A= coventional surfactant,

B= Gemini surfactant

for gemini two conventional surfactants must be connected by spacer.

(B) is gemini but (A) is not. Synergy originate if two (or more) hydrophobic (low-polar) tails are near in one molecule. Quantity and lenght of hydrophilic (polar) heads can vary. Hydrophobic spacers are not inert in self-organisation - In the case of -(CH2)n- and n>>8, effect increase considerably.

Hi Ahmed,

this is some literature

1) http://www.iisc.ernet.in/currsci/may102002/1101.pdf

2) Menger, F. M. and Keiper, J. S. (2000), Gemini Surfactants. Angew. Chem. Int. Ed., 39: 1906–1920.

- Very good review, but I have only hard copy of this publication.

Available for money from http://onlinelibrary.wiley.com/doi/10.1002/1521-3773(20000602)39:11%3C1906::AID-ANIE1906%3E3.0.CO;2-Q/abstract

Yes, trimer, tetramer and even polymer gemini surfactants are known. Synergy - it is cooperative effect. One extreme example demonstrate this. This is poly(pentafluoroethyl)oxazoline, -(N(COCH2C2F5)-CH2CH2-)n- . VERY short hydrophobic tails , very short spacers, but CMC and reducing of surface tension is in level of best perfluorinated surfactants, like C7F15COONa or PFOS.

Menger publication in attachment

Thank you very much Andrei Rogoza and Oyais Chat

but concerning the trimeric and tetrameric surfactants, can I say trimeric gemini surfactant? I ask this question because I saw several papers that don't use the word "gemini" when they deal with trimers and tetramers but they use the word "oligomer"

IMHO, term "gemini surfactant" describe whole class surfactants with more than one hydrophobic (liophobic) tail. Exact specification we get from chemical formula.

Trimer, tetramer and so on - it is more often slang. In the case of repeating elements of spacers and tails it is unusual graft-polymer, and in terms of polymer science may be say that we have "trimer, tetramer,...,oligomer.

ERRATUM in my previous message - (-N(COC2F5)-CH2CH2-)n- is right, this is element in diblock polymer (Macromolecules 1989,22, 3540-3543)

Please Dr Andrei Rogoza, what does "IMHO" refer to?