Simple coacervate of pullulan formed by the addition of poly(ethylene oxide) in an aqueous solution

• Published in: Polymer (Guilford) 1991, Vol.32 (16), p.3062-3066
• Main Authors: Ohno, Hiroyuki, Higano, Masanori
• Format: Article
• Language: English
• Subjects: Applied sciences; coacervate; dehydration; Exact sciences and technology; Hofmeister's series; Natural polymers; phase separation; Physicochemistry of polymers; poly(ethylene oxide); pullulan; starch; Starch and polysaccharides
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/0032-3861(91)90210-A

Pullulan was phase separated in an aqueous phase as coacervate by adding poly(ethylene oxide) (PEO). The coacervate formation required concentrated (>0.85 unit moll −1; final) PEO solution, and the amount of the coacervate formed was almost proportional to the pullulan content in the mixture. The coacervates were in a semi-stable state and tended to fuse with each other to reach a complete liquid-liquid two-phase separation. PEO was not detected in the coacervate on analysing the phase-separated coacervate phase using differential scanning calorimetry and infra-red measurements. The coacervate formed by the addition of PEO was concluded to be a simple coacervate composed of only pullulan. The concentration of pullulan in the coacervate was calculated using the hypothesis that all the pullulan remained in the coacervate. The concentration of pullulan in the coacervate phase was ∼ 160 g l −1, which is almost the maximum solubility of pullulan. Similar coacervate formation was carried out by adding other synthetic non-ionic polymers such as poly(vinyl alcohol) or poly( N-vinyl-2-pyrrolidone) to the pullulan solution. Coacervate formation is concluded to be induced by the dehydration of pullulan after the addition of non-ionic polymers which have higher affinity for water molecules than pullulan.