Polyphenylene, polymer-supported

After activation with MAO (molar ratios [Al] [Zr] = 1000) the polymerization of ethylene has been successfully carried out using the zirconocene functionalized dendrimer at 40 bar ethylene pressure and 70 °C. We obtained high activity and productivity values for the ethylene polymerization and polymers with very high molecular masses in the range of 2 x 10 g/mol. The polydispersity of the polymer is quite low (3.0) indicating the single site character of the catalytically active species. Optimization of this system and study of the mechanism are stiU under investigation. Nevertheless, these preliminary results reveal the suitability of polyphenylene dendrimers as supports for zirconocene catalysts. 

Flammability. Polyphenylene sulfide will not support combustion under atmospheric conditions. The oxygen index, the minimum concentration of oxygen required to maintain burning, is shown for a number of polymers (12) in Table IV. The PPS sulfide value of 44 places it among the least flammable plastics. PPS has been given a UL flammability classification of VE-O. 

As already briefly mentioned, easily the most obvious change regarding optical properties appears in the transition from the open-chain precursor polymers to the planarized PPP ladder polymers (LPPP). The primary single-stranded coupling product (a benzoyl-substituted polyphenylene) from a Suzuki-type polycondensation between an alkyl- or alkoxy-substituted 2,5-dibromo-1,4-dibenzoylbenzene derivative and 2,5-dihexyl-l,4-phenylenediboronic acid is colorless with an absorption maximum Amax of 264 nm [n-TT transition c = 39,000 L/(moI cm)l (19]. This absorption behavior supports the strongly twisted structure of the main PPP chain. The mutual distortion of the aromatic subunits reduces the conjugative interaction to a minimum, so that the typical electronic properties of a conjugated polymer are almost completely lost. 

The most widely used chemically modified PPO in the development of thin film composite membranes is sulfonated polyphenylene oxide (SPPO). The polymer in the acid form as well as salt form has been used by Bikson to produce multilayer composite membranes. These types of membranes have been described to have at least two chemically distinct layers deposited on a porous substrate in a single coating step process. The outer layer forms a protective defect-sealing surface whereas the inner layer is the selective SPPO layer. This layer is adjacent to the porous support membrane. The two top layers are formed simultaneously on top of porous polysulfone support hollow fibers. A coating solution of SPPO in the lithium salt form (SPPO-Li ) and amine functional silicone fluid was coated on top of the polysulfone fibers. These coated fibers were used to construct a hollow fiber separator permeator. 

The same reaction was also performed in a tube-and-shell reactor configuration with polymer membranes of polyphenylene oxide, polysulfone, or cellulose acetate coated on a porous alumina tube packed with silica supported tungstophosphoric acid. ... 

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