to cause phase separation. The results demonstrate the suitability of this system for discontinuous experiments even in the case of the higher molecular weight Solucell.

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Section: Phase Diagramssupporting

confidence: 66%

Fractionation of unsubstituted cellulose from solutions in either Ni-tren or (N,N-dimethylacetamide + LiCl)

Loske

Lutz

Striouk

et al. 2000

Macromol. Chem. Phys.

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“…Changes in the phase behavior of the polymer blend, which occur as a consequence of the stresses associated with melt flow, are likely to significantly influence the ultimate morphology of the processed and solidified materials. Flow field was found to exert a marked influence on the phase behavior of polymer blends, [1][2][3][4][5][6][7][8][9][10][11] and it is obvious that this effect must be considered, in particular, when trying to understand the state of polymer blends during processing. From a scientific perspective, the increased use of polymer blends has emphasized the need to understand i) the underlying thermodynamics that drive Full Paper: The phase behavior of polystyrene (PS) and poly(vinyl methyl ether) (PVME) blend has been investigated rheologically as a function of temperature, composition and oscillating shear rate as well as different heating rates.…”

Section: Introductionmentioning

confidence: 99%

Rheological Investigation of Shear Induced‐Mixing and Shear Induced‐Demixing for Polystyrene/Poly(vinyl methyl ether) Blend

Madbouly

Ougizawa

2004

Macro Chemistry & Physics

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Full Paper: The phase behavior of polystyrene (PS) and poly(vinyl methyl ether) (PVME) blend has been investigated rheologically as a function of temperature, composition and oscillating shear rate as well as different heating rates. An LCST (lower critical solution temperature)‐type phase diagram was detected rheologically from the sudden changes in the slopes of the dynamic temperature ramps of G′ at given heating and shear rate values. The rheological cloud points were dependent on the heating rate, $\dot q$, and oscillating shear rate, $\dot \gamma$. The cloud points shifted a few degrees to higher temperatures with increasing $\dot q$ and reached an equilibrium value (heating rate independent) at $\dot q \geq 2$ °C/min. The phase diagrams of the blends detected at $\dot \gamma$ = 0.1 and 1 rad/s were located in lower temperature ranges than the quiescent phase diagram, i.e., oscillating shear rate induced‐demixing at these two values for the shear rate. On the other hand, at $\dot \gamma$ = 10 rad/s, the phase diagram shifted to higher temperatures, higher than the corresponding values found under quiescent conditions, i.e., shear induced‐mixing took place. Based on these two observations, shear induced‐demixing and shear induced‐mixing can be detected rheologically within a single composition at low and high shear rate values, respectively, and this is in good agreement with the previous investigation using simple shear flow techniques. In addition, the William, Landel and Ferry (WLF)‐superposition principle was found to be applicable only in the single‐phase regime; however, the principle broke‐down at a temperature higher than or equal to the cloud point. Furthermore, different spinodal phase diagrams were estimated at different oscillating shear rates based on the theoretical approach of Ajji and Choplin.Spinodal phase diagrams at different oscillating shear rates.magnified imageSpinodal phase diagrams at different oscillating shear rates.

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“…GPC measurements were performed as described9 earlier, using a Waters Chromatography system with two detectors (SC200 UV and RI‐61) and Permagel 10 3 –10 6 polystyrene standard columns thermostatted at 25 °C. Calibration was performed with narrow polydispersity polystyrene standards using the universal calibration for PDMS.…”

Section: Methodsmentioning

confidence: 99%

Chain Connectivity and Conformational Variability of Polymers: Clues to an Adequate Thermodynamic Description of Their Solutions, 1

Bercea

Cazacu

Wolf

2003

Macro Chemistry & Physics

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This is the first of two parts investigating the Flory‐Huggins interaction parameter, χ, as a function of composition and chain length. Part 1 encompasses experimental and theoretical work. The former comprises the synthesis of poly(dimethylsiloxane)s with different molar mass and the measurements of their second osmotic virial coefficients, A2, in solvents of diverse quality as a function of M via light scattering and osmotic pressures. The theoretical analysis is performed by subdividing the dilution process into two clearly separable steps. It yields the following expression for χo, the χ value in range of pair interaction: χo = α − ζ λ. The parameter α measures the effect of contact formation between solvent molecules and polymer segments at fixed chain conformation, whereas the parameter ζ quantifies the contributions of the conformational changes taking place in response to dilution; ζ becomes zero for theta conditions. The influences of M are exclusively contained in the parameter λ The new relation is capable of describing hitherto incomprehensible experimental findings, like a diminution of χo with rising M. The evaluation of experimental information for different systems according to the established equation displays the existence of a linear interrelation between ζ and α. Part 2 of this investigation presents the generalization of the present approach to solutions of arbitrary composition and discusses the physical meaning of the parameters in more detail.

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Blends of PDMS and random copolymers of dimethylsiloxane and methylphenylsiloxane: Phase separation in the quiescent state and under shear

Cited by 15 publications

References 10 publications

Fractionation of unsubstituted cellulose from solutions in either Ni-tren or (N,N-dimethylacetamide + LiCl)

Fractionation of unsubstituted cellulose from solutions in either Ni-tren or (N,N-dimethylacetamide + LiCl)

Rheological Investigation of Shear Induced‐Mixing and Shear Induced‐Demixing for Polystyrene/Poly(vinyl methyl ether) Blend

Chain Connectivity and Conformational Variability of Polymers: Clues to an Adequate Thermodynamic Description of Their Solutions, 1

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