Cellulose from cotton fibers is highly pure, structurally ordered (crystalline) and of high molecular weight. Waste or discounted cotton fibers could be utilized in preparation of regenerated cellulosic materials. However, cellulose dissolution in energy efficient, cost effective, and overall environmentally friendly conditions  represents a major  challenge. This study investigated the effects of acid hydrolysis and cryogenic grinding of cotton fiber cellulose on its physicochemical properties and subsequent dissolution under mild conditions in ionic liquid based solvent system, 1-butyl-3-methylimidazolium acetate/N,N-dimethylacetamide (BMIMAc/DMAc). Acid hydrolysis and cryogenic grinding of high molecular weight (MW) cotton cellulose (DP&gt;4,000) was carried out to produce hydrolyzed cotton (HC) and cryo-ground (CG) samples for dissolution. The samples were characterized using gel permeation chromatography , Fourier transform infrared spectroscopy , X-ray diffraction , and thermogravimetric analysis , while the dissolution process was monitored using Polarized Light Microscopy . It was found that  even a drastic decrease of the MW of cellulose did not result in improvement of its dissolution at room temperature. As compared to the original cotton cellulose, the higher amount of undissolved fibers in solutions led to unstable rheological behavior of HC and CG solutions. However, increasing the temperature from room temperature to higher temperatures led to a significant improvement in cellulose dissolution. This phenomenon implies that reducing the MW of cellulose might not be able to improve its dissolution under certain conditions. During the dissolution process, the physical properties of cellulose including fiber aggregation status, solvent diffusivity, and cellulose crystallinity may play a critical role compared to the MW, while the MW may not be an important factor. This finding may help further understand the mechanism of cellulose dissolution and seek better strategies to dissolve cellulose under mild conditions for industrial applications.

Dissolution of cotton fibers in ionic liquid based solvent system: Effects of hydrolysis, cryogenic grinding and temperature

ACS Spring Meeting 2021

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