|Xu, Jingyuan - James|
|Ashby, Richard - Rick|
|Harry O Kuru, Rogers|
Submitted to: Starch
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/8/2016
Publication Date: 7/12/2016
Publication URL: http://handle.nal.usda.gov/10113/5715072
Citation: Xu, J., Solaiman, D., Ashby, R.D., Garcia, R.A., Gordon, S.H., Harry-O'kuru, R.E. 2016. Properties of starch-polyglutamic acid (PGA) graft copolymer prepared by microwave irradiation - Fourier transform infrared spectroscopy (FTIR) and rheology studies. Starch 68:1-7. doi: 10.1002/star.201600021.
Interpretive Summary: Starch-based polymers can have similar functional behaviors as synthetic polymers, but have much better environmental properties because of their biodegradability. Modified starch can be suitable for those uses that were historically filled by synthetic polymer. There is no information in the literature on the preparative of starch-gamma-polygutamic acid (PGA) graft copolymers. It is thought that these graft copolymers will have advantage properties and can replace some synthetic polymers. The scientists at NCAUR prepared corn starch-PGA graft copolymers using the microwave irradiation method. In this method, starch and PGA become graft copolymers during the microwave heating. The final product of the starch-PGA graft copolymers powder can absorb water and swell into gels at room temperature. How these gels flow is an important parameter in many markets, such as polymer processing and food producing. The science of rheology studies how materials flow. We explored both starch-starch control material and starch-PGA copolymer gel rheological properties. The results of our study suggest that starch-PGA copolymer gels may have applications in some cosmetic and skin wound healing dressings.
Technical Abstract: The rheological properties of waxy starch-'-polygutamic acid (PGA) graft copolymers were investigated. Grafting was confirmed by FTIR spectroscopy. The starch-PGA copolymers absorbed water and formed gels, which exhibited concentration-dependent viscoelastic solid properties. Higher starch-PGA concentrations resulted in stronger viscoelastic properties. The analysis for moduli of different concentrations indicated that starch-PGA graft copolymer gels were physical gels, meaning the cross-links between the molecules were physical junctions. However, stress relaxation measurements showed that the starch-PGA graft copolymer gels had long relaxation times, which result from the presence of the chemical cross-links that were evident in the FTIR spectra. The non-linear steady shearing rheological properties studies indicated that starch-PGA gels exhibited shear thinning behavior, which can be well fitted with the power law constitutive equation. The function and behavior of the starch-PGA graft copolymer gels suggest that this kind of starch-based biomaterial could be a potential candidate for applications in cosmetic gels, skin wound care materials, and agricultural products.