Alkali Hydrolysis of Sulfated Cellulose Nanocrystals: Optimization of Reaction Conditions and Tailored Surface Charge

Abstract

Cellulose nanocrystals (CNCs) are a biorenewable resource, which may be chemically modified to impart specific properties. Modified CNCs have found use in imaging applications, as rheology modifiers, polymer reinforcements, barrier and/or optical films, and nanocomposites. Nanoparticle dimensions of CNCs are typically 5–10 nm in width, with lengths of <100–300 nm. However, the physical properties are dependent upon the number and nature of the surface charge groups imparted during preparation. In the case of CNCs produced from sulfuric acid hydrolysis, the sulfated surface groups may be partially removed prior to further functionalization. This gives more available hydroxyls yet renders the CNCs less colloidally stable. Furthermore, conditions vary significantly and there is no consensus about the optimal conditions for partial removal of sulfate functionality or conditions developed to give specific surface charge. In the following, alkali hydrolysis of sulfate half-esters was quantified by conductometric titration of the strong acid groups, and using a design of experiments (DOE), optimal conditions were determined to produce CNCs with tailored surface charge.

Fabrication of Cellulose Nanocrystal/Silver/Alginate Bionanocomposite Films with Enhanced Mechanical and Barrier Properties for Food Packaging Application

“…Cellulose is the most abundant natural biopolymer on earth, occurring in wood and cell wall of plants [23,24]. It is composed of β-1,4-linked glucopyranose units that forms a high molecular weight linear homopolymer [25].…”

A Review on the Application of Nanocellulose in Cementitious Materials

“…It contains 64–98% cellulose I β depending on the source [ 34 ]. Normally, it can be produced using different methods, of which the hydrolysis with mineral acids, especially sulfuric acid (H 2 SO 4 ), is the most commonly used, and the phosphoric acid (H 3 PO 4 ) and hydrochloric acid (HCl) are also used [ 22 ]. The acid treatment can remove most amorphous cellulose and thus produce high purity cellulose crystals, leading the CNC to have a high crystallinity [ 38 ].…”

“…Also, during the sulfuric acid hydrolysis process, some negatively charged sulfate ester groups can be grafted on CNC’s surface [ 39 ]. CNC possesses some unique properties, such as high crystallinity, relatively high aspect ratio (10–100), high thermal stability (up to 300 °C), low density (~1.6 g/cm 3 ), low coefficient of thermal expansion (~1 ppm/K), large surface area, high tensile strength (~7.5 GPa), and high tensile modulus (up to 170 GPa), and even it can be easily functionalized because of easily accessible hydroxyl groups on its surface [ 22 , 23 , 24 , 25 ].…”

“…Whereas BC is obtained from bacteria (such as Gluconacetobacter xylinus ). Although these nanocelluloses are different from their origins and isolation methods, they have some similarities, such as low density, large aspect ratio, high strength, and high surface area, etc., [ 18 , 19 , 20 , 21 , 22 , 23 , 24 ]. Also, nanocelluloses are hydrophilic, with large amounts of hydroxyl groups on their surface, and can absorb some water while mixing with cementitious materials.…”

Novel Cellulose Nanofibers/Polyvinyl Alcohol/Polyethyleneimine Nanoparticle for Cu2+ Removal in Water

“…The adsorbents mainly include activated carbon, clay, biochar and polymers. Recently, nanocellulose based adsorbents become more and more popular as nanocellulose has higher speci c surface area, excellent mechanical properties and good biocompatibility (Du et al 2016;Jordan et al 2019).…”