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Molecular exchange between micelles or other assemblies is measurable during size and morphology changes by combining appropriate time-resolved small-angle neutron scattering (TR-SANS) measurements with the SRR approach.

 

Kinetically trapped (“persistent”) micelles enable emerging applications requiring a constant core diameter. Preserving a χN barrier to chain exchange with low- N requires a commensurately higher χ core–solvent for micelle persistence. Low- N , high- χ micelles containing fluorophobic interactions were studied using poly(ethylene oxide- b -perfluorooctyl acrylate)s (O 45 F X , x = 8, 11) in methanolic solutions. DLS analysis of micelles revealed chain exchange only for O 45 F 8 while SAXS analysis suggested elongated core block conformations commensurate with the contour lengths. Micelle chain exchange from solution perturbations were examined by characterizing their behavior as templates for inorganic materials via SAXS and SEM. In contrast to the F 8 analog, the larger χN barrier for the O 45 F 11 enabled persistent micelle behavior in both thin films and bulk samples despite the low T g micelle core. Careful measures of micelle core diameters and pore sizes revealed that the nanoparticle distribution extended through the corona and 0.52 ± 0.15 nm into the core–corona interface, highlighting thermodynamics favoring both locations simultaneously. 

Block polymer structure-directing agents (SDA) enable the production of porous nanoscale materials. Most strategies rely upon polymer equilibration where diverse morphologies are realized in porous functional materials. This review details how solvent selectivity determines the polymer SDA behaviors, spanning from bulk-type to solution-type. Equilibrating behavior of either type, however, obscures nanostructure cause-and-effect since the resulting sample series convolve multiple spatial variations. Solution-type SDA behaviors include both dynamic and persistent micelles. Persistent micelle templates (PMT) use high solvent selectivity for kinetic entrapment. PMTs enable independent wall thickness control with demonstrated 2 Å precision alterations. Unimodal PMT pore size distributions have spanned from 11.8 to 109 nm and multimodal pore sizes up to 290 nm. The PMT method is simple to validate with diffraction models and is feasible in any laboratory. Finally, recent energy device publications enabled by PMT are reviewed where tailored nanomaterials provide a unique perspective to unambiguously identify nanostructure–property–performance relationships.

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