New multiblock copolymers of sulfonated poly(4′-phenyl-2,5-benzophenone) and poly(arylene ether sulfone) for proton exchange membranes. II

Rigid-rod poly(4′-phenyl-2,5-benzophenone) telechelics were synthesized by Ni(0) catalytic coupling of 2,5-dichloro-4′-phenylbenzophenone and the end-capping agent 4-chloro-4′-fluorobenzophenone. The degree of polymerization was determined by ¹³C NMR. The telechelics produced were selectively sulfonated by concentrated sulfuric acid at 50 °C. The degree of sulfonation was controlled by varying the reaction time and was determined by titration. The nucleophilic step copolymerization of the fluoroketone activated sulfonated poly(4′-phenyl-2,5-benzophenone) oligomer (M_n=3.05×10³ g/mol) with hydroxyl terminated biphenol based polyarylethersulfone (M_n=4.98×10³ g/mol) afforded an alternating multiblock sulfonated copolymer that formed flexible transparent films, in contrast to the high molecular weight rigid rod homopolymers. They were tested for water absorption and proton conductivity by specific impedance. The synthesis and characterization of these multiblock copolymers are reported.     

The effect of temperature and humidity on the oxygen sorption in Diels-Alder polyphenylenes

The gas transport properties of post-sulfonated Diels-Alder polyphenylene (SDAPP) membranes were measured and compared to poly(perfluoro sulfonic acid) (Nafion 112). The SDAPP materials had ion exchange capacities of 1.6 and 2.2 mequiv/g. The O₂ gas permeability in the SDAPP 2.2 was about half that observed in Nafion@ 112. The O₂ sorption in each membrane was measured in both the non-humidified and humidified state. In the non-humidified state, the O₂ sorption followed Henry's Law behavior. The enthalpy of sorption for the SDAPP materials in the dry state was about double that measured for Nafion@ 112. In the presence of moisture, the O₂ sorption followed Type IV behavior typically exhibited by hydrophilic polymers. The SDAPP samples had a higher percent wet-O₂ mass uptake compared to Nafion@ 112, because of a higher ion exchange capacity.     

Benzocyclobutene-functionalized poly(m-phenylene): A novel polymer with low dielectric constant and high thermostability

A novel benzocyclobutene-functionalized poly(m-phenylene) was synthesized. This polymer showed good solubility and film-forming ability. When being heated at high temperature, the polymer film converted to an insoluble cross-linked network structure and did not show any cracks. Thermogravimetric analysis of the polymer film exhibited a weight loss of 5% at 547 °C and a char yield of 71% at 1000 °C in nitrogen. Moreover, the cured film had good dielectric and mechanical properties. In a range of frequencies from 0.10 MHz to 30 MHz, the cured film showed dielectric constant of less than 2.7, which was comparable with these of polyimides, polycyanates and the SILK resins. On a nano indenter system, the cured film showed an average hardness of 1.05 GPa and a Yong's modulus of 39.18 GPa. Those data imply that the polymer could be used as the varnish for enameled wire, sizing agents for high performance carbon-fiber, and encapsulation resins in microelectronic industry.     

Progress with Light‐Emitting Polymers

Light‐emitting polymers have been studied intensively as materials for light‐emitting diodes (LEDs). Here research efforts toward developing these materials for commercial applications are reviewed. The Figure shows the preferred two‐layer device structure for commercial polymer LEDs as well as polyfluorene, one of the polymers discussed.     

Solid‐State Pyrolysis of Polyphenylene–Metal Complexes: A Facile Approach Toward Carbon Nanoparticles

Novel polyphenylene–metal complexes with discotic, linear, and dendritic geometries are synthesized by using a facile approach consisting of reactions between Co₂(CO)₈ and ethynyl functionalities in dichloromethane. Various carbon nanoparticles (CNPs), including graphitic carbon nanotubes (CNTs), graphitic carbon rods, and carbon–metal hybrid particles are obtained from the solid‐state pyrolysis of these complexes. The ultimate structures of the CNPs are found to be dependant on the structure and composition of the starting compounds. Precursors containing graphenes always result in graphitic CNTs in high yield, whereas dendritic precursors give rodlike carbon materials. Alternatively, linear oligo(arylethylene) precursors afford mostly carbon–metal hybrids with large amounts of amorphous carbon. Furthermore, the CNP structures could be controlled by adjusting the carbon/metal ratio, the type and position of the metal incorporated into the precursor, and the mode of pyrolysis. These results provide further chances toward understanding the mechanism of CNP formation.