Understanding Microdomains and Molecular Level Mixing in Poly(hydroxyalkanoate) Bioplastic Blends and Laminates Using Simultaneously Collected Submicron Optical Photothermal Infrared and Raman Spectra
Monday, March 08, 2021: 4:05 PM - 4:40 PM
Realization of the potential harm caused by the accumulation of plastic waste in the environment has led to a search for alternative materials. Bioplastics made from natural resources, like vegetable oils and sugars, which can biodegrade back to nature under proper conditions, are emerging as a potential replacement for conventional petroleum-based plastics. In parallel, the use of cutting-edge analytical tools to guide the characterization and improved design of useful bioplastics has become common practice. Simultaneous Optical Photothermal Infrared and Raman (O-PTIR+R) spectroscopy is an emerging spectral microscopy technique requiring no contact with the sample. It provides highly spatially resolved IR and Raman hyperspectral images down to about the 500-nm level, well below the IR diffraction limit. This range of spatial resolution is well suited for the analysis of multicomponent and multiphase samples, including composites, blends, and laminates. Such systems often exhibit varying degrees of molecular level mixing and spatial segregation of constituents at their interfaces, which in turn strongly affect the end use performance of the material. Although O-PTIR+R spectra are obtained in the reflection mode, high quality spectra are obtained without any dispersive scattering artifacts and the spectral profiles resemble those of traditional FT-IR spectra collected in transmission mode and it is now possible to simultaneously measure Raman spectra at the same co-registered position with the same submicron spatial resolution. In this study, hyperspectral O-PTIR and Raman images were simultaneously obtained for a biodegradable laminate sample comprised of macroscopically immiscible polylactic acid (PLA) and a polyhydroxyalkanoate (PHA). Comparing the results on the PLA/PHA laminate with results on a blend sample prepared from the same two materials clearly shows that the manner in which the PLA and PHA components interpenetrate is significantly different.
Keywords: Please select up to 4 keywords ONLY:
Materials Characterization,Microscopy,Infrared Spectroscopy,Raman/Surface Enhanced Raman Spectroscopy