Enhancing the solubility and antimicrobial activity of cellulose through esterification modification using amino acid hydrochlorides

Most amino acid molecules have good water solubility and are rich in functional groups, which makes them a promising derivatizing agent for cellulose. However, self-condensation of amino acids and low reaction efficiency always happen during esterification. Here, amino acid hydrochloride ([AA]Cl) is selected as raw material to synthesize cellulose amino acid ester (CAE). Based on TG-MS coupling technology, a significantly faster reaction rate of [AA]Cl compared to raw amino acid can be observed visually. CAE with the degree of substitution 0.412-0.516 is facilely synthesized under 130-170 degrees C for 10-50 min. Moreover, the effects of amounts of [AA]Cl agent, temperature, and time on the esterification are studied. The CAE can be well dissolved in 7 wt% NaOH aq., resulting in a 7.5 wt% dope. The rheological test of the dope demonstrated a shear-thinning behavior for Newtonian-like fluid, and a high gel temperature (41.7 degrees C). Further, the synthesized products show distinct antibacterial activity and the bacteriostatic reduction rate against E. coli can reach 99.5 %.

Automated summary

Most amino acid molecules have good water solubility and functional groups, making them a promising agent for modifying cellulose. However, the self-condensation of amino acids and low reaction efficiency are common during esterification. In this study, amino acid hydrochloride ([AA]Cl) was used to synthesize cellulose amino acid ester (CAE), showing a faster reaction rate compared to raw amino acids. CAE with a degree of substitution of 0.412-0.516 was easily synthesized under specific conditions. The synthesized CAE showed good solubility in a 7 wt% NaOH solution and exhibited shear-thinning behavior and a high gel temperature. Additionally, the CAE exhibited significant antibacterial activity, with a bacteriostatic reduction rate against E. coli of 99.5%.