Visualization of Macrophase Separation and Transformation in Immiscible Polymer Blends

Abstract

Identification and visualization of phase structures inside polymer blends are of critical importance in the understanding of their intrinsic structure and dynamics. However, the direct optical observation of the individual component phase in a dense bulk material poses a significant challenge. Herein, three-dimensional fluorescence imaging of phase separation and real-time visualization of phase transformation in immiscible polymer blends of polypropylene and polystyrene is realized through multiphoton laser scanning microscopy. Owing to the specific fluorescence behavior of the cyanostyrene derivative 2-(4-bromophenyl)-3-(4-(4-(diphenylamino)styryl)phenyl)fumaronitrile, the high-contrast imaging of the macrophase of the component polymer in two and three dimensions with a maximum depth of 140 μm and a high signal-to-noise ratio of 300 can be achieved. Detailed spectroscopic and structural studies reveal that the distinctive fluorescence features of each phase domain should originate from the formation of a completely different aggregate between probes and component polymer. Furthermore, visualizations of the internal morphology deformation and macrophase transformation were realized by employing a stretched dumbbell sample under constant tension.