Negative Interfacial Tension Driven by Intrinsic Molecular Disorder

A fundamental challenge is to understand how sequence randomness, which cannot be averaged into effective parameters, drives the formation of such polydisperse assemblies. Using a minimal coupled field theory that explicitly links a conserved density field to a nonconserved “junction” field representing stochastic binding site density, we show that the attraction between two fields χ, together with the fluctuations in the junction field <i>T</i>_ϵ, renormalizes the effective interfacial tension to negative values: Δγ ∼ −<i>T</i>_ϵχ².

This negative interfacial tension suppresses coalescence and stabilizes a scale-invariant ensemble of clusters with a power-law size distribution, as confirmed by both numerical calculations and coarse-grained simulations of sequence-disordered biomolecules, and are consistent with diverse experimental observations. Our work reveals a general physicochemical mechanism by which intrinsic molecular disorder and fluctuations jointly govern phase separation in systems with built-in randomness, providing a unifying, chemistry-oriented framework for understanding and engineering heterogeneous soft matter systems.