Effect of Extreme Nanoconfinement and Polymer-Nanoparticle Interactions on the Thermodynamics of Polymer Blends in Dense Nanoparticle Packings

Infiltration of polymer into the interstices of dense nanoparticle (NP) packings leads to the formation of highly loaded nanocomposites with superb mechanical and transport properties. Polymers in such nanocomposites are subjected to physical confinement which alters their glass transition temperature and dynamics. The impact of confinement on polymer blend thermodynamics, particularly within the pores of NP packings, is less understood. Here we present a computational study using self-consistent field theory to understand the thermodynamics of highly confined polymer blends in the interstices of NP packings. Two polymers that undergo macroscopic phase separation in bulk become miscible when subjected to extreme nanoconfinement and the strength of repulsion required to induce phase separation increases significantly as confinement increases. We also explore the impact of polymer-NP interactions on the equilibrium behavior of confined composites. This study shows that confinement alone strongly increases the window of miscibility of polymer blends without inducing any chemical alterations to the system. The ability to create miscible polymer nanocomposites with normally incompatible blends would unlock a myriad of novel properties and applications.