Submicron-resolution polymer orientation mapping by optical photothermal infrared spectroscopy

A submicron-resolution infrared spectroscopy technique called optical photothermal infrared (O-PTIR) spectroscopy was applied to polymer orientation analysis in this work by measuring the wall cross-section of a commercial plastic bottle. Linear dichroism was observed in the O-PTIR spectra. Polarized O-PTIR mapping measurement through the entire wall thickness as wide as 350 µm with submicron spatial resolution visualized a highly oriented thin skin layer with a thickness of fewer than 10 µm near the outer surface, which has been difficult to perform using conventional IR microscopy techniques.