Published: July 20th, 2016
Synthesis schemes to prepare highly stable wood fiber-based hairy nanoparticles and functional cellulose-based biopolymers have been detailed.
Nanoparticles, as one of the key materials in nanotechnology and nanomedicine, have gained significant importance during the past decade. While metal-based nanoparticles are associated with synthetic and environmental hassles, cellulose introduces a green, sustainable alternative for nanoparticle synthesis. Here, we present the chemical synthesis and separation procedures to produce new classes of hairy nanoparticles (bearing both amorphous and crystalline regions) and biopolymers based on wood fibers. Through periodate oxidation of soft wood pulp, the glucose ring of cellulose is opened at the C2-C3 bond to form 2,3-dialdehyde groups. Further heating of the partially oxidized fibers (e.g., T = 80 °C) results in three products, namely fibrous oxidized cellulose, sterically stabilized nanocrystalline cellulose (SNCC), and dissolved dialdehyde modified cellulose (DAMC), which are well separated by intermittent centrifugation and co-solvent addition. The partially oxidized fibers (without heating) were used as a highly reactive intermediate to react with chlorite for converting almost all aldehyde to carboxyl groups. Co-solvent precipitation and centrifugation resulted in electrosterically stabilized nanocrystalline cellulose (ENCC) and dicarboxylated cellulose (DCC). The aldehyde content of SNCC and consequently surface charge of ENCC (carboxyl content) were precisely controlled by controlling the periodate oxidation reaction time, resulting in highly stable nanoparticles bearing more than 7 mmol functional groups per gram of nanoparticles (e.g., as compared to conventional NCC bearing << 1 mmol functional group/g). Atomic force microscopy (AFM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) attested to the rod-like morphology. Conductometric titration, Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), dynamic light scattering (DLS), electrokinetic-sonic-amplitude (ESA) and acoustic attenuation spectroscopy shed light on the superior properties of these nanomaterials.
Cellulose, as the most abundant biopolymer in the world, has been served recently as a key raw material to yield crystalline nanoparticles named nanocrystalline cellulose (NCC, also known as cellulose nanocrystals CNC)1. To understand the mechanism of NCC synthesis, the structure of cellulose fibers needs to be explored. Cellulose is a linear and polydispersed polymer comprising poly-beta(1,4)-D-glucose residues2. The sugar rings in each monomer are connected through glycosidic oxygen to form chains of (1-1.5) x 104 glucopyranose units2,3, introducing alternating crystalline parts and disordered, amorphous regions, first rep....
CAUTION: Read the material safety data sheets (MSDS) of all the chemicals before touching them. Many of the chemicals used in this work may cause severe health damages. Using personal protection such as lab coat, gloves, and goggles is a must. Do not forget that safety comes first. The water used throughout the synthesis is distilled water.
1. Preparation of Partially Oxidized Fibers as an Intermediate
The mass portion and charge content of each fraction during the periodate and chlorite oxidation of pulp depends on the reaction time (Table 1). Moreover, DAC molecular weight depends on heating condition and residence time (Table 2). Once SNCC and DAMC are made, they precipitate out by adding propanol (Figure 1). To measure the charge content of ENCC, conductometric titration is performed (Figure 2). NCC and ENCC colloid.......
Following the chemistry discussed in this visual paper, a spectrum of highly stable cellulose-based nanoparticles with tunable charge bearing both crystalline and amorphous phases (hairy nanocrystalline celluloses) are produced. Depending on the periodate oxidation time, as shown in Table 1, various products are yielded: oxidized fibers (fraction 1), SNCC (fraction 2), and DAMC (fraction 3) each of which providing unique properties, such as defined size, morphology, crystallinity, and aldehyde content. F.......
|Q-90 softwood pulp
|Light sensitive, Strong oxidizer, must be kept away from flammable materials
|Strong base, causes serious health effects
|Reactive with reducing agents and combustible materials
|Corrosive and oxidizing agent, keep in a cool and dark place
|Strong acid, causes serious health effects
|Unstable at high temperature and humidity, mutagenic
|High rotary speed
|Fixed angle rotor
|Tighten the lid carefully
|Spectra (Part No. 132676)
|Cutoff Mw = 12-14 kD, Length ~ 30 cm, width ~ 4.5 cm
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