Measuring Alkyl Chain Cross-Sectional Area for Gibbs Adsorption

AI Thread Summary
The discussion centers on the measurement of the cross-sectional area of surfactant alkyl chains, specifically whether to measure it vertically or horizontally, or to rely on theoretical values from literature, which estimate the area to be around 20-25 Ų. A key point raised is the contradiction in Gibbs adsorption theory, highlighted in a paper by Shibata et al., which states that the molecular surface area of certain surfactants (C16E8 and C18E8) is less than the cross-sectional area of their alkyl chains. This discrepancy raises questions about the adequacy of Gibbs adsorption at the air/water interface, suggesting that the assumptions underlying this theory may not hold true in these cases. The conversation emphasizes the complexity of measuring surfactant properties and the implications for understanding surfactant behavior in solutions.
bobey
Messages
29
Reaction score
0
1. Surfactant molecule is made from water-loving head and grease-loving tail (Figure 1). My question: How do we measure the cross-sectional area of the alkyl chain of surfactant? Do we measure it vertically (refer to GREEN DOUBLE ARROWS of Figure 1) or horizontally (refer to RED DOUBLE ARROWS of Figure 1)? Or do we just take the “theoretical value" of the alkyl chain from the literature (estimated 20-25 A˚2)[http://www.physics.uoguelph.ca/~dutcher/download/handbook%20of%20biological%20physics/7.pdf]?

2. I have read a paper entitled, "New Adsorption Model - Theory, Phenomena and New Concept - " by Shibata et. al. [2]. One of the sentences in para 3 page 2 stated that, i quoted, “The important finding is that molecular surface area is less than the cross-sectional area of the alkyl chain for C16E8 and C18E8. Such small molecular surface areas strongly suggest that Gibbs adsorption just at air/water interface in an adequate. This is one of contradictions for the Gibbs adsorption."

Why does when the molecular surface area is less than the cross-sectional area of the alkyl chain, it is said to be contradicted with the Gibbs adsorption?

Reference:

[1] http://www.physics.uoguelph.ca/~dutcher/download/handbook%20of%20biological%20physics/7.pdf

[2] http://www.jstage.jst.go.jp/article/jos/64/1/64_ess14213/_pdf
 
Chemistry news on Phys.org
bobey said:
How do we measure the cross-sectional area of the alkyl chain of surfactant?
Definition of the term "cross-section" gives you a "hint."
 

Thread 'Solubility of MgSO47H2O in water'

It seems like a simple enough question: what is the solubility of epsom salt in water at 20°C? A graph or table showing how it varies with temperature would be a bonus. But upon searching the internet I have been unable to determine this with confidence. Wikipedia gives the value of 113g/100ml. But other sources disagree and I can't find a definitive source for the information. I even asked chatgpt but it couldn't be sure either. I thought, naively, that this would be easy to look up without...
View full post »

Thread 'Why does having 8 valence electrons make an element inert?'

I was introduced to the Octet Rule recently and make me wonder, why does 8 valence electrons or a full p orbital always make an element inert? What is so special with a full p orbital? Like take Calcium for an example, its outer orbital is filled but its only the s orbital thats filled so its still reactive not so much as the Alkaline metals but still pretty reactive. Can someone explain it to me? Thanks!!
View full post »

Similar threads

Contradiction of Gibbs adsoprtion?
Replies
2
Views
2K

Hot Threads

Recent Insights

Back
Top