טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentShimoni Karin
SubjectNanoscopic Characterization of the Interaction between
Nonionic Amphipilic Block Copolymers and Nonionic
Surfactants in Aqueous Solutions
DepartmentDepartment of Biotechnology and Food Engineering
Supervisor Professor Dganit Danino


Abstract

Amphiphilic block copolymers can self-assemble into aggregates of a range of morphologies when dispersed in water, and there is a growing interest in using them in diverse applications such as in cosmetic products, shampoos, lotions, and as improved drug carriers. To further advance the use of block copolymers it is important to study their interactions with small amphiphiles. In the present study we mixed a vesicle-forming and a micelle-forming polybutadiene-co-ethylene oxide compounds (P2903-BdEO and P3017-BdEO, respectively), with the small micelle-forming detergent, Triton X-100, and examined the effects of detergent concentration and detergent-polymer contact time on the change in morphology and type of structures formed. The analysis involved direct-imaging cryo-transmission electron microscopy (cryo-TEM), light microscopy, dynamic light scattering, and spectroscopy, and we obtained specific as well as global structural information on assemblies ranging from a few nanometers to a few microns in size. Coexistence of vesicles, threadlike micelles, and spherical micelles is seen in the P2903-BdEO/Triton X-100 system, until vesicles dissolution is completed, and spherical micelles are exclusively observed. In the P3017-BdEO/Triton X-100 system large spherical polymer micelles transform directly into smaller mixed micelles of uniform size. The results of both systems show that addition of detergent into polymeric assemblies results in the formation of structures of higher curvature. Furthermore, mixing large and small amphiphiles can be used to yield unique structures, not obtainable in single or double-component small amphiphile systems, as the short-armed Y-branched threadlike micelles seen in the P2903-BdEO/Triton X-100 system. In addition, we show that mixing between large block copolymers and small-molecule detergent is instantaneous, and the assemblies seen immediately after mixing are identical to those observed after long periods of time, indicating that equilibrium is reached very quickly.