Communication: Microphase equilibrium and assembly dynamics

Abstract

Despite many attempts, ordered equilibrium microphases have yet to be obtained in experimental colloidal suspensions. The recent computation of the equilibrium phase diagram of a microscopic, particle-based microphase former (Zhuang et al., Phys. Rev. Lett. 116, 098301 (2016)) has nonetheless found such mesoscale assemblies to be thermodynamically stable. Here, we consider their equilibrium and assembly dynamics. At intermediate densities above the order-disorder transition, we identify four different dynamical regimes and the structural changes that underlie the dynamical crossovers from one disordered regime to the next. Below the order-disorder transition, we also find that periodic lamellae are the most dynamically accessible of the periodic microphases. Our analysis thus offers a comprehensive view of the disordered microphase dynamics and a route to the assembly of periodic microphases in a putative well-controlled, experimental system.

Generating dense packings of hard spheres by soft interaction design

“…As discussed in the Introduction, the Gibbs-Boltzmann uniform measure over hard sphere configurations can be biased by adding an arbitrary interaction potential to the hard core. From a physical point of view, even a microscopically small bias in the hard-core potential is generally known to induce large-scale non-trivial phase behaviours, such as water-like anomalies and multiple liquid phases [53][54][55][56], reentrancy and multiple glass phases [57][58][59][60][61][62], and instabilities towards disordered or periodic microphases [63][64][65].…”

Clustering and assembly dynamics of a one-dimensional microphase former

“…In CHMC, for instance, a cluster trial displacement is conducted with uniform probability within the space contained by its two nearest neighbors and then accepted using the criterion given in Eq. (16). For the purpose of comparing algorithmic dynamics, one attempted cluster displacement of n particles is deemed equivalent to n attempted MMC or HMC displacements.…”

“…Numeri-cal simulations display remarkably slow equilibrium and out-of-equilibrium dynamics as well [12,[23][24][25][26]. In addition, a recent numerical study suggests that the dynamics of disordered microphases is itself remarkably rich [16]. Dynamical crossovers were found to accompany the clustering and percolation of both particles and voids.…”

“…Although similar interactions in diblock copolymers result in the robust formation of both periodic and disordered microphases [2][3][4], only the latter have thus far been observed in colloidal suspensions [5][6][7][8][9]. From a theoretical viewpoint the situation is better controlled, thanks to various theoretical and methodological advances [1,[10][11][12][13][14][15][16]. But even then the formation of disordered microphases remains only partially understood.…”

“…Beyond this point a repulsive ramp of strength ξ decays linearly up to κσ. This particular potential form has been extensively studied in three dimensions [14][15][16][34][35][36], and a closely related form was also considered in two dimensions [37]. This interaction potential is known to display the same qualitative behavior as other SALR potentials, including those with a Yukawa repulsive form [38][39][40][41][42].…”