No abstract

In recent years, high-resolution optical imaging in the far field has provided opportunities for alternative approaches to nanocharacterization traditionally dominated by electron and scanning probe microscopies. Here, we report the optical super-resolution imaging of model block copolymer (BCP) thin film surface nanostructures through stochastic optical reconstruction microscopy (STORM). We compare a set of surface-functionalized fluorescent core–shell silica nanoparticles encapsulating two different organic dyes, Cy3 and Cy5, with the corresponding free dyes in STORM. Using various click-type chemistries, these probes are covalently attached to the surface of specific blocks of BCP thin films, enabling selective block labeling and optical visualization. We demonstrate that the enhanced brightness of these particle probes offers distinct advantages over conventional dye labeling, outperforming one of the best STORM dyes available (Cy5).

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.

Radical mediated thiol−ene emulsion polymerizations for the synthesis of aqueous dispersion of polymer particles with narrow particle size distributions are reported. Submicrometer polymer particles comprising of cross-linked or linear chains were obtained using a water-soluble thermal initiator, without the need for a high-intensity emulsification step. Particles were prepared using 1,3,5-triallyl-1,3,5-triazine-2,4,6­(1H,3H,5H)-trione, pentaerythritol tetrakis­(3-mercapto­propionate), trimethylol­propane diallyl ether, 1,6-hexane­dithiol, and 3,6-dioxa-1,8-dithiooctane monomers. Potassium persulfate was used as the water-soluble initiator, and sodium dodecyl sulfate was used as the surfactant. The effects of surfactant, initiator, and comonomer concentrations on the particle diameters in the emulsion polymers are reported. The order of dependence of particle diameter on the surfactant concentration was −(0.44 ± 0.03) and on the initiator concentration was −(0.53 ± 0.04). The particle size distributions in the cross-linked latexes were generally broad. A seeded emulsion polymerization reaction, consisting of delayed addition of the cross-linker, was found to result in cross-linked thiol–ene latexes with narrow particle size distribution.