| Nickel-mediated coupling of arylene dihalides in the presence of a reducing metal (normally activated zinc) results in the formation of aromatic carbon-carbon bonds and is one of the most recent approaches for the development of high performance materials. Poly(2,5-benzophenone) (PBP) is a member of a new class of rigid-rod, high strength and modulus, and high performance materials that is totally amorphous. PBPs with different microstructures were previously synthesized by nickel-mediated coupling of 2,5-dichlorobenzophenone in the presence of catalytic amounts of NiCl2, excess zinc, triphenylphosphine without 2,2′-dipyridine (PBP-A) or with 2,2′ -dipyridine (PBP-B). The photoluminescence and electroluminescence of these polymers have been investigated. PBP-B exhibits a bright blue photoluminescence and electroluminescence, while PBP A did not. The microstructures of PBPs have been investigated by different methods. Herein crystalline PBP-C has been synthesized using [1,2-bis-(diphenylphosphino) ethane] dichloronickel(II) (DPPE) and this polymer has been characterized by DSC and 13C NMR. In addition, a molecular model for understanding the effects of co-ligands on microstructure for PBPs has been developed. A new NMR method for distinguishing microstructures of poly(2,5-benzophenone)s has been proposed based on model compounds. The microstructure of PBP-A was assigned to be random; the microstructure of PBP-B was assigned to be head-to-tail; and the microstructure of PBP-C was assigned to be head-to-head. Regioselectivity has been ascribed to the steric and electronic effects of the co-ligands on the oxidative addition of the aryl chloride, which has been investigated by 3D molecular modeling.; Tailoring of the spectral characteristics and improvement of the processability are of current interest with respect to conjugated polymers that exhibit electroluminescence and photoluminescence. Poly(p-phenylene) is a typical electroluminescent polymer for light-emitting diodes (LED) and was the first conjugated polymer whose blue-emitting diode properties were realized. Poly(2-alkoxycarbonyl-1,4-phenylene)s with long alkoxy side groups are liquid crystalline, and some of them show amphotropism. Herein a series of poly(2-octoxycarbonyl-1,4-phenylene) (POP) copolymers with PBP was synthesized and their photoluminescence was investigated. Poly(2-octoxycarbonyl-1,4-phenylene) was obtained from Ni (0) coupling polymerization of octyl-2,5-dichlorobenzoate. Copolymers from octyl 2,5-dichlorobenzoate with 2,5-dichlorobenzophenone exhibit high thermal stability with tunable glass transition temperatures from 92 to 222°C. Pure poly(2,5-benzophenone) exhibits an emission wavelength at 440 nm while pure poly(2 octoxycarbonyl-1,4-phenylene) exhibits an emission maximum at 385 nm. The emission wavelengths of copolymers varied between the two wavelengths of homopolymers as a function of copolymers. |
