Autonomous Interfacial Assembly of Polymer Nanofilms via Surfactant-Regulated Marangoni Instability

Interfacial
polymerization (IP) provides a versatile platform for
fabricating defect-free functional nanofilms for various applications,
including molecular separation, energy, electronics, and biomedical
materials. Unfortunately, coupled with complex natural instability
phenomena, the IP mechanism and key parameters underlying the structural
evolution of nanofilms, especially in the presence of surfactants
as an interface regulator, remain puzzling. Here, we interfacially
assembled polymer nanofilm membranes at the free water–oil
interface in the presence of differently charged surfactants and comprehensively
characterized their structure and properties. Combined with computational
simulations, an in situ visualization of interfacial film formation
discovered the critical role of Marangoni instability induced by the
surfactants via various mechanisms in structurally regulating the
nanofilms. Despite their different instability-triggering mechanisms,
the delicate control of the surfactants enabled the fabrication of
defect-free, ultra-permselective nanofilm membranes. Our study identifies
critical IP parameters that allow us to rationally design nanofilms,
coatings, and membranes for target applications.