Аннотация:The goal of this work was to study the influence of the nature of hydrophilic IL anion on optical, mechanical, morphological, and sorption properties of films obtained by dissolution/regeneration of microcrystalline cellulose in IL.
Two IL with the same cation, 1-butyl-3-methylimidazolium (bmim+), and two different anions, acetate and chloride, were chosen for the investigation. The conditions for cellulose dissolution and regeneration from bmimCl in a form of thin films were known from the literature [1]; we developed a procedure to obtain the catalytically active cellulose films containing plant peroxidases [2]. The cellulose films using bmimAcO were obtained for the first time as a result of the optimization of cellulose : IL mass ratio in the melt, the melt temperature, the dissolution duration, the film expansion conditions, the selection of an appropriate antisolvent to remove the excess of IL.
Owing to the use of bmimAcO as a cellulose solvent, the cellulose content in the film increased from 4 to 14 mass.%, the time of the cellulose dissolution in IL decreased by 3 hours, and the temperature of the melt became 35°С lower (from 85 to 50°С). The transparent films cellulose-bmimAcO (type I) were obtained using ethanol as an antisolvent contrary to the cellulose-bmimCl (type II) films, which needed distilled water for their preparation. The cellulose films regenerated from acetic IL were about 10 times mechanically stronger and 2.5 times more elastic than type II films. To achieve the same transparency (93%) of both types of films, films of the type I had to be kept for 2 min in DMSO or DMFA. The most durable and flexible films were obtained with bmimAcO, using ethanol wash and keeping in acetonitrile for 3 min. It has been shown that cellulose-bmimAcO films absorb an anionic dye indigo carmine from aqueous solutions at pH~7 and do not absorb a cationic dye pyronin B. This fact is important for analytical purposes. Besides, it has been found that horseradish and soybean peroxidases immobilized in the cellulose films of the type I retain only 20% of their initial catalytic activity contrary to 95% activity of the enzymes in the films of the type II, due to the inactivating effect of acetic IL. The obtained data demonstrate the expediency of further investigations of the two types of cellulose films in different indicator systems and media to reveal the most promising areas of their use.
We are grateful for the financial support of this research from Russian Foundation for Basic Research (grant no. 12-03-00249-а).