Dirk Vangeneugden

Low band-gap polymeric photovoltaic devices

We present results on photovoltaic devices based on novel thiophene-isothianaphthene copolymers (PDTI) with π-π* band-gaps ranging from 1.2 eV to 1.8 eV. Single-layer photovoltaic devices were fabricated from films of PDTI doped with a soluble fullerene derivative [6,6]-phenyl-C 61 -butyric-acid-methyl-ester (PCBM) as the electron acceptor and blended into poly(methyl methacrylate) to enhance the film quality. These devices exhibit spectral response extending into the infrared and are better matched to the solar spectrum as compared to standard PPV based ones. Such low band-gap materials also make possible the construction of dye-sensitized photovoltaic devices that take advantage of energy transfer from high energy absorbing dyes to the host polymer.

Physical and chemical properties of hybrid barrier coatings obtained in an atmospheric pressure dielectric barrier discharge

The aim of this work is to develop barrier coatings by using an atmospheric pressure dielectric barrier discharge (DBD). For this purpose the plasma polymers obtained from a hybrid organic–inorganic precursor compound as well as from a purely organic compound were compared. The physical properties of the coatings were determined by scanning electron microscopy and scanning probe microscopy analysis as well as by profilometry and by determining their oxygen transmission rates. The chemical structure was revealed by ATR-FTIR analysis and 13C- and 29Si-CP/MAS solid-state nuclear magnetic resonance measurements. It is shown that atmospheric pressure plasma polymerization of hybrid polymer precursors leads to coatings with excellent barrier properties due to the unique synergistic effect of the organic and the inorganic network structures that are formed in the plasma.

“Formal” copolymers based on 1,3‐dithienylisothianaphthene derivatives: Promising materials for electronic devices

Univ Limburg, Inst Mat Res, Div Chem, B-3590 Diepenbeek, Belgium. IMEC, B-3001 Louvain, Belgium.Vanderzande, D, Univ Limburg, Inst Mat Res, Div Chem, Univ Campus D, B-3590 Diepenbeek, Belgium.dvanderz@luc.ac.be

Properties of a low band gap conducting polymer electrode used for amperometric detection in liquid chromatography

The performance characteristics of a conductive polymer, used as working electrode material in a wall-jet amperometric detector are described. The electrode coating consisted of a poly(5,6-dithio-octyl-1,3-dithienylisothianaphthene) layer. The material was coated on the surface of a glassy carbon electrode through evaporation from a dichloromethane solution. It is a low band gap polymer (1.41 eV), with an intrinsic conductivity of 10−2 S cm−1, which makes the use of a dopant unnecessary. Catecholamines were used as model substances in oxidative measurements. Detection limits in LC separations with 4.6 mm ID columns (1 mL min−1 flow-rate) were 250 pg; the t90response time was 3 s. Quinones and nitrophenolics were studied in reductive measurements. The material could be used at negative potentials down to −800 mV (vs. SCE) without losing its electrocatalytic and conductive properties. The coating was competitive to glassy carbon in most respects and superior to polypyrrole. It showed group specificity in reductive measurements, e.g., quinones were reduced whereas nitrogroups (electroactive on glassy carbon) were not. The material can be used over a large potential range, shows good electrochemical activity and is very stable. It is suggested for use in modified electrodes.

A general synthetic route towards soluble poly(1,3-dithienylisothianaphthene) derivatives

Abstract ‘Formal’ copolymers consisting of bithiophene and aromatic isothianaphthene units, based on 1,3-dithienylisothianaphthene (DTI) derivatives, have been synthesized. The obtained materials have low band gaps and show high intrinsic conductivities. The polymers are obtained after oxidative polymerization of the corresponding DTI monomers with FeCl 3 . Solubilizing alkyl and thioalkyl side chains where introduced on different locations of the DTI skeleton. The substituents also influence the stability of the DTI monomers and the band gap of the polymers.

