Self-assembly of Pseudo-Dipolar Nanoparticles at Low Densities and Strong Coupling

BRITO, MARIANO E.; CARIGNANO, MARCELO A.; MARCONI, VERÓNICA I.

Scientific Reports

Springer Nature Limited

Lugar: Londres ; Año: 2020 vol. 10 p. 1 - 13

Nanocolloids having directional interactions are highly relevant for designing new self-assembledmaterials easy to control. In this article we report stochastic dynamics simulations of finite-size pseudo-dipolar colloids immersed in an implicit dielectric solvent using a realistic continuous description ofthe quasi-hard coulombic interaction. We investigate structural and dynamical properties near the low-temperature and highly-diluted limits. this system self-assembles in a rich variety of string-like configurations, depicting three clearly distinguishable regimes with decreasing temperature:fluid, composed by isolated colloids; string-fluid, a gas of short string-like clusters; and string-gel,a percolated network. By structural characterization using radial distribution functions and cluster properties, we calculate the state diagram, verifying the presence of string-fluid regime. Regarding the string-gel regime, we show that the antiparallel alignment of the network chains arises as a novel self- assembly mechanism when the characteristic interaction energy exceeds the thermal energy in two orders of magnitude, ud/kBT ≈ 100. This is associated to relevant structural modifications in the network connectivity and porosity. Furthermore, our results give insights about the dynamically-arrested nature of the string-gel regime, where we show that the slow relaxation takes place in minuscule energy steps that reflect local rearrangements of the network.