Origin of Internal Viscosity Effects in Flexible Polymers:  A Comparative Neutron Spin-Echo and Light Scattering Study on Poly(dimethylsiloxane) and Polyisobutylene

Arbe, Arantxa; Monkenbusch, M.; Stellbrink, Jörg; Richter, D.; Faragó, B.; Almdal, Kristoffer; Faust, Rudolf

doi:10.1021/ma001628x

Cited by 64 publications

(104 citation statements)

References 22 publications

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“…19 For our analysis, it is essential to know the relaxation times (characteristic frequencies) at this temperature. The local segmental relaxation frequency ν R () ω/2π) estimated for PDMS (M ) 92 000 Da) from quasi-elastic neutron scattering experiments is ∼50 GHz at T ) 400 K. 9,20 The longest Rouse relaxation time for PDMS with M ) 6462 Da at 373 K is estimated from neutron spin echo (NSE) experiments, τ 1 ) 2〈R g 2 〉/π 2 D R ∼ 30 ns (both R g and D R are available in ref 6). This corresponds to a characteristic frequency for the longest Rouse mode, ν 1 ) (2πτ 1 ) -1 ∼ 0.005 GHz.…”

Section: Resultsmentioning

confidence: 99%

Observation of Chain Dynamics in Depolarized Light Scattering Spectra of Polymers

Ding¹,

Novikov²,

Sokolov³

et al. 2004

Macromolecules

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A theoretical model for the chain modes' contribution to the depolarized light scattering (DLS) spectrum of polymers is developed. It is shown that the frequency dependence of the DLS susceptibility spectrum is similar to that of the shear loss modulus. Specifically, the contribution of chain modes to the DLS spectrum is composed of a series of Lorentzians (single-exponential processes) having the same amplitude. The relaxation time associated with each mode follows the Rouse prediction, but with a value equal to one-half the mechanical Rouse time. DLS spectra of poly(dimethylsiloxane) melts with different molecular weights have been analyzed in the framework of the model. Reasonable agreement on both qualitative and quantitative levels is observed. In particular, the relaxation time of the longest Rouse mode extracted from DLS spectra is consistent with that from viscosity measurements.

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Section: Resultsmentioning

confidence: 99%

Observation of Chain Dynamics in Depolarized Light Scattering Spectra of Polymers

Ding¹,

Novikov²,

Sokolov³

et al. 2004

Macromolecules

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“…The difference in the behavior of the RIS models for PDMS and PIB in Table 1 is consistent with the experimentally observed behavior of these polymers. 1,2 For each polymer in Table 1, C s,n approaches its limit more steeply than does C n . The initial slopes are related by a factor of 3.…”

Section: Chains With C N * F(c ∞ N)mentioning

confidence: 99%

“…These two polymers have similar values of C ∞ , but the finite n effect on the mean square dimensions is significantly stronger in PIB than in PDMS. 1,2 When this behavior of real chains goes unrecognized, unphysical results for local chain properties, such as bead size or segment length, can be obtained from interpretation with eq 2 of data obtained at finite n. The problem was recognized three decades ago, when a "shift factor" was introduced to improve the range of applicability of the wormlike chain model. 3 Here we revisit the well-known analytical expressions for several textbook models of polymer chains, permits identification of the common feature of the FJ chain, FR chain, and simple wormlike chain that prompts their adherence to eq 2.…”

Section: Introductionmentioning

confidence: 99%

On the Relationship between the Characteristic Ratio of a Finite Chain, C_n, and the Asymptotic Limit, C_∞

2003

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Often experiments with chains containing a finite number of bonds, n, are interpreted with the assumption that the characteristic ratio, C n, is determined completely by C∞ and n. This assumption is supported by some, but not all, textbook models for simple flexible chains. The freely jointed chain, freely rotating chain with fixed bond angle, and simple wormlike chain predict C n ) f(C∞,n). These three models share the feature that the stiffness of the chain is specified by no more than one parameter. However, when more than one parameter affects the stiffness of the chain, as in the model with fixed bond angle and symmetric hindered rotation about independent bonds, C n is no longer determined by C∞ and n alone, Cn * f(C∞,n). Since virtually all real chains have hindered rotation, they cannot be expected to have the dimensions given by Cn ) f(C∞,n). This conclusion is supported by numerical calculations using previously published rotational isomeric state models for polyethylene, polyisobutylene, and poly-(dimethylsiloxane). Although these three polymers have similar values of C ∞, they may have quite different values of Cn. This conclusion from the calculations is consistent with the observed behavior of polyisobutylene and poly(dimethylsiloxane), as reported by Arbe et al. (Macromolecules 2001, 34, 1281 and by Sluch et al. (Macromolecules 2003, 36, 2721. The finite n effect in these polymers is three times stronger for the mean square unperturbed radius of gyration than for the mean square unperturbed end-to-end distance.

