Crystalline cellulose microfibrils are embedded in wall matrix polymers and assembled into hierarchical structures that are precisely designed for specific biological and mechanical functions of plant cell walls. The cellulose microfibril assemblies inside cell walls are extremely difficult to probe with linear optical spectroscopy such IR and Raman. This quandary can be resolved by the use of sum frequency generation (SFG) vibrational spectroscopy. The SFG process is a non-linear optical process which requires the noncentrosymmetry in space and phase synchronization over the optical coherence length. This principle can be used to distinguish the three-dimensional organization of crystalline cellulose microfibrils interspersed in amorphous polymer matrices such as plant cell walls. The overall SFG intensity, alkyl peak shape, and alkyl/hydroxyl intensity ratio are sensitive to the lateral packing and net directionality of the cellulose microfibrils within the SFG coherence length scale. This talk will address how SFG can be used to reveal the cellulose crystal structure and mesoscale cellulose microfibril packing in secondary cell walls and primary cell walls in their native states.

Mesoscale order of cellulose microfibrils in plant cell walls: Sum Frequency Generation (SFG) vibrational spectroscopy study

253rd National Meeting (2017)

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