Liquid-Crystalline Polymer Alloy Design through Interfacial Reactions Enabled by In Situ Polymerization and Reactive Blending

Abstract Liquid-crystalline polymers (LCPs), an important class of super engineering thermoplastics, exhibit outstanding melt processability and are attractive materials for designing high-performance polymer alloys. However, the fundamental insights required to overcome macroscopic phase separation arising from the intrinsic structural disparity between liquid-crystalline and isotropic polymers, and the design guidelines built on these insights, have not yet been clearly established. Here, we investigated an alloy design strategy for LCP-based systems through an interfacial-reaction approach, using poly(phenylene ether) (PPE) as a dispersed phase capable of copolymer formation with the LCP matrix. First, in melt-mixed LCP/PPE blends prepared by twin-screw extrusion, the PPE domain size was minimized when the viscosity ratio between the liquid-crystalline matrix and the isotropic dispersed phase approached unity. We then constructed LCP/PPE alloys through two reactive routes: in situ polymerization of the LCP in the presence of PPE and reactive melt blending of LCP and PPE. The results collectively indicate that copolymer formation at the liquid-crystalline/isotropic interface reduces melt-state interfacial tension while reinforcing the interface in the solid state, thereby enabling fine dispersion and enhanced mechanical performance. These findings highlight the central role of interfacial engineering beyond differences in higher-order structure and provide a general route to tough, highly processable LCP-based alloys.