Effect of the end-positioning of a lithium sulfonate group on the aggregation and micellization Behavior of ω-lithium sulfonate polystyrene-block-polyisoprenes

omega-Lithium sulfonate polystyrene-block-polyisoprenes were synthesized by anionic polymerization high vacuum techniques and a post-polymerization reaction with 1,1-diphenylethylene and 1,3-propane sultone. The solution properties of omega-lithium sulfonate block copolymers were studied in a low polarity solvent (CCl4) which is a good solvent for both blocks. The study revealed the formation of aggregates due to the association of the lithium sulfonate groups (SuLi). The mass, size and shape of the aggregates were studied by static and dynamic light scattering and viscometry. The aggregation number decreased as the length of the chain increased and the aggregates showed a behavior similar to that of star polymers. The micellization of omega-functionalized block copolymers was also studied in a polar selective solvent for polystyrene, N,N-dimethylacetamide (DMA). Micelles formed from block copolymers containing the sulfonate group at the polyisoprene end exhibited an association number which was about 80% of that of the neutral block copolymer and had a higher critical micelle concentration. The samples having the polar group at the PS end showed a similar behavior.