Structural Characterization of a Polymer of Intrinsic Microporosity: X-ray Scattering With Insight From Molecular Dynamics Simulations*

Polymers of intrinsic microporosity (PIMs) are high-T$_{g}$, amorphous materials exhibiting high gas permeability and a large concentration of pores smaller than 2 nm, arising from a combination of rigid segments and sites of contortion. Structures generated by molecular dynamics simulations accurately reproduce characteristic scattering features from PIM-1 at high $q$, allowing us to investigate their origin by examining partial structure factors. Unlike scattering patterns typical of nonporous amorphous polymers, broad $q$ range PIM scattering patterns include a shoulder at the size scale corresponding to pore sizes measured by other techniques. We discuss the development of a model for extracting pore sizes from scattering patterns.