Orthogonal Nanoprobes Enabling Two-Color Optical Super-Resolution Microscopy Imaging of the Two Domains of Diblock Copolymer Thin Film Nanocomposites

Multicolor optical super-resolution microscopy (OSRM) describes an emerging set of techniques for the specific labeling of distinct constituents of multicomponent systems with compatible optical probes, elucidating proximity relationships from far-field imaging of diffraction-limited features with nanometer-scale resolution. While such approaches are well established in the study of biological systems, their implementation in materials science has been considerably slower. In large part, this gradual adoption is due to the lack of appropriate OSRM probes that, e.g., by facile mixing or surface modification, enable orthogonal labeling of specific nanostructures in the condensed state, rather than in aqueous conditions as with biology. Here, OSRM probes in the form of ultrasmall (diameters <10 nm) aluminosilicate nanoparticles encapsulating different fluorescent dyes are tailored to visualize both nanodomains of polystyrene-block-poly[(allyl glycidyl ether)-co-(ethylene oxide)] (PS-b-P(AGE-co-EO)) diblock copolymer thin films. Careful design of nanoprobe surface chemical properties facilitates either selective compatibilization with the nonpolar PS matrix or preferential reactivity with surface allyl groups of the hydrophilic P(AGE-co-EO) minority block. Stochastic optical reconstruction microscopy (STORM) of the resulting polymer-inorganic nanocomposite thin films shows nanodomain features of the two chemically dissimilar blocks consistent with atomic force microscopy results. This work paves the way for multiplexed OSRM analysis of polymer nanocomposite bulk structures.

Automated summary

Multicolor optical super-resolution microscopy (OSRM) techniques are well established in biological systems but have been slower to implement in materials science due to a lack of appropriate probes for orthogonal labeling of specific nanostructures in condensed states. These techniques are essential for visualizing nanodomain features of polymer nanocomposite bulk structures.