Nanoscale chemical imaging of a deuterium-labeled polyolefin copolymer in a polyolefin blend by atomic force microscopy-infrared spectroscopy

Abstract

A combination of atomic force microscopy-infrared spectroscopy (AFM-IR) and a deuterium-labeled ethylene-propylene (EP) copolymer enables direct nanoscale chemical imaging of all three components in a polyethylene/polypropylene/ethylene-propylene copolymer blend for the first time. AFM-IR is a hybrid technique that provides the spatial resolution of AFM with the chemical selectivity of IR. Deuterium labeling of the EP copolymer enables it to be distinguished from the blend components. This combination enables chemical imaging of all components in the polyolefin blend at a spatial resolution (∼50 nm) that far exceeds conventional Fourier-transform infrared and Raman microscopy, which are limited by the diffraction of light. AFM-IR spectra and images of the C-D stretch in the polyolefin blend definitively establish that the deuterium-labeled EP copolymer is dispersed in the polyethylene matrix. This strategy is broadly applicable to other types of polymer blends that contain chemically-similar components.