Glucose/Glucuronate Alternating Copolymers Stripped from Oxidized Cell Wall Cellulose by Mechanical Shearing

Alternating copolymers often exhibit specific physical properties, such as a narrow glass transition temperature range and a highly uniform micelle size. Alternating copolymers are, however, synthesized from only limited combinations of monomers. Herein, we report the semisynthesis of copolymers with a basic skeleton composed of alternating glucose (G)/glucuronate (U) units via the regioselective surface oxidation of cellulose nanofibers (CNFs) or single cellulose crystallites, followed by mechanical shearing of the oxidized CNFs in water. The molecular weights and yields of the resulting G/U copolymers varied depending on the degree of oxidation (DO) of the CNFs and method of mechanical shearing but were approximately 8000‒15000 g/mol and 4‒16%, respectively. Interestingly, the molecular chain length distributions of the G/U copolymers were in good agreement with the length distributions of the dent defects formed on the CNF surfaces. We conclude that the oxidized CNF surface molecules were stripped during the mechanical shearing process to yield the G/U copolymers, and these parts of the surfaces were identified as the CNF dent defects. Thus, utilizing the two-fold helix structure of the crystallite surface molecules as a template, the chemical functionalization of CNF surfaces will lead to the production of novel functional polymers that cannot be artificially synthesized.