Preparation from Solution

There are several wet deposition procedures, including sedimentation, spin coating, electrochemical deposition, self assembly, and the Langmuir-Blodgett technique. Common for all these methods is that no ordered films of unsubstituted pure oligothiophenes can be prepared. 

The easiest (and most unreproducible) way is to elutriate the oligomer in an organic solvent, put a substrate in, and evaporate the organic solvent. Usually these films are not uniform in thickness, include remnants of solvent, and are 

Spin coating is a good alternative to produce uniform films on large substrates. However, this method is seldomly used for oligothiophenes, but will become of increasing importance if technical devices have to be produced by low-cost-methods. 

Electrochemical deposition of polythiophene films from solutions of mono- or bithiophenes is one of the commonly used methods and can also be applied to prepare oligothiophene films. The films are formed in situ during the polymerization process. Due to the oxidative polymerization only doped (oxidized) materials are obtained and appropriate counter-ions have to be added. This method can only be applied to conductive substrates. 

A related method is the Langmuir-Blodgett technique in which amphiphilic molecules like carbonic acid substituted thiophenes self-organize in a compressed layer on water which can be transferred onto a solid substrate [122]. An alternative way is to use unsubstituted molecules which are mixed with arachidic acid [123,124]. 

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Fig. 3.35 Mercury porosimetry intrusion-extrusion plots of alumina gels prepared from solutions of aluminium monohydrate in A, propan-2-ol (2-5w/v%) B, propan-2-ol (4-9w/v%) C, 2-methylpropan-2-ol (4-9 w/v%) D, 2-methylpropan-2-ol (9-5 w/v%) E,butan-2-ol (9-5 w/v%). -------, ascending, intrusion curve -----, descending, extrusion curve.

The reaction is driven to completion by distilling the lower boiling alcohol. Metal methoxides are frequentiy insoluble and caimot be employed as starting materials in this reaction by the same token, they can be convenientiy prepared from solutions of higher alkoxides by precipitation with methanol. Alcoholysis also gives mixed metal alkoxides ... 

The equilibrium, room temperature structure of pure cobalt is hep. The fee structure is stable at high temperatures (422 °C to 1495 °C) and has been retained at room temperature by rapid solidification techniques [101], X-ray diffraction analysis was used to probe the microstructure of bulk Co-Al alloy deposits containing up to 25 a/o Al and prepared from solutions of Co(II) in the 60.0 m/o AlCfi-EtMelmCl melt. Pure Co deposits had the hep structure no fee Co was observed in any of the deposits. The addition of aluminum to the deposit caused a decrease in the deposit grain size and an increase in the hep lattice volume. A further increase in the aluminum content resulted in amorphization of the deposit [44], Because the equilibrium... 

Dumond F., Marceau E., and Che M. 2007. A study of cobalt speciation in Co/Al203 catalysts prepared from solutions of cobalt-ethylenediamine complexes. J. Phys. Chem. C 111 4780-89. 

Because of the complexities involved in understanding cause-effect relationships, an alternative approach to control the thin film microstructure has been pursued by some investigators—the use of statistically designed experiments to identify key processing parameters.114115 In these approaches, as illustrated in Table 2.6 for a Plackett-Burman screening study,114 limiting values for various experimental parameters are chosen. Films are then prepared from solutions synthesized under these conditions, and resulting film... 

Optical Exposure. Multicomponent LB films were prepared from solutions of novolac/PAC varying in concentration from 5-50 wt% PAC, and transferred at 2.5 -10 dyn/cm. The films were composed of 15 - 20 monolayers, with an average film thickness of 30 nm, as measured by ellipsometry. Exposures were performed with a Canon FP-141 4 1 stepper (primarily g-line exposure) at an exposure setting of 5.2 and with a fine line test reticle that contains line/space patterns from 20 to 1 pm (40 to 2 pm pitch). They then were then developed in 0.1 - 0.2 M KOH, depending on the PAC content The wafers received a 20 min 120°C post development bake to improve adhesion to the Cr. Finally, the Cr was etched in Cyantek CR-14 chromium etchant, and the resist and Cr images were examined by SEM. 

