Dynamics of Entangled H-Polymers:  Theory, Rheology, and Neutron-Scattering

McLeish, Tom; Allgaier, Jürgen; Bick, D. K.; Bishko, G.; Biswas, Parbati; Blackwell, Richard J.; Blottière, Benoît; Clarke, Nigel; Gibbs, B.M.; Groves, D. J.; Hakiki, A.; Heenan, Richard K.; Johnson, Judith; Kant, Rama; Read, Daniel J.; Young, R. N.

doi:10.1021/ma990323j

Cited by 296 publications

(498 citation statements)

References 45 publications

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“…18 This knowledge is necessary to estimate the nonlinear response in this strain experiment. We will summarize the basic times and provide the expected amount of relaxing segments as a function of the annealing time in this transient experiment.…”

Section: Rheological Relaxation Processesmentioning

confidence: 99%

Arm Relaxation in Deformed H-Polymers in Elongational Flow by SANS

Heinrich¹,

Pyckhout‐Hintzen²,

Allgaier³

et al. 2002

Macromolecules

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We present a small-angle neutron scattering (SANS) investigation of the relaxation process of branched polymer melts under deformation. The selected model polymer is an H-shaped polyisoprene having deuterium-labeled blocks at the dangling tips of the arms. The melt is step strained in a strain rig especially built for that purpose, where the sample temperature and its deformation conditions are precisely controlled. Uniaxial extensions to values of 2 and 3 are performed at a temperature above the polymer glass transition temperature T g. The sample is then allowed to relax during a given time before being quenched to below its Tg in order to freeze the chains conformation to perform the SANS experiments. Very large anisotropies in S(q) develop on time scales corresponding to the relaxation of the dangling arms. The experimental structure function is then compared to theoretical ones obtained by the random phase approximation applied to the tube model. While theory describes well the scattering for short times, it seems not to be able to describe the increase of intensity in the direction parallel to the strain at higher times, even when highly nonaffine processes such as arm retraction and branch point withdrawal are taken into account.

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Section: Rheological Relaxation Processesmentioning

confidence: 99%

Arm Relaxation in Deformed H-Polymers in Elongational Flow by SANS

Heinrich¹,

Pyckhout‐Hintzen²,

Allgaier³

et al. 2002

Macromolecules

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“…From a theoretical perspective, several successful treatments for branched polymers have been proposed to explain their viscoelastic response [82][83][84][85][86][87][88][89]. The tube model theory has been shown to describe the viscoelastic behaviour of linear polymers [90][91][92].…”

Section: Model Polymersmentioning

confidence: 99%

“…This model is based on recent advances in branched polymer molecular theories on branch hierarchical relaxation by path arm fluctuations, arm collapse and reptation [84][85][86][87][88][89]. In his work, Larson discusses the limitations of Janzen and Colby's approach [158], and demonstrates that η o and the entire viscoelastic response depend not only on branching content, but also on the type and topology of branching.…”

Section: State-of-the-artmentioning

confidence: 99%

“…The reduction in J e o could be explained by an increased degree of branching that leads to a different physical state with lower entanglement density [81,174]. The concept of dilution proposed by McLeish et al [89] also serves to explain this behaviour: the relaxation of polymer chains with long relaxation times will be accelerated by surrounding chains or chain segments with shorter relaxation times, since they act as diluents. In highly branched materials (high volume fraction occupied by the branches), branches may relax more rapidly than entire molecules, thus diluting the immediate environment, leading to an overall reduction in elasticity.…”

