Synthesis and characterization of rigid‐chain polyacenaphthylene

Chen, Chi-Yu; Piirma, Irja

doi:10.1002/polc.5070650107

Cited by 10 publications

(3 citation statements)

References 10 publications

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“…These are problems yet to be solved. One already tackled is the equilibrium problem for the elastic energy density in (26) on a circular toroidal shell [18,49,50] (see also [62,63] for parallel treatments with only intrinsic, distortional energies, and [28] for an interesting application to toroidal shells of a promising Onsager excluded volume theory for wormlike polymer chains elaborated by Chen [64]). But, unfortunately, this problem has only been solved for the singular case where k 2 = k 3 , which by (27) implies that the fossil preferred direction coincides with the direction of minimal absolute curvature (that is, with either parallles or meridians).…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Bistable curvature potential at hyperbolic points of nematic shells

Sonnet

Virga

2017

Soft Matter

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Nematic shells are colloidal particles coated with nematic liquid crystal molecules which may freely glide and rotate on the colloid's surface while keeping their long axis on the local tangent plane. We describe the nematic order on a shell by a unit director field on an orientable surface. Equilibrium fields can then be found by minimising the elastic energy, which in general is a function of the surface gradient of the director field. We learn how to extract systematically out of this energy a fossil component, related only to the surface and its curvatures, which expresses a curvature potential for the molecular torque. At hyperbolic points on the colloid's surface, and only there, the alignment preferred by the curvature potential may fail to be a direction of principal curvature. There the fossil energy becomes bistable.

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Section: Conclusion and Discussionmentioning

confidence: 99%

Bistable curvature potential at hyperbolic points of nematic shells

Sonnet

Virga

2017

Soft Matter

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“…The algebraic third term takes into account the fact that both ds-DNA cannot intersect. This repulsion is accounted for in an effective way, with K = c/ 1/3 p where c is a dimensionless constant close to 1 [19,26,[28][29][30]. We set c = 1 in this work.…”

Section: The Free Energy Functionalmentioning

confidence: 99%

Energy required to pinch a DNA plectoneme

2018

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DNA supercoiling plays an important role from a biological point of view. One of its consequences at the supramolecular level is the formation of DNA superhelices named plectonemes. Normally separated by a distance on the order of 10 nm, the two opposite double strands of a DNA plectoneme must be brought closer if a protein or protein complex implicated in genetic regulation is to be bound simultaneously to both strands, as if the plectoneme was locally pinched. We propose an analytic calculation of the energetic barrier, of elastic nature, required to bring closer the two loci situated on the opposed double strands. We examine how this energy barrier scales with the DNA supercoiling. For physically relevant values of elastic parameters and of supercoiling density, we show that the energy barrier is in the k_{B}T range under physiological conditions, thus demonstrating that the limiting step to loci encounter is more likely the preceding plectoneme slithering bringing the two loci side by side.

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“…Remark. When melt flow stops the flow-induced stresses start to relax, which leads that the final stress distributions are different from those at the end of filling process due to different cooling effects [32,33]. The stress relaxation mainly depends on melt temperature.…”

Section: The Variational Problem Changes Tomentioning

confidence: 99%

Numerical simulation for flow‐induced stress in injection/compression molding

Cao

Min

Zhang

et al. 2015

Polymer Engineering & Sci

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Flow‐induced stress in compression stage is complex because compression flow combines both shear flow and extensional flow characters and involves the boundary change in melt front and compressing directions. To describe this kind of flow effectively, the theoretical model was established in terms of three‐dimensional compressible and viscoelastic fluid, and the material derivative which includes mesh moving velocity was introduced to modify the convective terms in governing and constitutive equations based on Arbitrary Lagrangian Eulerian description. The corresponding variational equations were derived via Gauss formula and the finite element method was used to discretize the flow variables with mixed elements. In order to decouple the interdependence of velocity, stress, and temperature, a new approach involves twofold iterations was proposed to solve nonlinear flow problem. A new mesh updating scheme was presented to keep consistent with compressed regions. Numerical results indicate the compression can reduce the flow‐induced stress significantly compared to conventional injection molding, increase compressing velocity enlarges flow‐induced stress, and high temperature decreases flow‐induced stress. The proposed method was verified by photoelastic pictures and measured pressures and temperatures during molding. POLYM. ENG. SCI., 56:287–298, 2016. © 2015 Society of Plastics Engineers

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Synthesis and characterization of rigid‐chain polyacenaphthylene

Cited by 10 publications

References 10 publications

Bistable curvature potential at hyperbolic points of nematic shells

Bistable curvature potential at hyperbolic points of nematic shells

Energy required to pinch a DNA plectoneme

Numerical simulation for flow‐induced stress in injection/compression molding

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