Fluorinated Nanocellulose-Reinforced All-Organic Flexible Ferroelectric Nanocomposites for Energy Generation

Abstract

We report here enhanced ferroelectric crystal formation and energy generation properties of polyvinylidene fluoride (PVDF) in the presence of surface-modified crystalline nanocellulose. Incorporation of only 2−5 wt % fluorinated nanocellulose (FNC) in PVDF has been found to significantly induce polar β/γ-phase crystallization as compared to the addition of unmodified nanocellulose (carboxylated nanocellulose). A device made up of electrically poled PVDF/FNC composite films yielded 2 orders of magnitude higher voltage output than neat PVDF in vibrational energy harvesting. This remarkable increase in energy generation properties of PVDF at such a low loading of an organic natural biopolymer could be attributed to the tailored surface chemistry of nanocellulose, facilitating strong interfacial interactions between PVDF and FNC. Interestingly, energy harvesting devices fabricated from PVDF/FNC nanocomposites charged a 4.7 μF capacitor at significantly faster rate and the accumulated voltage on capacitor was 3.8 times greater than neat PVDF. The fact that PVDF/FNC nanocomposites still retain a strain at break of 10− 15% and can charge a capacitor in few seconds suggests potential use of these nanocomposites as flexible energy harvesting materials at large strain conditions.

Surface modified microfibrillated cellulose‐poly(vinylidene fluoride) composites: β‐phase formation, viscoelastic and dielectric performance

“…found an improved β‐phase in PVDF/graphene oxide composites through interaction between the electron‐rich oxygenated groups and the fluorine atoms 23 . Furthermore, the modification of fillers with NH 2 and CF 2 functional groups was found to improve their dispersion state into the low surface energy PVDF 21,29 . Ionic fluorinated surfactants were also reported to promote the formation of β‐phase crystals in PVDF 30 …”

“…Some authors suggested that the hydroxyl groups of cellulose could promote heterogeneous nucleation and force the PVDF chains to crystallize into a β configuration 28,31,33 . However, PVDF and cellulose do not interact at a molecular level leading to the formation of cellulose aggregates in the polymer matrix 29,32 . Again, the surface chemistry of cellulose is the key factor, which controlled the nucleation of the β‐phase and was related by Bodkhe et al .…”

“…Among the studied nucleating particles, increasing attention is being paid to cellulose because it is the most abundant biopolymer on Earth and it is a low cost material with excellent mechanical properties 28,29,31–33 . Various forms of cellulose have been used to promote the formation of β‐phase in PVDF including nanofiber, nanocrystalline, microcrystalline and bacterial cellulose 32–36 .…”

“…For example, Ram et al . found that addition of trifluoroethylamine modified nanocellulose into PVDF promoted β‐phase crystallization compared to the addition of unmodified cellulose 29 …”

“…Most of the previous work on cellulose/PVDF composites were devoted to cellulose fibers and nanocrystals, with rather well‐defined morphologies and surface areas 28,29,31–33 . The present work focuses on microfibrillated cellulose (MFC), characterized by more complex fibrillar morphologies and challenging dispersion into hydrophobic polymers.…”