Polymers of intrinsic microporosity, or PIMs, are characterized by rigid and nonlinear or nonplanar backbones that inhibit space efficient packing, thus creating microporosity. PIM-1 has been well studied by both simulations and experiments and is compared in this work to two different PIM-1-like polymers, PIM-1c and PIM-1n. A detailed method for the generation of representative structures, including charge assignment from ab initio calculations, is presented along with simulated characterization of the pore size distributions, surface areas, structure factors, and methane adsorption isotherms. Simulated scattering for PIM-1c and PIM-1n show similar characteristic peaks as PIM-1, suggesting similar conformations. Adsorption isotherms of methane in PIM-1, PIM-1c, and PIM-1n were also predicted and compared to experimental data for PIM-1.

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The stiffness and tensile strength of biopolymers (e.g., polylactic acid (PLA)) are less than desirable for load-bearing applications in their neat form. The use of natural fibers as reinforcements for composites (for large-scale three-dimensional (3D) printing) has expanded rapidly, attributable to their low weight, low cost, high stiffness, and renewable nature. Silane and acid/alkali are typically used to modify the surface of natural fibers to improve the fiber/polymer interfacial adhesion. In this study, a simple method of impregnation was developed to modify pine fibers (loblolly, mesh size of 90–180 μm, 30 wt %) with a solvent-borne epoxy to reinforce PLA. As a benefit of the epoxy modification (0.5–10 wt %), the tensile strengths and Young’s moduli of the epoxy-modified pine/PLA composites increased by up to 20 and 82%, respectively, as compared to that of neat PLA. The epoxy-modified pine/PLA composites, with an optimum epoxy modification (1.0 wt %), had fewer voids on the fracture surface as compared with pine/PLA composites without the modification of pine fibers via epoxy. Results confirmed that epoxy partially penetrated the pore/hollow inner structures of pine fibers and improved the fiber/matrix interfacial adhesion. Epoxy modification is found to be a simple and effective technique to improve the properties of biocomposites.

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