Effects of divalent anionic catalysts on cross-linking of cellulose with 1,2,3,4-butanetetracarboxylic acid

Locating the Reaction Site of 1,2,3,4-Butanetetracarboxylic Acid Carboxyl and Cellulose Hydroxyl in the Esterification Cross-Linking

The modification of cellulose with polycarboxylic acid is an important technology to functionalize the substrate. 1,2,3,4-Butanetetracarboxylic acid (BTCA) can significantly improve the anti-wrinkle performance of treated cotton fabrics by cross-linking with cellulose. However, the reaction site of BTCA carboxyl and the cellulose hydroxyl has not yet been clarified, which hinders the in-depth understanding about the reaction mechanism and the development of new cross-linking reagents. This study combines Fourier transform infrared and two-dimensional correlation spectroscopy to try to make it clear. Results confirmed that BTCA anhydride is an active intermediate (corresponding to the generally accepted theory) to esterify with cellulose hydroxyl, especially the O(6)-H(6) and O(2)-H(2). Cellobiose was taken as a model of cellulose to react with BTCA at variable temperatures, proving the above conclusion. In addition, the C14- or C11-containing carboxyl of BTCA showed a higher reactivity. Based on calculating reaction kinetics and thermodynamics with Gaussian 09W software, the most likely reaction route between BTCA and cellulose was as follows: BTCA → BTCA C5C14 anhydride → C14O15 ester → C14O15 ester C31C34 anhydride → C14O15C33O ester.

Catalytic and ionic cross-linking actions of l-glutamate salt for the modification of cellulose by 1,2,3,4-butanetetracarboxylic acid

The sodium l-glutamate is reported as an efficient catalyst for the cross-linking between 1,2,3,4-butanetetracarboxylic acid (BTCA) and cellulose. Results presented ester absorbance of the treated fabrics strongly increased in the presence of the homemade l-glutamate salt, a mixture of l-glutamic acid (LGA) and NaOH at a specific ratio. Importantly, anti-wrinkle properties of the treated fabrics were significantly improved. Based on the relative concentration calculation, l-glutamate promoted the reaction of BTCA with cellulose by accelerating the formation of BTCA anhydrides and the esterification of anhydrides with cellulose. Besides, the improved anti-wrinkle property was partially attributed to the fact that the generated LGA reacted with cellulose and formed ionic cross-linking networks through amino groups with carboxyl groups in BTCA, which was confirmed by the Fourier transform infrared spectra and the computational calculations. Through detailed comparisons, l-glutamate catalyzed fabrics showed as good durability as sodium hypophosphite, indicating a possible alternative for phosphorus-containing catalysts.