(755g) Toward Dynamical Understanding of Fundamentals of Pretreatment of Cellulosic Biomass Via a High Resolution Broadband Sum Frequency Generation Vibrational Spectroscopy (HR-BB-SFG-VS)

Here we reported the first sub-wavenumber high-resolution broadband sum frequency generation vibrational spectroscopy (HR-BB-SFG-VS) study on both the C-H and O-H region spectra of crystalline cellulose. HR-BB-SFG-VS has about 10 times better resolution than the conventional scanning SFG-VS and was shown to be able to measure the intrinsic spectral lineshape and to resolve much more spectral details. With HR-BBSFG-VS, we found that in cellulose from different sources, including Avicel, cellulose Iα and Iβ, the spectral signatures in the OH regions were unique for different allomorphs, i.e. Iα and Iβ, while the spectral signatures in the C-H regions varied in all samples examined. Even though the origin of the different behaviors of the crystalline cellulose in the O-H and C-H vibrational frequency regions is yet to be correlated to the structure of cellulose, these results provided new spectroscopic methods and opportunities to classify and understand the basic crystalline structure, as well as variations, in polymorphism of the crystalline cellulose structure. In addition, dynamic changes of the crystalline structures were also investigated at specific temperatures from room temperature to 270 °C during the heating process.