Bimodal “matrix-free” polymer nanocomposites†
Maximum performance enhancement in polymer nanocomposites is predicated on the simultaneous realization of maximum filler loading, controlled filler dispersion and structural integrity. Through the example of high refractive index ZrO2/polydimethylsiloxane encapsulants for LEDs for enhanced light extraction efficiency, this paper demonstrates that all three properties can be achieved by eliminating the matrix in a single component polymer nanocomposite. Surface bound polymer brushes serve as both the matrix and stabilizing agent, to ensure uniform filler dispersion. The use of multimodal brush configurations that are at least bimodal is the key enabler. This provides sufficient crowding near the particle surface to screen core–core attraction, as well as entanglement between sparsely grafted long brushes to prevent premature cracking. A further widening of the applicability and processing windows are achieved by introducing crosslinkable moieties into the brushes.