Lookup NU author(s): Glenn Hurst,
Dr Katarina Novakovic
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Smart polymer gels are macromolecular networks that can exhibit significant and reversible conformational rearrangements upon variable changes in the local environment. Hydrogels are examples of such materials that can swell or deswell in aqueous solutions upon application of an external stimulus such as temperature or pH.1 Oscillatory chemical reactions (e.g. Belousov Zhabotinsky) exhibit the relevant stimuli to induce a simultaneous volume change within a responsive hydrogel if both environments are compatible.2 Pronounced oscillations in reaction heat output (e.g. 0.6 kJ/oscillation at 40°C) and pH (1-6) are exhibited by the phenylacetylene oxidative carbonylation (PCPOC) reaction studied in our group.3,4 It is therefore desirable to couple the PCPOC reaction with a cationic hydrogel able to swell in acidic media. Chitosan, a cationic polysaccharide, is known to be biocompatible, non-toxic, biodegradable, antimicrobial, mucoadhesive and a strong candidate for drug release. However, owing to its fragility and uncontrollable porosity, it has limited use. To overcome this, it is often chemically crosslinked with agents such as glutaraldehyde, formaldehyde or epoxy compounds, although all are cytotoxic and are inappropriate for biomedical applications. Genipin is an alternative natural crosslinking agent that is 10,000 times less cytotoxic than glutaraldehyde, has a slower degradation rate and fluoresces upon forming crosslinks. Poly(vinyl pyrrolidone) (PVP) is a haemocompatible, water soluble polymer that can control the porosity of chitosan structures. In this work, chitosan has been crosslinked with PVP using genipin to form smart hydrogels. Following initial experimental studies, the gel composition that produces stable structures is established. The degree of swelling and the rate at which equilibrium is reached are experimentally studied as a function of polymerisation temperature, polymerisation time and pH. Polymerisation temperatures considered were 37 and 50 °C with polymerisation times ranging from 24 to 72 h. In all experiments acidic environments were investigated. (1) Tanaka, T.; Fillmore, D.; Sun, S. T.; Nishio, I.; Swislow, G.; Shah, A. Physical Review Letters 1980, 45, 1636. (2) Yoshida, R. Adv. Mater. 2010, 22, 3463. (3) Novakovic, K.; Grosjean, C.; Scott, S. K.; Whiting, A.; Willis, M. J.; Wright, A. R. Chemical Physics Letters 2007, 435, 142. (4) Novakovic, K.; Mukherjee, A.; Willis, M.; Wright, A.; Scott, S. Physical Chemistry Chemical Physics 2009, 11, 9044.
Author(s): Hurst G, Novakovic K
Publication type: Conference Proceedings (inc. Abstract)
Publication status: Published
Conference Name: Gordon Research Conference on Oscillations and Dynamic Instabilities in Chemical Systems
Year of Conference: 2012