Dissolution and Interaction of Cellulose Carbamate in NaOH/ZnO Aqueous Solutions

Abstract

The dissolution and molecular interactions of cellulose carbamate (CC) in NaOH/ZnO aqueous solutions were studied using optical microscopy, differential scanning calorimetry (DSC), ¹H NMR, dynamic light scattering (DLS), atomic force microscopy (AFM), transmission electron microscopy (TEM), and molecular dynamic simulation. The dissolution of CC in NaOH/ZnO aqueous solutions using the freezing-thawing method was an exothermic process, and the lower temperature was favorable for the dissolution of CC. ZnO dissolved in NaOH aqueous solutions with the formation of Zn(OH)₄^2-, and no free Zn²⁺ ions existed in the solvents. NaOH/Na₂Zn(OH)₄ system formed strong interactions with the hydroxyl groups of CC to improve its solubility and the stability of CC solution. The results indicate that 7 wt% NaOH/1.6 wt% ZnO aqueous solution was the most appropriate solvent for the dissolution of CC. This work revealed the dissolution interaction of CC-NaOH/ZnO solutions, which is beneficial for the industrialization of the CarbaCell process.

Keywords: NaOH/ZnO aqueous solution; cellulose carbamate; dissolution interaction; freezing–thawing method.