(A) Molecular models and formulas of different polymers (i.e., PAN, PVP, PVA, and PS) with calculated dipole moments for the repeating units of each polymer. (B) Filtration efficiencies to PMs for the different types of membranes based on PAN, PVP, PVA, and PS. (C) Photographs of polyimide-based air filters with transmittances at 90% (T-90), 70% (T-70), 50% (T-50), and 40% (T-40), and SEM images of the air filter (D) before and (E) after capturing PMs. (F) The PM number concentration measurement of car exhaust with an air filter. The inset shows a stainless-steel pipe coated with a polyimide filter with transmittance at 50% shown by the red circle.(G) Filtration efficiency of PMs from car exhaust gas. (A and B) Reprinted with permission from ref 641. Copyright 2015 Springer Nature. (C−G) Reprinted with permission from ref 647. Copyright 2016 American Chemical Society.