Solid samples of histidine, prepared from solutions of different pH, show slow exchange between cationic and neutral forms. Furthermore, only a single tautomer (the NT—H) is observed for the neutral and anionic species. 

The structure solution of the cocrystal of 37 and 29 from powder XRD illustrates the current utility of this approach in the field of crystal engineering. While the material above was prepared from solution crystallisation, it is clear that this approach directly impacts cocrystals prepared by sohd-state grinding. 

In transmission electron microscopy (TEM), a beam of highly focused and highly energetic electrons is directed toward a thin sample (< 200 nm) which might be prepared from solution as thin film (often cast on water) or by cryocutting of a solid sample. The incident electrons interact with the atoms in the sample, producing characteristic radiation. Information is obtained from both deflected and nondeflected transmitted electrons, backscattered and secondary electrons, and emitted photons. 

The X-ray diffraction patterns obtained from potassium hyaluronate films prepared from solutions of pH 3.0-4.0 were representative of the patterns from Rb+, Cs+, and NH4 forms. At 90-98% r.h., the unit cell is tetragonal, with a = b = 1.714 nm, and c = 3.28 nm. Each chain is a 4(— 0.82) helix, and two such chains fonn an antiparallel-stranded double-helix. There are two double helices in the unit cell, and the space group is 14,22. There are no intramolecular hydrogen-bonds. 

A similar reaction is observed with the Cu+2 complex. No reaction occurs with glycine esters. A similar reaction occurs when cobalt (III) complexes are prepared from solutions of hydroxyethylethylenediamine and similar ligands (24, 25). The chelate ring-forming portion of the complex remains intact however, the products derived from the oxidized hydroxyethyl group appear complicated. 

The ZSM series (for Zeolite Socony Mobil) of highly siliceous zeolites is prepared from solutions containing alkylammonium bases. 

Parameters of the I9Si and 17 Al MAS NMR Spectra and the Chemical Composition of Solid Gel Intermediates and Zeolite Na-A Prepared from Solution B ... 

Some baths for flash plating of gold are prepared from solutions of the metal in aqua regia and contain a low concentration of free cyanide. The possibility that tetracyanoaurate(III), [Aum(CN)4], is present in such solutions has been discussed.29... 

Fig. 10.3. Electron micrographs (a, cross-section b, surface) of PZT film prepared from solution containing 10 mole % excess of Pb.

Double decomposition The process by which an insoluble salt is prepared from solutions of two suitable soluble salts. 

The composites were prepared from solutions of mNA and PMMA with varying loading degrees (between 30 wt % and 90 wt %), using toluene as a solvent. Thin films (30-40 fim) were cast on a glass slide and the solvent was... 

CYTOP has physical and chemical properties similar to PTFE and PFA. Its tensile strength and yield strength are higher than those of PTFE and PFA. It also has unique optical properties its films are transparent in the range from 200 to 700 nm and its clarity is very high even in the UV region.8 The properties of CYTOP are shown in Table 8.2.9 CYTOP is soluble in selected fluorinated solvents. Such solutions have a very low surface tension, which allows them to be spread onto porous materials and to cover the entire surface. Films without pinholes and of uniform thickness can be prepared from solutions.8... 

However, Tripp and Hair82 have shown that the second critical step (i.e. condensation of the silanol with the surface hydroxyls groups) does not occur. At the solid/gas interface, the silanol adsorbs on the surface but does not undergo condensation or polymerization, whereas at the solid/liquid interface, the silanol polymerizes in solution and adsorbs on the surface. In neither case there is a strong Sis-0-Si bond formed with the substrate. It is the absence of Sis-0-Si surface linkages that is responsible for the general lack of robustness of silanized surfaces prepared from solution. 

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