Hierarchical Self-Assembly of Polyhedral Oligomeric Silsesquioxane End-Capped Stimuli-Responsive Polymer: From Single Micelle to Complex Micelle

Responsive polymeric micelles have been widely studied because of their potential use in nanocontainers and nanocarriers. In this study, polyhedral oligomeric silsesquioxane (POSS) end-capped poly[2-(dimethylamino)ethyl methacrylate] (POSS-PDMAEMA), a stimuli-responsive organic-inorganic hybrid polymer, was synthesized via atom transfer radical polymerization (ATRP) using POSS-Br as a macroinitiator. The self-assembly behaviors of POSS-PDMAEMA in aqueous solution were studied by fluorescence probe, transmission electron microscopy (TEM), dynamic light scattering (DLS), high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD). The results revealed two self-assembly processes of POSS-PDMAEMA. First they self-assembled into a single micelle with the POSS molecules forming a crystal core and the PDMAEMA chains stretching as a corona. Then the single micelles, as building blocks, were able to reversibly form a hierarchical micelle-on-micelle structure (complex micelle) under external stimuli.