Towards Biomimicking Wood: Fabricated Free-standing Films of Nanocellulose, Lignin, and a Synthetic Polycation

Abstract

Woody materials are comprised of plant cell walls that contain a layered secondary cell wall composed of structural polymers of polysaccharides and lignin. Layer-by-layer (LbL) assembly process which relies on the assembly of oppositely charged molecules from aqueous solutions was used to build a freestanding composite film of isolated wood polymers of lignin and oxidized nanofibril cellulose (NFC). To facilitate the assembly of these negatively charged polymers, a positively charged polyelectrolyte, poly(diallyldimethylammomium chloride) (PDDA), was used as a linking layer to create this simplified model cell wall. The layered adsorption process was studied quantitatively using quartz crystal microbalance with dissipation monitoring (QCM-D) and ellipsometry. The results showed that layer mass/thickness per adsorbed layer increased as a function of total number of layers. The surface coverage of the adsorbed layers was studied with atomic force microscopy (AFM). Complete coverage of the surface with lignin in all the deposition cycles was found for the system, however, surface coverage by NFC increased with the number of layers. The adsorption process was carried out for 250 cycles (500 bilayers) on a cellulose acetate (CA) substrate. Transparent free-standing LBL assembled nanocomposite films were obtained when the CA substrate was later dissolved in acetone. Scanning electron microscopy (SEM) of the fractured cross-sections showed a lamellar structure, and the thickness per adsorption cycle (PDDA-Lignin-PDDA-NC) was estimated to be 17 nm for two different lignin types used in the study. The data indicates a film with highly controlled architecture where nanocellulose and lignin are spatially deposited on the nanoscale (a polymer-polymer nanocomposites), similar to what is observed in the native cell wall.

Adsorption Characteristics of Carboxymethylated Lignin on Rigid and Soft Surfaces Probed by Quartz Crystal Microbalance

“…Since buffer rinsing was used between CML and PDADMAC adsorption experiment, the existence of complexes postulates the detachment of PDADMAC from the adsorbed layer for complexation with CML in the solution, supporting the illustration of Figure . Comparably, a thinner film (23.4 ± 2.8 nm) after 16 layers of adsorption was reported for the deposition of three polymers of PDADMAC, unmodified lignin, and NC (nanocellulose with carboxylic acid content of 1 mmol/g) by Pillai and co-workers . In the current and abovementioned studies, PDADMAC did not change the thickness of LBL significantly.…”

“…Comparably, a thinner film (23.4 ± 2.8 nm) after 16 layers of adsorption was reported for the deposition of three polymers of PDADMAC, unmodified lignin, and NC (nanocellulose with carboxylic acid content of 1 mmol/g) by Pillai and co-workers. 67 In the current and abovementioned studies, PDADMAC did not change the thickness of LBL significantly. However, it highlighted the importance of the linking layer in which the sequential layer buildup was not possible without it.…”

Adsorption of a fabric conditioner on cellulose nanocrystals: synergistic effects of surfactant vesicles and polysaccharides on softness properties

“…Engström et al for instance studied the deposition and adhesion of latex nanoparticles on surfaces of cellulose nanofibrils by QCM-D, and have found that the particle softness, which can be modulated via the glass transition temperature of the polymers, was a key parameter for producing strong and tough materials of high nanocellulose content (Engström et al 2019;Engström et al 2017). Similar QCM studies have been carried out on CNC substrates for food packaging (Saini et al 2016), biomimicking wood (Pillai et al 2014) and enzymatic hydrolysis applications (Lin et al 2019). Finally, studies combining AFM and QCM have been performed using proteins, antibodies or enzymes (Raghuwanshi and Garnier 2019), showing again the importance of nanocellulose substrates in producing model substrates for material science or biochemistry studies.…”

Biosynthesis and Characterization of Silver Nanoparticles (Snps) by using Leaf Extracts of Ocimum Sanctum L (Tulsi) and Study of its Antibacterial Activities

“…In the last decade there had been tremendous developments in nanotechnology science, which resulted in the establishment of several new techniques for research. Nanotechnology has achieved the rate of combing all living organisms-plants, animal and microorganisms [1][2][3][4][5][6][7]. It includes multidisciplinary research interest like Biochemistry, Material Science, Polymer Science and etc.…”