Configuration of Semiflexible Polymer Chains in the Nematic Phase

Chen, Zheng Yu

doi:10.1021/ma00086a015

Cited by 11 publications

(6 citation statements)

References 17 publications

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“…The change in ionic strength from 5 mM to 110 mM corresponds to an L/D eff for the rods changing from ≈ 40 to ≈ 85. As the effective aspect ratio for our rods approaches the long rod limit, L/D eff > 100, the coexistence order parameter decreases, approaching the theoretically predicted value of S = 0.55, as calculated by Chen for long semi-flexible rods with a length to persistence length ratio, L/p = 0.4 [11]. Even though the persistence length of fd virus is more than twice its contour length, and thus can be considered fairly rigid, all of our co-existing samples had a nematic order parameter significantly lower than the Onsager prediction of S = 0.79 as measured by both diffraction and birefringence.…”

Section: B Orientational Orderingsupporting

confidence: 70%

“…Theoretical models suggest that semi-flexibility also acts to significantly lower the nematic order parameter at coexistence. For fd, a relatively rigid polymer with a ratio of persistence to contour length of 2.5, the nematic order parameter at coexistence is predicted to be S = 0.55, which is significantly smaller than predicted for rigid rods, approximately S = 0.79 [11]. Several review articles describe in more detail the theoretical and experimental aspects of this and other systems described by Onsager's theory [2,10,12,13,14,15,16,17,18].…”

Section: Introductionmentioning

confidence: 96%

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Measuring the nematic order of suspensions of colloidal fd virus by x-ray diffraction and optical birefringence

et al. 2003

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The orientational distribution function of the nematic phase of suspensions of the semiflexible rodlike virus fd is measured by x-ray diffraction as a function of concentration and ionic strength. X-ray diffraction from a single-domain nematic phase of fd is influenced by interparticle correlations at low angle, while only intraparticle scatter contributes at high angle. Consequently, the angular distribution of the scattered intensity arises from only the single-particle orientational distribution function at high angle but it also includes spatial and orientational correlations at low angle. Experimental measurements of the orientational distribution function from both the interparticle (structure factor) and intraparticle (form factor) scattering were made to test whether the correlations present in interparticle scatter influence the measurement of the single-particle orientational distribution function. It was found that the two types of scatter yield consistent values for the nematic order parameter. It was also found that x-ray diffraction is insensitive to the orientational distribution function's precise form, and the measured angular intensity distribution is described equally well by both Onsager's trial function and a Gaussian. At high ionic strength, the order parameter S of the nematic phase coexisting with the isotropic phase approaches theoretical predictions for long semiflexible rods S=0.55, but deviations from theory increase with decreasing ionic strength. The concentration dependence of the nematic order parameter also better agrees with theoretical predictions at high ionic strength indicating that electrostatic interactions have a measurable effect on the nematic order parameter. The x-ray order parameters are shown to be proportional to the measured birefringence, and the saturation birefringence of fd is determined enabling a simple, inexpensive way to measure the order parameter. Additionally, the spatial ordering of nematic fd was probed. Measurements of the nematic structure factor revealed a single large peak in contrast to nematics of rigid rods.

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Section: B Orientational Orderingsupporting

confidence: 70%

Section: Introductionmentioning

confidence: 96%

Measuring the nematic order of suspensions of colloidal fd virus by x-ray diffraction and optical birefringence

et al. 2003

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“…where Qo = [Jdfl/o1/,2(fl)]2. Using the numerical result for / ( ) calculated earlier,26 we obtain ( »1) = -0.3326 (27) within a relative error less than 1 %.…”

Section: Qwj0supporting

confidence: 51%

“…Most liquid-crystalline polymers have a certain finite flexibility,19,20 which can be described by the wormlike chain model of Saito, Takahashi, and Yunoki.21-23 Solutions comprised of monodisperse semiflexible polymer chains interacting with each other through the excludedvolume interaction have been used as simple models to represent lyotropic liquid-crystalline molecules in real systems. [24][25][26][27] In these treatments, the effects of polydispersity, which exist in most real systems, are neglected.…”

mentioning

confidence: 99%

Polydisperse Semiflexible Polymer Chains at the Isotropic-Nematic Phase Equilibrium

Chen¹,

Cui²

1994

Macromolecules

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“…The critical concentrations are inversely related to the rod axial ratio, approaching an asymptotic limit at large axial ratios. Recent theoretical advances provide a more realistic description of semirigid polymers by including the effects of charge and chain flexibility (Khokhlov and Semenov, 1981; Odijk, 1986;Stroobants et al, 1986;Sato et al, 1990; Inatomi et al, 1992;Chen, 1994; Tkachenko and Rabin, 1995;Sheng et al, 1996). For a given axial ratio, the critical concentrations increase significantly, relative to the rod limit, with increasing chain flexibility (decreasing persistence length) (Khokhlov and Semenov, 1981;Odijk, 1986).…”

Section: Introductionmentioning

confidence: 99%

DNA length and concentration dependencies of anisotropic phase transitions of DNA solutions

Merchant¹,

Rill²

1997

Biophysical Journal

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Critical concentrations for the isotropic to cholesteric phase transitions of double-stranded DNA fragments in simple buffered saline (0.1 M NaCl) solutions were determined as a function of DNA contour length ranging from approximately 50 nm to 2700 nm, by solid-state 31P NMR spectroscopy and polarized light microscopy. As expected for semirigid chains, the critical concentrations decrease sharply with increasing DNA length near the persistence length in the range from 50 to 110 nm, and approach a plateau when the contour length exceeds 190 nm. The biphasic region is substantially wider than observed for xanthan, another semirigid polyelectrolyte approximately twice as stiff as DNA, primarily because of low critical concentrations for first appearance of the anisotropic phase, C(i)*, in DNA samples > or =110 nm (320 base pairs) long. The limiting C(i)* for DNA > or =490 nm long is exceptionally low (only 13 mg/ml) and is substantially lower than the C(i)* of approximately 40 mg/ml reported for the stiffer xanthan polyelectrolyte. The much higher values of the critical concentrations, C(a)*, for the disappearance of the isotropic DNA phase (> or =67 mg/ml) are modestly higher than those observed for xanthan and are predicted reasonably well by a theory that has been applied to other semirigid polymers, if a DNA persistence length in the consensus range of 50-100 nm is assumed. By contrast, the broad biphasic region and low C(i)* values of DNA fragments > or =190 nm long could only be reconciled with theory by assuming persistence lengths of 200-400 nm. The latter discrepancies are presumed to reflect some combination of deficiencies in current theory as applied to chiral, strong polyelectrolytes such as DNA, and sequence-dependent variations in DNA properties such as flexibility, curvature, or interaction potential. The propensity of DNA to spontaneously self-order at low concentrations well in the physiological range may have biological significance.

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Configuration of Semiflexible Polymer Chains in the Nematic Phase

Cited by 11 publications

References 17 publications

Measuring the nematic order of suspensions of colloidal fd virus by x-ray diffraction and optical birefringence

Measuring the nematic order of suspensions of colloidal fd virus by x-ray diffraction and optical birefringence

Polydisperse Semiflexible Polymer Chains at the Isotropic-Nematic Phase Equilibrium

DNA length and concentration dependencies of anisotropic phase transitions of DNA solutions

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