Preparation of starch–poly–glutamic acid graft copolymers by microwave irradiation and the characterization of their properties

Published Date
20 April 2016, Vol.140:233–237, doi:10.1016/j.carbpol.2015.12.034

Title 

Preparation of starch–poly–glutamic acid graft copolymers by microwave irradiation and the characterization of their properties ☆

• Author 

• Jingyuan Xu ^a,,
• Elizabeth F. Krietemeyer ^a
• Victoria L. Finkenstadt ^a
• Daniel Solaiman ^b
• Richard D. Ashby ^b
• Rafael A. Garcia ^b

• aNational Center for Agricultural Utilization Research, Agricultural Research Service, US Department of Agriculture, 1815 North University Street, Peoria, IL 61604, USA
• bEastern Regional Research Center, Agricultural Research Service, US Department of Agriculture, 600 East Mermaid Lane, Wyndmoor, PA 19038, USA

Received 1 July 2015. Revised 8 December 2015. Accepted 15 December 2015. Available online 17 December 2015.

Highlights

• •
  Poly-γ-glutamic acid was grafted onto waxy starch using microwave irradiation.
• •
  The reaction conditions were optimized to temperature and pH.
• •
  The starch–g–PGA gel absorbed more than 20 times of its own weight amount of water.
• •
  The starch–g–PGA gel exhibited viscoelastic solid behavior.

Abstract

Graft copolymers of waxy maize starch and poly-γ-glutamic acid (PGA) were produced in an aqueous solution using microwave irradiation. The microwave reaction conditions were optimized with regard to temperature and pH. The temperature of 180 °C and pH7.0 were the best reaction conditions resulting in a PGA graft of 0.45% based on nitrogen analysis. The average graft content and graft efficiency for the starch–PGA graft copolymer prepared at 180 °C and pH7.0 were 4.20% and 2.73%, respectively. The starch–PGA graft copolymer produced at 180 °C and pH7.0 could absorb more than 20 times its own weight amount of water and form a gel. The preliminary rheology study revealed that the starch–PGA graft copolymer gel exhibited viscoelastic solid behavior while the control sample of waxy starch showed viscoelastic liquid behavior.

Keywords

• Graft copolymers
• Poly-glutamic acid (PGA)
• Starch

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• ☆
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• ⁎ 
  Corresponding author. Tel.: +1 309 681 6359; fax: +1 309 681 6691.

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