Hans-Juergen P. Adler

Self-assembling adhesion promoters for corrosion resistant metal polymer interfaces

The self-assembly process has been investigated for the replacement of the present chromating procedure on reactive metals like aluminium and to improve the lacquer adhesion and corrosion inhibition. It will be shown, that self-assembled layers can affect adhesion and corrosion inhibition on aluminium and its alloys. For self-assembly molecules (SAMs) substances are required which are able to react spontaneously on the surface for which terminated alkyl-phosphonic and phosphoric acid monoalkyl esters have been synthesised. The best anchor groups for aluminium were ascertained by pH-dependent flotation tests, dynamic contact angle measurements and corrosion tests. Grazing angle Fourier transform infrared spectroscopy (FTIR), angle dependent X-ray photoelectron spectroscopy (XPS) and Auger measurements show the existence and orientation of these new molecular structures. Model surface reactions with isocyanates demonstrate the binding capability to the lacquer.

Aqueous Microgels for the Growth of Hydroxyapatite Nanocrystals

In present article, we demonstrate that aqueous microgels can be used as containers for the in-situ synthesis of hydroxyapatite. The hydroxyapatite nanocrystals (HAp NCs) become integrated into microgels forming hybrid colloids. The HAp NCs loaded in the microgel can be varied over a broad range. The HAp NCs are localized within the microgel corona. The deposition of the inorganic nanocrystals decreases the colloidal stability of the microgels and leads to particle aggregation at high HAp NCs loading. Because of the strong interactions between HAp NCs and polymer chains, the swelling degree of microgels decreases, and temperature-sensitive properties disappear at high loading of the inorganic component. We demonstrate that hybrid colloids can be used as building blocks for the preparation of nanostructured films on solid substrates.

Synthesis and Characterization of Nanometer-sized Polypyrrole Composites

Stable core-shell polypyrrole (PPy) dispersions were prepared by using polystyrene (PST) or poly (styrene-co-butyl acrylate) (PST-co-BuA) as the core. and polypyrrole as the shell. SEM images showed that PPy/PST composites with a thin homogeneous overlayer of polypyrrole can he prepared when uncharged polymeric stabilizer is grafted onto the particle surface. Composite particles with raspberry morphology were obtained when the core particles were stabilized by surfactant with charge. The stability, morphology and conductivity of PPy composites have been investigated.

Ultrathin layers of phosphorylated cellulose derivatives on aluminium surfaces

In recent works the self-assembly process has been investigated to replace the present chromating procedure on reactive metals like aluminium and the improve the lacquer adhesion and corrosion inhibition. These self-assembling layers were formed of small bifunctional organic molecules with phosphate or phosphonic acid groups attached to the metal substrate. The idea of this work was to apply these results and techniques to cellulose derivatives on implant metals. The formation of ultra-thin layers of phosphorylated cellulose derivatives has been reported previously. These ultrathin layers were built on metal substrates like aluminium, titanium or steel for adhesion promotion and corrosion inhibition. Hydroxypropyl-2-phosphatepropyl cellulose was synthesised for adhesion on hydrophilic metallic surface. Hydroxypropyl-2-cinnamoylpropylester cellulose was prepared in order to crosslink the adsorbed layers. The layers were formed on metal surfaces via dip coating from dilute solutions and characterised by means of contact angle measurements, SEM investigations and FT-IR spectroscopy. Initial corrosion tests were performed.

Water dispersible electrically conductive poly(3,4-ethylenedioxythiophene) nanospindles by liquid crystalline template assisted polymerization

In this work, we demonstrate an inimitable liquid crystalline template strategy for the preparation of water dispersible electrically conducting poly(3,4-ethylenedioxythiophene) nanospindles (PEDOTSs). PEDOTSs were formed during the polymerization of the spindle shaped liquid crystalline phase of “EDOT–PDPSA” which was formed by the specific interactions of 3,4-ethylenedioxythiophene (EDOT) with 3-pentadecyl phenol-4-sulphonic acid (PDPSA). Liquid crystalline phases were characterized by Polarized Light Microscopic (PLM) analyses, rheology and XRD. Morphology and solid state ordering of conducting nanospindles were characterized by SEM, TEM and XRD. PEDOTSs exhibited an electrical conductivity of � 2.79 S cm � 1 and a good thermal stability (� 300 � C), which suggests their applicability in fabricating high temperature electronic devices. Furthermore, electrochemical studies of PEDOTS modified glassy carbon electrodes (GCEs) showed an oxidation peak of ascorbic acid at a lower potential of 0.046 V with a peak current about 10 times (91.68 mA) higher than that of the bare GCE with excellent electrode stability, proposing that it can be used as a steady electrode for the electro-catalytic oxidation of similar molecules.

