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Polyimide coatings containing azo-chromophores as structural units

Results are presented on the vacuum deposition of polyimide layers containing azochromophore as structural unit. The imidization process of the polymer thin films was studied by FT-IR and optical spectroscopy. After microwave and thermal treatment the, polyimide layers are E-diastereomers only, with a homogeneous smooth surface devoid of cracks. The technique used is suitable for preparing polyimide coatings containing chromophores with tailored properties.

As2S3 and AgI thin layers as ion sensitive membranes

Abstract The possibilities of using thin layers of As 2 S 3 and AgI as ion sensitive membranes for ion selective field-effect transistors (ISFETs) are investigated. The thin films have been prepared by vacuum deposition on static and rotating substrates. The As 2 S 3 layers were additionally doped with silver. The influence of the type of substrates and preparation conditions on electrochemical properties of the layers was studied. Electrochemical measurements revealed a reasonable sensitivity of chalcogenide and halide layers to silver and iodide ions, respectively. The near Nernstian behavior of sensitivity of As 2 S 3 layers to Ag + ions and of AgI layers to I − ions is observed. The results obtained are promising for the development of ISFETs.

Properties of vacuum-deposited polyimide films

Abstract Vacuum-deposited polyimide (PI) thin films have been prepared by co-deposition of precursor pyromellitic dianhydride (PMDA) and 4,4′-oxydianiline (ODA) followed by thermal treatment. The dependency of the optical and electrical properties, chemical resistivity and mechanical stability on the composition (ODA:PMDA) and the degree of imidization of the PI layers have been investigated and discussed. The experimental results have yielded possibilities to microstructure the vacuum-deposited PI films by excimer laser irradiation or reactive ion etching in gas mixture CF 4 /O 2 .

Excimer laser structuring of bulk polyimide material

Abstract A bulk polyimide system prepared by pressing of the precursor monomers 4,4′-oxidianiline (ODA) and 1,2,4,5-benzenetetracarboxylic or pyromellitic dianhydride (PMDA) mixtures has been investigated. The synthesized bulk polyimide is formed as a result of a polycondensation reaction of monomers in solid state phase. A change of the monomers polycrystalline structure to an amorphous one of the bulk polyimide after imidization is established. The possibility for excimer laser microstructuring by drilling at various diameters and depths is demonstrated. The scanning electron microscopic observations reveal alterations in the so formed blind holes as a consequence of the laser action parameters variation. The changes observed and the dependencies obtained are discussed.

Chemical and Physical Properties of Polyimides: Biomedical and Engineering Applications

© 2012 Georgiev et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Chemical and Physical Properties of Polyimides: Biomedical and Engineering Applications

Preparation of Polyimide Thin Films by Vapour Deposition and Solid State Reactions

In this chapter we describe the preparation of polyimide thin films by physical vapour deposition and comment on their potential application as a pure material or a thin layer matrix for producing nanocomposite layers. Their superb properties, such as a low dielectric constant, high thermaland photo-stability, high chemical resistance and high optical transmittance predetermine their widespread applications as a casts and layers used as insulators, protective or capsulation layers, mechanical or diffusion barriers, in optoand microelectronics. The bulk properties of the polyimide allowed the preparation of nanocomposite materials with organic chromophores as a “guest” (the embedded in the matrix nanosized particles). Moreover, some of the “guest” could bind to the polyimide chain. There are numbers of aromatic polyimides which are broadly used as thin layers in nanotechnology. Vapour deposition of the precursors and solid state reactions of imidization are of a greater priority than the spin coating and dipping methods. These as-deposited films by the vacuum deposition process consist of a dianhydride and diamine mixture, which by solid state reactions is converted to polyimide by thermal treatments or by combined microwave and thermal treatments. The physical vapour deposition as a “dry” method provides high purity for producing thin polymer films of controlled thickness, ratio of precursors and composition control of the so prepared layers. In this chapter we suggest possibilities for the practical application of vapour deposition of precursors and the following solid state reactions. By the used spectral methodFourier Transform Infrared Spectroscopy for analysis of the investigated kinetics of imidization reactions and microstructure of the layers are studied. The relationship between vapour deposition conditions and the presence of regular chains leading to the appearance of infrared bands is discussed. Polymers are also capable of forming a range of conformations depending on the backbone structure. The conditions for preparation by physical vapour deposition and solid state reaction of polyimide or nanocomposite polyimide layers are discussed.

Polyimide-matrix-based composite materials

A polycondensation solid-state-reaction-based polyimide (PI) matrix has been used for composite material formation. Two types of PI matrix have been employed – a bulk PI system prepared by pressing a mixture of the powdered precursors (4, 4′-oxidianiline (ODA) and pyromellitic dianhydride (PMDA)) and a thin-film matrix formed by vapor co-deposition of the same precursors, PI monomers. A variety of different “guests” (trimethylaminalan, phthalocyanine, carbon) and the methods for their incorporation into the PI matrix are presented. The influence of the “guest” concentration and the thermal-treatment conditions on the surface morphology are shown and discussed.

Synthesis of “Main – Chain” Type Polyimide Matrix with a Chemically Bound Azo Group

A method for obtaining thin vacuum deposited azopolyimide layers is established. On the basis of the thermogravimetric and differential thermal analyses, the chemical reaction in the solid state between the initial precursors - 4,4’-diaminoazobenzene and pyromellitic dianhydride is discussed. Also, the preparation parameters allowing for a condensation of films of desired composition are determined. Fourier Transform Infrared Spectroscopy analyses confirm that the azo group is chemically bound in a thin polyimide layer matrix. This is a solution to the task of preparing a “Main – Chain” type polyimide matrix with a chemically bound azo- group.

STRUCTURAL TRANSFORMATIONS IN A-AS2S3 UNDER AU+ IONS IRRADIATION

Abstract The ion induced structural changes in evaporated layers of a-As 2 S 3 under the action of Au + ions with energies in the range of 6–19 keV and beam fluxes between 10 12 to 10 15 ions\cm 2 are studied. It is shown that the solubility of the evaporated layers of As 2 S 3 increases under Au + ions irradiation at a fluence up to 10 14 ions\cm 2 and decreases at a fluence of more than 10 14 ions\cm 2 . Thus, a positive or a negative ion resists with high resolution can be developed depending on the irradiation dose. Ion-induced changes in the solubility of the layers occur at a depth greater than the penetration range calculated by the TRIM code of the Au + ions. XPS study supports the TRIM results and provides the data for understanding this phenomenon.

Vacuum deposited composite polyimide – phthalocyanine films☆

Abstract Polyimide (PI) – phthalocyanine (Pc) composite films prepared by means of simultaneous vacuum deposition of vapours of PI precursors — oxydianiline (ODA) and pyromellitic dianhydride (PMDA), and Pc — metal-free — or copper phthalocyanine, were investigated. Thermal treatment regimes for imidization of ODA and PMDA to PI without essential changes in the chromophore concentration and in the surface morphology of the layers have been determined. The changes observed in the optical transmission and adsorption of the films, and in the optical density of the irradiated areas have been discussed as resulting from the different composition of the layers. Also laser modification and structuring in different film depths were accomplished. The threshold energies of excimer laser irradiation necessary for these purposes were determined. The obtained results render the possibilities for the study of the layers’ properties in optical element formation.