Reference : Dynamic tuning of the director field in liquid crystal shells using block copolymers
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Physics
Physics and Materials Science
Dynamic tuning of the director field in liquid crystal shells using block copolymers
Noh, Junghyun [> >]
Wang, Yiwei [> >]
Liang, Hsin-Ling [> >]
Jampani, Venkata Subba Rao [> >]
Majumdar, Apala [> >]
Lagerwall, Jan mailto [University of Luxembourg > Faculty of Science, Technology and Medicine (FSTM) > Department of Physics and Materials Science (DPHYMS)]
Physical Review Research
American Physical Society (APS)
College Park
[en] Topological defects ; Liquid crystal shells ; Confinement ; surfactants ; Boundary conditions
[en] When an orientationally ordered system, like a nematic liquid crystal (LC), is confined on a self-closing spherical shell, topological constraints arise with intriguing consequences that depend critically on how the LC is aligned in the shell. We demonstrate reversible dynamic tuning of the alignment, and thereby the topology, of nematic LC shells stabilized by the nonionic amphiphilic block copolymer Pluronic F127. Deep in the nematic phase, the director (the average molecule orientation) is tangential to the interface, but upon approaching the temperature TNI of the nematic-isotropic transition, the director realigns to normal. We link this to a delicate interplay between an interfacial tension that is nearly independent of director orientation, and the configuration-dependent elastic deformation energy of an LC confined in a shell. The process is primarily triggered by the heating-induced reduction of the nematic order parameter, hence realignment temperatures differ by several tens of degrees between LCs with high and low TNI, respectively. The temperature of realignment is always lower on the positive-curved shell outside than at the negative-curved inside, yielding a complex topological reconfiguration on heating. Complementing experimental investigations with mathematical modeling and computer simulations, we identify and investigate three different trajectories, distinguished by their configurations of topological defects in the initial tangential-aligned shell. Our results uncover a new aspect of the complex response of LCs to curved confinement, demonstrating that the order of the LC itself can influence the alignment and thereby the topology of the system. They also reveal the potential of amphiphilic block copolymer stabilizers for enabling continuous tunability of LC shell configuration, opening doors for in-depth studies of topological dynamics as well as novel applications in, e.g., sensing and programed soft actuators.
European Commission - EC ; Fonds National de la Recherche - FnR
Researchers ; Professionals
H2020 ; 648763 - INTERACT - Intelligent Non-woven Textiles and Elastomeric Responsive materials by Advancing liquid Crystal Technology
FnR ; FNR11703329 > Venkata Subba Rao Jampani > TRENDSETTER > Template-free Reconfigurable Nematic Defect-arrays For Designing Self-organisable Topological Three-dimensional Elastomer Responsive-rafts > 15/11/2017 > 14/10/2020 > 2017

File(s) associated to this reference

Fulltext file(s):

Open access
Noh et al 2020 30.pdfPublisher postprint7.66 MBView/Open

Bookmark and Share SFX Query

All documents in ORBilu are protected by a user license.