CELLULOSE MODEL SURFACES STUDIED BY FEMTOSECOND SUM FREQUENCY SPECTROSCOPY

CELLULOSE MODEL SURFACES STUDIED BY FEMTOSECOND SUM FREQUENCY SPECTROSCOPY

By Lei Li

Thesis Advisor: Dr. David J. Neivandt

A Lay Abstract of the Thesis Presented In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy (in Physics) May, 2012

Keywords: laser spectrometer, cellulose, surface structure, thickness, AKD, hydrophobicity, degradation

In this thesis, a high energy laser spectrometer has been used to study the surface structure of cellulose, the primary building block of trees. The spectrometer allowed the determination of detail of the cellulose surface well beyond that which can be obtained by eye. In order to enable analysis of the data, pure smooth cellulose films were employed rather than wood. The thicknesses of these smooth cellulose films can affect the detected signal, hence a theoretical model of the effect was developed and verified. With the ability to both measure and interpret data from cellulose films, the system was applied to investigate two processes of great importance to the pulp and paper industry: the means by which a chemical known as AKD acts to make paper repel water, and the mode of action of enzymes in degrading cellulose. It was found that physical spreading of AKD on cellulose is the critical parameter in creating hydrophobicity, as opposed to chemical reaction and re-orientation. Further, it was demonstrated for the first time that the laser system may be used to study the molecular level degradation of cellulose.