Analysis of the Conformation of a Stiff-Chain Polyester by Measurements of the Magnetic Birefringence in Solution

Tiesler, Ulrich; Rehahn, Matthias; Ballauff, M.; Petekidis, George; Vlassopoulos, Dimitris; Maret, Georg; Krämer, H.

doi:10.1021/ma960765k

Cited by 13 publications

(21 citation statements)

References 18 publications

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“…From the measured rates in Figure 9a, we get Θ ) 34 s -1 and D ) 5 × 10 -10 cm 2 /s. A single size R H cannot account for these values through the usual expressions (for stick boundary conditions 42 ), namely Θ ) k B T/( 4 / 3 )πηR 3 and D ) k B T/ 6πηR H , respectively. Thus, in order to rationalize these findings, we consider the diffusion coefficients for ellipsoids.…”

Section: Resultsmentioning

confidence: 99%

“…In addition, and in contrast to the most widely studied rigid-rod polymers (such as poly(γ-benzyl L-glutamate), hydroxypropylcellulose, denaturated DNA, and tobacco virus), poly(p-phenylene)-based polymers exhibit significant inherent optical polarizability anisotropy; this property can provide valuable information concerning the reorientational dynamics, 2 as well as the conformation of the macromolecules in solution. 3 Strong molecular anisotropy is necessary for the measurement of the above mentioned distinct physical properties of rigidrod polymers, by utilizing static and dynamic depolarized light scattering, which is an extremely sensitive probe of collective orientation fluctuations, and thus structural changes or transitions, even at a molecular scale. Of particular importance is the coupling of orientational to translational degrees of freedom, since it is related to the complicated interactions of these rigid macromolecules, especially at high concentrations.…”

Section: Introductionmentioning

confidence: 99%

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Association Dynamics in Solutions of Hairy-Rod Polymers

et al. 1997

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Photon correlation spectroscopy in the polarized (VV) and depolarized (VH) geometries has been utilized in order to investigate the aggregation dynamics in toluene solutions of a hairy-rod polymer, poly(p-phenylene) with flexible dodecyl side chains. Static and dynamic results from the dilute regime suggest that polymer molecules form small aggregates, typically trimers, even at very low concentrations. In the semidilute regime, results at different scattering wavevectors (q) in both the VV and VH geometry reveal two new relaxation processes (slow and ultra slow), in addition to the faster cooperative diffusion and reorientation of the trimers, respectively. They are attributed to the formation of large anisotropic clusters (of typical size 570 nm), with inherent crystallization, as revealed by X-ray scattering. After about 2 weeks the clusters settle under the action of gravity and form an opaque sediment. Assessment of the aggregation modes has been carried out by sediment redispersion. The first stages of this process, which exhibit multiple scattering, reveal a steeper than exponential relaxation, associated with a sedimentation-induced velocity gradient in a transient pseudonetwork formed by the dispersed clusters. In the single scattering limit, reached at later stages, the two relaxation processes are related to reorientation (slow) and number density fluctuation (ultraslow) of the anisotropic clusters. On the basis of simple thermodynamic arguments, we argue that rodlike macromolecules exhibit a larger activation energy barrier compared to their flexible counterparts, in agreement with the experimental evidence.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Association Dynamics in Solutions of Hairy-Rod Polymers

et al. 1997

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“…5 Another point of interest is the conformation of such a ladder-like macromolecule in solution. A number of studies [6][7][8][9][10] conducted on single-stranded stiff-chain polymers has demonstrated that these structure are characterized by rather low persistence lengths which are of the order of 5-15 nm. It is thus interesting to investigate the effect of the two-dimensional ribbon-type structure on the shape of the chains in solution.…”

Section: Introductionmentioning

confidence: 99%

Characterization of a Ladder Polymer by Small-Angle X-ray and Neutron Scattering

Hickl¹,

Ballauff²,

Scherf³

et al. 1997

Macromolecules

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An analysis of the conformation of a ribbon-type polymer in dilute solution is given. By combination of small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS) the effect of the finite dimensions of the repeating units can be assessed separately. It is thus possible to evaluate the experimental data to yield the form factor of the corresponding infinitely thin chain. This form factor could be evaluated for three samples differing in molecular weight and compared to the theoretical expression furnished by Kholodenko (Macromolecules 1993, 26, 4179). Good agreement for all molecular weights under consideration here could be achieved. The analysis shows that the ribbon-type polymers under consideration here are wormlike chains with a persistence length of 6.5 nm.

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“…These data are complemented by studies of electric field induced birefringence, the Kerr effect, in polymer solutions [30,31]. The magnetic analog in the Cotton-Mouton coefficient for magnetic birefringence provides access to the chain magnetic susceptibility anisotropy as C m = (∆n/cB 2 ) ∼ ∆χ∆γ, with ∆χ interpreted again in the context of the chain statistical element [32,33]. Precise measurements of magnetic birefringence and segmental susceptibility anisotropy of chains in the melt are challenging, and there is little reported data that can be used in the present context.…”

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Magnetic Alignment of Block Copolymer Microdomains by Intrinsic Chain Anisotropy

et al. 2015

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We examine the role of intrinsic chain susceptibility anisotropy in magnetic field directed selfassembly of a block copolymer using in situ X-ray scattering. Alignment of a lamellar mesophase is observed on cooling across the disorder-order transition with the resulting orientational order inversely proportional to the cooling rate. We discuss the origin of the susceptibility anisotropy, ∆χ, that drives alignment, and calculate its magnitude using coarse-grained molecular dynamics to sample conformations of surface-tethered chains, finding ∆χ ≈ 2 × 10 −8 . From field-dependent scattering data we estimate grains of ≈ 1.2 µm are present during alignment. These results demonstrate that intrinsic anisotropy is sufficient to support strong field-induced mesophase alignment and suggest a versatile strategy for field control of orientational order in block copolymers.

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Analysis of the Conformation of a Stiff-Chain Polyester by Measurements of the Magnetic Birefringence in Solution

Cited by 13 publications

References 18 publications

Association Dynamics in Solutions of Hairy-Rod Polymers

Association Dynamics in Solutions of Hairy-Rod Polymers

Characterization of a Ladder Polymer by Small-Angle X-ray and Neutron Scattering

Magnetic Alignment of Block Copolymer Microdomains by Intrinsic Chain Anisotropy

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