Experimental Evidence of Chain Extension at the Transition Temperature of a Nematic Polymer

D'allest, J. F.; Maïssa, P.; Bosch, A. ten; Sixou, P.; Blumstein, A.; Blumstein, R. B.; Teixeira, J.; Noirez, Laurence

doi:10.1103/physrevlett.61.2562

Cited by 87 publications

(42 citation statements)

References 17 publications

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“…2). This spontaneous change in the polymer conformation at the transition T p N I has been reported [8,10,11]. Further decreasing temperatures, we find the phase transition between the two different rodlike conformations at T N N .…”

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confidence: 83%

Conformational transitions of a semiflexible polymer in nematic solvents

Matsuyama

2003

Phys. Rev. E

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Conformations of a single semiflexible polymer chain dissolved in a low molecular weight liquid crystalline solvents (nematogens) are examined by using a mean field theory. We takes into account a stiffness and partial orientational ordering of the polymer. As a result of an anisotropic coupling between the polymer and nematogen, we predict a discontinuous (or continuous) phase transition from a condensed-rodlike conformation to a swollen-one of the polymer chain, depending on the stiffness of the polymer. We also discuss the effects of the nematic interaction between polymer segments. 61.25.Hq, 64.70.Md Mesomorphic mixtures consisting of polymers and low molecular weight liquid crystals (nematogens) are of current interest for fundamental scientific reasons and for many technological applications in electro-optical devices and high modulus fibers. The performances of these systems are related to a conformation of a polymer in a liquid crystal phase. One of the fundamental problem is how the polymer in a nematic phase interacts with a nematic field surrounding the polymer. Polymer chains have the variety of their stiffness and so when the polymer is mixed with the nematogens we can expect various conformations.Mixtures of a flexible polymer and a nematogen show a macroscopic phase separation between an isotropic and a nematic phase below the nematic-isotopic transition (NIT) temperature of the pure nematogen [1][2][3][4][5]. Flexible polymers present a weak anisotropy in a nematic phase [6]. In contrast, liquid crystalline polymers, or stiffer polymers, have good miscibility with nematogens [7] due to the strong anisotropic coupling between the polymer and the nematogen. Anisotropy of the conformation for liquid crystalline polymers has been experimentally [7][8][9] and theoretically [10-16] studied in melt and in dilute nematic solutions. It is now important to consider the conformation of a polymer chain with various degrees of stiffness dissolved in nematogens. Recently we presented a mean field theory to describe partial orientational ordering (induced rigidity) of semiflexible polymers dissolved in nematogens and showed various phase diagrams for the mixtures [16].In this Rapid Communication we theoretically study the conformation of a semiflexible polymer dissolved in nematic solvents by combining the previous model [16] with an elastic free energy of the chain [17]. We show a discontinuous (or continuous) conformational transition between two different nematic states, depending on the stiffness of the polymer.Consider a single linear polymer chain dissolved in nematogens. In order to take into account the stiffness of the polymer, we here assume that two neighboring bonds on the polymer chain have either bent (gauche state) or straightened (trans state) conformations [18,19]. Hereafter we refer the segments in straightened bonds as "rigid" segments.Let V = R 3 be the volume of the region occupied by a polymer, n be the number of segments on the polymer chain and n l be the axial ratio of the nematogen...

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confidence: 83%

Conformational transitions of a semiflexible polymer in nematic solvents

Matsuyama

2003

Phys. Rev. E

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“…It should be noted however that for a highly segmented polymer, such as that shown in Figure 3D, the nematic environment can align segments of the polymer without elongating the polymer by forming hairpin turns in the chains, which when induced by single bond defects have little energy penalty over more elongated defect geometries, e.g., a chain zigzag. A similar interplay between the anisotropic solvation and the intrinsic flexibility of mainchain nematic polymers with flexible spacers between mesogenic groups has previously been inferred from small angle neutron scattering 14 and viscosity 15,16 measurements.…”

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Nematic Solvation of Segmented Polymer Chains

Link

Scholes

et al. 2005

Nano Lett.

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We examine the effect of polymer chain segmentation on the recently discovered ability of nematic solvents to elongate and align polymer chain solutes. Coordinated single molecule spectroscopy and beads-on-a-chain simulations are used to study the orientational and conformational order of a series of segmented conjugated polymers, dissolved in the nematic liquid crystal 5CB. The order parameters for alignment and elongation are both observed to decrease with increasing segmentation, reflecting an interplay among conformational entropy, solvation anisotropy, and bending energy of the chain.

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“…[121] for a detailed look at the nematic and smectic systems respectively. In nematic polymer systems where the mesogens are incorporated directly into the backbone the chains will elongate in their nematic phase when all of the mesogens are aligned [122][123][124] and will relax when the polymer is in the isotropic state and the chains are allowed to coil up into their entropically favored positions. [125] Similar effects are observed when the mesogens are attached as grafts to the elastomeric backbone.…”

Section: Liquid Crystal Elastomersmentioning

confidence: 99%

Advances in Dielectric Elastomers for Actuators and Artificial Muscles

Brochu¹,

Pei²

2009

Macromol. Rapid Commun.

1,259

1,130

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A number of materials have been explored for their use as artificial muscles. Among these, dielectric elastomers (DEs) appear to provide the best combination of properties for true muscle-like actuation. DEs behave as compliant capacitors, expanding in area and shrinking in thickness when a voltage is applied. Materials combining very high energy densities, strains, and efficiencies have been known for some time. To date, however, the widespread adoption of DEs has been hindered by premature breakdown and the requirement for high voltages and bulky support frames. Recent advances seem poised to remove these restrictions and allow for the production of highly reliable, high-performance transducers for artificial muscle applications.

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Experimental Evidence of Chain Extension at the Transition Temperature of a Nematic Polymer

Cited by 87 publications

References 17 publications

Conformational transitions of a semiflexible polymer in nematic solvents

Conformational transitions of a semiflexible polymer in nematic solvents

Nematic Solvation of Segmented Polymer Chains

Advances in Dielectric Elastomers for Actuators and Artificial Muscles

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