Formation and expansion of dark spots in stratifying foam films

The stratification of thin liquid films formed from micellar solutions or latex suspensions can be explained by layer-by-layer destruction of a colloid crystal structure inside the film. The stepwise decrease of the film thickness is due to appearance and growth of dark spots (of less thickness) in...

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Bibliographic Details
Published in:Langmuir 1990-06, Vol.6 (6), p.1180-1189
Main Authors: Kralchevski, P, Nikolov, A, Wasan, D. T, Ivanov, I
Format: Article
Language:English
Subjects:
02 PETROLEUM
020300 - Petroleum- Drilling & Production
400201 - Chemical & Physicochemical Properties
Chemistry
Colloidal state and disperse state
COLLOIDS
DISPERSIONS
ELASTOMERS
Exact sciences and technology
FOAMS
General and physical chemistry
INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
LATEX
MICELLAR SYSTEMS
Micelles. Thin films
ORGANIC COMPOUNDS
ORGANIC POLYMERS
PHASE TRANSFORMATIONS
POLYMERS
RUBBERS
STRATIFICATION
SURFACTANTS
THIN FILMS
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Summary:The stratification of thin liquid films formed from micellar solutions or latex suspensions can be explained by layer-by-layer destruction of a colloid crystal structure inside the film. The stepwise decrease of the film thickness is due to appearance and growth of dark spots (of less thickness) in the film. This phenomenon is analyzed in the present paper, and an explanation is proposed. The driving force for the stepwise thinning of the film is attributed to the gradient of the chemical potential of micelles at the film periphery. Therefore, the appearance and expansion of spots in the film are controlled by the micellar self-diffusion, rather than by normal instabilities. The spots are considered as condensed states of vacancies in the micellar structure inside the film, and the appearance of dark spots is interpreted as a phase transition. This explanation of the mechanism of stratification phenomenon is supported by the data for formation and expansion of spots.
ISSN:0743-7463
1520-5827
DOI:10.1021/la00096a026