TY - JOUR

T1 - Diffusivity and viscosity of concentrated hydrogenated polybutadiene solutions

AU - Tao, Hui

AU - Lodge, Timothy P.

AU - Von Meerwall, Ernst D.

PY - 2000/3/7

Y1 - 2000/3/7

N2 - We report measurements of diffusion (D) and viscosity (η) in hydrogenated polybutadiene (hPB)/alkane solutions. The volume fractions (φ) extend from 0.20 up to the melt and the molecular weights (M) from 4900 up to 440000; the number of entanglements per chain, M/Me, ranges up to about 450. The temperature dependences of both D and η are similar, consistent with literature values, and independent of φ and M. We thus conclude that the monomeric friction factor is also independent of φ and M. For all samples with M/Me ≥ 3 the data are consistent with the scaling relations D approx. M-2.4±0.1φ-1.8±0.2 and η approx. M3.4±0.1φ3.8±0.2; within the precision of the data the M exponents do not depend on φ, and the φ exponents do not depend on M. The M exponent for D in solution is consistent with previously reported studies for φ ≤ 0.4 but apparently conflicts with the reptation value of -2.0 in the melt. However, by comparing with the literature melt self-diffusion data for hPB and six other polymers, it is clear that the exponent is, in fact, universally stronger than -2.0. Furthermore, if a single universal exponent is assumed, the best value based on all the data is -2.28 ± 0.05. Our PHB data resolve the longstanding anomaly that the longest relaxation times τ1 based on translation (approx. Rg2/D) and orientational relaxation (approx. η) appeared to have different M dependences. The data also indicate that for both solutions and melts the dynamics are determined primarily by the number of entanglements per chain. The data are compared with current models of polymer dynamics, both reptative and nonreptative. In the former case it is clear that a self-consistent theory incorporating both 'constraint release' and 'contour length fluctuations' is required.

AB - We report measurements of diffusion (D) and viscosity (η) in hydrogenated polybutadiene (hPB)/alkane solutions. The volume fractions (φ) extend from 0.20 up to the melt and the molecular weights (M) from 4900 up to 440000; the number of entanglements per chain, M/Me, ranges up to about 450. The temperature dependences of both D and η are similar, consistent with literature values, and independent of φ and M. We thus conclude that the monomeric friction factor is also independent of φ and M. For all samples with M/Me ≥ 3 the data are consistent with the scaling relations D approx. M-2.4±0.1φ-1.8±0.2 and η approx. M3.4±0.1φ3.8±0.2; within the precision of the data the M exponents do not depend on φ, and the φ exponents do not depend on M. The M exponent for D in solution is consistent with previously reported studies for φ ≤ 0.4 but apparently conflicts with the reptation value of -2.0 in the melt. However, by comparing with the literature melt self-diffusion data for hPB and six other polymers, it is clear that the exponent is, in fact, universally stronger than -2.0. Furthermore, if a single universal exponent is assumed, the best value based on all the data is -2.28 ± 0.05. Our PHB data resolve the longstanding anomaly that the longest relaxation times τ1 based on translation (approx. Rg2/D) and orientational relaxation (approx. η) appeared to have different M dependences. The data also indicate that for both solutions and melts the dynamics are determined primarily by the number of entanglements per chain. The data are compared with current models of polymer dynamics, both reptative and nonreptative. In the former case it is clear that a self-consistent theory incorporating both 'constraint release' and 'contour length fluctuations' is required.

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U2 - 10.1021/ma991983r

DO - 10.1021/ma991983r

M3 - Article

AN - SCOPUS:0033898191

VL - 33

SP - 1747

EP - 1758

JO - Macromolecules

JF - Macromolecules

SN - 0024-9297

IS - 5

ER -