Section: Rheological Polydispersity and Steady State Compliancementioning

confidence: 99%

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Effect of long chain branching on linear-viscoelastic melt properties of polyolefins

et al. 2002

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Abstract:The aim of this review is to provide evidence that rheological testing is a potent tool for characterising polymers in the melt. An effort has been made in order to gather results in conventional and model polyolefins, and correlating them with phenomena occurring at the molecular level. We have focused our interest on long chain branching (LCB). In the case of materials containing long side-chain branches, strong effects on viscosity, elastic character and activation energy of flow are general features. Literature results mostly indicate that the effect of polydispersity on these parameters could be very similar to that expected due to the presence of LCB -notwithstanding that the effects of LCB seem to be stronger than those due to polydispersity for a given molecular weight. Different relaxation processes appear as a consequence of the presence of LCB: slower terminal relaxation behaviour than of linear counterparts, and faster additional branch relaxation at higher frequencies, clearly distinguishable from polydispersity effects. To measure the amount of LCB from limited viscoelastic data and molecular properties seems to be a suitable instrument to explain the rheological features of the different polymers, but it fails when the results are compared with measured values of LCB density in model polymers. The actual framework leads us to say that the number of branches is less important than the topology itself. Therefore, the position and architecture of the branches along the polymer main chain are the main factors that control the rheology of the material.

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“…Star polymers with varying numbers of arms have been widely produced and studied [1][2][3][4][5][6][7][8] and branched polymers of increasing complexity and diverse structures have evolved. These include H-shaped polymers [9][10][11][12][13][14][15], comb-shaped polymers [16][17][18][19][20][21][22][23][24][25][26][27][28] and more recently dendritically branched polymers [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48]. Fundamental to all these studies is the ability of the synthetic polymer chemist to control structural homogeneity and produce branched ...…”

Section: Introductionmentioning

confidence: 99%

Synthesis and temperature gradient interaction chromatography of model asymmetric star polymers by the “macromonomer” approach

Agostini¹

2013

European Polymer Journal

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. (2013) 'Synthesis and temperature gradient interaction chromatography of model asymmetric star polymers by the "macromonomer"approach.', European polymer journal., 49 (9). pp. 2769-2784. Further information on publisher's website:http://dx.doi.org/10.1016/j.eurpolymj.2013.06.021Publisher's copyright statement: NOTICE: this is the author's version of a work that was accepted for publication in European Polymer Journal. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be re ected in this document. Changes may have been made to this work since it was submitted for publication. A de nitive version was subsequently published in European Polymer Journal, 49, 9, 2013Journal, 49, 9, , 10.1016Journal, 49, 9, /j.eurpolymj.2013.021. Additional information:Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Abstract. We describe herein the synthesis and characterisation of a series of asymmetric three arm polystyrene stars via the "macromonomer" approach. The stars have been designed as model polymers to probe branched polymer dynamics and in particular to establish the chain-length of side-arm which precipitates a change in the rheological properties of the resulting polymers from "linear-like" to "star-like". Thus, a homologous series of three arm stars have been prepared in which the molar mass of two (long) arms are fixed at 90 000 gmol -1 and the molar mass of the remaining (short) arm is varied from below the entanglement molecular weight (M e ) to above M e . The arms were prepared by living anionic polymerisation, resulting in well-defined chain lengths with narrow molecular weight distribution. In contrast to the usual chlorosilane coupling approach, the macromonomer approach involves the introduction of reactive chain-end functionalities on each of the arms, either through the use of a functionalised (protected) initiator or a functional end-capping agent, which allows the stars to be constructed by a simple condensation coupling reaction. In this study we will compare the relative efficiency of a Williamson and 'click' coupling reaction in producing the stars. Most significantly, although this approach maybe a little more time-consuming than the more common silane coupling reaction, in the present study the "long" arm may be produced in sufficient quantity such that all of the asymmetric stars are produced with long arms of identical molecular weight -the only remaining variable being the molecular weight of th...

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Dynamics of Entangled H-Polymers: Theory, Rheology, and Neutron-Scattering

Cited by 296 publications

References 45 publications

Arm Relaxation in Deformed H-Polymers in Elongational Flow by SANS

Arm Relaxation in Deformed H-Polymers in Elongational Flow by SANS

Effect of long chain branching on linear-viscoelastic melt properties of polyolefins

Synthesis and temperature gradient interaction chromatography of model asymmetric star polymers by the “macromonomer” approach

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