Localization of I-alpha and I-beta phases in algal cellulose revealed by acid treatments

Highly crystalline I-alpha-rich type Cladophora cellulose, which had been kept in never-dried condition, was treated in 60wt% sulfuric acid at 100 degreesC, for 1-48 h. The cellulose microcrystals thus obtained were analysed by X-ray diffractometry, FT-IR, and transmission electron microscopy. The I-alpha component was found to be more degraded than the I-beta component. The cellulose I-alpha/I-beta ratios of the samples acid-treated for 0, 24, and 48 h were about 8:2, 6:4, and 4:6, respectively. After the acid treatment, the microcrystals became narrower in width, and very sharp at their ends. These results indicate that the I-alpha phase is mostly located at the surface of the microcrystals, which is morphologically more susceptible to the acid treatment.