3:00 PM - SB09.02.04
Effects of Lignin on Bacterial Cellulose Nanocomposite Materials
Eleftheria Roumeli1,Andrew Jimenez1,Esther Law1,Mallory Parker1,Jeremy Fredricks1,Hareesh Iyer1,Marissa Nelsen1,Bichlien H. Nguyen1,2,Karin Strauss1,2
University of Washington1,Microsoft2
In recent years, there has been a significant thrust towards the creation of sustainable green polymers and polymer composites 1,2. Reductions in manufacturing resources, synthetic polymer waste, and greenhouse emissions are all driving forces for advancements in this area. Cellulose, the world’s most abundant polymer, is not only derived from renewable resources, but also combines remarkable specific mechanical properties (comparable to steel wire, Kevlar and carbon fibers 3,4) with biodegradability, biocompatibility, and a molecular structure that allows for easy functionalization 4–6. Compared to cellulose extracted from wood, nanocellulose secreted from bacterial cultures (also referred to as bacterial cellulose, ‘BC’) is matrix-free, has high aspect ratio and crystallinity, and can be obtained with minimal processing 3,4. Emerging applications of BC include nanopapers and microfibers showing remarkable Young’s modulus (~66 GPa3), strength (~1GPa3) and toughness (16.9 MJ/m3 7) for binder-free, pure nanocellulose materials. The incredible mechanical properties and ability to self-bind without additives stem from the combination of high aspect ratio nanofibrils, vast hydrogen bonding network, high degree of crystallinity, and for the mentioned cases arise from fiber alignment effects that enhance further the hydrogen bonding interactions between the cellulose nanofibrils7,8. However, BC-based materials are naturally brittle and hydrophilic due to the molecular structure of cellulose. In natural wood, phenolic molecules forming large lignin networks, serve, together with other biopolymers, as a binder to the cellulose matrix, tuning mechanical properties, conferring hydrophobicity, and protecting against pathogens4. In fact, recent research into sustainable biocomposites has shown significant increases of mechanical properties, thermal stability and hydrophobicity on wood-extracted cellulose-lignin composite papers with hot press treatment, compared to conventional cellulose paper9.
In this work, we present an exploration into the development of BC-lignin nanocomposites through a design of experiments approach which allows the systematic investigation of the governing structure-processing-property relationships in these nanocomposites. Specifically, we explore a matrix of hot press processing conditions including time (10-30 minutes), temperature (120-160 °C), and pressure (5-15 MPa) and correlate the performance of those nanocomposites in response to the processing conditions. Our characterization includes scanning electron microscopy, thermogravimetric analysis, X-ray diffraction and nanoindentation tests. Additionally, the effects of lignin binding the cellulose matrix are further examined through contact angle analysis and Fourier-transform infrared spectroscopy.
1. Mohanty, A. K., Vivekanandhan, S., Pin, J.-M. & Misra, M. Science 362, 536–542 (2018).
2. Liu, C. et al. Adv. Mater. n/a, 2001654.
3. Wang, S. et al. Adv. Mater. 29, 1702498 (2017).
4. Moon, R. J., Martini, A., Nairn, J., Simonsen, J. & Youngblood, J. Chem. Soc. Rev. 40, 3941 (2011).
5. Rahman, M. M. & Netravali, A. N. ACS Macro Lett. 5, 1070–1074 (2016).
6. Qiu, K. & Netravali, A. N. Polym. Rev. 54, 598–626 (2014).
7. Zhu, H. et al. Proc. Natl. Acad. Sci. 112, 8971–8976 (2015).
8. Ling, S. et al. Prog. Polym. Sci. 85, 1–56 (2018).
9. Jiang, B. et al. Adv. Funct. Mater. 30, 1906307 (2020).