A systematic Monte Carlo study of self-assembling amphiphiles in solution

Abstract

In this paper, we present a systematic Monte Carlo study of the self-assembly of nonionic, amphiphilic, chainlike molecules in dilute solution. The focus is on the regime in which the molecules form relatively weakly segregated micelles, which are in equilibrium with small submicellar aggregates. We study the size and shape distributions of the aggregates, and the structure of the aggregates’ cores and surfaces. In some cases, spherical micelles, relatively large nonspherical micelles, and submicellar aggregates, all coexist. The size distributions of the spherical micelles are approximately Gaussian, while the nonspherical micelles contribute non-Gaussian tails at relatively large aggregation numbers. The simulation results are interpreted in terms of a simple theory of spherical micelles, and the size distributions are compared with its predictions. For the cases where the agreement is good, we combine the simulations and the theory to calculate the critical micelle concentration as functions of the chain lengths and solvent quality. In cases where there are nonspherical aggregates, the asphericity is quantified using the principal radii of gyration of the micelles, and the size distributions are compared with mean field predictions that account for both spherical and nonspherical aggregates.

Simulations of Tetra-Tethered Organic/Inorganic Nanocube−Polymer Assemblies

“…Furthermore, these aggregates (with the exception of M ) 2 and M ) 3) have asphericity parameter values less than the maximum value of 0.1 that characterizes spherical objects. 63 Thus, micelles containing up to approximately M ) 11 NBBs have a roughly spherical geometry. Snapshots of configurations reveal that the micelles consist of the cubes assembled in the core and the tethers pointing outward in accordance with the selective solvent condition.…”

Simulation study of intra- and intermicellar ordering in triblock-copolymer systems

“…The system was then allowed to equilibrate, using standard Monte Carlo moves for lattice chains. 30,32,39 We used five different kinds of moves to generate new configurations with the following typical weights: end segment kink flip ͑7%͒, middle segment kink flip ͑23%͒, reptation ͑40%͒, crankshaft move ͑25%͒, Brownian move ͑5%͒. These frequencies were changed slightly as a function of volume fraction to ensure optimal efficiency.…”

“…The majority of these papers deal with AB diblock chains, where the A block is hydrophilic ͑or, more generally, ''solvophilic''͒ while interactions between the solvent and the B block are less favorable. [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] Triblock copolymer-solvent systems ͑either ABA or BAB͒, have been the subject of a smaller number of simulation studies. [33][34][35][36] In the context of the present study, the simulations by Kim and Jo of an ABA system 35 are of direct relevance.…”

Molecular dynamics simulation of micelle formation in amphiphilic solution

“…Over the last decade, numerous computer simulations have been carried out in relation to self-assembly of amphiphilic solutions. The equilibrium size and shape distributions of self-assembled micelles were studied using Monte Carlo simulation by Nelson et al [4] and Kenward et al [5]. Molecular dynamics (MD) simulations of coarse-grained amphiphilic molecules in solution were performed by Goetz et al [6] in order to investigate the spontaneous self-assembly of amphiphilic molecules into bilayer membranes.…”