Water-dispersible multifunctional polyaniline-laponite-keggin iron nanocomposites through a template approach

Water dispersible nanostructured multifunctional polyaniline-laponite-keggin iron cation composites (PPIL) were prepared by the oxidative polymerization of aniline in the presence of an aqueous dispersion of keggin iron-laponite (PIL) at room temperature. Negatively charged ions on the surface and residual positive charges on the edges of the laponite disc adsorb both keggin iron and aniline through ion-dipole and ionic interactions and can act as a micellar template during polymerisation. We suggest that keggin cages act as linkages between disorganized laponite sheets and during polymerisation, the disorganised PIL discs are co-structured and self-assembled with the formed PANI and engulfed layers and rolled sheets of nanotubes. These multifunctional composites exhibited electrical conductivity ∼ 5.7 × 10−1 S cm−1, saturation magnetization ∼ 9.0 × 10−1 emu g−1 with coercivity 8.2 Oe and thermal stability ∼ 300 °C, revealing their utility as a novel precursor for many high technological applications.

Synthesis of adhesion promoters for grafting polythiophene onto metal oxides

A new class of compounds, ω-(thiophen-3-yl) alkyl phosphonic acids, was used to link conductive polythiophene layers and several metal oxide substrates. In general, the adhesion between polythiophene films and metal substrates is insufficient for technical and microelectronic applications. The use of adhesion promoters between the substrate and the polymer enables the formation of a strongly bonded composite. Adhesive compounds were synthesized which contained a phosphonic acid group attached to the substrate and a thienyl group for surface polymerization with thiophene monomers. The properties of these created adhesion promoters were characterized on several substrates by contact angle measurements and IR investigations. First successful attempts were made to obtain a structured polymer surface via micro-contact printing.

Ultrathin layers for adhesion promotion

Many technical applications require substances providing special abilities in connecting different materials to each other. Beginning from applications for corrosion inhibition to improved adhesion abilities of laquers on selected metals like aluminium, titanium or tantalum, some special adhesion promoters on base of phosponic acid and trichlorsilane were developed. At last electronic devices basing on conducting polymers need adhesion promoters to bound the conducting polymers to supporting materials consisting of technical polymers or silicon wafers and other inorganic surfaces. This requires new adhesion promoters with polymerizable groups like thiophen or pyrrol.

Reactive dispersions for corrosion inhibition

Several concepts have been developed for the improvement of adhesion promotion and corrosion inhibition of reactive metal surfaces, like aluminum. The aim of these studies was to replace the present technical procedure for pretreatment of aluminum surfaces with chromium acid. Therefore, the adsorption and organization process of mono- and bifunctional alkyl phosphonic acids and mono alkyl phosphoric acid esters has been investigated. The properties of the adsorbed SAMs were confirmed by industrial linked adhesion and corrosion tests. By functionalization of the terminal position with thiophene, molecules are prepared which can graft conducting polythiophene layers via surface polymerisation on silicon/metal substrates. Also polymeric nano-particles with phosphoric acid groups form thin and smooth well-packed films on aluminum surfaces. Stable core-shell polypyrrole (PPy) dispersions were prepared by using polystyrene (PST) or poly (styrene-co-butyl acrylate) (PST-co-BuA) as the core, and polypyrrole as the shell.

Surface modification of aluminium with reactive microgels

The adsorption and organisation process of reactive microgels has been investigated on technical aluminium. The aim was to replace the present chromating procedure on reactive metals like aluminium because this process was been considered as an ecological problem. By means of a two-step emulsion polymerization with phosphate substituted monomer we have obtained polymeric nano-particles with phosphate groups on the surface. The core is synthesized by copolymerization from styrene (St) and butyl acrylate (BuA). The results of several analytical methods like contact angle SEM or TEM measurements showed, that these microgels were able to adsorb spontaneously onto the substrate surface and subsequently a structured molecular order was formed. The properties of the adsorbed microgel layers were confirmed by industrial linked adhesion and corrosion tests.