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Synthesis and characterization of organic/inorganic hybrid star polymers of 2,2,3,4,4,4-hexafluorobutyl methacrylate and octa(aminophenyl)silsesquioxane nano-cage made via atom transfer radical polymerization Part A Polymer chemistry

Hussain, H., Tan, B.H., Gudipati, C.S., Xaio, Y., Liu, Y., Davis, Thomas P., He, C.B.
Journal of polymer science 2008 v.46 no.22 pp. 7287-7298
catalysts, contact angle, differential scanning calorimetry, evaporation, glass transition temperature, molecular weight, nanocomposites, nuclear magnetic resonance spectroscopy, polymerization, polymers, solvents, thermal degradation, thermogravimetry, transmission electron microscopy
Well-defined organic/inorganic hybrid fluorinated star polymers were synthesized via atom transfer radical polymerization (ATRP) of 2,2,3,4,4,4-hexafluorobutyl methacrylate (HFBMA) using octa(aminophenyl)silsesquioxane (OAPS) nano-cage as initiator. For this purpose, OAPS was transformed into ATRP initiator by reacting with 2-bromoisobutyrylbromide. ATR polymerization of HFBMA was carried out in trifluorotoluene at 75 °C using CuCl/2,2-bipyridine or N,N,N',N",N"-pentamethyldiethylenetriamine as catalyst system. GPC and ¹H NMR data confirmed the synthesis of OAPS/PHFBMA hybrid star polymer. Kinetics of the ATR polymerization of HFBMA using OAPS nano-cage initiator was also investigated. The OAPS/PHFBMA hybrid stars were found to be molecularly dispersed in solution (THF); however, TEM micrographs revealed the formation of spherical particles of ~ 120-180 nm by the OAPS/PHFBMA hybrid star polymer after solvent evaporation. Thermal characterization of the nanocomposites by differential scanning calorimetry (DSC) revealed a slightly higher glass transition temperature (Tg) (when compared with the linear PHFBMA) of higher molecular weight OAPS/PHFBMA hybrid star polymers. In contrast, lower Tg than the linear PHFBMA was observed for OAPS/PHFBMA of relatively lower molecular weight (but higher than the linear PHFBMA). Thermal gravimetric analysis (TGA) showed a significant retardation (by ~60 °C) in thermal decomposition of nanocomposites when compared with the linear PHFBMA. Additionally, surface properties were evaluated by measuring the contact angles of water on polymer surfaces.