INTELLECTUAL MERIT: Cellulose nanocrystals (CNCs) are highly crystalline organic polymers that can be extracted from natural materials. They are stiffer than aluminum and theoretical calculations place their tensile strength at 7500 MPa, higher than glass fibers or steel. Inasmuch as these crystals are biocompatible, lightweight, low cost, and sustainable they offer potential for applications in biomedical materials, energy technologies, electronics, and microelectromechanical systems devices. To date, no experimental tests have been utilized to investigate the strength properties of CNCs. This proposal aims to fill these gaps. In order to evaluate such properties the underlying mechanisms responsible for nanoscale mechanics should be determined. In-situ experiments and multiscale models for deformations in small-scale components can open possibilities for improved design and applications of CNCs. The objectives of this research are (1) to explore the nanoscale mechanics of individual CNCs as a function of the biological source, (2) to determine the dependence of CNC's mechanical properties on cellulose crystal dimensions, and (3) to fully characterize the elastic moduli of CNCs as function of their crystallographic orientations. To meet these objectives, nanomechanical properties will be investigated through the use of a novel in-situ characterization technique that enables atomic force microscopy (AFM) experiments inside the chamber of a transmission electron microscope. The in-situ data will then be used to develop and validate the continuum mechanics and molecular dynamics models of CNCs.
BROADER IMPACTS: CNC-based materials are expected to have beneficial uses in a variety of technical applications, such as composite materials, packaging, tissue engineering scaffolds, drug delivery vectors, Li-ion batteries, and electronic displays. Several exchanges of OSU and Michigan Tech students are planned to promote multidisciplinary education (microscopy, cellulose nanocrystals preparation, and computational mechanics). The PIs will recruit female and minority undergraduate research students through the Michigan Community College/University Partnership program at Michigan Tech and the Saturday Academy's Apprenticeships in Science and Engineering Program at OSU. The Michigan Tech PI will also participate in outreach activities for local high school female and underrepresented students during the Engineering Scholars Program at Michigan Tech. The Oregon State PI will increase local area awareness by providing lectures/discussions on Oregon State Public Radio. In-situ videos of microscopy experiments will also be made available to the community via YouTube©, ACS Chemical and Engineering News, and the NanoHuB© network.
My role in this collaborative project was to supply samples of nanocellulose to the other cooperators. We supplied samples of cellulose nanocrystals (CNCs) from both wood and tunicates. We have also supplied samples of CNCs dispersed in a polymer matrix, namely poly(vinylidene fluoride) (PVDF). It is our understanding that the cooperator’s experiments are challenging and taking longer than originally planned. Thus a no cost extension was obtained from NSF. The Simonsen lab remains active in the project and will continue to supply samples as requested. Data acquisition is currently underway in the cooperator’s lab and publications are expected in the near future. In the process of working with cellulose nanocrystals, we developed new technology and scientific understanding, which has been published in: Smith, Sean, Christian Buesch, Dave Mathews, John Simonsen,** John F. Conley. (2014) Improved oxidation resistance of organic/inorganic composite atomic layer deposition coated cellulose nanocrystal aerogels. J. Vac. Sci. Technol. A 32(4), 041508/1-041508/8 Jeremiah Kelley, John Simonsen,* and Jie Ding. 2012. Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDFHFP) Nanocomposites Incorporating Cellulose Nanocrystals with Potential Applications in Lithium Ion Batteries. J. Appl. Poly. Sci. DOI:10.1002/app.37790 Pakzad, Anahita; Simonsen, John**; Heiden, Patricia; Shahbazian-Yassar, Reza. 2012. Observation of Size-Scale Effects on the Nanomechanical Properties of Cellulose I Nanocrystals. Journal of Materials Research, 27(3), 528-536. Pakzad, A., Simonsen, J.**, Yassar, R.S. 2012. Gradient of nanomechanical properties in the interphase of cellulose nanocrystal composites. Composites Science and Technology, 72(2), 314 – 319.
