Cellulose Nanofibrils and Diblock Copolymer Complex: Micelle Formation and Enhanced Dispersibility

Abstract

A great challenge to the utilization of bioderived cellulose nanofibrils (CNFs) is related to dispersion, where the hydrophilic nature makes them difficult to disperse in both organic solvents and hydrophobic polymers. In this study, an amphiphilic diblock copolymer, poly­(methyl methacrylate-b-acrylic acid) (PMMA-b-PAA), which contains a short interactive block of PAA and a long hydrophobic block of PMMA, was utilized to modify the surface of CNFs covered with carboxylic acid groups (CNF-COOH). The PAA block binds to the surface carboxylic acid groups on the CNFs through the formation of multiple hydrogen bonds, while the hydrophobic PMMA block enables better dispersion of the CNFs as well as interfacial adhesion with the matrix polymer. The attachment of PMMA-b-PAA to the CNFs was confirmed through Fourier transform infrared spectroscopy. Micelles were observed to form from a dispersion of CNF-COOH/PMMA-b-PAA complex in H2O. Good dispersion with individualized nanofibrils has been achieved in dimethylformamide, dimethyl sulfoxide, ethanol, and methanol even when a low amount of block copolymer was functionalized on the CNF surface. The dispersion level of CNF-COOH/PMMA-b-PAA correlates well with the dielectric constant of the solvents, where solvents with high dielectric constants are better able to disperse the PMMA-b-PAA modified nanofibrils.

Recent Advances in Nanocellulose Composites with Polymers: A Guide for Choosing Partners and How to Incorporate Them

“…The adsorption of an amphiphilic BCP, PMMA- b -PAA, onto TOCN was also facilitated by the H-bonding interaction between the –COOH groups of TOCN and PAA [ 236 ]. As a result, the aqueous dispersion of PMMA- b -PAA/TOCN composite showed the formation of micelles by the amphiphilic BCP and those micelles were found to be attached to the nanofibrils ( Figure 4 ).…”

“… TEM image of the aqueous dispersion of PMMA- b -PAA/TOCN composite showing the formation of spherical micelles attached to the nanofibrils (reproduced with the permission from [ 236 ]). …”

Preparation and Characterization of Soy Protein Isolate-Based Nanocomposite Films with Cellulose Nanofibers and Nano-Silica via Silane Grafting

“…To high-efficiently utilize the potential of NS as reinforcement in composites, rational surface structure designs are essential for altering the interfacial performance of NS matrix. In this respect, cellulose nanofibers (CNF) have shown promise as green dispersing agents for various nanoparticles such as graphene oxide, carbon nanotubes [22], silver nanoparticles [23], and PMMA– b –PAA complex [24]. Different from other natural nanocrystals (e.g., CNCs or SNCs), CNF hold a special net-like morphology with typical interspersed crystalline regions throughout the nanofibrils, thus endowing them higher specific surface area, excellent mechanical properties, and superior efficient dispersing effect.…”

Dispersibility of freeze-drying unmodified and modified TEMPO-oxidized cellulose nanofibrils in organic solvents

“…-poly(ethylene glycol) (PEG)-grafted TOCNF-COO were individually dispersed in chloroform, toluene, dichloromethane, 1,4-dioxane, DMA [15][16][17]; -n-dodecylamine-modified TOCNF-COO were dispersed at the level of individual nanofibrils in isopropyl alcohol [18]; -cetyltrimethylammonium bromide-modified TOCNFs demonstrated increased hydrophobicity and improved redispersibility in DMF [19]; -TOCNFs, modified with tannic acid and hexadecylamine, were dispersed in toluene, ethanol, acetone [20]; -TOCNF-COO with amphiphilic diblock copolymer-modified surface exhibited an increased dispersibility in such organic solvents as DMSO, DMF, ethanol, and methanol [21]. It should be noted that the aforementioned solvent exchange process is quite laborious because of the use of intermediate solvents and multiple centrifugation cycles.…”