Cellulose is an excellent choice for creating sustainable and renewable polymers, however there are still gaps in our knowledge. In order to make novel polymers tuned for specific applications it is necessary to modify the fibers and fibers that a in a specific/targeted way. The purpose of this work is to derive a better understanding of the mechanism of modification to allow for precise modifications to obtain predictable properties of the new material. To do this we selected the TEMPO oxidation reaction that is used in numerous applications. In this project we explore how parameters such as variation in solvent mixtures and 2nd oxidant effect the oxidation efficiency and location within the fiber structure the oxidation occurs. While maintaining the fiber integrity of different cellulose sources. Solvent systems using different ratios of water-acetonitrile mixtures is evaluated. Acetonitrile was chosen as the co-solvent due to its effect on swelling of cellulose in combination with its reported enhancing oxidation efficiency in TEMPO/BAIB-oxidations. A range of co-catalysts were chosen based on their selectivity, reactivity and size. The TEMPO oxidation is carried out using various cellulose sources while changing the reaction conditions. These sources include bleached Kraft pulp (BKP), thermomechanical pulp (TMP), microcrystalline cellulose (MCC), milled cotton linters (MCL) and rayon. When the fibers are pre-swelled by stirring in solvent overnight, we observe an enhanced reaction rate and the addition of acetonitrile improves the degree of oxidation. It was found that by changing the co-catalyst from sodium hypochlorite (NaOCl) to (diacetoxyiodo)benzene (BAIB) the reaction stops at the aldehyde state if only water is used as the solvent on microcrystalline cellulose. Oxidation to the carboxylic state occurs when acetonitrile is used. pH changes were used to monitor the reactions and the oxidized cellulose material was characterized by titration, FT-IR, MS-imaging, microscopy and single-fiber tensile measurements.

Influence on solvent and 2nd oxidant on TEMPO oxidation of cellulose

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