Nanocomposites Assembled via Electrostatic Interactions between Cellulose Nanocrystals and a Cationic Polymer

Abstract

On account of their high strength and stiffness and their renewable nature, cellulose nanocrystals (CNCs) are widely used as a reinforcing component in polymer nanocomposites. However, CNCs are prone to aggregation and this limits the attainable reinforcement. Here, we show that nanocomposites with a very high CNC content can be prepared by combining the cationic polymer poly[(2-(methacryloyloxy)ethyl) trimethylammonium chloride] (PMETAC) and negatively charged, carboxylated CNCs that are provided as a sodium salt (CNC-COONa). Free-standing films of the composites can be prepared by simple solvent casting from water. The appearance and polarized optical microscopy and electron microscopy images of these films suggest that CNC aggregation is absent, and this is supported by the very pronounced reinforcement observed. The incorporation of 33 wt % CNC-COONa into PMETAC allowed increasing the storage modulus of this already rather stiff, glassy amorphous matrix polymer from 1.5 ± 0.3 to 6.6 ± 0.1 GPa, while the maximum strength increased from 11 to 32 MPa. At this high CNC content, the reinforcement achieved in the PMETAC/CNC-COONa nanocomposite is much more pronounced than that observed for a reference nanocomposite made with unmodified CNCs (CNC-OH).

Cathodic electrodeposition of organic nanocomposite coatings reinforced with cellulose nanocrystals

“…These findings confirm that the addition of CNCs and PDA to the cathodic PA matrix can reduce the penetration rate of corrosive electrolytes to metallic substrates. They further demonstrate good barrier properties of the electrodeposited PA-CNC and PA-CNC-PDA nanocomposite coatings and prove their dense and homogeneous structure via the formation of strong interfaces between CNCs, PDA and PA matrix caused by electrostatic 28 and hydrogen bonding interactions. 19…”

“…It is reported that when the absolute value of the ζ -potential is above 30 mV for colloidal suspensions, the particles are electrically stable in the suspension. 28,37 Despite the drop observed in ζ -potential after CNC addition, the values remain positive and above +30 mV even at the highest CNC concentration indicating a stable positively charged PA–CNC dispersion. On the other hand, the particle size steadily increases from 130.4 ± 0.7 nm to 149.7 ± 9.1 nm with increasing CNC concentration (see Fig.…”

“…Being hydrophilic, CNCs are prone to aggregation in (mostly hydrophobic) polymer matrices limiting the achievable mechanical properties of the CNC-based nanocomposites. [28][29][30] Therefore, one of the most important factors affecting their mechanical performance is the state of CNC dispersion and hence polymer matrix-CNC interactions. Considering the anionic sulfate half-ester groups grafted onto CNC surfaces during acid hydrolysis, 21 their colloidal stability in an aqueous medium can be exploited for dispersion in waterborne cathodic polymers widely used in EPD (e.g., epoxy-, acrylic-or polyurethane-based).…”

“…Indeed, sonication has been extensively used as a physical method for dispersion of cellulosic nanomaterials in different media and polymer matrices to create homogeneous nanocomposites with improved mechanical, thermal and optical performances. 28,42 Prior to sonication, the size distribution curves of the mixtures show the presence of a small amount of microscopic aggregates (see Fig. 1c) which readily disappear This journal is © The Royal Society of Chemistry 2023 after sonication at 2400 J g À1 (see Fig.…”

Alignment-Assisted Networks of Polyelectrolyte-Grafted Cellulose Nanocrystals

“…The high crystallinity and well-defined high aspect ratios of cellulose nanocrystals (CNCs) when used as fillers induce excellent mechanical properties in polymer matrices. – Like other colloidal rods, such as DNA fragments and chitin nanocrystals, CNC suspensions show interesting properties of a liquid crystal. , At above critical concentration, the CNC suspension phase separates into an upper isotropic phase and a lower anisotropic chiral nematic phase. – This concentration-dependent phase transition leads to research questions related to how addition of moieties, salts, or polymer influences the structural transition of CNCs. – CNC stabilization in suspensions and underpinning their interactions with other entities or particles enable their use for a wide range of applications, such as catalysis, self-healing membrane technologies, or conductive thin films. – …”