Localization of Crystalline Allomorphs in Cellulose Microfibril

We report an FTIR spectroscopic technique combined with intracrystalline deuteration and rehydrogenation of cellulose samples to investigate the localization of Iα and Iβ domains within a cellulose microfibril obtained from Iα-rich algae. When Glaucocystis cellulose incompletely converted from Iα to Iβ was deuterated and rehydrogenated at elevated temperature, OD groups involved in hydrogen bonding in the Iβ domain first reverted to OH, followed by those in the Iα domain, suggesting that the Iα core domain was surrounded by the Iβ domain in an artificially induced sample. We concluded that this Iα → Iβ conversion proceeded from the surface toward the core. Native celluloses from Valonia and Cladophora were first deuterated without changing the allomorphic composition, and rehydrogenation was studied from Iα- and Iβ-specific absorbances. Surprisingly, both absorbances changed synchronously, clearly indicating that the simple “skin-core” distribution model of Iα and Iβ domains is not realistic at least for these native celluloses.