Evaporation, deposition polymers

Although the diffusion-reaction method may vary, the results of aluminization remain similar and depend on the steel composition and on the temperature of the reaction processing. Methods that have been used for steels include hot dipping, " - -29,34-37 plasma spraying, " - - pack aluminizing, which is a form of chemical vapor deposition vacuum evaporation, and polymer slurry methods." ... 

Our screening concept is depicted in Fig. 19.2. For simplicity, operation of only one of the sensors from the sensor array is illustrated. An initially clean sensor crystal is exposed to a solvent containing a small amount of polymer followed by sensor withdrawal from the solution (Fig. 19.2a). Quantification of the residual dissolved polymer deposited onto the sensor is done by the measurements of the mass increase of the crystal, which is proportional to the amount of polymer film deposited onto the sensor from a polymer solution. Depending on the solvent-resistance of the polymers, the dissolution rate of polymers in solvents will be different as determined from multiple measurements of deposited polymers during the experiment (Fig. 19.2b). The measurements of frequency changes are done when the sensors are periodically withdrawn from the solvents and the solvents are evaporated. In this way, the measured signal change is indicative of the amount of the deposited material from the solution. 

Depositing polymer membranes from solution is probably the oldest and simplest method for polymer deposition. Typically a solution of the polymer is deposited onto the transducer surface and allowed to dry. Although this technique is simple to practice, it is a fine art to perfect. Polymer concentration, solvent composition, amount of solution deposited, and solvent evaporation rate are all crucial parameters to control in order to obtain films that adhere well to the substrate, are uniform in thickness, and are free from defects. Gregg and Heller have solution cast redox-functional hydrogels containing glucose oxidase on an electrode to fabricate a glucose sensor [19]. 

When the product is applied to wet hair and the hair is set and combed, after the solvent evaporates (as for styling lotions and mousses), the deposited polymer still influences the hair assembly character, by increasing the interfiber forces, but not as much through rigid contacts (Figure... 

The important difference between these two classes of materials lies in the formation of thin films. The small molecular weight materials are usually deposited from the gas phase by sublimation or evaporation meanwhile polymers form the film from... 

Electrospinning can be used to produce novel fibers wifh the diameters in the range from 100 nm to 10 p,m. As the solvent evaporates, the polymer molecules can come together by either a phase separation through a spinodal reaction or through classic nucleation and growth of the crystalline phase. As a result, the structure in the polymer deposited on the collector may form a totally amorphous, a part of oriented, spherulitic, or textured fibrillar structure. 

Thin films of CTC or RIS deposited on several substrates (e.g. glass, polymer, metal) can be prepared by the evaporation- deposition method [327,328], or the Langmuir-Blodgett technique [330,47b]. 

The oxidative polymerization of aniline was performed to produce PANI, when 40 mM of aniline was dissolved in 25 ml 0.5 M aqueous hydrochloric acid solution. The potential of the GC electrode was scanned between -0.4 to 1.1 V vs. Ag/AgCl at a scan rate 100 mV/s, the polymerization was stopped at -0.4 V when the charge passed from the reduction of deposited polymer reached to 0.65. The PANI film had a green color. The film was washed with distilled water, then with tetrahydrofurane (THF). The GC electrode with film was immersed in a large glass tube with THF solution contained 0.01 g FeCl3 and 0.5 ml of 3-chloropropylthiol the top of tube was closed to prevent evaporation of the solvent. The reaction was carried out at 60°C for 24 h in a temperature controlled mineral oil bath. The... 

Polymers can be evaporated, deposited as a thin film, and cured in a vacuum system to provide a basecoat. For example, acrylate coatings can be deposited and cured with an e-beam. The deposited liquid flows over the surface and covers surface flaws, reducing pinhole formation. This technique can be used in vacuum web coating and has been found to improve the barrier properties of transparent barrier coatings. 

Fig. 10. Schematic of casting machine used to make microporous membranes by watervapor imbibition. A casting solution is deposited as a thin film on a moving stainless steel belt. The film passes through a series of humid and dry chambers, where the solvent evaporates from the solution, and water vapor is absorbed from the air. This precipitates the polymer, forming a microporous membrane that is taken up on a collection roU (25).

Figure 10-12. Lcfi hand side Slruclure of a PPV microcavily. A thin film of ihe conjugated polymer is deposited on top of a highly reflective distributed Bragg refieclor (DBR). The second mirror is then fabricated by evaporation of a silver layer. Right hand side Emission spectra of the microcavily at excitation cnetgics or 0.0S pJ (dashed line) and l. l pJ (solid line), respectively. Laser pulses ol duration 200-300 ps and a wavelength of 355 nm were used for optical excitation (according to Ref. [39]).

The relatively high volatility of Tg[CH = CH2]8 has enabled it to be used as a CVD precursor for the preparation of thin films that can be converted by either argon or nitrogen plasma into amorphous siloxane polymer films having useful dielectric propertiesThe high volatility also allows deposition of Tg[CH = CH2]g onto surfaces for use as an electron resist and the thin solid films formed by evaporation may also be converted into amorphous siloxane dielectric films via plasma treatment. ... 

Alternatively, the amount of polymer deposited can be determined via droplet evaporation by microsyringe application of known amounts of polymer solution on the electrode surface, but the problem of homogeneity of the film is still not solved. 

Chemical alternation of the surface layer and deposition of a new layer on top of the silicone mbber can be achieved by physical techniques. For the inert surface of silicone rubber, the former requires the generation of high-energy species, such as radicals, ions, or molecules in excited electronic states. In the latter case, coatings of atoms or atomic clusters are deposited on polymer surfaces using technique such as plasma (sputtering and plasma polymerization) or energy-induced sublimation, like thermal or electron beam-induced evaporation. 

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