Directional dispersion of ultralong single-walled carbon nanotubes induced by solvent crystallization for effective electromagnetic interference shielding

Single-walled carbon nanotubes (SWCNTs) have promising applications in flexible electromagnetic interference (EMI) shielding materials owing to their electrical and mechanical properties. However, their macroscopic performance has long been constrained by bundle aggregation and processing-induced structural damage. Conventional turbulent-based dispersion methods inevitably trade dispersion efficiency for structural integrity, resulting in a long-standing processing bottleneck. Here, we propose a novel solvent crystallization-induced directional dispersion (SCIDD) strategy, which engineers a rheological phase transition to couple shear force direction with nanotube debundling orientation. Temperature-controlled solvent crystallization along SWCNTs surfaces increases viscosity and drives a turbulent-to-laminar transition, thereby enabling dispersion of ultralong SWCNTs bundles under aligned shear conditions. Computational fluid dynamics and in situ electrical measurements confirm rheological phase transition and flow induced SWCNTs orientation-establishing the mechanistic link between crystallization, rheological phase transition, and non-destructive dispersion. SCIDD has achieved a high-concentration slurry (1 wt%) that maintains stability for over 10 months, resulting in the production of ultralong SWCNTs (mean aspect ratio ~ 1600; I_D/I_G = 0.012). This significant advancement enables the creation of high-performance freestanding films that exhibit high conductivity (500 S cm^-1), specific shielding effectiveness (SSE/t) up to 47762 dB cm² g^-1. This work resolves the longstanding efficiency–integrity dilemma in SWCNT processing while offering a scalable, green route to harness the intrinsic properties of one-dimensional nanocarbons for advanced electromagnetic and flexible electronic applications.