Phenolic Ester-Decorated Cellulose Nanocrystals as UV-Absorbing Nanoreinforcements in Polyvinyl Alcohol Films

Abstract

Grafting novel and nature-inspired phenolic esters onto cellulose nanocrystals (CNCs) provides nanofibers with excellent protection against UV radiation when incorporated into a polymer matrix. In this work, CNCs decorated with a novel UVabsorbing phenolic diester (CNC-diethyl ferulate or CNC-DEF) obtained via a click-type copper-catalyzed azide/alkyne cycloaddition reaction were incorporated into a polyvinyl alcohol (PVA) matrix to produce transparent films with excellent photostability and UV-absorbing properties. PVA films filled with 20 wt % CNC-DEF exhibited complete UV protection (0% transmittance) and high transparency in the visible region (70− 90% transmittance). In contrast, PVA films loaded with the pristine CNCs do not show any UV-shielding properties. Importantly, the grafting of DEF moieties on CNCs significantly aids the dispersion of the phenolic diester in the aqueous PVA matrix, which was not achieved with DEF blended with PVA. Mechanical tests also show that the addition of 20 wt % CNC-DEF in PVA increases the tensile strength and modulus by 91 and 150%, respectively, relative to neat PVA. The oxygen barrier properties of the composite film also improve with CNC-DEF addition. This study shows the great potential of the phenolic-ester-decorated CNCs as dispersible, multifunctional UV-absorbing nanoreinforcements in PVA films for industrial and packaging applications.

A Superhydrophobic Moso Bamboo Cellulose Nano-Fibril Film Modified by Dopamine Hydrochloride

“…From Figures 3A-C, the nanofibers on the surface of CNF film are arranged and randomly distributed, thus forming a dense network interwoven structure under 300 um. As can be seen from Figures 3D-F, the surface of the CNF film became more smooth after being soaked in PVA solution, and the internal pores were filled with PVA solution, which became more compact (Mendoza et al, 2021). From Figures 3G,H,L, it could be seen that the surface of the film after silane modification became rough and has small protruding antennae, which was the main reason for the film superhydrophobicity.…”

From Biomass-Derived p-Hydroxycinnamic Acids to Novel Sustainable and Non-Toxic Phenolics-Based UV-Filters: A Multidisciplinary Journey

“…Such molecules turned out to provide a full coverage of the UV-A and UV-B regions of the electromagnetic spectrum, by increasing the conjugation throughout a longer backbone. It is noteworthy to mention that the free phenol can also be functionalized in order to be grafted onto materials—providing them with anti-UV properties ( Peyrot et al, 2020a ; Joram Mendoza et al, 2020 ; Mendoza et al, 2021a ; Mendoza et al, 2021b )—or even be used for polymerization to directly provide anti-UV materials ( Sasiwilaskorn et al, 2008 ). As previously mentioned, an increased steric hinderance on the β position is a key factor to improve absorption and stability against UV radiation exposure.…”

Thermoresponsive Poly(N-isopropylacrylamide) Grafted from Cellulose Nanofibers via Silver-Promoted Decarboxylative Radical Polymerization

“…Grafting functional polymers onto nanocellulose has been investigated to produce smart materials for advanced applications . Nanocellulose, which can either be cellulose nanofibers (CNFs), cellulose nanocrystals (CNCs), or bacterial cellulose (BC), has been widely used as a building block and scaffold for polymer functionalization because of desirable properties such as great abundance and sustainability, excellent mechanical behavior, unique optical properties, and tunable surface chemistry. − Due to the high density of hydroxyl groups present on its surface, nanocellulose can easily be functionalized by a variety of chemical reactions to graft polymers. Indeed, several studies on polymer-grafted nanocellulose materials demonstrated stimuli responsive and other functional properties as reported in the literature …”