Simple Strategies to Quantify and Control Polymer Threading into Micropores

Blends of polymers with microporous particles are essential to many modern technologies, including membranes, catalysts, nanocomposites, and porous liquids. However, the design space and performance of these technologies are substantially limited because it is difficult to quantify and control how polymers thread into the particles' sub-2 nm micropores. Here, we address these issues with two new strategies. First, we show that traditional solution-state NMR can be used to directly monitor polymer chains and quantify their diffusivities as they thread into microporous particles from the surrounding solvent. This label-free, high-resolution, in situ monitoring is possible because once a polymer chain enters the particles, its NMR signal becomes invisible due to excessively slow molecular tumbling. Second, we show that threading rates can be tuned across at least 6 orders of magnitude─without changing the particle size, micropore topology, or polymer chain length─by rationally modifying the particles' external surface with different coatings that form via noncovalent self-assembly after simple mixing. The strategies described here to quantify and control polymer threading are simple and generalizable to a wide range of polymer/particle combinations, solvents, temperatures, and concentrations; thus, they may spark advances in diverse technological and fundamental areas that rely on blends of polymers with microporous particles.