Assembly of Helical Structures in Systems with Competing Interactions under Cylindrical Confinement

Abstract

The behavior under confinement of nanoparticles interacting with the short-range attraction and long-range repulsion potential is studied by means of Monte Carlo simulations in the grand canonical ensemble. The study is performed at thermodynamic conditions at which a hexagonal cylindrical phase is the most stable phase in bulk. In these conditions, cylindrical confinement promotes the formation of helical structures whose morphology depends upon both the pore radius and boundary conditions. As the pore radius increases, the fluid undergoes a series of structural transitions going from single to multiple intertwined helices to concentric helical structures. When the pore ends are closed by planar walls, ring and toroidal clusters are formed next to these walls. Dependent upon the cylinder length, molecules away from the pore edges can either keep growing into ring and toroidal aggregates or arrange into helical structures. It is demonstrated that the system behaves in cylindrical confinement in the same way as the block copolymer systems. Such behavior has not been observed for the colloidal systems in cylindrical confinement with only repulsive interactions.

The influence of confinement on the structure of colloidal systems with competing interactions

“…16,17 In our former studies we have shown that pores with circular cross-section induce the formation of helical structures. 11 It has to be stressed that we have never observed structures composed of straight cylindrical clusters (with the exception of a single cylindrical cluster in the center of the pore for some selected pore diameters).…”

“…In addition, we found that the length of the channel plays an important role as the helical structures have a preferred pitch about 8.0s. 11 We need to keep the length of the channels as multiples of the optimal pitch to guarantee the proper formation of helical structures when the geometry of the channels allows it. Thus, the channel length was set to L z = 24s for all the studied geometries in this work.…”

“…Different types of confinement may be used to promote the formation of structures beyond the well-known ordered phases in bulk. 10,11 The process of selfassembling may be highly useful for development of new technologies with applications in different fields like drug delivery, bioelectronics and catalysis. 12,13 In particular, colloidal particles confined in channels of different geometries are used to build wave-guide devices with applications in sensing 14,15 In this article we investigate, by means of Monte Carlo simulations in the grand canonical ensemble, how the structures stable in bulk can be altered by confinement.…”

A New Conceptual ‘Cylinder’ Framework for Sustainable Bioeconomy Systems and Their Actors

“…Does the cylinder confinement enable systems to evolve in a sinusoidal-like manner? Yes, one can learn from fluid dynamics that under specific thermodynamic conditions and considering interacting (nano-)particles with short-range attraction and long-range repulsion, cylindrical confinement promotes the formation of helical structures (Jung & Ha, 2019 ; Serna et al, 2019 ). Their morphology depends on pore size and boundary conditions (Fig.…”

“…

Fig. 2 Helical structures; a A single, double, and triple concentric helix in the cylinder confinement (modified from Serna et al, 2019 ); b DNA c Alpha-helix with top and side views; d spiral structures in nature; e spiral structures in food and non-food products; f two propagating sinusoidal curves form a helix; g predator–prey populations in time; h helicoid structure. Source: Fig.

…”