Spider Silk Inspired Processing of Liquid Crystalline Complex Coacervates.

Spider silk spinning begins with coacervation into a dense protein phase that organizes into liquid crystalline domains. Changes in salt concentration, together with shear forces, then direct the alignment needed to form highly ordered fibers. Inspired by this process, we developed a fully synthetic system of liquid crystalline complex coacervates designed to replicate the hierarchical organization and alignment mechanisms of spider silk, focusing on processing pathways. We show that salt concentration (tetrabutylammonium bromide, TBAB) governs the balance between isotropic and liquid crystalline states, with coacervation suppressed above 0.5 M, smectic order stabilized at ≤0.2 M, and isotropic chain networks prevailing at intermediate concentrations. Crucially, the degree of shear alignment depends strongly on salt: higher salt concentrations accelerate molecular relaxation and raise the threshold shear rate required to induce ordering, echoing the cooperative role of the ion composition and shear in natural silk spinning. Rheological and X-ray scattering measurements confirm that this salt-shear interplay dictates both the viscoelastic response and the molecular anisotropy. Finally, we demonstrate directional alignment through stretching and extrusion-based 3D printing and show that the unique tunability of salt concentration provides direct control over both processability and shear-induced alignment, offering a powerful biomimetic route to anisotropic material design.