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“…An intriguing question in polymer physics is how does the crossover from segmental to Rouse dynamics take place. One of the key ingredients to answer this question is to know when the Rouse model ceases to be valid, which has been the subject of a number of NS investigations on different polymers [65][66][67] during the past years. However, the uncertainties involved in the experiments and the impossibility to experimentally access the Rouse correlators prevent a thorough analysis of the sources for Rouse deviations.…”

Section: Chemically Simple Linear Amorphous Homopolymersmentioning

confidence: 99%

Recent progress on polymer dynamics by neutron scattering: From simple polymers to complex materials

Colmenero

Arbe

2012

J Polym Sci B Polym Phys

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ABSTRACT:The recent (from 2010 onward) contributions of quasielastic neutron scattering techniques (time of flight, backscattering, and neutron spin echo) to the characterization and understanding of dynamical processes in soft materials based on polymers are analyzed. The selectivity provided by the combination of neutron scattering and isotopic-in particular, proton/deuterium-labeling allows the isolated study of chosen molecular groups and/or components in a system. This opportunity, together with the capability of neutrons to provide space/time resolution at the relevant length scales in soft matter, allows unraveling the nature of the large variety of molecular motions taking place in materials of increasing complexity. As a result, recent relevant works can be found dealing with dynamical process which associated characteristic lengths and nature are as diverse as, for example, phenyl motions in a glassy linear homopolymer like polystyrene and the chain dynamics of a polymer adsorbed on dispersed clay platelets. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 51: 2013 KEYWORDS: molecular dynamics; neutron scattering; relaxation POLYMER DYNAMICS AT DIFFERENT LENGTH AND TIME SCALES: FROM SIMPLE POLYMERS TO COMPLEX MATERIALSPolymers are composed of macromolecules which are built up by a large number N of monomer units linked together by covalent bonds. Because of this macromolecular nature, the structural and dynamic properties of polymeric systems strongly depend on a hierarchy of length and time scales. From a structural point of view, the random coil shape of linear polymer chains in the melt and glassy state-proposed by Flory in the 50s 1 -is nowadays well established by small angle neutron diffraction (SANS). At smaller length scales than those characteristic for the chain dimensions, the local arrangements of the atoms give rise to broad maxima in the static structure factor S(Q) also accessible by neutron diffraction. Usually, a first main peak centered at Q-values ≈ 1 . . . 1.5 Å −1 is present. The T-dependence of this maximum, following the expansion coefficient, indicates an interchain origin, that is, it mainly relates to correlations between atoms belonging to different chains (or to the same chain but well separated segments).2 A second peak located at ∼3 Å −1can also be usually found in S(Q). The small value of the associated characteristic length and its weak T-dependence indicate the intrachain nature of the correlations giving rise to this maximum. We also note that the broadening of the Bragg peaks found in polymers reveals a clear amorphous character. In fact, the features shown in S(Q) in polymeric systems are universal for amorphous materials, not only for polymers, and in particular for glass forming systems. Thus, a universal behavior common for all glass forming materials can also be expected in the dynamics, including the observation of the glass transition phenomenon. 3As anticipated, the complexity of amorphous polymers shows up not only in the structural propertie...

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Origin of Internal Viscosity Effects in Flexible Polymers: A Comparative Neutron Spin-Echo and Light Scattering Study on Poly(dimethylsiloxane) and Polyisobutylene

Cited by 64 publications

References 22 publications

Observation of Chain Dynamics in Depolarized Light Scattering Spectra of Polymers

Observation of Chain Dynamics in Depolarized Light Scattering Spectra of Polymers

On the Relationship between the Characteristic Ratio of a Finite Chain, C_n, and the Asymptotic Limit, C_∞

Recent progress on polymer dynamics by neutron scattering: From simple polymers to complex materials

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Origin of Internal Viscosity Effects in Flexible Polymers: A Comparative Neutron Spin-Echo and Light Scattering Study on Poly(dimethylsiloxane) and Polyisobutylene

Cited by 64 publications

References 22 publications

Observation of Chain Dynamics in Depolarized Light Scattering Spectra of Polymers

Observation of Chain Dynamics in Depolarized Light Scattering Spectra of Polymers

On the Relationship between the Characteristic Ratio of a Finite Chain, Cn, and the Asymptotic Limit, C∞

Recent progress on polymer dynamics by neutron scattering: From simple polymers to complex materials

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Product

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On the Relationship between the Characteristic Ratio of a Finite Chain, C_n, and the Asymptotic Limit, C_∞