Prof. Dr. Axel Müller

Telechelic ("dumbbell-shaped") POSS-containing inorganic/organic hybrid poly(tert-butyl acrylate) (POSS-PtBA-POSS) was prepared by the combination of ATRP and the copper-catalyzed azide-alkyne "click" reaction. Telechelic bromo-terminated PtBAs with different molecular weights were first prepared via ATRP using a dibromo-functionalized ATRP initiator; subsequently, the bromo groups were transformed to azido groups using sodium azide in DMF via nucleophilic substitution. The "click" coupling between azido-terminated PtBA and alkyne-functionalized POSS was successfully accomplished to afford telechelic POSS-PtBA-POSS, which is confirmed by NMR and GPC. The telechelic POSS-PtBA-POSS was then hydrolyzed to amphiphilic telechelic POSS-functional poly(acrylic acid) (POSS-PAA-POSS). The self-assembly behavior of POSS-PAA-POSS with three different molecular weights in aqueous solution at pH = 8.5 was investigated by transmission electron microscopy, scanning electron microscopy and light scattering (SLS, DLS). The results show that POSS-PAA₄₀-POSS and POSS-PAA₈₂-POSS can self-assemble in water into ellipsoidal aggregates with a moderately uniform size, whereas POSS-PAA₁₄₀-POSS with a long PAA chain only self-assembles into aggregates with a broad size distribution. We discuss the formation of layered crystals of POSS within these aggregates.