“Smart” Self-Assembled Quantum Dots Regulate and Stabilize Structure in Phase-Separated Polymer Blends

Abstract

Cadmium sulfide (CdS) quantum dots (QDs) coated with mixed polystyrene (PS)/poly(methyl methacrylate) (PMMA) brush layers (PS/PMMA–CdS) self-assemble at the polymer/polymer interface of a phase-separating blend of the corresponding homopolymers, forming an encapsulating shell surrounding PMMA islands in a PS matrix. The segregated QDs regulate phase separation during spin-coating and dramatically stabilize the spin-coated blend morphologies during subsequent annealing, compared to neat PS:PMMA blends which undergo rapid phase inversion and coarsening. PS/PMMA–CdS QDs are shown to retain their photoluminescence following interfacial self-assembly and subsequent annealing. Free-standing arrays of polymer/QD rings formed via directed self-assembly can be developed by selective solvent washing and removal of homopolymers from the spin-coated films. This work demonstrates the principle that colloidal inorganic elements such as QDs, along with possessing interesting optical properties, can also play a key role ...