Fluctuation spectra in polymer nematics and Frank elastic constants: a coarse-grained modelling study

Gemünden, Patrick; Daoulas, Kostas Ch.

doi:10.1039/c4sm02075h

Cited by 28 publications

(32 citation statements)

References 76 publications

(226 reference statements)

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“…The phenomenological potential thus mimics the π-π interaction between conjugated subunits. Realistic values for ν and λ can be derived from the mechanical properties of the polymer, and are on the order of several k B T [72,73]. By tuning their relative strengths, it is furthermore possible to simulate amorphous, nematic and biaxial systems within the same framework.…”

Section: Chapter 2 Charge and Energy Transport Simulationsmentioning

confidence: 99%

The (Non-)Local Density of States of Electronic Excitations in Organic Semiconductors

Poelking

2018

Springer Theses

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The (Non-)Local Density of States of Electronic Excitations in Organic Semiconductors The rational design of organic semiconductors for optoelectronic devices relies on a detailed understanding of how their molecular and morphological structure condition the energetics and dynamics of charged and excitonic states. Investigating the role of molecular architecture, conformation, orientation and packing, this work reveals mechanisms that shape the spatially resolved densities of states in organic, small-molecular and polymeric heterostructures and mesophases. The underlying computational framework combines multiscale simulations of the material morphology at atomistic and coarse-grained resolution with a long-range-polarized embedding technique to resolve the electronic structure of the molecular solid. We show that longrange electrostatic interactions tie the energetics of microscopic states to the mesoscopic structure, with a qualitative and quantitative impact on charge-carrier level profiles across organic interfaces. The computational approach provides quantitative access to the charge-density-dependent opencircuit voltage of planar heterojunctions. The derived and experimentally verified relationships between molecular orientation, architecture, level profiles and open-circuit voltage rationalize the acceptor-donor-acceptor pattern for donor materials in high-performing solar cells. Proposing a pathway for barrier-less dissociation of charge transfer states, we highlight how mesoscale fields generate charge splitting and detrapping forces in systems with finite interface roughness. The associated design rules reflect the dominant role played by lowest-energy configurations at the interface. Acknowledgements 121 Die (nicht-)lokale Zustandsdichte elektronischer Anregungen in organischen Halbleitern List of Publications 123Bibliography 125 Chapter 1 Organic Electronics in a NutshellThe discovery of conductive polymers in the 1970s [1,2] -rewarded with the Nobel prize in chemistry in the year 2000 -and subsequent development of the first polymeric electronic devices in the 1980s [3-5] have marked the beginnings of a vast interdisciplinary research field referred to as organic electronics. Drawing from both polymeric and small-molecular semiconductors, organic thin-film transistors, solar cells, light-emitting diodes, photodetectors and sensors name just a few out of many applications that make use of the supreme chemical versatility and mechanical flexibility of the underlying "soft" molecular materials. Furthermore enabling low-temperature solution-based processing, printing and spray coating, organic electronics is set to complement the conventional silicon-based electronics in diverse waysadding functionality and improving sustainability. This introductory chapter will provide a short review of the materials and device physics, as well as of new trends and challenges that emerged in the field over the past decade. MaterialsOrganic semiconductors are molecular materials that exist at the interface between orga...

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Section: Chapter 2 Charge and Energy Transport Simulationsmentioning

confidence: 99%

The (Non-)Local Density of States of Electronic Excitations in Organic Semiconductors

Poelking

2018

Springer Theses

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“…Recently, Gemünden and Daoulas also observed the oscillatory behavior in their Monte Carlo study of uniaxial nematic polymer melts based on a discrete wormlike chain model combined with soft, anisotropic non-bonded potentials. 41 In physics, the oscillatory behaviors can be interpreted as the fact that the polymer chain behaves like an elastic string strongly stretching along the nematic director. In the large-Lk regime, Lk S ∥ for different L/a asymptotically approaches their individual steady value which is partially determined by the single chain partition function Q depending on field strength Γ IN as presented in Eq.…”

Section: B Structure Factor Of a Wormlike Chain In The Nematic Fieldmentioning

confidence: 99%

The study of the structure factor of a wormlike chain in an orientational external field

Jiang

Zhang

Miao

et al. 2015

The Journal of Chemical Physics

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A precise representation of the structure factor of a wormlike chain for the arbitrary chain flexibility in an orientational external field is obtained by virtue of the numerical solution to the modified diffusion equation satisfied by the Green's function. The model is built from a standard wormlike chain formalism in a continuous version which crossovers from the rigid-rod limit to the flexible chain limit and the Maier-Saupe interaction which describes the orientational effects from the nematic field. The behaviors of the structure factor in the distinct wavevector k regimes are numerically investigated as functions of chain flexibility and tilt angle between the directors of the nematic field and k. The radius of gyration extracted from the structure factor in small-k regime is also carefully analysed in both the directions along and perpendicular to the nematic axis. Our calculations exactly recover the prediction of the structure factor undergoing an orientational field in the rigid rod limit.

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“…In particular, the continuity constraints certainly apply also to coarse-grained bead-spring polymer models that are convenient for computational studies [10,11,18,25]. While the limit where hairpins are abundant cannot be explored in state-of-the-art microscopic simulations, we nevertheless expect that at least significant deviations from the vectorial constraint towards the predictions of the tensorial constraint will not evade detection in the numerical simulation studies that will follow this work.…”

Section: Introductionmentioning

confidence: 99%

Correlation functions of main-chain polymer nematics constrained by tensorial and vectorial conservation laws

Svenšek

Podgornik

2015

The Journal of Chemical Physics

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We present and analyze correlation functions of a main-chain polymer nematic in a continuum worm-like chain description for two types of constraints formalized by the tensorial and vectorial conservation laws, both originating in the microscopic chain integrity, i.e., the connectivity of the polymer chains. In particular, our aim is to identify the features of the correlation functions that are most susceptible to the differences between the two constraints. Besides the density and director autocorrelations in both the tensorial and vectorial cases, we calculate also the density-director correlation functions, the latter being a direct signature of the presence of a specific constraint. Its amplitude is connected to the strength of the constraint and is zero if none of the constraints are present, i.e., for a standard non-polymeric nematic. Generally, the correlation functions with the constraints differ substantially from the correlation functions in the non-polymeric case, if the constraints are strong which in practice requires long chains. Moreover, for the tensorial conservation law to be well distinguishable from the vectorial one, the chain persistence length should be much smaller than the total length of the chain, so that hairpins (chain backfolding) are numerous and the polar order is small.

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Fluctuation spectra in polymer nematics and Frank elastic constants: a coarse-grained modelling study

Cited by 28 publications

References 76 publications

The (Non-)Local Density of States of Electronic Excitations in Organic Semiconductors

The (Non-)Local Density of States of Electronic Excitations in Organic Semiconductors

The study of the structure factor of a wormlike chain in an orientational external field

Correlation functions of main-chain polymer nematics constrained by tensorial and vectorial conservation laws

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