Demixing by a Nematic Mean Field: Coarse-Grained Simulations of Liquid Crystalline Polymers

Abstract

Liquid crystalline polymers exhibit a particular richness of behaviors that stems from their rigidity and their macromolecular nature. On the one hand, the orientational interaction between liquid-crystalline motifs promotes their alignment, thereby leading to the emergence of nematic phases. On the other hand, the large number of configurations associated with polymer chains favors formation of isotropic phases, with chain stiffness becoming the factor that tips the balance. In this work, a soft coarse-grained model is introduced to explore the interplay of chain stiffness, molecular weight and orientational coupling, and their role on the isotropic-nematic transition in homopolymer melts. We also study the structure of polymer mixtures composed of stiff and flexible polymeric molecules. We consider the effects of blend composition, persistence length, molecular weight and orientational coupling strength on the melt structure at the nano-and mesoscopic levels. Conditions are found where the systems separate into two phases, one isotropic and the other nematic. We confirm the existence of non-equilibrium states that exhibit sought-after percolating nematic domains, which are of interest for applications in organic photovoltaic and electronic devices.

Developments in Polymer Theory and Simulation

“…Conditions were found where the systems separate into two phases, one isotropic and the other nematic. Ramirez-Hernandez et al [8], furthermore, confirm the existence of non-equilibrium states that exhibit sought-after percolating nematic domains, which are of interest for applications in organic photovoltaic and electronic devices.…”

“…Liquid crystalline polymers exhibit a particular richness of behavior that stems from their rigidity and their macromolecular nature. A soft, coarse-grained model has been introduced by Ramirez-Hernandez et al [8] to explore the interplay of chain stiffness, molecular weight, and orientational coupling, and their roles in the isotropic-nematic transition in homopolymer melts. For this system the orientational coupling rather than excluded volume can be considered as the driving force.…”

Photoactive Blend Morphology Engineering through Systematically Tuning Aggregation in All‐Polymer Solar Cells

“…The morphologies found in the simulations are nonequilibrium due to the different constraints arising from blending molecules with different degrees of flexibility; similar trends have been observed in Monte Carlo simulations on liquid crystalline polymers using a coarse-grained model. [82] Finer bundles of P(NDI2OD-T2) give rise to smaller polymer domains and larger donor/acceptor interfacial areas.…”

Density–Nematic Coupling in Isotropic Linear Polymers: Acoustic and Osmotic Birefringence

“…To confirm the existence of the tensorial constraint, we employ Monte Carlo (MC) simulations of discrete worm‐like chains (WLC), and compare the simulated correlation functions of static long wavelength fluctuations with Equations to following from the continuum theory. Validating the predictions of the macroscopic theory with molecular‐level computer simulations of polymers is challenging, since such simulations must i) address the long‐wavelength limit and ii) realize different regimes of chain backfolding (hairpin formation). Thus, it is essential to consider large systems of preferably long polymer chains, where the sampling must include statistically independent (decorrelated) configurations.…”