Complexes of starch polysaccharides and poly(ethylene co-acrylic acid): Structure and stability in solution

✍ Scribed by R. L. Shogren; R. V. Greene; Y. V. Wu

• Publisher: John Wiley and Sons
• Year: 1991
• Tongue: English
• Weight: 698 KB
• Volume: 42
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/app.1991.070420625

✦ Synopsis

SYNOPSIS

Chiroptical methods have been used to study the conformation and interactions of amylose and amylopectin with poly( ethylene co-acrylic acid) (EAA) in aqueous solution. These studies, along with X-ray diffraction and solid-state NMR data, show that amylose and EAA, as well as amylopectin and EAA, form helical V-type inclusion complexes when mixed in aqueous suspension. This structure apparently accounts for the partial compatibility observed in films containing starch and EAA. About 3 by weight of EAA does not interact with amylose and probably represents the ethylene-rich central core of the EAA micelle. EAA/amylose complexes in 10 m M NaOH were stable to temperatures > 90°C, whereas EAA/ amylopectin complexes in the same solvent were largely disrupted a t this temperature. Urea, at a concentration of 8 M, further destabilized both EAA/amylopectin and EAA/amylose complexes. Solutions with an alkaline pH (> 9.5) dispersed EAA optimally and allowed maximum complexing with amylose. At pH values > 13, the EAA/ amylose complexes were weaker, most likely due to electrostatic repulsion between ionized hydroxyl groups of amylose and carboxyl groups of EAA.

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