Laura O. Péres

On the electrochemical polymerization of poly(p-phenylene vinylene) and poly(o-phenylene vinylene)

Abstract This paper describes the electrochemical synthesis of poly(p-phenylene vinylene) and poly(o-phenylene vinylene), via potentiostatic cathodic reduction of α,α,α′,α′-tetrabromo-p-xylene and α,α,α′,α′-tetrabromo-o-xylene. The polymerization yield obtained from the electrochemical quartz crystal microbalance were 88 and 25% for poly(p-phenylene vinylene) and poly(o-phenylene vinylene), respectively. The films were characterized by infrared spectroscopy. The polymer has been identified by the vibrational features characteristic of the trans-vinylene units (3024 and 965xa0cm−1 for the p-PPV and 2991 and 1002xa0cm−1 for the o-PPV). A quinoid structure has been identified, indicating that the polymer is partially doped, probably the Br2, formed during the polymerization process. The insoluble phase was identified as p-PPV and o-PPV oligomers by the characteristic bands of the vinylene group. The p-PPV presents oligomers with molar mass corresponding to oligomers of seven monomeric units, while the o-PPV presents shorter chains, probably containing three to four units, as determined by gel permeation chromatography.

Easy synthesis of phenyl oligomers using a Ni complex.

In this work are described the syntheses of p-sexiphenyl and p-octiphenyl starting from 4-bromo-p-terphenyl and 4-bromo-p-quaterphenyl, respectively, by using a nickel complex in the presence of bipyridine with DMF as solvent. This type of synthesis was shown to give an improved yield as well as easy preparation and purification of these phenylene oligomers.

Electronic properties of poly(1,4-phenylene methylidynenitrilo-1,4-phenylene nitrilomethylidyne) (PPI)

Poly(1,4-phenylene methylidynenitrilo-1,4-phenylene nitrilomethylidyne) (PPI) was prepared and investigated using UV spectroscopy and tunneling current measurements at metal/PPI interfaces. The difference between the LUMO and HOMO level energies of PPI is determined as well as its electron affinity. The measured shift of the LUMO level of PPI relative to unsubstituted poly(p-phenylene vinylene) (PPV) agrees with semi-empirical quantum mechanical calculations performed on the dimer using the CNDO/S method which predicts a stabilization of both LUMO and HOMO levels with respect to unsubstituted PPV.

Synthesis and characterization of modified polymer of p-bromo-styrene by "living" free radical and Suzuki reaction

The synthesis of homopolymer of p-bromo-styrene using benzoylperoxide (BPO) and (2,2,6,6-tetramethylpiperidinyloxi radical) TEMPO as initiators by a free radical polymerization process and the modification of this polymer with p-stilbenylboronic acid by Suzuki synthesis were reported in this work. The modified homopolymer was characterized by infrared and UV spectroscopy, photoluminescence and /sup 1/H-NMR spectrometry.

The Influence of halogen substituent in oxidation and reduction potential values of PPV-type polymer and block copolymer

PPV and conjugated block copolymer contains PPV units were synthesized. Cyclic voltammetry measurements were performed in order to evaluate the change in the electronic structure caused by the inclusion of these substituents. The values of the oxidation and reduction potentials were measured as the current threshold potential. It was observed that the inclusion of the both Chlorine and bromine substituent in the aromatic ring of the studied materials provoked a more pronounced displacement in the reduction picks to less negative potential and a less pronounced displacement in the oxidation picks to less positive values, related the material without substituent. This behavior results in a small bang gap for all the substituted polymers.