Volume 144, 2010

Lyotropic self-assembly mechanism of T-shaped polyphilic molecules

Abstract

We present coarse-grained molecular dynamics simulations of mixtures of a model of T-shaped polyphilic bolaamphiphile liquid crystal molecules with a solvent. Based on the premise that the most important features of the liquid structure stem from the balance between the close range repulsions and the strong directional forces typical of hydrogen bonding and association, we have employed a coarse-graining approach that simplifies and minimises the attractions present in the system. The model consists of six fused rigid spheres, where the two end spheres have a significant attraction amongst themselves while the rest are repulsive in nature. A weakly self-attracting lateral chain consisting of fully flexible tangently bonded spheres is attached to one of the central spheres. Thus, the T-shaped molecule is composed of three mutually repulsive segments which allow the pure system to self-assemble into a liquid crystalline honeycomb columnar phase. The stability of the columnar phase is probed by the sequential addition of a solvent that has affinity with only one of the segments of the molecule. Our coarse-graining technique allows us to observe dynamically not only the 1st level nanoscale segregation but also the 2nd level reorganization which leads to the formation of replicated periodic structures. It is seen how this latter structuring takes place at times which are an order of magnitude longer than the former, and by itself explains the practical limitations of studying self-assembly with more detailed atomistic models. Mobility coefficients (related to diffusion constants), order parameters and direct visualization of the configurations are used to present a phase diagram for the solvated system in the whole concentration range. At low solvent density, the solvent solvates the honeycomb structure, but does not alter the order significantly. At modest volume fractions of solvent, the solvent mostly segregates into a distinct phase, while the T-shaped molecules retain a phase with columnar structure. At very large solvent concentrations, the T-shaped molecules form structureless aggregates, while at the infinite dilution limit present themselves as dimers and monomers.

Article information

Article type
Paper
Submitted
26 Jan 2009
Accepted
20 Feb 2009
First published
10 Aug 2009

Faraday Discuss., 2010,144, 187-202

Lyotropic self-assembly mechanism of T-shaped polyphilic molecules

A. J. Crane and E. A. Müller, Faraday Discuss., 2010, 144, 187 DOI: 10.1039/B901601E

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements