Brewster angle microscope

In situ observation of monolayers of fatty acids on the water surface by a Brewster angle microscope. 

Collapsing and nucleation processes of a stearic acid monolayer have been also studied on the different aqueous subphases by a Brewster angle microscope [15]. Both of the temperature and the pH value of the aqueous subphase can influence the nucleation process and produce very different collapsing patterns. 

The Brewster angle microscope (BAM) has been used to investigate the mono-layers of polyamic acid at the air-water interface in situ and without the addition of probes. The morphology of the monolayer was observed as a function of surface... 

Amphiphilic behaviour at an air-water interface was studied using monolayer experiments. Surface pressure-area isothenns were recorded for PS-rfe dr-(NH2) with = 1-16. The formed monolayers were also investigated with a Brewster angle microscope (BAM) [53], which made it possible to investigate the type of structures that are formed in the monolayer. The results are shown in Figure 15. 

The Brewster angle microscope developed by Henon and Meunier (1991) does not require addition of a probe and also yields information on the morphology of surface phases. VoUhardt (1996) reviewed results obtained with this... 

The HT voltammetry with gold electrodes was also recently used to measure the surface partitioning constant of a soluble, redox-active surfactant at the air/water interface [25]. Malec and coworkers modified the surface of gold electrodes by self-assembly of short alkane chain thiols in order to mimic the thermodynamic properties of the air/water interface. They relied on the fact that the surface tensions of the air/water interface and of the liquid alkane/water interface are similar [8]. Indeed, the HT measurements of the Gibbs monolayer formation constant were in agreement with their surface tensiometry and Brewster angle microscopic measurements [25]. 

Fig. 14 Three Brewster angle microscopic images of Os(DPP)3 monolayer on a 50-mM HCIO4 subphase recorded at 360 A /molecule showing typical shapes and sizes of 2D aggregates formed on the water surface upon spreading. The length of the vertical edges of these images corresponds to 730 mm (from Ref. 75).

It is remarkable that in the 2D monolayer, two distinct L phases (LE and LC) exist, whereas this is not the case in the 3D situation. The coexistence of LE and LC phases can be made visible, for instance, by using a Brewster angle microscope. Examples are shown in Figure 7.5. 

The Brewster angle microscope is positioned over the monolayer trough such that the incident laser beam hits the part of the water surface where the monolayer is present at all stages during the experiment. The surface pressme (n) and (if used) surface potential (AV) transducers also need to be positioned in this segment of the trough. The trough itself may be either commercial or home built in... 

Figure 5 BAM image of multilayer regions coexisting in spread and compressed films of the liquid crystal 8CB. Reproduced from Ref. 31. American Physical Society, 2007, and the figure caption reads as follows Brewster angle microscope image of the coexistence of 8CB multilayers. The background is 8CB trilayer. The layer reflectivity increases with thickness, so that different gray levels correspond to different thicknesses. The rippled variation in color within one domain is due to variations in illumination. The black scale bar is 1.0 mm.

Fig. 2 Scheme of the Brewster angle microscope a denotes the angle of incidence... 

Riviere, S., Henon, S., Meunier, J., Schwartz, D. K., Tsao, M. W. and Knobler, C. M., Texture and phase transitions in Langmuir monolayers of fatty acids - a comparative Brewster angle microscope and polarized fluorescence study, J. Chem. Phys., 101, 10045-10051 (1994). 

The spontaneous spreading of thin microdroplets on solid substrates is slow and can be conveniently monitored using spatially resolved ellipsometry. On the other hand, extended thin wetting films can be spin-coated on solids or deposited on liquid substrates and thereafter studied under a polarized microscope for nanometric thicknesses or a Brewster angle microscope for molecular ones. X-ray reflectometry provides complementary information. 

Problem 8.4. If one wants to use either a Brewster angle microscope or an ellipsometer to determine the thickness of an adsorbate as one changes the temperature of the surface, which of them will give rise to the largest uncertainty ... 

Although the surface pressure-area (tt-A) isotherm tells us much about the properties of monolayers at the air-water surface, direct observation of the film morphology also gives us much information. The fluorescent [27] and Brewster angle microscopes [28,29] are powerful tools for this purpose. As the film-forming material usually has a large optical density, UV/visible spectroscopy of the monolayers is easily employed. The conductivity of the monolayer can be measured at the same time on n-A isotherm measurements. 

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