Investigation on Reaction Sequence and Group Site of Citric Acid with Cellulose Characterized by FTIR in Combination with Two-Dimensional Correlation Spectroscopy

Abstract

Cotton fabrics are prone to wrinkles and can be treated with citric acid (CA) to obtain good anti-wrinkle properties. However, the yellowing of the CA-treated fabrics is one big obstacle to the practical application of citric acid. The changing sequence order of CA anhydride and unsaturated acid (the reason for yellowing), such as aconitic acid (AA), has not been investigated. Herein, Fourier transform infrared (FTIR) spectroscopy, two-dimensional correlation spectroscopy (2Dcos), and Gaussian calculation were employed to characterize the reaction mechanism between CA with cellulose. FTIR spectra of the CA-treated fabrics heated under different temperatures were collected and further analyzed with 2Dcos. The results indicated the changing sequence order: 1656 cm −1 →1784 cm −1 →1701 cm −1 , ("→" means earlier than), i.e., unsaturated acid→anhydride→ester. Moreover, a change of Gibbs free energy (∆G) showed that trans-AA (∆G = −22.10 kJ/mol) is more thermodynamically favorable to be formed than CA anhydride 1 (∆G = −0.90 kJ/mol), which was proved by Gaussian computational modeling. By taking cellobiose as a model of cellulose, the ∆G results proved that O(6)-H(6) on the glucose ring is the most likely hydroxyl to react with anhydride originated from CA or AA, especially with the terminal carbonyl group.2 of 13 the most promising ones. Among PCAs, 1,2,3,4-butanetetracarboxylic acid (BTCA) [11,15,16], citric acid (CA) [17][18][19] and 3,3 ,4,4 -benzophenonetetracarboxylic acid (BPTCA) [20,21] show outstanding performance. Furthermore, CA is a cheap and renewable compound, but it will result in yellowing of the treated fabrics [17,18].Yang confirmed the formation of various unsaturated acids from CA in the anti-wrinkle finishing process [18] and adopted polyols to improve the whiteness index of the CA-treated fabrics [17]. Consequently, the whiteness index of the CA-treated fabrics was improved by polyols, especially xylitol, due to the dicitrate that is formed between CA and polyols being more thermally stable than CA. However, this method means more chemicals being required for the anti-wrinkle finishing of cotton fabrics and brings a greater burden on the environment.Hydrogen peroxide (H 2 O 2 ) is a strong and green oxidant that can break the C=C bonds, which is the basic principle for the bleaching of raw cotton fabrics. Similarly, H 2 O 2 was employed to bleach the CA-treated fabrics under alkaline conditions (alkaline post-bleaching) [22] or ultraviolet B conditions (UVB post-bleaching) [23], which are aimed at improving the whiteness index. Interestingly, the whiteness index of the CA-treated fabrics was improved, but the anti-wrinkle properties decreased a little. Luo [24] reported that the active agent N-[4-(triethylammoniomethyl)benzoyl] caprolactam chloride (TBCC) could be used in H 2 O 2 bleaching of the CA-treated fabrics at a lower temperature and near-neutral conditions (TBCC post-bleaching). Although TBCC post-bleaching improved the whiteness index, the strength retention of the bleached fabrics decr...

Silk ProteinsEnriched Nanocomposite Hydrogels Based on Modified MMT Clay and Poly(2-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropane Sulfonic Acid) Display Favorable Properties for Soft Tissue Engineering

“…Peak at 1863 cm −1 can be assigned to asymmetric C=O stretching in anhydride group (strong). Peak at 1692 cm −1 can be attributed to symmetric C=O stretching in carboxyl group [ 30 , 31 ].…”

The Simple Method of Preparation of Highly Carboxylated Bacterial Cellulose with Ni- and Mg-Ferrite-Based Versatile Magnetic Carrier for Enzyme Immobilization

“…The main significant negative cross-band appeared between 1720 cm −1 and ≈ 980 cm −1 assigned to different conformations of primary alcohol at C6-O6H. This site in glucopyranose molecules is most susceptible to modification by CA, which was manifested by reducing this band intensity resulting in ester bond formation [40,41]. Successive visible negative cross-peaks at 1580 cm −1 , 1400 cm −1 vs. ≈ 980 cm −1 also indicated changes in carboxylate amount in a carrier structure.…”

Evaluation of Selected Thermal Changes in Textile Materials Arising in the Wake of the Impact of Heat Radiation

“…Natural (i.e., cotton, flax, hemp) and man-made (viscose, modal and lyocell) cellulosic fibres react substantially differently than synthetic fibres, e.g., polyesters, when exposed to a heat source. The heating of cellulose fibres in the presence of oxygen causes some amount of hydrolysis and dehydration, the extent of which is directly proportional to the temperature [3,4]. It should be noted that even a high degree of thermal destruction of cellulosic fibres does not usually cause clearly visible changes in their morphological structure [5,6].…”