Sharing of Strain Between Nanofiber Forests and Liquid Crystals Leads to Programmable Responses to Electric Fields

Abstract

Fibers embedded in soft matrices are widely encountered in biological systems, with the fibers providing mechanical reinforcement or encoding of instructions for shape changes. Here, the mechanical coupling of end-attached polymeric nanofiber forests and liquid crystals (LCs) is explored, where the nanofibers are templated into prescribed shapes by the chemical vapor polymerization of paracyclophane-based monomers in supported films of the LCs. It is shown that the elastic energies of the nanofibers and LCs are comparable in magnitude, leading to reversible straining of nanofibers via the application of an electric field to the LC. This coupling is shown to encode complex electrooptical responses in the LC (e.g., optical vortices), thus illustrating how LC-templated nanofiber forests offer the basis of fresh approaches for programming configurational changes in soft materials.

Chemical and Topological Control of Surfaces Using Functional Parylene Coatings

“…Advancing the fundamental understanding on nanofiber-templates, it is critical to explore how nanofibers share elastic strain with LC template under an electric field. 90 One of the interesting properties of LC is dielectric property, which causes changes in molecular orientation when an electric field is applied. From morphological modulation by inherent LC phases in their previous report, they demonstrated the synthesis of bent nanofiber arrays that exhibit programmed response under electric application, thereby stretching in z -direction by the elastic strain from the LC template ( Figure 10 ).…”

Stimuli-Responsive Materials from Liquid Crystals

“…In contrast to the colloids dispersed in isotropic liquids (e.g., water), the colloids in LCs induce elastic deformations and are accompanied by topological defects to satisfy the geometrical theorem. 23,31,69 For example, a colloid with planar anchoring forms a director profile with quadrupolar symmetry and two point defects (called boojums) at the poles of the colloidal surface (Figure 5a). 29,31 Under the homeotropic anchoring condition, the colloid generates either a dipolar director deformation with one point defect (hyperbolic hedgehog, Figure 5b) 23,29 or a quadrupolar deformation with a disclination loop at the colloidal equator (Saturn ring, Figure 5c).…”

“…As described in Section ., the introduction of immiscible guest inclusions of R > ξ within an LC host gives rise to the rearrangement of neighboring LCs, which in turn significantly affect the behavior of the guests in order to minimize the cost of the elastic free energy . To provide insights into this context, previous studies have extensively investigated spherical colloids dispersed in LCs.…”

“…In related studies, the shape of templated nanofibers is shown to be reconfigurable by stimuli-induced director reorientation in the LC template. As shown in Figure e, an array of bent nanofibers (blue solid lines in the schematic of Figure e) can be templated from an LC film with a radial director configuration (when viewed from above, black dotted lines in the schematic of Figure e) characterized by crossed-extinction lines under a polarizing optical microscope (dark brushes denoted by white dotted lines in the micrograph of Figure g­(i)) . When E is applied across the film (along the z -axis) of an LC with a positive dielectric anisotropy (Δ ε > 0), the reorientation of LCs into the homeotropic configuration is shown to drive the reshaping of the nanofibers along the rearranged director profile (Figure f).…”

Bent and Twisted: Synthesis of an Alkoxy-Substituted (1,5)Naphthalene-paracyclophanediene

“…[2.2]­Paracyclophane (pCp) 1 (Figure ), the prototypical cyclophane, with para -bridged benzene moieties as decks and ethylenes as bridges, has long been investigated, and its chemistry is well-understood, enabling access to a variety of ring substitutions (especially on the decks) . Many applications have been found for pCp such as ligands for chiral catalysts used in stereoselective synthesis, , chiroptics and optoelectronics, ,− pharmaceuticals, , and materials science. ,− The much more strained structural analog of 1 is [2.2]­paracyclophane-1,9-diene (pCpd) 2 , which has ethynylene bridges instead of ethylene bridges, bringing the benzene decks closer together than in the parent compound 1 resulting in more-bent benzenes . While altering the aromatic decks of pCp is common, dienes like pCpd have seen much less structural diversity due to the harsher reaction conditions required for their synthesis …”