Visco‐relaxation studies of polystyrene solutions in different solvents by ultrasonic

Hassun, Subhi Kemal; Hussain, Kadhim H.; Hassan, Najiba A.

doi:10.1002/actp.1990.010410804

Cited by 3 publications

(1 citation statement)

References 11 publications

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“…For the overlapping polymer chains at c > c *, the hydrodynamic interactions and excluded volume effects are screened. , In this semidilute, unentangled regime, the relaxation time λ is expected to obey a scaling law, , λ ≈ c (2–3ν)/(3ν–1) with ν being the solvent quality parameter (ν = 0.5 and 0.588 for theta and good solvents, respectively). In fact, ordinary linear polymer solutions in good solvents (such as polystyrene in toluene), experiments − indicate λ ≈ c 0.31 which is consistent with the scaling law with ν = 0.588. Nevertheless, the PEO/water solutions exhibit λ E ≈ c m with m ≅ 1 despite the fact that water is a good solvent for PEO, as noted in this study and also in the literature. , Thus, the anomalous exponent value of m ≅ 1 is very specific to the PEO/water solutions.…”

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confidence: 64%

Concentration Dependence of the Extensional Relaxation Time and Finite Extensibility in Dilute and Semidilute Polymer Solutions Using a Microfluidic Rheometer

Kim

Lee

2019

Macromolecules

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We investigated the composition dependence of the finite extensible nonlinear elastic (FENE) constant of poly(ethylene oxide) (PEO) solutions by the Tikhonov regularization method with the measured normal stress in microfluidic channels. We measured the normal stress of the PEO solutions in response to the extensional flows in microfluidic channels. Additionally, we extracted the extensional relaxation time distributions and the FENE constants of the PEO solutions from the measured normal stress by inverse calculations. The linear average value of the extensional relaxation times was consistent with that measured using a capillary breakup extensional rheometer. The shortest extensional relaxation time was close to the mean value of the Zimm relaxation time distribution. The FENE constant evaluated in the semidilute regime was 10.3 times higher than that in the dilute regime. The proposed method is promising for the determination of the Zimm time, FENE constant, as well as the extensional relaxation times of low-viscosity solutions.

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Section: Resultssupporting

confidence: 64%

Concentration Dependence of the Extensional Relaxation Time and Finite Extensibility in Dilute and Semidilute Polymer Solutions Using a Microfluidic Rheometer

Kim

Lee

2019

Macromolecules

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Chain Dynamics of Ethylene Oxide Oligomer Melts. An Ultrasonic Spectroscopy Study

Wald

Kaatze

2014

J. Phys. Chem. B

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Between 0.2 and 2000 MHz, the ultrasonic attenuation spectra of oligomer melts have been measured at 25 °C. The oligomers comprise ethylene glycols with eight different mean degrees [Formula: see text]of polymerization (1 ≤ [Formula: see text] ≤ 13.2), a poly(propylene glycol) ([Formula: see text] = 16.9) and three poly(ethylene glycol) dimethyl ethers (3 ≤ [Formula: see text] ≤ 10.3). The complexity of the ultrasonic spectra increases with [Formula: see text]. The spectra have been analyzed assuming up to four discrete relaxation terms. The relaxation times of these terms are assigned to the first odd modes in the oligomer conformational dynamics and are discussed in the light of the Rouse spring-and-dashpot and the Tobolsky torsional oscillator models of chain variations. The relaxation amplitudes indicate that not only the shear viscosity but also the volume viscosity is involved in ultrasonic relaxation processes. Comparison of relaxation times and shear viscosities for the ethylene glycols with the corresponding data for dimethyl ethers and also n-alkanes reveals significant effects of association.

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Broadband ultrasonic spectrometry of polystyrene-cyclohexane critical mixtures

Mirzaev

Kaatze

2013

Phys. Rev. E

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Mutual diffusion coefficients, shear viscosities, and broadband ultrasonic attenuation spectra in the frequency range 100 kHz to 300 MHz have been measured for solutions of polystyrene in cyclohexane at two degrees of polymerization N and various temperatures near the critical. The exponent y(η) in the power law representation of the critical part in the viscosity deviates substantially from the universal value y(η) = 0.0435: y(η) = 0.028 (N = 288) and y(η) = 0.014 (N = 6242). Also, the adiabatic coupling constant g and the amplitudes ξ(0) and Γ(0) in the power laws of the correlation length and the relaxation rate of fluctuations, respectively, depend on N. This is especially obvious with the relaxation rates, for which Γ(0) = 5.8×10(9) at N = 288 and Γ(0) = 6.1×10(7) with the larger polymer results. A noteworthy feature is the difference between the relaxation rates from the diffusion coefficients and shear viscosities on the one hand and from the ultrasonic spectra on the other. Near the critical temperatures the latter Γ values deviate from power law behavior, indicating a coupling between the concentration fluctuations and structural isomerizations of the polymers.

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Visco‐relaxation studies of polystyrene solutions in different solvents by ultrasonic

Abstract: Acta Polyrnerica 41 ((990) Nr. 8 438 HASSUN, HUSSAIN and HASSAN: Visco-relaxation studies of polystyrene solutions Danksagung Literatur

Cited by 3 publications

References 11 publications

Concentration Dependence of the Extensional Relaxation Time and Finite Extensibility in Dilute and Semidilute Polymer Solutions Using a Microfluidic Rheometer

Concentration Dependence of the Extensional Relaxation Time and Finite Extensibility in Dilute and Semidilute Polymer Solutions Using a Microfluidic Rheometer

Chain Dynamics of Ethylene Oxide Oligomer Melts. An Ultrasonic Spectroscopy Study

Broadband ultrasonic spectrometry of polystyrene-cyclohexane critical mixtures

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