US EPA

5304986 

Journal Article 

Phase separation in microcapsule membranes composed of soybean lecithin, cholesterol, stearic acid and polyvinylpyrrolidone 

Jono, K; Ichikawa, H; Fukumori, Y; Kanamori, R; Nakamura, K; Et al 

1996 

Yes 

Chemical and Pharmaceutical Bulletin
ISSN: 0009-2363
EISSN: 1347-5223 

44 

Feb 1996 

392-398 

English 

WOS:A1996TW80500019 

IPA COPYRIGHT: ASHP A phase diagram of a soybean phosphatidylcholine (soybean lecithin) (SL)-cholesterol (CH)-stearic acid (SA) system incorporating 42% povidone (polyvinylpyyrolidone) was estimated by differential scanning calorimetry (DSC), x-ray diffractometry (XRD), and polarizing microscopy to relate it to dissolution and disintegration properties of microcapsules whose membranes consisted of these compounds. At the weight ratio of SL:CH=4:1, SL:SA=4:1, or SL:CH:SA=3:1:1, SL liquid crystalline phase (SL(LCP)) dissolved the maximum amount of CH and/or SA without any other crystalline phases detected. Mixtures remained anisotropic over 20-90DGC or SA-containing anisotropic phases became isotropic at 70-80DGC without any peaks on DSC. With increase in CH and/or SA, these were separated from SL(LCP) dissolving CH and/or SA. The separated CH(CH(c)) was found to have the same crystalline structure as the parent CH from XRD. The separated SA, in contrast, showed 2 types of XRD patterns: 1 had the same pattern as the parent SA (SA(c)) and the other had a pattern with some peaks shifted to shorter spacings (SA(c')). The mixtures gave a phase diagram with 6 regions. 

microcapsule membrane; phase separation; lecithin; cholesterol; stearic acid; polyvinylpyrrolidone