ИСТИНА

Amphiphilic block copolymers of polyisobutylene (PIB) as hydrophobic and poly(acrylic acid) (PAA) as hydrophilic part were synthesized via combination of cationic and anionic polymerization. Thiophene was used as endcapping group of cationic polymerization of isobutylene. This can be converted into an anionic macroinitiator by activation with butyllithium and be used for the polymerization of acrylic and methacrylic esters. After hydrolysis of the acrylate block, the copolymers are known to be water-soluble in a certain pH-range. Block copolymers of PIB and poly(methacrylic acid) (PMAA) were already intensively investigated in the framework of this project. Changes in pH and salt concentration of the aqueous solutions have an effect on the aggregation number and size of the aggregate. At pH < 4, the micelles start becoming insoluble and precipitate. At high pH-value, the size of the micelles can be tuned by addition of salt. Now we synthesized PIB-b-PAA copolymers, which are expected to behave somehow different due to the lack of the hydrophobic α-methyl group. In fact, the behaviour is different. Solutions with different salt content and different way of preparation are compared with respect to their optical appearance as well as by cryo-TEM and DLS. dramatic differences are observed depending on the point of time, when salt ia added to the polymer. The size of the particles differs from results expected from equilibrium structures. The results are compared with PMAA-containing block copolymers.