Surface and Colloidal Properties of Cyclic Amides. 1. Two-Dimensional Virial Coefficients for Adsorbed Monolayers of N-Alkyl-2-pyrrolidones at the Air/Water Interface

The N-(n-alkyl)pyrrolidones are low vapor pressure polar solvents which are surface active in aqueous solutions. From measurements at low surface pressures and low concentrations the two-dimensional second virial coefficients B 2(T) at the air/water interface are obtained for the series of even-numb...

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Bibliographic Details
Published in:Langmuir 1996-11, Vol.12 (24), p.5845-5850
Main Authors: Lou, Anjing, Pethica, Brian A, Somasundaran, Ponisseril
Format: Article
Language:English
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Summary:The N-(n-alkyl)pyrrolidones are low vapor pressure polar solvents which are surface active in aqueous solutions. From measurements at low surface pressures and low concentrations the two-dimensional second virial coefficients B 2(T) at the air/water interface are obtained for the series of even-numbered alkyl substituents from ethyl to octyl. At 25 °C, B 2(T) is positive for the ethyl compound and becomes increasingly negative as the chain length increases. The effect of temperature on B 2(T) is unusual, increasing temperature leading to more negative B 2(T) values. The virial coefficients, heats of adsorption, and Traube coefficients are discussed in terms of molecular packing, chain−chain van der Waals attraction, and the interaction of the chains and large molecular dipoles with water.
ISSN:0743-7463
1520-5827
DOI:10.1021/la9602325