Identification of nanoscale polymer structures by Infrared Nanospectroscopy

Nanoscale resolved infrared imaging & spectroscopy achieves spatial resolution of < 10-20 nm enabling chemical identification of polymer nanostructures at unprecedented length scales and sensitivity. Infrared nanospectroscopy exploits the unique capabilities of two well established analytical techniques: The high spatial resolution in the nm range of atomic force microscopy (AFM) and the chemical sensitivity of infrared spectroscopy. Combining these two technologies, enables bypassing the diffraction limit of light and to probe the local chemical composition with a wavelength-independent spatial resolution of 10-20nm [1]. In this work we demonstrate identification of PMMA, PC or PVAC polymer nanostructures based on the comparison of measured nano-IR absorption spectra with ATR-FTIR reference spectra. Tuning the laser source to specific frequencies (e.g. 1735cm-1 for PMMA or 700cm-1 for PS) enables to selectively map the spatial distribution and determine domain sizes of materials with sensitivity down to few nm thin films or particles. Nano-IR measurements on easy-to-handle silicon membrane filters compatible with microplastic analysis routines are demonstrated. Nano-IR identification of polymer nanostructures has already been demonstrated for analysis of small micro- and nano-plastics which are difficult to access by other methods [2,3]. Further, weathering of PET was compared to fresh samples verified the high quality of nano-IR based material identification. References: [1] F. Keilmann, R. Hillenbrand, Phil. Trans. Royal Society A, 362, 787–805, (2004). 2 M. Meyns, et al., Analytical Methods, 15, 606 (2022) 3 M. Goikoetxea, et al., Marcomolecules, 54, 995 (2021)