Order and strain in main-chain smectic liquid-crystalline polymers and elastomers

Jeu, Wim H. de; Obraztsov, E. P.; Ostrovskiǐ, B. I.; Ren, Wanting; McMullan, Philip J.; Griffin, Anselm C.; Sánchez‐Ferrer, Antoni; Finkelmann, Heino

doi:10.1140/epje/i2007-10254-8

Cited by 28 publications

(31 citation statements)

References 33 publications

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“…Other reports on main-chain systems find correlation lengths in the range of ζ = 1200 Å . 34 The correlation length found here is in the same order of magnitude. Upon shear, the layers k -θ show only a small decrease in the correlation length until reaching a plateau of ζ = 800 Å .…”

Section: Scheme 2 Synthesis Of the Liquid Crystalline Elastomers (Lcsupporting

confidence: 75%

Shear Deformation and Ferroelectricity in Chiral SmC* Main-chain Elastomers

Heinze

Finkelmann

2010

Macromolecules

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Ferroelectric smectic main-chain liquid crystalline elastomers were synthesized and subjected to simple shear deformation to achieve reorientation of the layer structure and the formation of a macroscopic spontaneous polarization. The phase behavior and structural parameters of these elastomers are investigated and discussed. A shear-induced splitting of the X-ray scattering intensity distribution is found. A splitting of the sample in domains of two director orientations that couple differently to the shear deformation is proposed. The smectic layers also move at different affinities depending on their initial orientation. The smectic layer spacing was found to be nearly constant even though the smectic tilt angle changes significantly. The realignment of the smectic layers indicates a migration process, where depending on their original orientation the layer normals are leaving or entering the X-ray scattering plane. The spontaneous polarization was found to be linearly dependent on the dopant concentration with Ps = 30 nC/cm 2 for a system doped with 11 wt % of chiral dopant.

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Section: Scheme 2 Synthesis Of the Liquid Crystalline Elastomers (Lcsupporting

confidence: 75%

Shear Deformation and Ferroelectricity in Chiral SmC* Main-chain Elastomers

Heinze

Finkelmann

2010

Macromolecules

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“…Thus, no linear elastic region is present and a continuous deformation appears along the experiment (see Supporting Information, Figure SI -5). The analysis of the intensity distribution of the smallangle reflections reveals a correlation length of the smectic structure of about j ¼ 38 AE 2 nm (15 AE 1 layers), [1,41,42] which remains unchanged during the deformation process a) of the elastomer. The area ratio and intensity ratio between the small-angle and wide-angle reflections show the same tendency (Figure 3b).…”

Section: Polydomain-monodomain Structure Transformationmentioning

confidence: 95%

Polydomain–Monodomain Orientational Process in Smectic‐C Main‐Chain Liquid‐Crystalline Elastomers

Sánchez‐Ferrer

Finkelmann

2010

Macromol. Rapid Commun.

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The polydomain-monodomain (PM) transformation takes place when a polydomain of a smectic-C main-chain liquid-crystalline elastomer (SmC MCLCE) is uniaxially stretched. We present results based on a combination of mechanical and X-ray experiments which show how the domains initially rearrange to finally form a perfect conical layer distribution (monodomain) when the sample is fully stretched. The rearrangement and orientational process of the domains is quantified and compared to the parallel and perpendicular uniaxial stress-strain deformations of a monodomain sample. The stress-strain behaviour of the polydomain lays between the uniaxial deformations, parallel and perpendicular to the director, of the monodomain sample.

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“…This leaves as the most plausible explanation that the Lorentzian line shape is due to a broad exponentiallike distribution of domain sizes in the sample, similar to as found for some main-chain smectic polymers. 22 The average domain size along layer normal can be estimated from the Gaussian reproducing the central part of the X-ray peak (Table 1) as L ¼ 2p/FWHM z 180 nm. 28 In this picture the broadening of the smectic peaks with increasing harmonic number n is due to non-uniform strain in the sample associated with multiple defects of the layer structure.…”

Section: 26mentioning

confidence: 99%

Order, disorder and stretching of a smectic elastomer with ‘side-on’ mesogenic side groups

et al. 2009

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We report an X-ray study of the order in a 'side-on' smectic-A elastomer in which both the polymer backbone and the mesogenic side groups are, on average, parallel to the smectic layer normal. The present system shows in all phases locally correlated structures as evidenced by systematic diffuse scattering at small angles, attributed to the fluorinated end groups of the mesogens. The elastomer shows order of the smectic layers over a limited range in spite of the relatively low crosslink concentration (4%). Upon stretching along the layer normal we find a linear increase of the smectic layer period for small loading (elastic regime). These changes parallel the stress variation for the elastic part of the macroscopic stress-strain curve and saturate at larger strains. The attendant increase in the width of the X-ray peaks indicates a decrease of the average domain dimensions. In the plastic regime no distortion of the smectic monodomain structure or layer rotation is observed. Instead the stress is relieved by 'melting' of the layer structure giving rise to a nematic-like state with short-range layer correlations: at the final stage about four smectic layers.

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Order and strain in main-chain smectic liquid-crystalline polymers and elastomers

Cited by 28 publications

References 33 publications

Shear Deformation and Ferroelectricity in Chiral SmC* Main-chain Elastomers

Shear Deformation and Ferroelectricity in Chiral SmC* Main-chain Elastomers

Polydomain–Monodomain Orientational Process in Smectic‐C Main‐Chain Liquid‐Crystalline Elastomers

Order, disorder and stretching of a smectic elastomer with ‘side-on’ mesogenic side groups

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