Argonne National Laboratory

Soft Matter

Di-block copolymer templates for directed self-assembly and nano-manufacturing

Di-block copolymer templates for directed self-assembly and nano-manufacturing

Soft matter research at Argonne focuses on the fundamental aspects of out-of-equilibrium and directed self-assembly of highly compliant materials for emerging energy applications and nano-fabrication. Our research paves the way for the discovery of tailored self-assembled materials and structures that may adopt useful ordered structures spontaneously, provide selective conductivity, regulate porosity or strength, control water permeability or air resistance, or manipulate optical and electrical properties.

Soft matter research combines experiment, theory, and simulations. It emphasizes strong cross-disciplinary ties with other research programs at Argonne, the Institute for Molecular Engineering at the University of Chicago, and leading soft matter groups in the United States and worldwide. This theme makes active use of Argonne’s scientific user facilities, including the Center for Nanoscale Materials, the Advanced Photon Source, and the Argonne Leadership Computing Facility.

Our long-term goals are to develop a fundamental understanding of equilibrium and out-of-equilibrium self-assembly in synthetic and bio-inspired systems, as it relates to DOE missions in materials science and engineering. We explore new approaches to synthesis and discovery of a broad range of self-assembling systems, including synthetic and bio-inspired materials, and create functional 2D and 3D self-assembled tunable structures by design. In much of our work, the assembly of distinct building blocks — such as biopolymers, block polymers, functionalized colloidal particles, or liquid crystals — is directed through the application of external fields. Some aspects of our research include dynamic active matter formed by microswimmers suspended in structured liquids (liquid crystals), or colloidal particles energized by an external field. For all these complex out-of-equilibrium systems, we develop predictive theoretical multi-scale models, and state-of-the-art software designed for leadership class computers.

Projects

Dynamics of Active Self-Assembled Materials (A. Snezhko, A. Sokolov, A. Glatz)

The program integrates experiments, theory, and simulations and focuses on the fundamental aspects of out-of-equilibrium dynamics and self-assembly of bio-inspired materials for emerging applications. In particular, it investigates the structure and dynamics of active (i.e. actively consuming energy from the environment) self-assembled materials, such as colloids energized by external fields or suspensions of microswimmers, for the purpose of control, prediction, and design of novel bio-inspired materials.

Our experimental activities are focused on, but not limited, to two major subjects: control of electromagnetic self-assembly and manipulation of colloidal particles, and collective behavior of active micro-swimmer suspensions. The main difference between these systems is the way energy is injected: colloids are energized by an external applied electric or magnetic field whereas micro-swimmers are self-propelled. We have chosen these seemingly different model systems for the following reasons: they are relatively simple but practically relevant, with primary physical/biological interaction mechanisms that are well characterized, and amenable to in-depth investigation using methods of non-equilibrium statistical physics.

The self-assembly in these systems is obviously governed by fundamentally different mechanisms; however, a mathematical description treating individual constituents of these complex systems as some kind of “grains” or “macro-atoms” with complex interactions helps to unify them. The program is highly interdisciplinary and correlates the dynamics of both synthetic and live agents to develop understanding of the fundamental rules governing the emergence of self-assembly and organization away from equilibrium.

Directed assembly of polymeric materials (P. Nealey, J. de Pablo, M. Tirrell)

The directed assembly of block copolymers has been shown to provide a promising approach towards the commercial nanofabrication of devices with critical dimensions below 10 nm. The morphologies produced through spontaneous self-assembly generally lack the long-range order and the level of perfection that are required for emerging technologies. Through the judicious application of external fields, our research has shown that it is possible to direct the assembly of block copolymers and composites into programmable structures that meet stringent criteria.

In our research, we rely on the use of surface chemical and topographic nanoscale patterns and programmable solvent-assisted assembly processes to develop a fundamental understanding of directed assembly at the smallest of length scales. This research involves the tight integration of experiment, theory and simulation to investigate molecular assembly phenomena at the forefront of molecular engineering. While the research performed in this project has applications in a wide range of areas, recent efforts have focused on controlling the assembly of charged polymers for applications in energy harvesting and storage.

We have developed strong collaborations worldwide and maintain close ties to world-leading research facilities and industrial partners, including the Institute for Molecular Engineering at the University of Chicago. Research in this area relies extensively on Argonne facilities, including the use of advanced X-ray scattering techniques and sophisticated computing to characterize polymer assembly behavior and formation of quasi-equilibrium structures.

Charge driven assembly of polymeric materials (M. Tirrell, W. Chen, J. de Pablo)

Most polymeric materials encountered in nature are charged. Most applications of polymeric materials in the coatings, biomedical, or food industries are used in aqueous solutions and are also charged. In spite of their importance, charged polymeric materials are poorly understood. Under a particular set of circumstances, polymers of opposite charge in solution can phase separate into what is known as a complex coacervate. Complex coacervates exhibit a medium that is rich in water, ionic and polymeric species. As such, it offers intriguing opportunities for innovative chemical and separation processes that are just beginning to be conceived. This project seeks to develop a fundamental understanding of charge driven complexation in polymeric materials, including complex coacervation, and to exploit electrostatic interactions to discover and exploit new forms of soft matter assembly for materials design.