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>3.3.co;2-i

Cited by 4 publications

(6 citation statements)

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“…How the demixing temperature changes with shear rate as compared with that of the stagnant system is shown in Figure 9 for a solution containing 2 wt.‐% polymer. In agreement with earlier observations33 the disruption of favorable clusters by shear (energy storage via enthalpy) is less consequential for the phase state than the deformation of polymer chains (energy storage via entropy). It is interesting to note that the flow‐induced extension of the two‐phase range results considerably larger for saline water than for pure water.…”

Section: Resultssupporting

confidence: 92%

Shear Induced Demixing and Rheological Behavior of Aqueous Solutions of Poly(N‐isopropylacrylamide)

Badiger¹,

Wolf²

2003

Macro Chemistry & Physics

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The interrelation between the phase separation behavior and the rheological performance of aqueous solutions of high molecular weight (Mw = 1 600 kg/mol) poly(N‐isopropylacrylamide) was investigated. The system demixes upon heating and the cloud point temperature, Tcp decreases steadily with rising polymer concentration up to 10 wt.‐%. The application of shear supports phase separation and reduces Tcp markedly. This observation is interpreted in terms of destruction of intersegmental clusters formed in the quiescent state owing to favorable interactions. Intrinsic viscosities and Huggins coefficients as well as the viscosities, η at higher polymer concentrations are closely connected with the thermodynamic conditions. [η] decreases by almost two orders of magnitude upon heating, whereas the corresponding increase of kH is less pronounced. The η values (constant shear rate) of the moderately concentrated solutions as function of T pass a maximum at the corresponding phase separation temperatures. The existence of clusters also manifests in terms of stress overshoot and of particularities observed with solutions that are sheared for the first time.

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Section: Resultssupporting

confidence: 92%

Shear Induced Demixing and Rheological Behavior of Aqueous Solutions of Poly(N‐isopropylacrylamide)

Badiger¹,

Wolf²

2003

Macro Chemistry & Physics

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“…The lower demixing temperatures measured under shear (about 10–15 °C lower) as compared with those obtained in the absence of shear can be tentatively explained by a partial orientation of the macromolecules under shear to break favorable specific interactions. Similar effects were observed experimentally and were theoretically explained for a homopolymer/copolymer blend where the first sizeable effect of shear also consisted in an extension of the two phase area 22…”

Section: Resultssupporting

confidence: 83%

“…This is one of the reasons why we have performed the present study. In one of our previous papers22 it was shown that in dilute solutions, c pol = 1 mg · mL −1 , an interpolymer complex with a stoichiometry of the components HPC/MAc‐S of 40:60 (w/w) is formed.…”

Section: Introductionmentioning

confidence: 97%

Interpolymer Complex between Hydroxypropyl Cellulose and Maleic Acid–Styrene Copolymer: Phase Behavior of Semi‐Dilute Solutions

Bumbu

Eckelt

Wolf

et al. 2005

Macromolecular Bioscience

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The phase behavior of a water/hydroxypropyl cellulose/maleic acid-styrene copolymer (H2O/HPC/MAc-S) system was investigated in the semi-dilute range by turbidimetry, rheology, and optical microscopy. The two polymers under investigation form interpolymer complexes via hydrogen bonding. In the case of a total polymer concentration of cpol = 5 mg . mL(-1) a second phase segregates upon heating the homogeneous ternary system. By applying a constant shear rate (gamma = 50 s(-1)) the phase separation temperature of the system is 10-15 degrees C lower than for an unsheared one. For cpol = 10 mg . mL(-1) phase separation has already occurred at room temperature when the two binary polymer solutions are mixed. The distribution of the partners among the coexisting phases was examined by FT-IR spectroscopy. The stoichiometry of the interpolymeric complex (IPC) was estimated to be HPC/MAc-S = 40:60 (w/w) independent of cpol.

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“…Cloud points were measured visually as well as by means of turbidimetry. [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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Blends of PDMS and random copolymers of dimethylsiloxane and methylphenylsiloxane: Phase separation in the quiescent state and under shear

Cited by 4 publications

References 0 publications

Shear Induced Demixing and Rheological Behavior of Aqueous Solutions of Poly(N‐isopropylacrylamide)

Shear Induced Demixing and Rheological Behavior of Aqueous Solutions of Poly(N‐isopropylacrylamide)

Interpolymer Complex between Hydroxypropyl Cellulose and Maleic Acid–Styrene Copolymer: Phase Behavior of Semi‐Dilute Solutions

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

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