A general and scalable strategy to achieve transparent and hazy cellulose films with excellent mechanical properties, especially folding endurance, remains an obstacle. Herein, we incorporate transparent carboxymethyl cellulose (CMC) into opaque but hazy paper of uniformly distributed lignocellulosic fiber network by a facile and scalable impregnation to fabricate transparent and hazy all-cellulose composite films with strong mechanical properties. The CMC serves as a matrix to enhance the transparency and smoothness, whereas the isotropic intertwined network of long and slender lignocellulosic fibers simultaneously acts as a reinforcing phase to improve the mechanical properties and a light scatting source to enhance the optical haze. Consequently, the resulting composite film combines a high transparency (up to 90%) and optical haze (up to 82%) at 550 nm with superior mechanical properties (140 MPa tensile strength, 8.5 MJ m–3 toughness, and 3342 folding times). Moreover, this composite film demonstrated ultrasmoothness (Rq: 0.9 nm) and improved flame retardant performance. Mechanically robust, transparent, and hazy composite films with ultrasmoothness and enhanced fire retardancy may extend their opportunities in flexible optoelectronics.
Optical haze nanopapers were fabricated based on a self-assembly process of lanthanide complexes with tris(2-benzimidazolylmethyl) amine (NTB) [(Tb(NTB)Cl3 and/or Eu(NTB)Cl3] and TEMPO-oxidized cellulose nanofibrils (tCNFs), using a subsequent simple blending-vacuum filtration method. These optical haze nanopapers were characterized in terms of visible light transmittance, efficiency of ultraviolet (UV) light harvesting, and soft-fluorescence emission. The lanthanide complexes acted as a light-scattering source to enhance optical haze (∼100%) and a light emitter to emit soft-fluorescence under a UV light-emitting diode (UV-LED, λex, 365 nm). Due to excellent light-scattering behavior induced by the optical haze nanopaper, UV harvesting efficiency was increased from 53% to 98%, and the absolute quantum efficiency was enhanced from 21% to 25%. The optical haze nanopaper with high efficiency UV harvesting and soft-fluorescent emission presented potential applications in solar cells, lampshades, light diffusers, UV-blocking devices, anticounterfeiting devices, and organic light-emitting diodes.
Nowadays, organic pollutants have been major concerns in many fields. Production of functional materials based on renewable and sustainable resources for organic pollutants detection and removal was of much interest. Herein, multi-functional nanocomposite films based on cellulose nanocrystals (CNCs) with high optical haze, organic pollutant detection and emulsion separation capabilities, have been successfully fabricated based on hydrophobically-modified CNCs suspensions by 2-dodecen-1-succinic anhydride (DDSA) followed by radical polymerization with tridecafluorooctyl (TFMA). The suspensions displayed satisfying oil-in-water emulsion stabilization capabilities and the vacuum-dried films showed birefringence , high transparency, and optical haze (~85 %), due to the ordered arrangements of cellulose nanocrystals. The organic pollutant can be detected through the iridescent colors disappearing by Polarizing Optical Microscope observation. In addition of improved mechanical strength for application (27 MPa) and high contact angle of 131.6°, the hydrophobic films performed as high separation efficiency as >90 % of emulsion, due to the successfully grafting of hydrophobic molecules on the surface of CNCs. Thus, the surface modification for CNCs provide a facile approach of emulsification, pollutants detection and separation properties, which would widen the application potentials of renewable cellulosic resources in fields of environmental protection, engineering control and petroleum industry.
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