63 / 2021-06-01 11:02:43

Study on adsorption of hemicellulose from cellulose nanofibers by QCM

QCM；Hemicellulose；Microfiber surface；Adsorption,;cellulose

Cellulose and hemicellulose are the most abundant natural polymer materials in the world, and they are very important renewable resources. A variety of functional materials with good mechanical properties, low expansion coefficient, good formability and adhesion can be prepared by combining hemicellulose and other polymers based on cellulose or cellulose nanofibers, which can be used as the matrix or skeleton material for most inorganic materials and organic polymer materials.  Metals and their oxides can also be combined with some drugs to prepare slow-release nanoparticles. The adsorption or deposition behavior has an important influence on the properties of the final materials in the process of cellulose nanofibers compounding with other materials such as hemicellulose. Quartz crystal microbalance (QCM) is a surface sensitive analytical technique based on the piezoelectric effect of quartz crystal. It is a highly sensitive tool for on-line surface and interface process analysis. It has the sensitivity of nanogram level and can be used for in-situ and real-time study of adsorption deposition behavior. Adsorption behavior is monitored from the microscopic level.

A rigid film on the surface of SiO2 chip covered by polyethylene (PEI) was used as the substrate. Nanocellulose whiskers CNF were adsorbed to form using the hydrophobicity and charge of PEI. The CNF adsorption surface was constructed.  The adsorption behavior of polyxylose hemicellulose extracted from bagasse on CNF surface was studied. It was found that cellulose could adsorb 2000 ng stably on the rigid film with PEI as substrate when the cellulose concentration was 0.05%. The cellulose can be stably adsorbed on the rigid film with PEI as substrate 5000 ng when the cellulose concentration is 0.15%.

There is a certain affinity between the hemicellulose and the cellulose surface, which leads to adsorption. However, only a small amount of hemicellulose can be directly adsorbed on cellulose. This is attributed to the electronegativity of CNF surface and the electrostatic repulsion generated by the weak negative charge formed by the hydroxyl group on the hemicellulose molecules in solution, which offset the adsorption between the two to a certain extent. Calcium ions were found to be adsorbed on cellulose. Adsorption of hemicellulose onto cellulose was enhanced by the addition of calcium ions.

Therefore, the adsorption behavior of cellulose nanofibers to hemicellulose was studied by QCM. The assembly mechanism, formation mechanism, structure and functional properties of cellulose self-assembly process were elucidated. The high value applications of cellulose derivatives and nanocellulose self-assembled functional materials were promoted.