Investigation of the structural variations of cellulose microcrystals obtained after acid hydrolysis of waste cotton: a statistical approach

Abstract

The intricate and complex network of inter- and intramolecular hydrogen bonds in cellulose exerts a significant influence on the overall crystallographic structure of the cellulose polymer. Hence, understanding the hydrogen bonding interactions during cellulose hydrolysis is vital for tailoring the degree of crystallinity of cellulose-based materials like cellulose microcrystals (CMCs). In this study, we used a Box–Behnken statistical tool to optimize the experimental parameters for synthesizing CMCs with a high total crystallinity index (TCI). We then used field emission scanning electron microscopy, X-ray photoelectron spectrometry, X-ray diffraction, and Fourier transform infrared spectroscopy to investigate the morphological, chemical, crystalline, and structural changes that occurred in the CMC sample with the highest TCI. Our results showed that the hydrolysis process modified the hydrogen bonding network in cellulose, which resulted in an enhanced TCI. The changes in hydrogen bonding significantly affected CH bending and stretching absorption, resulting in an increased TCI of the cellulose samples. This increased TCI plays a significant role in enhancing the reinforcing properties of CMCs. Our findings highlight new insights into the role of hydrogen bonding in the TCI of CMCs and could lead to the development of new methods for controlling the TCI of cellulose. Highlights of the article Optimization of the acid hydrolysis process of waste cotton using Box–Behnken design to obtain cellulose microcrystals (CMCs). Extraction of the mathematical model that influences the total crystallinity index of CMCs. Investigation of morphological, chemical, crystalline, and structural changes in CMCs. Comparison of hydrogen bonding network between waste cotton fibers and CMCs. Increased TCI enhances CMCs’ reinforcing properties in composites.