Development of Structure-property Relationships for Intrinsically Microporous Polymers through Molecular Simulations

Open Access
Author:
Hart, Kyle E
Graduate Program:
Materials Science and Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
June 06, 2014
Committee Members:
  • Coray M Colina, Dissertation Advisor
  • William George Noid, Committee Member
  • James Patrick Runt, Committee Member
  • Adrianus C Van Duin, Committee Member
Keywords:
  • Molecular Simulation
  • Polymers of intrinsic microporosity
  • carbon dioxide adsorption
  • gas separation
  • PIMs
Abstract:
Creating a safe and effective means to store and/or capture small molecules is of paramount importance, as these processes are some of the highest energy consumers today. New materials will have profound impacts on various environmentally conscious applications, such as alternative fuel storage, hydrogen recovery, natural gas purification, and carbon dioxide capture and storage. Designing a material that meets the demanding performance criteria of real-world use has proven a challenging endeavor, but microporous polymers are a promising alternative. This is primarily due to the material's pore sizes being on the order of molecular dimensions, while simultaneously retaining the ability for the polymer--gas physicochemical interactions to be tailored for specific gas separation applications. Both experimental and computational investigations have shown that seemingly minor changes in the chemical structure can have a profound effect on the gas adsorption and separation properties of a polymeric material; however, the vast number of possible functionalities makes the evaluation of potential structures a daunting challenge. This dissertation focuses on developing and utilizing computationally efficient means to analyze candidate polymeric materials for use in carbon dioxide adsorption and separation applications. After validating the simulation models for structural and adsorptive performance, several important structure--property relationships are described. In particular, this work proposes and analyzes multiple families of functionalized polymers of intrinsic microporosity, from which we obtain important design principles of gas separation performance. It is shown that the explicit modeling of a polymer's micropore structure facilitates a fundamental understanding of the nature of the polymer--gas interactions, which was used as a means to reveal the most influential pore characteristics for each application. The molecular simulation results discussed here will aid membrane researchers in creating an improved polymeric material tailored for a specific gas separation, after which the energy-saving potential of these materials may begin to be realized.