A dielectric study of the dynamics of polyisoprene trapped in polybutadiene networks

Adachi, Keiichiro; Nakamoto, Tetsuo; Kotaka, Tadao

doi:10.1021/ma00197a036

Cited by 24 publications

(37 citation statements)

References 7 publications

(11 reference statements)

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“…Moreover, dielectric data on PI dispersed in high molecular weight polybutadiene, wherein constraint release should be less important, are still at odds with the tube model. 8,10,12,33,34 An alternative modification of the Rouse model accounts for entanglements by multiplying the Rouse relaxation rate by the quantity (t/t c ) -1 , in which t c is …”

Section: Resultsmentioning

confidence: 99%

Normal Mode Relaxation in Linear and Branched Polyisoprene

Roland

Bero

1996

Macromolecules

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Dielectric spectroscopy was carried out on linear and three-arm star polyisoprenes (PI). The shape of the normal mode peak differed significantly from the corresponding mechanical terminal relaxation function, although the temperature dependencies measured for the two spectroscopies were similar. This represents a departure from the usual correlation between time and temperature dependencies. In accord with mechanical relaxation data on these same polymers, the normal mode peak is found to be broader and more sensitive to temperature for star-branched PI than for the linear polymer.

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Section: Resultsmentioning

confidence: 99%

Normal Mode Relaxation in Linear and Branched Polyisoprene

Roland

Bero

1996

Macromolecules

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“…De Gennes theoretically classified the types of guest-chain dynamics as functions of M x and M g , 49 and corresponding experiments were reported by several researchers. [50][51][52] But these earlier studies had some drawbacks: the mesh size was not precisely controllable owing to random crosslinking and/or the difference in chemical structure between the host networks and guest chains complicated the data interpretation. We prepared elastomeric networks with well-defined mesh sizes and containing guest chains with identical chemical structures by end-linking reactive PDMS in the presence of a small amount of inert linear PDMS.…”

Section: Viscoelasticity Of End-linked Pdms Net-work With Unattachedmentioning

confidence: 99%

Network Topology–Mechanical Properties Relationships of Model Elastomers

Urayama

2008

Polym J

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We review our recent studies on the mechanical properties of model elastomers with well-characterized network structures. Model elastomers were prepared by end-linking precursor poly(dimethylsiloxane) (PDMS) of known molecular weight with multifunctional crosslinkers. We then strictly assessed the modern entanglement models for rubber elasticity on the basis of the stress-strain data under general biaxial strains covering almost the entire range of accessible deformations for the model PDMS networks. We also demonstrated marked extensibility of more than 3000% for the deswollen networks prepared by removing the solvent from the end-linked gels prepared in the diluted state. The highly deswollen networks comprising the considerably compact conformation (supercoil) exhibited unusually weak strain dependence of stress. We also studied the viscoelastic properties of PDMS networks containing either unattached free chains or pendant chains. The former systems provided a model system to investigate the dynamics of the guest chains in invariant networks. The dynamics of the guest chains, as functions of their own sizes as well as the mesh sizes of host networks, were compared with the predictions of reptation theories. With the model networks with pendant chains, we elucidated the correlation between the damping properties and the amount of pendant chains. The elastomers with highly irregular structures exhibited high damping almost independent of both temperature and frequency.KEY WORDS: Elastomers / Gels / Rubber Elasticity / Rheology / Reptation / Entanglements / Crosslinked polymer networks composed of flexible strands exhibit many unique properties that stem from their threedimensional network structures: they behave as soft solids because they do not flow macroscopically owing to the presence of crosslinks, but they still possess a liquid nature due to the weak constraints at the crosslinks, allowing the micro-Brownian motion of network strands. Rubber elasticity-reversible large deformability under small external forces-is one of the salient characteristics of polymer networks, and hence, they are often called ''elastomers.'' Elastomers are widely employed in industry, and the fundamental aspects of their physical properties have been extensively investigated over the past half century.1,2 The molecular understanding of their physical properties, however, still remains incomplete because their network structures are not well characterized:3 the rubbery networks prepared by randomcrosslinking of the precursor chains have inhomogeneous structures with a broad length distribution of the network strands; in addition, the characterization of the strand length distribution in elastomers is not possible by current analytical techniques. However, end-linking end-reactive precursor chains of known molecular weight using multifunctional crosslinkers affords a tailor-made model network with a wellcharacterized structure. [4][5][6] To the first-order approximation (which is accurate in the case of the complete reaction), the...

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“…It has become evident that the low frequency side of the measured GW(o) peak is narrower than is predicted by eq 6 with n120.40. Dielectric normal mode relaxation measurements on high cis content polyisoprene (PI) have revealed [36- [43]. It was generally recognized by various workers that the topological constraints imposed by other chains in an entangled linear polymer melt are primarily lateral, running parallel along the chain contour [44-461, even before the reptation mechanism of DeGennes [47] and the tubefreptation model of Doi and Edwards [48] were proposed.…”

Section: Coupling Model For Terminal Relaxation Of Entangled Polymersmentioning

confidence: 99%

“…This trend is consistent with the ratio MPB/Mpl being larger and the suppression of LCM being more complete in the former than in the latter. Adachi and coworkers studied the dielectric normal mode relaxation of PI trapped in crosslinked natural rubber networks [52J and in PB networks [43]. The experimental data were reviewed by Adachi and Kotaka [36,53].…”

Section: Dilute Polyisoprene Probes In Polybutadiene Matricesmentioning

confidence: 99%

General Applicability of the Coupling Model to Viscoelasticity of Polymers : from Local Segmental Motion to Terminal Flow

1996

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Abstract. We survey the important problems in polymer viscoelasticity that impede progress in this field. These problems manifest themselves as spectacular anomalies in the viscoetastic data that have been reproduced in different polymers and in different laboratories, but have largely been put aside for lack of explanation. Without solving these difficult problems, there can be no satisfactory understanding of the viscoelastic properties of polymers spanning across the local segmental motion, the glass-rubber softening dispersion, the rubbery plateau and the terminal dispersion. The coupling model, which has general applicablity to various relaxation mechanisms of polymers and beyond polymers, is able to resolve all these problems.

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A dielectric study of the dynamics of polyisoprene trapped in polybutadiene networks

Cited by 24 publications

References 7 publications

Normal Mode Relaxation in Linear and Branched Polyisoprene

Normal Mode Relaxation in Linear and Branched Polyisoprene

Network Topology–Mechanical Properties Relationships of Model Elastomers

General Applicability of the Coupling Model to Viscoelasticity of Polymers : from Local Segmental Motion to Terminal Flow

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