Effects of the thermal history and concentration on the aggregation of Erwinia gum in an aqueous solution

✍ Scribed by Lina Zhang; Xiaojuan Xu; Su Pan

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 135 KB
• Volume: 38
• Category: Article
• ISSN: 0887-6266
• DOI: 10.1002/(sici)1099-0488(20000515)38:10<1352::aid-polb120>3.0.co;2-l

✦ Synopsis

The aggregation of Erwinia (E) gum in a 0.2 M NaCl aqueous solution was investigated by multi-angle laser light scattering and gel permeation chromatography (GPC) combined with light scattering. The GPC chromatograms of five fractions contained two peaks; the fractions had the same elution volume but different peak areas, suggesting that aggregates and single chains coexisted in the solution at 25 °C. The apparent weight-average molecular weights (M w ) of the aggregates and single chains for each fraction were all about 2.1 ϫ 10 6 and 7.8 ϫ 10 4 , respectively. This indicates that the aggregates were composed of about 27 molecules of E gum in the concentration range used (1.0 ϫ 10 Ϫ6 to 5.0 ϫ 10 Ϫ4 g/mL). The weight fraction of the aggregates (w ag ) increased with increasing concentration, but the aggregates still existed even in an extremely dilute solution. The fractionation process and polymer concentration hardly affected the apparent aggregation number but significantly changed w ag . The E-gum M w decreased sharply with an increase in temperature. When the E-gum solution was kept at 100 °C, w ag decreased sharply for 20 h and leveled off after 100 h. Once the aggregates were decomposed at a higher temperature, no aggregation was observed in the solution at 25 °C, indicating that the aggregation was irreversible.