I Hoogmartens

New synthetic routes to poly (isothianaphthene) I. Reaction of phthalic anhydride and phthalide with phosphorus pentasulfide

Abstract A new route for the formation of the low bandgap polymer poly(isothianaphthene) is presented. The route comprises the reaction of phthalic anhydride or phthalide with phosphorus pentasulfide at elevated temperatures ( T ⩾ 120 °C), and leads to the formation of poly(isothianaphthene) in one single step. The product obtained was analysed by elemental analysis, IR, Raman and solid state NMR spectroscopy. Chemical doping and dedoping of the material were investigated, and the maximum conductivity obtained was 10 S cm −1 by doping with NOSbF 6 . Both doped and undoped samples of poly(isothianaphthene) prepared by this new route were thermally very stable in air or in an inert helium atmosphere as shown by thermogravimetric analysis. Furthermore, the conductivity of a doped sample remained unchanged up to 250 °C in air. Preliminary results showed that the reaction with phosphorus pentasulfide can also be used to obtain nitrogen analogues of poly(isothianaphthene).

An investigation into the electronic structure of poly(isothianaphthene)

Using selective, solid-state NMR pulse sequences, we have estimated the 13C chemical shift of inequivalent carbons of the title polymer. In order to investigate the electronic structure of PITN, several model compounds of aromatic and quinoid structure were synthesized. The NMR results suggest a bulk structure for neutral PITN with a high quinoid contribution that has been confirmed by Raman spectroscopy.

Improving selectivity by using a multipurpose cross polarization magic angle spinning NMR pulse sequence : characterization of π-conjugated compounds

Abstract The use of a multipurpose cross polarization magic angle spinning nuclear magnetic resonance pulse sequence to simplify high resolution solid state 13 C NMR spectra is reported. Several kinds of experiments such as cross polarization, cross depolarization, proton dipolar dephasing and combinations of these are demonstrated for the well characterized trans -3,3′-bibenzo[ c ]thienylidene-1,1′-dione. The pulse sequence is further applied to the analysis of insoluble poly(isothianaphthene).

A 13C CP/MAS NMR investigation of poly(isothianaphthene)

Abstract The title was prepared by several different approaches. 13 C CP/MAS NMR spectra of these insoluble powders are reported. The results have been obtained by cross-polarization with proton decoupling and magic angle spinning techniques. Using selective polarization, we have been able to separate the lines of inequivalent carbons and to estimate their chemical shift. In order to obtain more information about the geometry of these polymers, we used 1,3-diphenylisothianaphthene ( 4 ) and 1,3-dibenzal-thiophthalan ( 5 ) as model compounds for an aromatic ( 3a ) and a quinoidal structure ( 3b ) of PITN. The results suggest a quinoidal structure for this narrow bandgap polymer.

Antistatic polymer layers based on poly(isothianaphthene) applied from aqueous compositions

Abstract Electrostatic charging of photographic materials can be avoided by applying an antistatic coating to one or both sides of the photographic film. Electronically conducting polymers can be used for this application especially because the conductivity is independent from the relative humidity. However, these polymers usually are deeply coloured. It has been suggested that the absorption of polyisothianaphthene in the visible part of the spectrum is low, due to its low energy band gap. Application of polyisothianaphthene, however, is difficult due to its insolubility. A method is provided wherein an antistatic layer of polyisothanaphthene is coated from an aqueous dispersion. In this method polyisothianaphthene is polymerised in concentrated sulphuric acid and dispersed in water with the help of lambda carrageenan as a polymeric surfactant. Coating from this dispersion on a polyethylene terephthalate substrate yields a transparent antistatic film whose logarithm of the surface resistivity is 8.48 Ω/Square.