Chitosan: a smart polymer for (bio)materials

J.J. Thevarajah1,2, D.L. Taylor1,2, M.D. O'Connor3, R. Wuhrer4, P. Castignolles2, M. Gaborieau1

1University of Western Sydney (UWS), Molecular Medicine Research group (MMRG), School of Science and Health (SSH), Parramatta, 2150, Australia;

2UWS, Australian Centre for Research on Separation Science (ACROSS), SSH, Parramatta, 2150, Australia;

3UWS, MMRG, School of Medicine, Campbelltown, 2560, Australia;4UWS, Advanced Materials Characterisation Facility, Parramatta, 2150, Australia.

e: m.gaborieau@uws.edu.au

Chitosan is extracted from chitin, the second most abundant polysaccharide on earth, and the main component of crab and shrimp shells. Chitosan is a 'smart' polymer, i.e. it responds to changes in its environment, specifically to changes in pH (Figure 1). It is also renewable, biocompatible and biodegradable, which makes it attractive for applications in renewable plastics and as substrate for cell culture.

Figure 1: Molecular structure of chitosan and its response to changes in pH.

The composition of chitosan (degree of acetylation DA, and charged / neutral form) plays a crucial role in the chitosan films properties. Nuclear magnetic resonance spectroscopy (NMR) yields the average DA of a chitosan sample, and capillary electrophoresis (CE) the heterogeneity of composition.[1]

Solid-state characterisation methods are valuable because of chitosan's limited solubility, and of the need to understand the material's performance in its solid state. Solid-state NMR yields the composition of bare chitosan films (DA), and of chitosan films grafted with synthetic polymers.[2] The interplay between structure and dynamics was probed with solid-state NMR in chitosan films prepared from different acids, before and after neutralisation (Figure 2).[3] Acidic films have a better defined long-range order, but films from acetic acid are more flexible and films from hydrochloric acid are more brittle than neutral films.

Figure 2: Interplay between structure and dynamics in chitosan films with solid-state NMR [3].

References[1] M. Mnatsakanyan, J.J. Thevarajah, R.S. Roi, A. Lauto, M. Gaborieau, P.

Castignolles, Analytical and Bioanalytical Chemistry 405, 6873 (2013).[2] C. Lefay, Y. Guillaneuf, J.J. Thevarajah, P. Castignolles, M. Gaborieau, et al.,

Polymer Chemistry 4, 322 (2013).[3] C. Gartner, B.L. Lopez, L. Sierra, R. Graf, H.W. Spiess, M. Gaborieau,

Biomacromolecules 12, 1380 (2011).