(729i) Selective Partitioning of Polymer-Grafted Nanoparticle Blends Via Entropic Confinement

It is well understood that the entropic forces arising from architectural and flexibility differences between polymer components can induce phase separation. Recent research from our group reveals that the entropic forces coming from the topological confinement (PDMS pattern) can induce the selective partitioning of polymer-grafted nanoparticles (PGNPs) to the less confined 'mesa' region (higher region of the patterned surface) in chemically identical homopolymer matrix. We here report that similar ordering can be achieved in pure chemically identical PGNPs blends. We find that the larger-sized PGNPs move and selectively segregate in the mesa region when the residual layer's film thickness ('trench' region) is smaller than the PGNPs' dimension. As the two PGNPs only differ in dimensions, we conclude that the preferential partitioning of large-sized PGNPs is induced by the entropic driving force from PDMS topological pattern. Further research reveals that the selective partitioning can be easily controlled by the initial film thickness of the PGNPs blends and the size difference between the two kinds of PGNPs. This research further proves that the previous approach of using entropic confinement to induce selective partitioning of PGNPs/homopolymer mixtures is robust and can be easily extended to other systems. It also provides an important method to control the ordering of chemically identical PGNPs blends, which may be significant in creating novel materials.

Funding Acknowledgment : DOE GRANT #: DE-SC0018854