Theoretical and Computer Simulation Insights into Stimuli-Responsive Polymer Systems

Open Access
Kisselev, Alexei M.
Graduate Program:
Doctor of Philosophy
Document Type:
Date of Defense:
September 28, 2007
Committee Members:
  • Evangelos Manias, Committee Chair
  • Jorge Osvaldo Sofo, Committee Chair
  • Milton Walter Cole, Committee Member
  • Leonid Berlyand, Committee Member
  • solution thermodynamics
  • aqueous polymer solutions
  • copolymers
  • polymer systems
  • light-responsive
  • temperature-responsive
  • stimuli-responsive
  • phase diagrams
  • equation of state
  • hydrogen bonding
  • molecular dynamics
The phase behavior of temperature-responsive polymers with tunable lower critical solution temperatures (LCST) and light-responsive polymers was explored using statistical mechanics and molecular dynamics (MD) simulations. The LCST in water of (ethylene oxide)/ethylene copolymers is tailored by their chemical composition, specifically by the balance of hydrophilic to hydrophobic groups in the polymer. For the first time, the general formalism of the lattice-fluid with hydrogen-bonding (LFHB) theory has been successfully applied to a water-polymer system, a type of system known to be particularly difficult from the modeling perspective. This theory, modified here to account for multiple types of hydrogen bonds, has been shown to be effective when making theoretical predictions as justified by comparison with experimental results. It has been shown that a successful implementation of the LFHB theory is contingent upon an effective numerical implementation, and a numerical algorithm has been developed that specifically targets the computational complexities associated with this model. The series of (ethylene oxide)/ethylene copolymers were studied further with the modified Flory-Huggins with hydrogen bonding (FHHB) approach. A comparative study of LFHB and FHHB theories was undertaken and their relative advantages and drawbacks were revealed. Both theoretical models were shown to be successful in describing the phase behavior of these systems, and the model parameters were found to be transferable between different homologous copolymer series. Expanding beyond temperature-responsive polymer solutions, systems that can potentially find applications in antifouling, drug delivery, and surfaces with switchable tackiness, we subsequently focused on a light-responsive polymer film systems that have applications in photolithography. Similarly to the temperature-responsive solutions above, for photolithography light-responsive materials exposure to UV radiation triggers the hydrophobic-to-hydrophilic transition in thin poly(methyl methacrylate)-based polymer films by removing a hydrophobic protection group from polymer side chain. We employed the molecular dynamics technique to study the mobility in the polymer blend consisting of a mixture of hydrophobic/hydrophilic copolymers and the concentration and orientation profile of the hydrophilic reactive groups.