The Synthesis And Characterization Of Monofunctionalized Polyhedral Oligomeric Silsesquioxane (POSS) And PS/POSS Hybrid System

Organic - inorganic hybrid materials is a new research focus among composites. In this paper,the incompletely condensed silsesquioxane (cyclo-C₅H₉)₇Si₇O₉(OH)₃ was prepared in good yield by Feher's method. The reaction between (cyclo-C₅H₉)₇Si₇O₉(OH)₃, allyltrichlorosilane and excess triethylamine in dry THF gave the corner-capped product (cyclo-C₅H₉)₇Si₈O₁₂CH₂-CH=CH₂,recorded as POSS-allyl.The chemical structure of POSS-allyl was characterized by FT-IR,¹H- and ²⁹Si- NMR, mass spectrometry .DSC result showed that POSS-allyl had excellent thermal stability. The crystal structure of POSS-allyl was characterized by X-ray diffraction. And then a series of polystyrene/POSS hybrid materials were prepared by free radical solution polymerization under nitrogen atmosphere. The results indicate that POSS was completely dispersed at molecular level in PS matrix when 5wt% POSS was introduced, while some POSS-rich nanoparticals were present when content of POSS was beyond 5 wt %; the molecular weight of the PS/POSS hybrid materials were decreased with addition of POSS; the thermal stabilities of PS/POSS hybrid material had been improved compared to neat PS; The PS/POSS hybrid material displayed much higher glass transition temperatures (T_g) in comparison with neat PS.The POSS polymer itself has a significant tendency to segregating at the surfaces,which produce a hydrophobicity.