  Molecular self-assembly, the function of biomembranes, and the performance of
organic solar cells rely on molecular interactions on the nanoscale. The
understanding and design of such intrinsic or engineered heterogeneous
functional soft matter has long been impeded by a lack of spectroscopic tools
with sufficient nanometer spatial resolution, attomolar sensitivity, and
intermolecular spectroscopic specificity. We implement vibrational
scattering-scanning near-field optical microscopy ($s$-SNOM) in a
multi-spectral modality with unprecedented spectral precision to investigate
the structure-function relationship in nano-phase separated block-copolymers.
We use a vibrational resonance as a sensitive reporter of the local chemical
environment and resolve, with few nanometer spatial resolution and 0.2
cm$^{-1}$ spectral precision, spectral Stark shifts and line broadening
correlated with molecular-scale morphologies. By creating images of
solvatochromic vibrational shifts we discriminate local variations in electric
fields between the core and interface regions of the nano-domains with
quantitative agreement to dielectric continuum models. This new
nano-chemometric ability to directly resolve nanoscale morphology and
associated intermolecular interactions can form a basis for the systematic
control of functionality in multicomponent soft matter systems.
