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)42−, 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.
Highlights
Polymers 2021, 13, 1092. https://It is well known that the rapidly growing awareness of environmental pollution has shifted researchers’ focus from traditional petroleum-derived synthetic polymers to more environmentally friendly alternatives [1]
We reported the fast synthesis of cellulose carbamate (CC) in several minutes by microwave heating without using a solvent or catalyst [27,28,29]
Cellulose can be dissolved in NaOH [34], NaOH/urea [17] and NaOH/zinc nitrate hexahydrate aqueous solutions [35] using the freezing–thawing method to obtain transparent solutions
Summary
It is well known that the rapidly growing awareness of environmental pollution has shifted researchers’ focus from traditional petroleum-derived synthetic polymers to more environmentally friendly alternatives [1]. Cellulose can be dissolved in NaOH [34], NaOH/urea [17] and NaOH/zinc nitrate hexahydrate aqueous solutions [35] using the freezing–thawing method to obtain transparent solutions. This can be ascribed to the partial cleavage of hydrogen bonds between the hydroxyl groups of cellulose [35]. The desired amount of CC can be dissolved into the NaOH/ZnO aqueous system, and a transparent CC solution can be obtained by the freezing–thawing method [36]. We found that adding a small amount of ZnO to NaOH aqueous solution can significantly improve the solubility of CC and the stability of the spinning dope. These stronger interactions may include H-bonding, ionic, and electrostatic interactions
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