Microphase-Separated Elastomers Enable Synergistic Dispersion and Coalescence Control in Conductive Pastes for Fine Printing.

Abstract

With the advancement of high-power and fine-feature electronic devices, metallic pastes have emerged as essential conductive materials, whose performance largely depends on the structure of the organic carrier. Conventional polyamide wax thixotropic agents, based on amide hydrogen-bonded networks, are often overly rigid, leading to poor leveling after demolding and local aggregation or porosity under high silver loadings. To overcome these limitations, this study introduces a microphase-separated styrene-ethylene-propylene-styrene (SEPS) block copolymer as a thixotropic agent. Through the synergy between hard and soft segments, SEPS forms a reversible microgel network that enhances organic-inorganic interfacial interactions and metal particle dispersion. The hard segments interact with particle surfaces to improve dispersion, while soft segments enable shear-thinning and rapid viscoelastic recovery, thereby achieving high-resolution, fine-line printing. Moreover, during thermal treatment, the stepwise decomposition of the organic phase promotes silver particle necking and grain growth, further densifying the electrode. Consequently, a low porosity (8.66%) and uniform electrode morphology are achieved, resulting in an extremely low resistivity (3.03 µΩ·cm). Through synergistic control of rheology and particle coalescence, this work provides a strategy for optimizing metallic functional pastes toward precision-printed electronic devices.