Figure 2

SEM images of cotton fibres disrupted by phosphoric acid treatments. SEM micrographs of cotton fibres after treatment with a range of o-phosphoric acid concentrations. After control treatment (nanopure water, 0% (w/w) acid), cotton fibres appear smooth, with few surface features. As the acid concentration was increased to near the point of cellulose dissolution (~73%-78%), manifestations of amorphogenesis begin to appear at the surface of the cotton fibres. At 74% phosphoric acid, initial signs of splitting, roughening, fibrillation and peeling/delamination of the fibres appear. As the acid concentration is increased from 74% to 76%, these effects become more pronounced. At 77%, the fibre structure has been almost completely destroyed, with large portions of the outer layer of the fibre appearing to peel off, revealing a rough, fibrillated underlying structure. After treatment with 78% phosphoric acid no fibre structure remains. All cellulose present appears to have been dissolved and reprecipitated into amorphous cellulosic ‘mats’. All images were taken at x1200 magnification and each image depicts a representative fibre for the indicated acid concentration.