Thesis Title

Design of Mechanically-Assembled Monolayers and Coatings

Simulation of the formation of copolymers of varying blockiness Through Molecular Modeling and Simulation

Co-Advisor: Jan Genzer

Systems of Interest

  • Mechanically-assembled monolayers (MAMs)
  • Random-blocky copolymers

Methods and Software

  • Discontinuous Molecular Dynamics (DMD) Simulations
  • Fortan 90
  • Rasmol molecular visualization program

Abstract

MAMMy research applies modeling and computer simulation to mechanically-assembled monolayers, or MAMs. As seen in the inset, these monolayers are created by first stretching the surface. UV light then establishes the grafting sites for the polymer layer to attach. Last, relaxing the extended surface brings the polymers together, thereby increasing the surface density beyond what may be attainable through self-assembly. MAMs have been shown to possess long-lasting superhydrophobic properties.(1)

Low Density Polymer Brush


Computer simulation of the grafted polymer layer (also known as a 'brush') using discontinuous molecular dynamics (DMD) allows a molecular-level analysis of the individual interactions between particles, which is impossible in laboratory experiments.
High Density Polymer Brush
Thus, one can adjust system properties such as polymer chain length, grafted surface density, system temperature, particle-particle interaction strength and rate of surface relaxation (from low to high surface density). In turn, key system characteristics such as brush thickness and monomer density profile can be investigated explicitly.




The second phase of my research has been the modeling and computer simulation of copolymer formation and performance. We define here a copolymer as a polymer of two components, A and B, of the form AxB1-x. Current research has shown that these copolymers can act as blend compatilizers and adhesion promoters due to the unique blockiness of the A and B components. We have researched a theoretical approach for copolymer formation first proposed by Khokhlov and coworkers -- a A-type homopolymer is placed in a poor solvent and then the outer shell of exposed monomers is "colored" to the B-component (see figure to the right). The blockiness of the resulting A-B copolymers can be adjusted by judicious choice of A- and B-solubility, system temperature, time allowed to react, weight percent (or ratio) of A and B. Additionally, researchers can vary the chain length, further adjusting blockiness.


Publications

L. A. Strickland, C. K. Hall, J. Genzer, "Simulation of Mechanically-Assembled Monolayers In Poor Solvent Using Discontinuous Molecular Dynamics," Macromolecules 43, 3072-3080 (2010).
L. A. Strickland, C. K. Hall, J. Genzer, "Controlling Comonomer Distribution in Random Copolymers by Chemical Coloring of Surface-Tethered Homopolymers: An Insight from Discontinuous Molecular Dynamics Simulation," Langmuir 26, 8810-8820 (2010).
L. A. Strickland, C. K. Hall, J. Genzer, "Design of Copolymers with Tunable Randomness Using Discontinuous Molecular Dynamics Simulation," Macromolecules 42, 9063-9071 (2009).
L. A. Strickland, C. K. Hall, J. Genzer, "Simulation of Mechanically Assembled Monolayers and Polymers in Good Solvent Using Discontinuous Molecular Dynamics," Macromolecules 41, 6573-6581 (2008).
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Conferences

Thermo 2005 -- College Park, MD, April 28-30, 2005

AIChE Annual Meeting -- San Francisco, CA, Nov 12-17, 2006

APS Annual Meeting -- New Orleans, LA, March 10-14, 2008

Presentations

"Design of Mechanically-Assembled Monolayers Using Discontinuous Molecular Dynamics", AIChE, 2006

"Computer Simulation of the formation of random-blocky copolymers", Gilbert Symposium, 2008

"Computer Simulation of the formation of random-blocky copolymers", APS, 2008