Radiation curing of hybrid polymer coatings

SummariesThe curing of wet films is the essential step in coatings technology. Coatings are applied more and more on thermally-sensitive substrate materials, and the tendency to shorten production cycles is also permanently growing. For this reason, the use of radiation curing at ambient temperatures is also increasing in coatings technology in order to meet these requirements. In this paper, radiation curing of inorganic-organic hybrid polymer coating materials is described. The synthesis of suitable precursors, the preparation of the coating material via sol-gel processing, and the curing behaviour under the influence of radiation is described. In particular, the effect of ambient pressure plasma and UV radiation as curing techniques on hybrid polymer coating materials is discussed.RésuméLe séchage des films humides est l’étape essentielle de la technologie des revêtements. De plus en plus les revêtements sont appliqués à des substrats thermosensibles, et la tendance à raccourcir les cycles de production va grandissant. Afin de répondre à ces exigences l’emploi du séchage à rayons, à des températures environnantes, va toujours croissant dans le domaine de la technologie des revétements. Dans cet article, le séchage à rayons du matériau de revêtements polymères hybrides inorganiques-organiques est décrit.On décrit aussi la synthèse de précurseurs convenables, la préparation du matériau de revêtement grâce au procédé sol-gel, et le comportement pendant le séchage sous l’influence des rayons. On discute en particulier l’effet du plasma à tension environnante et des rayons UV, en tant que techniques de séchage, sur le matériau des revétements polymères hybrides.ZusammenfassungDie Härtung von nassen Filmen ist ein wichtiger Schritt in der Lacktechnologie. Lacke werden zunehmend auf hitzeempfindlichen Substraten aufgetragen. Dazu kommt ein Trend, Produktionszyklen zu verkürzen. Aus diesem Grund nimmt die Verwendung von Strahlenhärtung bei Raumtemperatur ständig zu. Diese Arbeit beschäftigt sich mit der Strahlenhärtung von anorganisch/organischen Hybridpolymerlacken. Die Synthese von geeigneten Ausgangsstoffen, die Vorbereitung des Anstriches durch den Sol-Gel Prozeß und das Härteverhalten unter Strahleneinfluß werden beschrieben. Insbesondere diskutieren wir die Wirkung von Umgebungsdruckplasma und UV-Strahlung als Härtungsmittel.

Atmospheric Pressure Plasma Polymerization of In Situ Doped Polypyrrole

The conjugated polymer polypyrrole can be useful in a lot of applications such as LEDs, solar cells, organic thin film transistors, (bio)sensors, corrosion protection and antistatic layers. However, today, large area coating is still difficult. For this reason, plasma deposition at atmospheric pressure is presented as an alternative synthesis method, because of its possibility for inline processing and in situ doping. Furthermore, plasma polymerization is a more environmental friendly dry technique. Injection of a pyrrole aerosol into a nitrogen plasma and in situ doping by co- injection of NOBF4 or iodine, results in polymerization and coating deposition. The so formed coatings are analyzed with XPS, FTIR, UV/VIS, and resistance measurements. Conductivities up to 10 -3 S/cm were reached.

Antimicrobial Coatings Obtained in an Atmospheric Pressure Dielectric Barrier Glow Discharge

Abstract : This paper addresses the development of plasma polymer coatings that should prevent bacteria from adhering to medical devices, implants, textile fibers, packaging materials, etc. The two main parameters affecting bacterial colonization onto surfaces are the surface energy and the surface roughness. Both parameters can be adjusted by the deposition of a thin plasma polymer coating in an atmospheric pressure dielectric barrier glow discharge. According to SEM, FTIR, SPM, XPS and contact angle measurements, smooth, hydrophilic plasma polymer coatings were obtained under specific plasma conditions starting from 2-hydroxyethyl methacrylate (HEMA) and ethyl diazoacetate (EDA).

Chemical sensors based on a new low band gap material

Abstract Sensor properties of a low band gap poly(1,3-dithienylisothianaphthene) derivative have been tested. The materials has been used as the active layer in organic gas sensors and in amperometric sensors for HPLC detection. Responses where followed by monitoring the changes in film resistance. Due to the relatively high intrinsic conductivity, doping of the material was not necessary.