The Synthesis And Characterization Of Magnetic Polyhedral Oligomeric Silsesquioxane (POSS) And PS/POSS Nanocomposites

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, 4-chlorobenzyl trichlorosilane and excess pyridine in dry THF gave the corner-capped product, 4-chlorobenzylcyclopentyl-POSS whcih transformed to the benzyl-POSS triphenylphosphonium chloride by treatment with triphenylphosphine. The salt was transformed to the benzyl-POSS triphenylphosphonium ylid in situ, which was treated with the ferrocenecarboxaldehyde to give a novel magnetic POSS 4-(2-Ferrocenylethenyl)-phenyl-cyclopentylPOSS containing metal and C=C double bond as a mixture of the E- and Z-isomers. 4-(2-Ferrocenylethenyl)-phenyl-isobutylPOSS was also firstly synthesized as a mixture of E/Z isomers by the Wittig reaction according to above process. The chemical structure of POSS1 and POSS2 was characterized by FTIR, ¹H- ¹³C- and ²⁹Si- NMR, mass spectrometry and elemental analysis. TGA result showed that POSS1 and POSS2 had good thermal stability. The magnetic property of POSS1 and POSS2 had been studied.The crystal structure of POSS1 was determined by Wide-Angle X-ray Diffraction (WAXD). Their diffraction line was indexed by Ito method. The indexing result showed that the crystal was the cube system with simple lattice. All the cell parameters of POSS1 were listed as below: a= 8.069932, b= 8.069932, c= 8.069932 , Alpha= 90.00000 , Beta= 90.00000, Gama=90.00000.Polystyrene composites containing inorganic-organic hybrid polyhedral Oligomeric silsesquioxane (POSS1) were prepared by bulk free radical polymerization with stirring. XRD and TEM studies indicate that POSS1 was completely dispersed at molecular level in PS matrix when 1wt% POSS1 was introduced, while some POSS1-rich nanoparticals were present when content of POSS1 was beyond 3 wt %. GPC results showed that molecular weight of the PS/POSS1 nanocomposites were increased with addition of POSS1. TGA and TMA data showed the thermal stabilities of PS/POSS1 nanocomposites had been improved compared to neat PS. The PS/POSS1 nanocomposites also displayed much higher glass transition temperatures (Tg) in comparison with neat PS. Viscoelastic properties of PS/POSS1 nanocomposites were investigated by DMTA. The results showed the storage modulus (E') values (temperature > Tg ) and the loss factor peak values of the PS/POSS1 nanocomposites were higher than that of neat PS. Mechanical properties of the PS/POSS1 nanocomposites were improved compared to the neat PS. Tensile strength and impact strength of PS/POSS1 namocomposites were increased by 33% and 84.4% respectively when POSS1 content was up to 3wt%. Only addition of 1wt% POSS1 resulted in 44.3% increase for the elongation at break. However, the presence of POSS1 had no apparent effect on elastic modulus of PS.Polystyrene composites containing inorganic-organic hybrid polyhedral Oligomeric silsesquioxane (POSS1) were prepared by bulk free radical polymerization under magnetic field and no magnetic field without stirring. XRD and TEM studies indicated that POSS1 was completely dispersed at molecular level in PS matrix when 1 wt% POSS1 was introduced, while some POSS1-rich nanoparticals were present when content of POSS1 was beyond 3 wt %. But dispersion of POSS1 in PS/POSS1 97/3 nanocomposites prepared under magnetic field was better than that under no magnetic field. GPC results showed that molecular weight and polydispersity of PS/POSS1 nanocomposites were decreased with increasing the amount of POSS1. But there was no apparent effect of magnetic field on molecular weights and polydispersity. TGA data showed the thermal stabilities of PS/POSS1 nanocomposites had been improved compared to pure PS. The PS/POSS1 nanocomposites also displayed much higher glass transition temperatures (Tg) in comparison with neat PS. The initial decomposed temperature and Tg of PS/POSS1 nanocomposites under magnetic filed wass higher than that with same content of POSS1 under no magnetic field. Viscoelastic properties of PS/POSS1 nanocomposites were investigated by DMTA. The results showed the storage modulus (E') values and the loss factor peak values of the PS/POSS1 nanocomposites were higher than that of pure PS except that the storage modulus (E') values of PS/POSS1 95/5 nanocomposites was lower below 57℃. The presence of the POSS1 also showed significant effects on the mechanical properties of PS. But there was no apparent difference for mechanical properties of those composites obtained under magnetic field and no magnetic field. Tensile strength of PS/POSS1 97/3 was increased by about 46.42% than that of the neat PS. The elongation at break was increased with increasing POSS1 content. The elongation at break was increased by about 300% after addition of 5wt% POSS1. However, the presence of POSS1 had no apparent effect on elastic modulus of PS.PS/acrylate - POSS and PS/amino - POSS nanocomposites were prepared according to the process prepared PS/POSS1 nanocomposites with stirring. XRD result indicated that acrylate-POSS was completely dispersed at molecular level in PS matrix, while some aggregated amino-POSS-rich nanoparticals were present in PS matrix. TGA data showed the thermal stabilities of PS/acrylate - POSS and PS/amino—POSS nanocomposites had been improved compared to neat PS. addition of acrylate-POSS shift Tg of PS towards a higher value by about 8°C. But the DSC curves of PS/amino-POSS nanocomposites did not display the glass transition during measurement temperature.