Coating ability

Mono- and multilayer films of polyimides were successfully prepared using Langmuir-Blodgett technique. Monolayer films of polyamic acid long alkylamine salts were prepared at the air-water interface. The mono-layer films were deposited on appropriate plates to produce multilayer films of the precursor to polyimide films. Finaly, the polyimide multilayer films were obtained by treatment of the multilayer films of the polyamic acid amine salts with acetic anhydride and pyridine. The polyimide multilayer films had excellent coating ability giving a very smooth surface. They also exhibited insulating characteristics as reliable as polyimide thick films. 

The surface of the polyimide film of was observed by SEM to be as flat as that of The multilayer film of was prepared on a silicon wafer which contained evaporated aluminum lines in order to examine the coating ability of the present LB films. Figure 3(a) exhibits the mechanical stylus probe (Talystep) pattern of aluminum lines (30 nm high and 2000 nm wide) and (b) shows the lines after 120 layers of were deposited. Since the depth was observed as 30 nm in both cases, it is concluded that the multilayer film can conformally coat the uneven surface. This feature can be directly observed in the photographs of Figure 4 where a 60 layer film of is coated on an aluminum line (200 nm of high and 2000 nm wide). 

Each emulsion, depending on its grade, should also meet the requirements of other properties, such as viscosity, storage stability, coating ability, oversized particles (residue on sieving) and so on. Additionally, the recovered bitumen should satisfy the penetration, softening point, ductility, solubility and viscosity requirements, to name a few, depending on the specification employed. 

Bituminous emulsion s coating ability depends directly on the water added to the aggregates before mixing. For this reason, the coating test is conducted at various percentages of added water. The test takes place at room temperature (21°C 3°C). 

PEO, pDMA, and polyvinylpyrrolidone (PVP) have self-coating abilities, which allows DNA sequencing in bare fused-silica capillaries. A mixture of two molecular mass populations of PEO is possible to separate DNA sequencing fragments over 1000 bases, too, but the separation time exceeds 7 hr. pDMA and PVP are low-viscosity sieving matrices (<100 cP). They have moderate separation efficiencies and can provide maximum read lengths of about 500-600 bases. 

Single-stranded DNA has a more hydrophobic character than double-stranded DNA and presents stronger interaction with the silica wall. Thus, capillary wall coating is greatly preferred. A few of polymers, such as pDMA, PEG, and PVP, as mentioned, have self-coating abilities. They can be used for DNA sequencing in bare capillaries or bare microchips. However, the life of the bare walls is limited because their performance deteriorates with repeated runs. Therefore, extensive and, sometimes, harsh rinsing is indispensable between runs. 

In both cases, the coating ability to suppress the surface activity is strongly correlated to the hydrophobicity recovery process. Material formulation in combination with the stresses applied and their influence on the LMW migration mechanism are the crucial parameters that determine the application efficiency and material lifetime. 

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