Near-critical behavior of the dynamic stress-optical coefficient in liquid crystalline elastomers

Sigel, R.; Stille, W.; Strobl, G.; Lehnert, R. F.

doi:10.1021/ma00068a024

Cited by 17 publications

(12 citation statements)

References 7 publications

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“…When dealing with non-crosslinked nematic polymers rather than low molar mass nematics, the equations (3)(4)(5)(6)(7)(8) can still be applied. The only difference are the larger viscosities [11].…”

Section: Light Scattering Of Nematics a Summary Of Theoretical Resultsmentioning

confidence: 99%

“…From molar mass dependent studies of the rotational viscosity of non-crosslinked nematic polymers [18] we know that entanglements do not play an important role up to moderate values of the molar mass M , resulting in ∆γ 1 ∼ M µ with µ ≈ 1. On the other hand, from combined stress-optical and dynamic mechanical studies in the isotropic phase of a nematic elastomer [4] we have evidence that entanglements, acting as additional physical junction points, strongly contribute to the viscoelastic properties of elastomers.…”

Section: Viscositymentioning

confidence: 89%

“…Optical studies depending on a high transparency then are restricted to the isotropic phase, where, as an example, the frequency dependent stress-optical coefficient was measured [4]. Küpfer [5] prepared a nematic elastomer with a permanent, macroscopically uniform alignment by applying mechanical stress before the second of two crosslinking steps.…”

Section: Introductionmentioning

confidence: 99%

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Effect of the network on the director fluctuations in a nematic side-group elastomer analysed by static and dynamic light scattering

Schönstein

Stille

Strobl

2001

The European Physical Journal E

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Static and dynamic light scattering experiments were performed on monodomains of a crosslinked nematic side-group polysiloxane. The depolarized scattering caused by fluctuations of the nematic director was analysed. Due to a superposed strong static scattering produced by heterogeneities the fluctuating part of the scattering intensity was found to be rather small. In contrast to low molar mass nematics, the relaxation rates and strength did not show a significant dependence on the scattering vector. The results can be explained by restoring torques on the director originating from the coupling to the network elasticity which dominate those originating from the Frank elasticity. Quantities describing the coupling as well as effective viscosities for the director reorientation were obtained.

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Section: Light Scattering Of Nematics a Summary Of Theoretical Resultsmentioning

confidence: 99%

Section: Viscositymentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

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Effect of the network on the director fluctuations in a nematic side-group elastomer analysed by static and dynamic light scattering

Schönstein

Stille

Strobl

2001

The European Physical Journal E

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“…Based on such a mechanical approach, it might be worth investigating SFPCs in a good solvent by depolarized light scattering, as a local stress is transferred to a birefringence via the polymer's stress-optical coefficient. 30,31 The EVIs between the monomers extend the chain, and this effect has a longer range than the chain persistence. The EVIs are basically not affected by chain distortions, and so the large scale behavior of distorted and undistorted SFPCs is very similar.…”

Section: Persistence Length Of Semi-flexible Polymers In a Good Solventmentioning

confidence: 99%

Form factor for distorted semi-flexible polymer chains

Sigel

2018

Soft Matter

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The statistical presence of kinks which form defects in semi-flexible polymer chains leads to a polydispersity in the effective persistence length. The form factor of a distorted semi-flexible polymer results as an average over this persistence polydispersity. It turns out that the scattering behavior of an ensemble of distorted semi-flexible polymer chains is quite well approximated by a form factor of an undistorted chain with a R-equivalent persistence length. An apparent length polydispersity is observed for short distorted chains. The R-equivalent persistence length is significantly smaller than the innate persistence length multiplied by the fraction of regular monomers. The results are compared to related work on DNA from the literature.

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“…in Eqs (71). and(72) are to be taken at time t.Sinceˆ J ci ( r, t) andˆ J ε ( r, t) are of odd order in the momentum p…”

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confidence: 99%

Extended dynamical density functional theory for colloidal mixtures with temperature gradients

Wittkowski

Löwen

Brand

2012

The Journal of Chemical Physics

111

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In the past decade, classical dynamical density functional theory (DDFT) has been developed and widely applied to the Brownian dynamics of interacting colloidal particles. One of the possible derivation routes of DDFT from the microscopic dynamics is via the Mori-Zwanzig-Forster projection operator technique with slowly varying variables such as the one-particle density. Here, we use the projection operator approach to extend DDFT into various directions: first, we generalize DDFT toward mixtures of n different species of spherical colloidal particles. We show that there are in general nontrivial cross-coupling terms between the concentration fields and specify them explicitly for colloidal mixtures with pairwise hydrodynamic interactions. Second, we treat the internal energy density as an additional slow variable and derive formal expressions for an extended DDFT containing also the internal energy density. The latter approach can in principle be applied to colloidal dynamics in a nonzero temperature gradient. For the case without hydrodynamic interactions the diffusion tensor is diagonal, while thermodiffusion--the dissipative cross-coupling term between internal energy density and concentration--is nonzero in this limit. With finite hydrodynamic interactions also cross-diffusion coefficients assume a finite value. We demonstrate that our results for the extended DDFT contain the transport coefficients in the hydrodynamic limit (long wavelengths, low frequencies) as a special case.

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Near-critical behavior of the dynamic stress-optical coefficient in liquid crystalline elastomers

Cited by 17 publications

References 7 publications

Effect of the network on the director fluctuations in a nematic side-group elastomer analysed by static and dynamic light scattering

Effect of the network on the director fluctuations in a nematic side-group elastomer analysed by static and dynamic light scattering

Form factor for distorted semi-flexible polymer chains

Extended dynamical density functional theory for colloidal mixtures with temperature gradients

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