Molecular structure and conformation in phospholipid vesicles sterically stabilized by (tri)-block copolymers investigated by multi-nuclear magnetic resonance techniques

Soybean lecithin was dispersed in water and sonicated to form unilamellar vesicles of 40-45 nm in diameter. (Tri)- block copolymer molecules of the A-B-A type (A is polyethylene oxide (PEO) and B is polypropylene oxide (PPO)) were added to enhance the stability of the vesicles. The hydrophobic (PPO) group of the copolymer was thought to be buried inside the vesicle bilayer after sonication of the phospholipids in the presence of copolymer. 13C- and 31p-NMR were used to investigate the specific localization of the block copolymer and its interaction with the phospholipids.