|402. Zhang, W.; Yuan, J.; Weiss, S.; Ye, X.; Li, C.; Müller, A.H.E.: Telechelic Hybrid Poly(acrylic acid)s Containing Polyhedral Oligomeric Silsesquioxane (POSS) and Their Self-Assembly in Water, Macromolecules 44(17), 6891 (2011) -- DOI: 10.1021/ma201152t|
|Key words: ATRP, Click chemistry, Polyhedral oligomeric silsesquioxane (POSS), Poly(acrylic acid), Self-assembly|
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.