Abstract
Kinetically controlled nonequilibrium self-assembly is ubiquitous in biological systems and plays a critical role in self-organization. Yet, achieving precise control over such nonequilibrium phase transitions remains a fundamental challenge in materials design. Here, we demonstrate that conjugated homopolymers can form uniform nanostructures with well-defined dimensions through a solution-phase kinetic-to-thermodynamic transition (KTT). This process proceeds via a rationally designed liquid-like intermediate that mediates nucleation and directional growth, affording morphologically pure nanostructures. Remarkably, the solvent environment critically dictates nucleation within the liquid-like intermediates, enabling the formation of either one-dimensional (1D) nanowires or two-dimensional (2D) nanoplatelets from the same polymer. Seed-assisted KTT further reveals that the liquid-like intermediate imparts both morphologies with living growth behavior, yielding nanostructures with precisely tunable dimensions across multiple length scales. These findings provide key insights into programmable kinetically controlled nonequilibrium self-assembly of π-conjugated polymers and establish a versatile strategy for fabricating structurally defined nanomaterials.