Block Copolymer Assemblies Beneath the Surface: Modeling Intra-Domain Textures and Chirality Transfer to Mesodomains
Greg Grason (U. of Massachussets, Amherst)
This seminar replaces that of Thierry Bizebard, was rescheduled to May 31st. Please note the more soft matter focus.
Self-assembled block copolymer (BCP) melts are a chemically-versatile platform for generating a rich spectrum of periodically-ordered nanostructures of various morphologies, from arrays of layers and columns to cubic arrays of spheres and bicontinuous networks. They are also a model system for understanding processes and properties of self-assemblies, more broadly. Decades of study of BCP assembly have uncovered the principles that connect molecular BCP structure to the translational order of the (scalar) composition profiles in the ordered states. In this talk, I will describe recent efforts to understand the generic, yet poorly known, patterns of orientational ordering of constituent chain segments that underlie the otherwise well-known “standard” BCP morphologies1. From generic properties of the random-walk statistics in BCPs, we show that the direction and degree of alignment of segments varies non-trivially from place-to-place in self-organized domains, and from one morphology to another, leading to new opportunities to manipulate and harness the physics sub-domain textures. Specifically, I will discuss how our efforts to model chiral BCPs2 which have been observed to transfer handedness of chain chemistry to the chiral symmetry of mesodomain shapes that are not formed in achiral BCPs. Our generalized orientational self-consistent field (oSCF) theory framework3 shows that the thermodynamic drive for twisted, or cholesteric, packings of segments of chiral blocks stabilizes observed helical cylinder morphologies, and suggests new mechanisms for driving formation as of yet, unobserved mesochiral domain symmetries4.
- I. Prasad, Y. Seo, L. Hall and G. M. Grason arxiv.org/1612.07994 (2016)
- G. M. Grason ACS MacroLetters 4, 526 (2015). Front Cover Story
- W. Zhao, T. Russell and G. M. Grason, J. Chem. Phys. 137, 104911 (2012).
- W. Zhao, T. Russell and G. M. Grason, Phys. Rev. Lett. 110, 058301 (2013).