(14c) Designing Polymeric & Soft Material Systems Via Inverse Computational Methodologies

Research Interests:

My research focuses on the design of polymeric and soft material systems where a new material can be designed for a specific application in silico with new properties not possible from conventional combinatorial experime­ntation. Computational resource capabilities have increased dramatically over the past few decades both in terms of processing speed and parallelizability, thus enabling simulation methodologies that combine multi-length scale virtual experiments with optimization algorithms to find new systems of interest faster than ever. There have been many successful examples of such design work in the areas of metallic and ceramic materials, but equivalent methodologies for polymeric and soft materials are still in their infancy. By combining and integrating the current state of the art computational tools in polymeric systems such as self-consistent field theory (SCFT), coarse grained Monte Carlo molecular dynamics, atomistic molecular dynamics, dissipative particle dynamics, and finite element methods, polymers can be designed for a given functional purpose considering effects at all length scales. By starting with the desired application such as advanced energy storage, ultrafast electronic devices, or biomedical interfacing materials, a chemical engineering system can be designed computationally to produce a given device with optimal properties to perform that application.

Postdoctoral Research:

â?? Awarded National Research Council Research Associateship Program Fellowship.

Proposal Name:

â??Enhancing the Measurement and Morphology Control of Thin Film Block Copolymers using Feedback Between Inverse SCFT Simulations and Resonant Soft X-Ray Scatteringâ?

Under supervision of R. Joseph Kline & Christopher Soles, Materials Science and Engineering Division, National Institute of Standards and Technology (NIST)

Doctoral Thesis:

â??Modeling and Theoretical Design Methods for Directed Self-Assembly of Thin Film Block Copolymer Systems.â?

Under supervision of Caroline A. Ross and collaboration with Alfredo Alexander-Katz, Department of Materials Science and Engineering, Massachusetts Institute of Technology (MIT)

Research Experience:

As an undergraduate at the Georgia Institute of Technology (GT) I performed undergraduate research under a Presidentâ??s Undergraduate Research Award (PURA) examining the miscibility of fullerene based molecules with styrene based copolymers through both ultraviolent-visible spectroscopy and molecular dynamic simulations. In graduate school at MIT, I continued work in the self-assembly of copolymers. In particular, I examined thin film block copolymer systems and their incorporation into current manufacturing processes as a method to extend lithography methods for next generation microelectronic devices beyond the sub-10 nm node. I did this work by advancing SCFT simulations for examining directed self-assembly systems with topographical templates under solvent vapor annealing conditions. In this simulation framework, I developed an inverse design algorithm to find post template configurations necessary to produce given target complex morphologies. Currently at NIST I am investigating novel methods for characterizing nanoscale patterns fabricated by processes such as block copolymer directed self-assembly as a National Research Council postdoctoral research fellow. Using X-ray scattering techniques, I am optimizing the inverse computation methods needed to find the real space structure of underlying nanoscale patterns. I am also using physically integrated simulation methods (e.g. SCFT of block copolymers) that predict what structures are formed for different directed self-assembly boundary conditions.

Teaching Interests:

As an undergraduate at GT, I instructed introductory electromagnetism physics labs as well as served as a one-on-one tutor for the Learning Assistance Program. At MIT I taught organic chemistry labs, mechanical testing labs, traditional chalk lectures via recitations for a combined quantum mechanics and solid state physics course, and also helped develop course content for an in class demonstration driven thermodynamics course. I completed a teaching minor in Teaching Materials Science and Engineering for my teaching assistance accomplishments as well as a teaching certificate through the MIT Teaching Learning Laboratory. A copy of the letter for the teaching certification is available upon request. Based on these experiences as well as my research interest, I am well versed to teach any thermodynamic, processing, quantum mechanics, or organic chemistry related courses.

Future Direction: 

There are many areas in designing polymeric and soft materials systems I would be excited to investigate in my future research. Here I highlight three particular areas. The inverse design paradigm I have used in my research is applicable to all of these areas. The areas examined in increasing order of difficulty and expected research timeline are (I) controlling the self-assembly of heterogeneous polymer, copolymer, and nanoparticle blends/composites, by finding the optimal processing conditions and chemical structures needed for a given application computationally, (II) characterizing designed polymer samples for computational model validation, and (III) determining the optimal chain sequence in proteins and other complex copolymers that can have precise control over the repeat unit sequence.

Area (I) is important as copolymer based systems naturally form ordered structures and complex morphologies essential to applications such as photovoltaics, light emitting diodes, memory storage, integrated circuits, and batteries. Area (II) is essential in both supporting area (I) by validating the systems designed for the given applications as well as enhancing the computational models needed to design such systems through direct comparison with the model results and experiment. Area (III) is the ultimate goal of any polymer scientist or engineer in being able to program desired properties via a carefully designed polymer sequence which can only be done with robust design algorithms. Each of these research areas naturally lead into the next and provide the pathway for the design, fabrication, and characterization of new polymeric and soft materials.

Selected Publications:

A.F. Hannon, D.F. Sunday, G. Khaira, J. Ren, P.F. Nealey, J.J. de Pablo, R.J. Kline. â??Optimizing Self-Consistent Field Theory Block Copolymer Models with X-Ray Metrology,â? In Preparation

A.F. Hannon, D.F. Sunday, D. Windover, R.J. Kline. â??Advancing X-Ray Scattering Metrology Using Inverse Genetic Algorithms,â? Accepted by SPIE: Journal of Micro/Nanolithography, MEMS, and MOEMS. (2016).

D.F. Sunday*, A.F. Hannon*, S. Tein, R.J. Kline. â??Thermodynamic and Morphological Behavior of Block Copolymer Blends with Thermal Polymer Additives,â? Macromolecules doi:10.1021/acs.macromol.6b00651 (2016). *Contributed equally

A.F. Hannon, W. Bai, A. Alexander-Katz, C.A. Ross. â??Simulation Methods for Solvent Vapor Annealing of Block Copolymer Thin Films,â? Soft Matter 11(19), 3794-3805, (2015).

A.F. Hannon, Y. Ding, W. Bai, C.A. Ross, A. Alexander-Katz. â??Optimizing Topographical Templates for Directed Self-Assembly of Block Copolymers via Inverse Design Simulations,â? Nano Letters 14(1), 318â??325, (2014).

A.F. Hannon, K.W. Gotrik, C.A. Ross, A. Alexander-Katz. â??Inverse Design of Topographical Templates for Directed Self-Assembly of Block Copolymers,â? ACS Macro Letters 2(3), 251-255 (2013).

A. Tavakkoli K.G., K.W. Gotrik, A.F. Hannon, A. Alexander-Katz, C.A. Ross, K.K. Berggren. â??Templating Three-Dimensional Self-Assembled Structures in Bilayer Block Copolymer Films,â? Science 336, 1294-1298 (2012).