关键词: 季铵盐/酰胺类低共熔溶剂, 氢键, 纤维素, 溶解

Abstract: A series of ammonium-based ammonium salts and amides were used as raw materials to prepare deep eutectic solvents(DES), namely, tetramethylammonium chloride/caprolactam(TMACl/CPL), tetraethylammonium chloride/caprolactam(TEACl/CPL), tetrabutylammonium chloride/caprolactam(TBACl/CPL), tetrabutylammonium acetate/caprolactam(TBAAc/CPL),tetrabutylammonium hydrogen sulfate/caprolactam(TBAHSO₄/CPL), and tetrabutylammonium bromide/caprolactam(TBABr/CPL). The formation process of hydrogen bonds of CO-H-C and C-N-H-C between ammonium salt and caprolactam were studied by FI-IR, ¹H NMR, ¹³C NMR and MS. Then, DES was used to dissolve cellulose. The effects of alkyl chain length, anion, time, temperature, viscosity and the hydrogen-bond network structure of DES on the dissolution of cellulose were explored, respectively. It was found that butyl had higher ability to dissolve cellulose than that of ethyl and methyl. Ac^- could afford more reactive sites than Br^-, Cl^-, Ac^- and HSO^-₄. TBAAc/CPL was a preferable solvent and the dissolubility of cellulose was 7.8% under 100℃ and 75 min. Moreover, the dissolution mechanism of hydrogen bond on cellulose was investigated. The results showed that the raw dense and ordered structure of cellulose were changed to coarse and disordered state,and the structure of -OH,-CH and C-O-C didn't change.The cellulose was directly dissolved in ammonium-based DES, and no other derivatives were generated. XRD analysis showed that the 2θ of cellulose before and after regeneration changed from 15.36°, 16.68°, and 22.10° to 21.99°, and the cellulose crystal form was changed from cellulose I to type Ⅱ.

Key words: ammonium salt/caprolactam deep eutectic solvent, hydrogen bond, cellulose, dissolution