Submitted to: Journal of Applied Polymer Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2003
Publication Date: 3/3/2004
Citation: Liu, L.S., Cooke, P.H., Coffin, D.R., Fishman, M.L., Hicks, K.B. 2004. Pectin and polyacrylamide composite hydrogels: effect of pectin on structural and dynamic mechanical properties. Journal of Applied Polymer Science. 92:1893-1901.
Interpretive Summary: In order to develop value-added materials from low-valued by-products of agricultural processes, studies on new applications of abundant pectic polysaccharides found in citrus wastes were conducted. We found that cross-linking polyacrylamide in pectin solution resulted in a composite hydrogel, which has greater capacities to absorb and retain water than polyacrylamide alone, and possesses improved mechanical properties over pectin alone. Furthermore, the polymerization of acrylamide in an existing pectin scaffold can protect the network architecture of polyacrylamide from collapse resulting from freeze-drying. The technologies developed from this study will be useful for the construction of pectin-based hydrogels with properties tailored for biomedical and industrial applications. Especially, it highlights a new use of pectin in formulation of biomacromolecule based drugs. Citrus fruit growers and juice processors could benefit from this research because new uses and markets for pectin will increase the value to their by-products and improve their overall profitability.
Technical Abstract: Composite hydrogels of pectin and polyacrylamide were synthesized and evaluated by scanning electron microscopy, atomic force microscopy, light microscopy, and by dynamic mechanical analysis. The cross-linking polymerization of acrylamide in pectin solution resulted in a composite having a macroporous pectin domain with an interstitial polyacrylamide domain. This composite had improved mechanical properties compared to either polymer alone, and it absorbed and retained more water than cross-linked polyacrylamide alone. Furthermore, cross-linking polymerization of acrylamide in an existing pectinate scaffold resulted in a double network architecture, where filamentous polyacrylamide networks penetrated through pores of the pectin scaffold. It was found that pectins dictated the features of microstructure in the composites through regulating the coordination of phase separation of the two components and water partition between the two phases. Results from this study highlight potential new uses of pectins in protecting the physical structure of environmentally sensitive polymers from mechanical damage related to freezing, lyophilization, and other conditions experienced during their use in biomedical and industrial products.