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On the Characteristic Curvature of Alkyl‐Polypropylene Oxide Sulfate Extended Surfactants
Author(s) -
Hammond Charles E.,
Acosta Edgar J.
Publication year - 2012
Publication title -
journal of surfactants and detergents
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.349
H-Index - 48
eISSN - 1558-9293
pISSN - 1097-3958
DOI - 10.1007/s11743-011-1303-2
Subject(s) - alkyl , chemistry , branching (polymer chemistry) , pulmonary surfactant , ethylene oxide , electrolyte , propylene oxide , polypropylene , curvature , oxide , polymer chemistry , sulfate , chemical engineering , organic chemistry , polymer , biochemistry , geometry , mathematics , electrode , copolymer , engineering
The hydrophobicity of alkyl‐polypropylene oxide sulfate surfactants was evaluated via their characteristic curvature (Cc) using the hydrophilic‐lipophilic difference (HLD) framework. A close examination of the relationship between the molecular structure of the surfactants considered (structure of the alkyl group and the number of propylene oxide groups in each surfactant) and their Cc led to a group contribution model that, for the first time, takes into consideration the geometry of the alkyl tail group. Based on this group contribution model, branching at the C2 (beta‐carbon) position of the alkyl group produces the largest increase in characteristic curvature. This observation is consistent with the notion that the Cc is associated with the packing factor for anionic surfactants. Branching at the C2 position tends to produce cylindrical or inverse cone shape packing, typical of more hydrophobic (positive Cc) surfactants. This study also confirms previous observations that, different from conventional anionic surfactants, the phase behavior of alkyl polypropylene oxide sulfates is less sensitive to electrolyte concentration and that these formulations turn hydrophobic with increasing temperature, akin to the behavior of nonionic surfactants.