An Investigation Of Octavinylsilsesquioxane (OVS) Functionalization, Preparation And Properties Of Hybrid Porous Materials Derived From OVS

As a kind of inorganic-organic hybrid compounds with three-dimensional structure, polyhedral oligomeric silsesquioxanes (POSS) have been extensively applied to the construction of the hybrid porous polymers. But, the existing POSS could not meet many special requirements for the new characteristics. Thus, it is necessary to modify the traditional POSS for obtaining stable and more reactive molecules. Many organic reactions have been applied to the post functionalization of POSS. And it is an important development direction to construct functional hybrid porous materials by novel POSS monomers, which can meet some different requirements. The dissertation is based on the following three aspects.1. Octabromophenylethyl-functionalized POSS (BrPh-POSS) was synthesized efficiently by the Friedel-Crafts alkylation of octavinylsilsesquioxane (OVS) with bromobenzene catalyzed by anhydrous AICl3. The structure of BrPh-POSS was characterized by FT-IR, NMR, and elemental analysis. The ortho- and para-substituents of BrPh-POSS were also analyzed clearly. The fluorescence spectrum showed that BrPh-POSS was fluorescent with maximum characteristic emissions at 311 nm, and there were two absorption peaks at 239 and 268 nm in the UV/Vis spectrum, due to the two different substituents. BrPh-POSS exhibited good thermal stability with Td,5,wt%at 410℃, according to the TGA curve.2. BrPh-POSS was used as a building block in Heck reactions with octavinylsilsesquioxane and tetrakis(4-vinylphenyl)silane to form two hybrid network polymers. The first polymer showed moderate porosity with Brunauer-Emmett-Teller specific surface areas of 334 m2g-1.And the porous polymer possessed amorphous structure, high thermal stability, and moderate carbon dioxide uptake.3. Three easily available monomers (OVS,1,3,5-tribromobenzene, and 4,4’-dibromoazobenzene) were selected to design hybrid porous polymers (HPPs) via Heck reaction based on the one-step ternary cross-linking strategy. Those hybrid polymers possessed micropores and mesopores structures with BET surface areas at 545-686 m2g-1. And HPPs exhibited lower BET surface areas, almost constant total pore volumes with the azobenzene molar percent. Moreover, these porous polymers were endowed with high thermal stabilities; especially Td of HPP-4 was up to 402℃. In addition, their CO2 uptakes were in a range of 4.18-5.45 wt% at 273 K and 101 kPa, and the azobenzene could enhance the CO2 adsorption capacity of the porous polymers.