Nanocellulose was prepared from wood pulp via a one-pot oxidation reaction using only a highly concentrated solution of sodium hypochlorite pentahydrate (NaClO•5H 2 O) and subsequent mechanical treatment. The concentration of NaClO in the solution was 22%, and the oxidation reaction times were 0.5, 2, and 6 h. The carboxy group content in the pulp increased with reaction time and reached 0.87 mmol/g after oxidation for 6 h. The oxidized pulp fibers were successfully refined down to nanocellulose by gentle mechanical disintegration such as ultrasonic homogenizer treatment. The obtained nanocellulose showed good colloidal stability in water because of the introduced carboxy groups, and the dispersion showed high optical transparency. Scanning probe microscopy showed that the nanocelluloses had an average height and length of 2.7−3.2 and 173−398 nm, respectively. Nuclear magnetic resonance spectroscopy analysis of the oxidized pulp suggested that NaClO oxidized the C2 and C3 hydroxy groups of the glucose units.
We herein report the preparation of thermo-and redox-responsive branched polymers by the condensation reaction of three-armed oligo(ethylene glycol) (trisOEG) and cystamine (CA). The prepared branched polymers exhibited a soluble-insoluble transition at a lower critical solution temperature (LCST) and formed coacervate droplets through a liquidliquid phase separation process. We then demonstrated control of the LCSTs of the branched polymers by varying the feed ratio of CA and the surrounding salt concentration close to body temperature. In addition, the trisOEG-cys x polymer formed coacervate droplets above the LCST, in which hydrophobic molecules were condensed. The redox response of the branched polymers was also investigated. Interestingly, the branched polymers degraded to low-molecular-weight materials (i.e., trisOEG) in the presence of dithiothereitol as a reducing agent through cleavage of the disulfide bond of CA. This facile preparation of branched polymers is expected to be valuable in the context of functional biomedical materials and modifiers for materials surfaces, such as the bases for drug delivery carriers and separation materials.Additional supporting information may be found in the online version of this article.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.