Microporosity in ladder polymers from coarse-grained molecular simulations

Solution-processable ladder polymer with stiff backbone is ideal for preparing membranes with intrinsic microporosity used for gas separation and sensing. Understanding the molecular factors affecting the pore size distribution is crucial for engineering the mechanical strength and selective permeability for specific gases. The trial-and-error approach is expensive and time-consuming, and is not feasible for screening a large number of molecular architectures. We developed a bead-stick model that properly captures the structure and backbone stiffness of ladder polymers and performed coarse-grained MD simulations to generate equilibrated configurations. The pore size distribution are obtained by Voronoi tessellation and by imposing a mesh and introducing distance criteria to tessellate the space. The histograms and their variations with molecular architecture and molecular weights are reported and compared to indirect evidence obtained from experimental gas separation studies.