Formation of Block Copolymer and Surfactant Vesicles

Sammanfattning: In this thesis temperature induced vesicle formation in both a block copolymer system and nonionic surfactant system have been investigated. The block copolymer is a triblock copolymer of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO), PEO-PPO-PEO, with the average molecular composition of EO5PO68EO5 and the commercial trade name Pluronic L121 (papers I, II). In the L121 system the formation of amphiphilic particles with internal structure has also been observed (paper III). The nonionic surfactant studied is tetraethyleneglycol dodecyl ether (C12E4) (paper IV). In addition, a study of the miscibility of L121 and soybean phosphatidylcholine also denoted Lecithin, with the commercial trade name Epikuron 200, was performed (paper V). To characterize the systems, static and dynamic light scattering (SLS and DLS), nuclear magnetic resonance (NMR), cryogenic transmission electron microscopy (cryo-TEM) and small angle X-ray scattering (SAXS) have been used. The most important conclusions are: i) The Pluronic L121 and lecithin do not form mixed aggregates (paper V). ii) L121 can form vesicles in water (paper I, II). iii) In the L121 system one can study vesicle self-assembly from a solution of monomers (unimers) (paper II). iv) In the L121 system the block copolymer polydispersity affects the vesicle self-assembly and its temperature dependence (paper II). v) In the C12E4 system, vesicles can form upon heating a micellar solution (paper IV). vi) The vesicle size distribution depends on the heating rate, and can be roughly understood from the diffusion limited aggregation/fusion of micelles (paper IV). vii) In the L121 system nanosized particles with an internal structure can be formed (paper III).