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

Hadjichristidis, N.; Roovers, Jacques

doi:10.1002/pol.1974.180121211

Cited by 157 publications

(75 citation statements)

References 29 publications

(7 reference statements)

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“…Values of 3.4-3.5 have been found for concentrated polyisoprene solutions. 14,25,26 Dielectric spectroscopy measurements 32,33 on a very similar polyisoprene with slightly smaller vinyl content (∼4%) also revealed a very comparable molecular weight dependence with a slope 4. The data from this study, shown also in Figure 3, add another independent confirmation of the derived M c value.…”

Section: Resultsmentioning

confidence: 99%

Rheological Properties of 1,4-Polyisoprene over a Large Molecular Weight Range

et al. 2004

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The dynamic viscoelastic properties of anionically polymerized model 1,4-polyisoprene (PI) with 6-8% 3,4 microstructure and in the range of molecular weights between 1.5 × 10 3 and 3.2 × 10 6 g/mol were reanalyzed using linear rheology. Viscosities obtained in the zero shear-rate limit, η0, up to sufficiently high molecular weight PI samples indicated a clear transition to the pure reptation regime. All characteristic molecular weights, dividing the [η 0,M]-interval in three different regimes could be obtained in high accuracy and a new "triangle" is proposed. The experimental data were analyzed in terms of the empirical Winter-relaxation BSW-model description for both dynamic moduli. The BSW parameters are determined and interpreted in terms of the packing model where possible. Limitations of the packing model are detected and discussed. Additionally, the parameters of the assumed distribution of relaxation times are compared to predictions of microscopic dynamic theories and useful correlations made. The publication deals, in part, with a misconception in the literature for estimates of the constraint release contribution. The monomeric friction coefficient 0, determined in this study for the first time rheologically for anionic PI itself agrees with the natural rubber analogue.

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Section: Resultsmentioning

confidence: 99%

Rheological Properties of 1,4-Polyisoprene over a Large Molecular Weight Range

et al. 2004

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“…Hadjichr is tides and Roovers [29] synthesized 4-and 6-armed polyisoprene stars in the mid 1970*3 and later produced 8-and 12-armed stars using tetra(methyl-dichlorosilylethane)silane and tetra(trichlorosilylethane)silane respectively [30]. concluded that the encapping increased the reaction rate but had no effect on the functionality [31].…”

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A compositional study of the morphology of 18-armed poly(styrene-isoprene) star block copolymers

Herman¹,

Kinning²,

Thomas³

et al. 1987

Macromolecules

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“…The intrinsic viscosity of branched polymers is conveniently expressed by (5) where ['l]b and ['1]1 are the intrinsic viscosity of branched and linear polymers having the same molecular weight, respectively. For ·regular star-shaped polymers under the non-freedraining condition, no exact closed expression could be derived for but the result of ZK theory can be approximately written as (6) If the Zimm-Kilb relationship is valid for regular stars and ['1] measured in theta solvent is proportional to M 1!2, 'lo can be expressed by following equations:…”

Section: Ii) Reduction By the Gaussian Mean-square Radius Of Gyrationmentioning

confidence: 99%

Viscosity and Steady-State Compliance of Multi-Branched Star Polystyrenes

Ohta

Masuda

Onogi

1986

Polym J

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ABSTRACT:Reductions of molecular weight dependences of the zero-shear viscosity IJo and the steady-state compliance for multi-branched star polystyrenes with different numbers (P=7 -40) and molecular weights (M, = 1.3-20 x 10 4 ) of branches as well as those of smallnumber (six or less) branched polystyrenes and linear ones have been investigated. The reduction methods of IJo and ever established both theoretically and experimentally for small-number branched star polymers could not be applied to multi-branched star polymers. We tried to reduce the data of IJo and for multi-branched star polymers by corrected molecular weights by considering the expansion of molecules. In the course of discussions we proposed a new method to estimate the unperturbed dimensions of star polymers from the rheological measurements.KEY In the terminal or flow zone, the viscoelastic behavior of polymer melts can be characterized by the zero-shear viscosity rJo and the steady-state compliance A lot of experimental studies on the viscoelastic properties for star-shaped polymers having the number of branches six or less have been carried out 3 -20 and have established the molecular weight dependences of rJo and which quantitatively agree with recent theories. 21 -23 In the previous paper, 24 the viscoelastic properties of multi-branched star polystyrenes having a variety of number (P) and molecular weight (M 5 ) of branches were measured in wide ranges of temperature and frequency, and the effects of temperature, total molecular weight M, M,, and P were investigated. In this paper, the multi-branched star polymer means that having more than seven branches in a molecule.Mean square radius of gyration of multi-1 Rheological Properties of Anionic Polystyrenes XII.* To whom all correspondences should be addressed.branched star polystyrene prepared by coupling narrow-distribution polystyryl anions with divinylbenzene (DVB) was found to be larger than that the random-walk model predicts, 25 • 26 because of a microgel nodule at the center of molecule. 25 • 27 -31 In recent studies, 32 • 33 however, it was found that the extra expansion of multi-branched star polymer is due to the effect of increased segment density near its center. The non-Gaussian distribution of the chain segments not only makes the molecules expanded but also reduces flexibility of chain near the central branch point. This effect gives rise to a core formed at the center of molecule, which behaves rheologically like a nodule. Both the extra expansion and the reduced flexibility at the center of multi-branched star molecule necessarily affect the rheological properties of the melts. This paper describes reduction of the mo-337

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

Cited by 157 publications

References 29 publications

Rheological Properties of 1,4-Polyisoprene over a Large Molecular Weight Range

Rheological Properties of 1,4-Polyisoprene over a Large Molecular Weight Range

A compositional study of the morphology of 18-armed poly(styrene-isoprene) star block copolymers

Viscosity and Steady-State Compliance of Multi-Branched Star Polystyrenes

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