PolyWhips: Directional Particle Transport by Gradient‐Directed Growth and Stiffening of Supramolecular Assemblies

Abstract

Growth of rigid rods occurs via supramolecular assembly of a nonconjugated π-donor π-acceptor monomer and is triggered by a NaCl gradient. The mechanical stiffness of this material is controlled by the local salt concentration and is ion specific. The continuous and well-controlled growth process is exploited to power the directional transport of sub-millimeter polymer particles.

Under Diffusion Control: from Structuring Matter to Directional Motion

“…The continuous and directional material growth along a chemical gradient can itself work as an actuator and, for instance, be employed to power the directional transport of objects. We recently reported the self‐assembly of thin and flat millimeter‐long flexible ribbons in water through supramolecular polymerization of an organic salt CAMCl 2 ( Figure a) . The fibers form through intermolecular donor‐acceptor π‐stacking interactions oriented along the main growth axis and they are further stabilized along the minor axes by electrostatic and hydrogen bonding interactions with chloride ions.…”

“…The same particle (blue‐marked) is further shifted by the stiffening of a second fiber (blue). Panels (a)–(d) reproduced with permission . Copyright 2017, Wiley‐VCH.…”

Stimulated Transitions of Directed Nonequilibrium Self‐Assemblies

“…biomedical), where on-demand gelation occurs without chemical modification. Like a spark, [35] a marginal trigger can ignite huge changes in the colloidal system along the thermodynamic landscape toward the global free energy minimum.…”

Light-responsive self-assembly towards supramolecular machines

“…84 While a number of synthetic and responsive tubules have been reported in the last decade, [53][54][55][85][86][87] only a very limited number of these systems have demonstrated the generation macroscopic work. 88,89 As most of them operate in solution, the main challenge to transfer work from molecular to macroscopic levels lies in overcoming viscous forces and the Brownian storm. 16,17 Possible approaches to harness, combine and transfer small work across increasing length scales include the integration of dynamic molecules into polymer networks, 90 liquid crystals, 91,92 supramolecular systems, 88,89 and the interfacing of these small molecules with surfaces.…”

“…88,89 As most of them operate in solution, the main challenge to transfer work from molecular to macroscopic levels lies in overcoming viscous forces and the Brownian storm. 16,17 Possible approaches to harness, combine and transfer small work across increasing length scales include the integration of dynamic molecules into polymer networks, 90 liquid crystals, 91,92 supramolecular systems, 88,89 and the interfacing of these small molecules with surfaces. 93 Prolonging systems out of equilibrium continuously require maintaining dynamic changes of molecular states, while avoiding accumulation of chemical waste products.…”