Quantitative Analysis of Isotopic Blends by Infrared Nanospectroscopy*

Atomic-force microscopy coupled with infrared spectroscopy (AFM-IR) deciphers surface morphology by mapping physical topography as a function of relative chemical composition. While AFM-IR analysis provides information on the domain size and distribution of specific chemical moieties, it remains unclear if nanoscale phase separation obtained by AFM-IR can be compared to phase separation acquired by scattering-based techniques. Additionally, AFM-IR is severely limited by the lack of quantitative compositional information inherent to the detected signal. Herein, we resolve nanoscale phase separation in isotope polymer blends and compare the result to data acquired by small-angle neutron scattering and resonant soft X-ray scattering. Fundamental FTIR analysis is also applied to obtain quantitative blend composition of isotopic, polymer blends. Quantitative composition information is calculated by the construction of a calibration curve and applied to spectra acquired across phase-separated domains in each polymer blend. Demonstratively, combining fundamental FTIR analysis with AFM-IR is a robust technique and compliments scattering-based measurements for probing nanoscale morphology and composition.