Rigidity-tailored crosslinked networks with deep-trapped charges enable electret membranes for humidity-resilient aerosol filtration

Rational design molecular-level crosslinked structures of electret membranes remain a significant challenge for stable electrostatic filtration of airborne particles. Here, rigidity-tailored crosslinked networks, designed by modulating the molecular rigidity of interchain covalent bonds in crosslinked poly(styrene-co-maleic anhydride) (CS-IDDA), are exploited to function as deep traps to immobilize charges in electret membranes. The trapping sites capture charge carrier injected by corona discharging, obtaining deep-trapped electret CS-IDDA membranes. The electret CS-IDDA membranes maintain 99.83 % filtration efficiency after prolonged exposure to 95 % relative humidity environment. The remarkable filtration efficiency stability is attributed to deep-trapped charges with high energy level and improved charge retention enabled by restricted segmental mobility. Noteworthily, deep-trapped charges are anchored by connectivity defects and spatial inhomogeneity within rigid crosslinked networks. Moreover, the rigid crosslinked networks confine molecular chain movement by reducing interchain spacing and free volume, effectively suppressing charge migration, and hence dominate stable electrostatic capture of airborne particles. This study highlights the significance of modulating the molecular-scale rigidity engineering of crosslinked networks to effectively design electret membranes for advance air purification and safeguarding public health security.