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Chemically modified silicon dioxide surfaces. Wetting properties of compact n‐alkyl‐dimethylsiloxy layers, and their mixed surface crystals. The Question of Wetting of Molecularly Rough and of Swollen Surfaces
Author(s) -
Riedo François,
Czencz Maria,
Liardon Olivier,
Kováts Ervin sz.
Publication year - 1978
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19780610533
Subject(s) - wetting , alkyl , chemistry , contact angle , alkane , wetting layer , silicon , wetting transition , chemical engineering , polymer chemistry , crystallography , layer (electronics) , composite material , organic chemistry , hydrocarbon , materials science , engineering
By means of contact angle measurements, it has been shown that compact alkyl‐dimethyl‐siloxy layers can be obtained on the surface of acid leached glass using the method previously developed for fume silica. Subsequently, a series of densest possible alkyl‐dimethylsiloxy layers were prepared having non‐branched alkyl substituents, C z H 2z+1 , (with z=1, 2, 3, 6, 10, 14, 18 and 22) and wetting angles were measured as a function of the temperature. On surfaces coated with longer alkyl substituents the formation of mixed crystals, consisting of the sparse chemically bonded alkyl layer and a n‐alkane acting as a wetting agent, has been observed at low temperatures. At higher temperatures such surfaces appeared to be «molten», and at the same time swollen by the wetting agent. Equations have been derived to deduce the free surface energies and to account for the wetting properties of rough and swollen surfaces. Application of the results to the data presented in this paper revealed that glass surfaces covered with short alkyl chains (methyl, ethyl and propyl) are rough and those covered with long chains (tetradecyl, octadecyl and docosyl) are swollen. Surfaces formed by hexyl‐ and decyl‐dimethylsiloxy substituents exhibit intermediate properties.