Magnetic Cellulose Nanocrystal Based Anisotropic Polylactic Acid Nanocomposite Films: Influence on Electrical, Magnetic, Thermal, and Mechanical Properties

Abstract

This paper reports a single-step co-precipitation method for the fabrication of magnetic cellulose nanocrystals (MGCNCs) with high iron oxide nanoparticle content (∼51 wt % loading) adsorbed onto cellulose nanocrystals (CNCs). X-ray diffraction (XRD), Fourier transform infrared (FTIR), and Raman spectroscopic studies confirmed that the hydroxyl groups on the surface of CNCs (derived from the bamboo pulp) acted as anchor points for the adsorption of Fe3O4 nanoparticles. The fabricated MGCNCs have a high magnetic moment, which is utilized to orient the magnetoresponsive nanofillers in parallel or perpendicular orientations inside the polylactic acid (PLA) matrix. Magnetic-field-assisted directional alignment of MGCNCs led to the incorporation of anisotropic mechanical, thermal, and electrical properties in the fabricated PLA-MGCNC nanocomposites. Thermomechanical studies showed significant improvement in the elastic modulus and glass-transition temperature for the magnetically oriented samples. Differential scanning calorimetry (DSC) and XRD studies confirmed that the alignment of MGCNCs led to the improvement in the percentage crystallinity and, with the absence of the cold-crystallization phenomenon, finds a potential application in polymer processing in the presence of magnetic field. The tensile strength and percentage elongation for the parallel-oriented samples improved by ∼70 and 240%, respectively, and for perpendicular-oriented samples, by ∼58 and 172%, respectively, in comparison to the unoriented samples. Furthermore, its anisotropically induced electrical and magnetic properties are desirable for fabricating self-biased electronics products. We also demonstrate that the fabricated anisotropic PLA-MGCNC nanocomposites could be laminated into films with the incorporation of directionally tunable mechanical properties. Therefore, the current study provides a novel noninvasive approach of orienting nontoxic bioderived CNCs in the presence of low magnetic fields, with potential applications in the manufacturing of three-dimensional composites with microstructural features comparable to biological materials for high-performance engineering applications.

Silk nano‐discs: A natural material for cancer therapy

“…Furthermore, CSNs are prepared through acid hydrolysis which removes amorphous domains and only hard to digest crystalline domains remain intact resulting in strain‐free crystallites this is the reason for such high crystallinity. CSNs have an orthogonal orthorhombic unit cell (9.11× 7.6 × 10.5 Å) as per Scherrer calculations . The d‐spacings from XRD could be well corroborated with the bright spots of electronic diffraction data for CSN (Figure S10 and Table S2, Supporting Information).…”

“…Fe content of ~35 wt%, corresponds to the Fe 3 O 4 nanoparticles adsorbed onto CSNs. Higher loadings (~51 wt%) of magnetite onto cellulose nanocrystals have been reported due to ‐OH clusters . TEM images (Figure c) show that MGCSNs have diameter of 58.2 ±4.6 nm and thickness of 16.0 ±2.6 nm.…”

“…MGCSNs showed all these characteristic peaks, although with subdued intensities because of the immobilization of Fe 3 O 4 nanoparticles onto CSN surface. Furthermore, MGCSNs show new peak and shoulder at ~685 and 620 cm −1 respresenting bending and stretching vibrations of Fe‐O, which attributed to the formation of iron‐oxide nanoparticles . CSNs show characteristic Raman peaks (Figure b) at 905 cm −1 , 965 cm −1 , 1093 cm −1 , 1224 cm −1 and 1669 cm −1 corresponding to the ‐CN stretching, ‐CH 3 rocking, ‐C α ‐C β stretching, ‐NH in‐plane bending, and C=O stretching, respectively .…”

“…CSNs possesses a low BET ~ 3.9 m 2 g −1 due to nonporous structure, whereas their functionalization exhibits ~20‐fold increase (Figure e), suggesting that iron‐oxide nanoparticles have adsorbed onto CSN. Amide groups on CSN at close to neutral pH gain slight anionic character and the addition of iron salt (Fe 3+ ) which are positively charged leads to virile electrostatic interaction forming a uniform dispersion of iron salt‐CSN solution . Subsequently, reduction of iron salts in presence of CSN directed the formation of Fe 3 O 4 nanoparticles on the amide groups of the CSN surface.…”

“… There are few reports on magnetizing of nanoparticles obtained from naturally occurring fibers. Recently, magnetite‐supported cellulose nanocrystals were prepared for high performance applications. Further, silk microspheres/fibers‐supported Fe 3 O 4 composite materials have been explored for anti‐cancer drug delivery .…”