Self-assembly of polymers, block copolymers and supramolecular systems

In biological systems, the self-assembly of soft materials like amino acids is responsible for the organization of complex structures from proteins to cells. Mimicking the self-assembly rules seen in biology using synthetic systems may be a powerful way to design new templates for computer chips or other applications. We are interested in using simple simulation protocols to understand the self-assembly and phase behavior of polymeric and supramolecular systems for a variety of applications. We are particularly interested in:

  1. Self-assembly of disk-coil systems

    Inspired by the molecular architecture of chlorophyll, the group has investigated the self-assembly of polymeric disk-coil systems for use in organic photovoltaics. Biological chlorosomes achieve a nearly perfect 99% light harvesting efficiency, much greater than the ~6% conversion efficiency achieved by other polymer-based solar cells. The group used novel Monte Carlo simulations to discover the phase behavior of disk-coil molecules; future work will be of much in use in emerging energy applications.

  2. Phase behavior of mixed polymer brushes

    Mixed polymer brushes consist of multiple polymer species, often of distinct molecular weights, that are grafted to a surface at a sufficiently high density to induce elongation of the chains away from the surface and into the surrounding solvent. The group has investigated the phase separation of polymer brushes on different substrates as a function of the enthalpic and entropic interactions between different polymer species. This work may lead to novel nanotemplating applications.

  3. Self-consistent field theory simulations of block copolymers

    In conjunction with experimental collaborators, the group has used self-consistent field theory to predict the morphologies of block copolymers when influenced by a template. This work has applications in the templated assembly of block copolymers for nanolithography.

Selected publications

Lateral phase separation of mixed polymer brushes physisorbed on planar substrates
R. C. Van Lehn and A. Alexander-Katz
J. Chem. Phys. 135, 141106 (2011).

Phase behavior of disk-coil macromolecules
Y. Kim, E. Ha, A. Alexander-Katz
Macromolecules 44(17), 7016-7025 (2011).

Phase behavior of symmetric disk-coil macromolecules with stacking interactions
Y. Kim, A. Alexander-Katz
J. Chem. Phys. 135, 024902 (2011).

Enhancing the potential of block copolymer lithography with polymer self-consistent field theory simulations
R.A. Mickiewicz, J.K.W. Yang, A.F. Hannon, Y.S. Jung, A. Alexander-Katz, K.K. Berggren, C.A. Ross
Macromolecules 43, 8290-8295 (2010).

Using a model based on Flory-Huggins and Alexander-de Gennes theory, we can predict the lateral phase separation of mixed polymer brushes.

A simple disk-coil model of conductive polymers leads to a vast array of ordered structures, captured in this three-dimensional phase diagram.

Department of Materials Science and Engineering MIT