| Spherical, cylindrical and vesicle micelles were formed from polystyrene-block-polyisoprene copolymer in heptane. The micelle morphology, critical micelle concentration, aggregation number, hydrodynamic radius, core radius, shell thickness, core density, and cylindrical micelle length were studied by a combination of scattering techniques and atomic force microscopy. The experimental results were compared with recently developed theoretical models. The crew-cut asymptotic model was found to inaccurate for all measured parameters even in the range of small polyisoprene blocks where it should be most applicable. The start-like asymptotic model correctly captured most of the data in the range of large polyisoprene block size, i.e. when the micelles were the most star-like. The numerical solution was seen to accurately predict most of the physical properties in the full range of polyisoprene block size studied.; In addition it was found that reversible morphological transitions from cylindrical to spherical micelles as well as vesicle to cylindrical micelles can be induced solely through temperature changes. However, the reverse process, upon cooling, is much slower than the transition while heating. |
