Film thickness determination procedure

There is not often cause to determine ethylene glycol and diethylene glycol in surfactants. If the analysis becomes necessary, two procedures for determining EG and DEG in PEG found in the National Formulary are suitable (60). The first is a colorimetric method, while the second is a gas chromatography procedure. The GC procedure specifies use of a 5% phenyl/95% methyl polysiloxane capillary column, 0.32 mm x 50 m, 5 pm film thickness. Determination of EG by headspace GC requires higher temperatures and achieves higher detection limits than is the case for EG and 1,4-dioxane (61-63). 

The rate-based models suggested up to now do not take liquid back-mixing into consideration. The only exception is the nonequilibrium-cell model for multicomponent reactive distillation in tray columns presented in Ref. 169. In this work a single distillation tray is treated by a series of cells along the vapor and liquid flow paths, whereas each cell is described by the two-film model (see Section 2.3). Using different numbers of cells in both flow paths allows one to describe various flow patterns. However, a consistent experimental determination of necessary model parameters (e.g., cell film thickness) appears difficult, whereas the complex iterative character of the calculation procedure in the dynamic case limits the applicability of the nonequilibrium cell model. 

The procedure for the THG measurements of thin films needs less steps. As the thin films can be directly measured in vacuum, the calibration of the air contribution is not required. Furthermore, the film substrate is usually fused silica that makes also the initial calibration of the THG setup with a fused silica plate superfluous. However, the film thickness and its refractive index have to be determined prior to the THG analysis. 

Depth profiling techniques applied to thermodynamically equilibrated thin films characterize the compositions of coexisting phases and the spatial extent of the separating interface. This procedure repeated at different temperatures yields the coexistence curve and the corresponding temperature variation of the interfacial width. Determined coexistence curves are well described by the mean field theory with composition-dependent bulk interaction parameter [74]. The same interaction parameter also seems to generate the interfacial widths in accordance with results presented here [107] (Sect. 2.2.2) and elsewhere [88, 96, 129]. These predictions may however need to be aided by capillary wave contributions to fit another observations [95, 97, 98], especially those tracing the change of the interfacial width with film thickness [121,130] (see Sect. 3.2.2). 

Dielectric constants of metals, semiconductors and insulators can be determined from ellipsometry measurements [38, 39] Since the dielectric constant can vary depending on the way in which a film is grown, the measurement of accurate film thicknesses relies on having accurate values of the dielectric constant. One common procedure for determining dielectric constants is by using a Kramers-Kronig analysis of spectroscopic reflectance data [39]. This method suffers from the series-termination error as well as the difficulty of making corrections for the presence of overlayer contaminants. The ellipsometry method is for the most part free of both these sources of error and thus yields the most accurate values to date [39],... 

Film thickness is associated with the richness modulus (k) used in France in mix design procedures to determine the minimum binder content. For more details, see Corte and Di Benedetto (2004). 

Starch adipate, a cross-bonded starch for food use, is made by reaction with adipic anhydride, which is formed from adipic acid in the presence of excess acetic anhydride. It is also a labile ester, and after hydrolysis with alkali, followed by acidification, is extracted with ethyl acetate and silylated. Gas chromatographic analysis is performed on a capillary column of fused silica coated with dimethyl siloxane, film thickness 5 pm. Pimelic acid is the internal standard. The method cannot differentiate between mono- and disubstitution. Alkyl succinate substitution can be determined using the same procedure as for adipate. 

Samples were prepared from dilute toluene solutions by spincoating thin films onto the wafers. The polymer adsorbed onto the oxide surface of silicon wafers which were cleaned in a water-saturated UV-ozone atmosphere. By this cleaning procedure, we created a surface with a high density of hydroxyl groups. The initial film thickness has been determined by eUipsometry. Crystallization and subsequent thermal treatment (annealing) were performed directly under an optical microscope in an inert atmosphere (nitrogen flow). 

---