Designing PEEK-based high-performance ternary systems displaying highly controlled hierarchical morphologies

In this work, ternary systems of melt-processed poly(ether ether ketone) (PEEK) combined with various combinations of meta -poly(ether imide) ( m -PEI), para -poly(ether imide) ( p -PEI), polycarbonate (PC), or poly(phenyl sulfone) (PPSU) are shown to result in uniquely sophisticated and tunable hierarchical morphologies. By combining, for the first time, concepts of thermodynamics of mixing, and surface and interface thermodynamics, it is possible to comprehensively design, predict and generate highly controlled morphologies in ternary systems. To do so, a selected variety of polymer pairs, showing different states of mixing behavior - from fully miscible, to partially miscible, to completely immiscible, are combined into ternary systems and analyzed using spreading coefficients theory. The structure evolves from a biphasic system, as observed when PEEK is combined with PC and m -PEI, to fully triphasic systems when PEEK is instead combined with PC and p -PEI or PPSU. In all cases, PEEK systematically and fully separates the other two components, as predicted by the spreading coefficients, a unique result for ternary systems displaying low interfacial tensions involving miscible or partially miscible polymer pairs. These insights then enabled the preparation of hierarchically porous PEEK monoliths comprised simultaneously of both macro and meso-porous network structures with tunable pore sizes, and even ultraporous materials containing as little as 5 vol% PEEK. The average pore sizes span a considerable range of nearly 4 orders of magnitude, from a few nanometers to several microns. These results underscore the potential of such blends for designing PEEK porous monoliths for very lightweight, high-temperature applications. • Ternary blends of PEEK with m -PEI, p -PEI, PC or PPSU show hierarchical morphologies. • PEEK separates the other two components as predicted by the spreading coefficients. • Tunable porous PEEK monoliths with networks of macro and mesopores are obtained. • Ultraporous monoliths containing as little as 5 vol% PEEK can be prepared. • The average pore size spans 4 orders of magnitude, from a few nm to several μm's.