Premium
Incorporation of bromo‐octadecane into long‐chain ester monolayers at the air/water interface
Author(s) -
Baskar Geetha,
Shanmugharaj A. M.,
Venkatesh S.,
Mandal A. B.
Publication year - 2001
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/s11746-001-0293-0
Subject(s) - monolayer , octadecane , stearate , mole fraction , chemistry , molecule , organic chemistry , polymer chemistry , chemical engineering , biochemistry , engineering
Surface compatibility of 2‐methoxy ethyl stearate and oleate esters with 1‐bromo‐octadecane (RBr) has been investigated at the air/water interface with a Langmuir film balance. The methoxy ethyl head group in the esters promotes flat conformation at the air/water interface as observed from its higher surface area (stearate, 22.41 Å 2 /molecule; oleate, 57.20 Å 2 /molecule) in comparison to the corresponding acids. The stearate ester forms a homogeneous mixed monolayer with maximal incorporation of 0.5 mole fraction of RBr. This is indicated by the retention of liquid condensed and solid condensed phases of stearate ester, and the positive deviation of the mean molecular area of the mixed film from the calculated additive areas. When the mole fraction of RBr ( x 2 ) exceeds 0.5, the onset of formation of heterogeneous mixed film is indicated by the appearance of initial and final collapse pressures. On the contrary, oleate ester shows the least compatibility with RBr, which is indicated by the progressive decrease in mean molecular area with x 2 . The more liquid expanded‐phase structure of oleate ester probably does not promote compatibility with RBr at the air/water interface.