Title: Raman spectroscopy and imaging in organization, processing and functionalization of polysaccharide materials
Abstract:
The Raman spectra of polysaccharide materials provide plenty information on the local organization of polysaccharides in biological materials, their structural variations during processing and surface composition upon functionalization. Each of these aspects are covered by three case studies in our laboratory. First, the organization of polysaccharides in a chitin-protein matrix of crustacean exoskeleton is monitored to reveal differences in microstructure and composition throughout the cuticle cross-section of different skeletal segments with mineral and polysaccharide regions. A Raman study on organized layers provides better insight in the structure of biological materials and consequent possibilities for their extraction. Second, the processing of cellulosic nanofibers from pulp fibers by swelling in ionic liquids is a favourable pre-treatment to facilitate fiber fibrillation. Therefore, the selection of an appropriate swelling medium and conditions should be based on monitoring the influence of ionic liquid composition on swelling efficiency and resulting cellulose properties after different processing time. The local structural variations in crystallinity and internal stress distributions are monitored by in-situ micro-Raman mapping at single fiber-level as a function of time, indicating variations between mild and severe pre-treatment with possible increase in crystallinity, while extreme degradation upon complete dissolution is noticed. Third, the functionalization of micro- to nanofibrillated cellulose by deposition of oil-filled organic nanoparticles provides an active system for tuning of the surface hydrophobicity, which is quantified and visualized as a controlled thermal release of oil from the fiber surface by Raman mapping. After melt-processing of the functionalized fibers with a biopolymer, the different crystallization kinetics within the polymer matrix can be followed from specific spectral bands. All observations from Raman analysis are further supported by complementary analytical techniques and/or theoretical calculations.
