Fibre and Particle Engineering Research Unit, University of Oulu, P.O. Box 4300, FI-90014, Finland.
Wood Materials Science, University of Eastern Finland, P. O. Box 111, FI-80101, Finland.
Carbohydr Polym. 2018 Nov 1;199:219-227. doi: 10.1016/j.carbpol.2018.07.024. Epub 2018 Jul 10.
Deep eutectic solvents (DESs) are potential green systems that can be used as reagents, extraction agents and reaction media. DESs are often biodegradable, easy to prepare and have low toxicity. In this work, a recyclable DES formed from aminoguanidine hydrochloride and glycerol (AhG) was used as a reaction medium and reagent (aminoguanidine hydrochloride) for the production of cationic nanocelluloses. Under mild conditions (i.e., a reaction time of 10 min at 70 °C), dialdehyde celluloses (DACs) with two different aldehyde contents (2.18 and 3.79 mmol g) were cationized by AhG DES to form cationic dialdehyde celluloses (CDACs). Both CDACs achieved a similar high charge density of approximately 1.1 mmol g. At 80 °C (for 10 min), a very high cationic charge density of 2.48 mmol g was obtained. The recyclability of AhG DES was demonstrated by reusing it five times without decreasing the reaction efficiency. In particular, due to the low consumption of amoniguanidine hydrochloride, high recycling efficiency could be achieved without the use of any additional chemicals. The cationized celluloses, CDACs, were further mechanically disintegrated to obtain cationic nanocelluloses. According to the initial aldehyde content of DACs, the morphology of the nanocellulose could be tailored to produce highly cationic cellulose nanofibrils (CNFs) or cellulose nanocrystals (CNCs). Transmission electron microscopy confirmed that individual CNFs and CNCs with an average width of 4.6 ± 1.1 nm and 5.7 ± 1.3 nm, respectively, were obtained. Thus, the results presented here indicate that the AhG DES is a promising green and recyclable way of producing cationized CNFs and CNCs.
深共熔溶剂（DESs）是一种有潜力的绿色体系，可用作试剂、萃取剂和反应介质。DESs 通常具有生物降解性、易于制备且毒性低。在这项工作中，使用由盐酸氨基胍和甘油形成的可回收 DES（AhG）作为反应介质和试剂（盐酸氨基胍）来制备阳离子纳米纤维素。在温和的条件下（即 70°C 下反应 10 分钟），两种不同醛含量（2.18 和 3.79mmol g）的二醛纤维素（DACs）被 AhG DES 季铵化，形成阳离子二醛纤维素（CDACs）。两种 CDACs 均实现了约 1.1mmol g 的相似高电荷密度。在 80°C（10 分钟）下，获得了非常高的阳离子电荷密度 2.48mmol g。通过重复使用五次而不降低反应效率，证明了 AhG DES 的可回收性。特别是由于盐酸氨基胍的消耗量低，即使不使用任何额外的化学品，也可以实现高的回收效率。季铵化的纤维素，CDACs，进一步通过机械分散得到阳离子纳米纤维素。根据 DACs 的初始醛含量，可以将纳米纤维素的形态进行调整，以制备高阳离子纤维素纳米纤维（CNFs）或纤维素纳米晶体（CNCs）。透射电子显微镜证实，分别获得了平均宽度为 4.6±1.1nm 和 5.7±1.3nm 的单根 CNFs 和 CNCs。因此，这里的结果表明，AhG DES 是一种有前途的绿色且可回收的生产阳离子 CNFs 和 CNCs 的方法。
