The Self-Assembled Structure of the Diblock Copolymer PCL-b-P4VP Transforms Upon Competitive Interactions with Octaphenol Polyhedral Oligomeric Silsesquioxane

Abstract

This paper describes the miscibility and self-assembly, mediated by hydrogen-bonding interactions, of new block copolymer/nanoparticle blends. The morphologies adopted by the immiscible poly[(epsilon-caprolactone)-block-(4-vinyl pyridine)] (PCL-b-P4VP) diblock copolymer changes upon increasing the number of competitive hydrogen-bonding interactions after adding increasing amounts of octaphenol polyhedral oligomeric silsesquioxane (OP-POSS). Transmission electron microscopy reveals morphologies that exhibit high degrees of long-range order, such as cylindrical and spherical structures, at relatively low OP-POSS contents, and short-range order or disordered structures at higher OP-POSS contents. Analyses performed using differential scanning calorimetry, wide-angle X-ray diffraction, and FT-IR spectroscopy provide positive evidence that the pyridyl units of the P4VP block are significantly stronger hydrogen-bond acceptors toward the OH group of OP-POSS than are the C=O groups of the PCL block, thereby resulting in excluded and confined PCL phases.