Determination of the intermolecular entanglement coupling spacings in polyisoprene by viscosity measurements

Fetters, Lewis J.

doi:10.6028/jres.069a.006

Cited by 26 publications

(11 citation statements)

References 24 publications

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“…Unlike the dimensionless coefficient in eq 3, the coefficient C has dimensions, an observation that we return to below. As shown in Figure , the best-fit straight line in Figure is also consistent with the solution-derived results − (Table ) of PC, PVC, and 1,4-PI. Equation 6 is consonant as well with the M c estimate from melt-based data , for PMA−CH 3 (Table and Figure ).…”

Section: Resultssupporting

confidence: 86%

Packing Length Influence in Linear Polymer Melts on the Entanglement, Critical, and Reptation Molecular Weights

et al. 1999

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We have shown in previous studies that the entanglement molecular weight for a polymer melt, M e, is related by a power law to p, the packing length of the polymer species. We now find that power laws also describe the molecular weights characterizing the melt viscosity, M c marking the onset of entanglement effects and M r the crossover to the reptation form. The packing length exponents for M e, M c, and M r differ significantly, however. The long-held notion that the ratio M c/M e has the same value for all species is therefore incorrect. Further, the observed and predicted values of M r for two species, 1,4-polybutadiene and polyisobutylene, have been found to agree, within the uncertainties, with the projected values. Finally, the variations with packing length are such that all three characteristic molecular weights would appear to converge on the same value near p = 9 Å. As yet, no species with such a large packing length has been completely studied rheologically. But the range is not outlandish and is clearly reachable by appropriate synthetic methods.

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Section: Resultssupporting

confidence: 86%

Packing Length Influence in Linear Polymer Melts on the Entanglement, Critical, and Reptation Molecular Weights

et al. 1999

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“…Log-log plot of the viscosity of 14.56% (w/v) of polyisoprene in n-decane at 25OC against the square of the 8 condition intrinsic viscosity.The experimental data cover viscosities over a 104-fold range and are comparable with results obtained under similar experimental conditions 31. Curvatures13 in the log-log plots of the viscosity against Mw make it difficult to determine accurately the entanglement molecular weight for any of the polyisoprene structures.…”

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confidence: 70%

Synthesis and solution properties of linear, four‐branched, and six‐branched star polyisoprenes

Hadjichristidis

Roovers

1974

J. Polym. Sci. Polym. Phys. Ed.

157

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A number of linear, four‐ and six‐branched regular star polyisoprenes were synthesized by anionic polymerization techniques in benzene using lithium as the counterion and polyfunctional silicon chloride compounds as the coupling agents. Light‐scattering measurements in dioxane were performed in order to establish Θ solvent conditions. Determinations of the radius of gyration of the polymers of different structure indicate that g = 〈S2〉0,br/〈S2〉0,lin agree closely with random flight calculations for the ratios. Intrinsic viscosities determined in a Θ solvent establish g′ = [η]br/[η]lin to be 0.773 and 0.625 for the four‐ and six‐branched polyisoprenes, respectively. In a good solvent g′ values are slightly lower. These values are compared with theoretical estimates. Viscosities of 19.29% (w/w) solutions of the polyisoprenes in n‐decane at 25°C are correlated with the intrinsic viscosities of the polymers under Θ conditions.

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“…The validity of equation (8) at these concentrations has been demonstrated elsewhere [27,49]. The value of lvIe was taken as 7, 000 [49].…”

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confidence: 99%

Anionic polymerization of isoprene at low concentrations of polyisoprenyllithium

Fetters¹

1965

J. RES. NATL. BUR. STAN. SECT. A.

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The kinetics of polymerization of isoprene with n-butyUithium initiator was investigated in n-hexane solution over an extended concentration range of poly-organolithium. The propagation reaction was found to be first-order with r egard to monomer a nd half-order with respect to chain anion concentration. The degree of chain anion aggregation, in the associa tion equilibrium between active single chains and inactive associated cha ins, was concurrently scrutinized. The evidence acc!'ued from the studies indicates t hat the associated chains exist only as binary a ggregates. These experimental findings are in concert with those results obtained at higher concentrations of polyorga nolithium .

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Determination of the intermolecular entanglement coupling spacings in polyisoprene by viscosity measurements

Cited by 26 publications

References 24 publications

Packing Length Influence in Linear Polymer Melts on the Entanglement, Critical, and Reptation Molecular Weights

Packing Length Influence in Linear Polymer Melts on the Entanglement, Critical, and Reptation Molecular Weights

Synthesis and solution properties of linear, four‐branched, and six‐branched star polyisoprenes

Anionic polymerization of isoprene at low concentrations of polyisoprenyllithium

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