Confinement induced lateral segregation of polymer coated nanospheres

Abstract

The equilibrium structures of polymers end-tethered to nanoparticles or to nanomicelles interacting with surfaces have been studied theoretically. Polymer chains chemically grafted to nanoparticles are laterally immobile. On the other hand, nanosized polymer micelles formed by polymer chains conjugated with lipids, have end-tethered chains that are laterally mobile within the self-assembled structure. Using a molecular theory, we investigated the influences of the mobile nature of the tethered chains and the nanoscale dimension of the anchoring surface on the structures and interactions of the polymers during the process of binding of the nanoparticle to a surface. We show that polymer chains with bidisperse molecular weight distributions end-tethered to a nanomicelle/nanoparticle surface segregate upon approach to a surface. The shorter chains preferentially locate in the vicinity of the surface, while the longer ones are excluded from the region between the micelle and the surface and thus become more concentrated on the opposite side of the micelle surface. The extent of this segregation is controlled by the overall surface coverage and compositions of the tethered chains, and the sizes of the short and long chains. Combining lateral mobility of the polymer tether with an end-binding capability of the chain (e.g., through a ligand–receptor interaction) can give rise to an enhancement of the interaction of the polymer nanoparticle with a surface. The results demonstrate that laterally mobility of tethered chains is an important aspect that needs to be taken into account in designing polymeric nanoparticles with enhanced surface interaction properties.