THERMODYNAMIC STUDIES OF BIS(QUATERNARYAMMONIUM) AND (N-ALKYL-) IONIC SURFACTANTS
Date
2000
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ORCID
Type
Degree Level
Masters
Abstract
Thermodynamic properties and aggregation behaviour of n-alkyl m-3-m
(where m = 8, 12, 16 carbon atom chains) and cyclododecyl c12-s-c12 (where s =
3,4,6) gemini surfactants containing dimethylammonium bromide head groups
have been studied. The synthesized surfactants have been characterized
according to their cmc, a, and surface coverage at the air-water interface. The
cmc is found to decrease with increasing chain tail length in the m-3-m salt
series. The cmc and counterion association to the micelle reaches a maximum
value in the c12-s-c12 surfactant series for a butyl head group spacer, whereas
the area per head group was observed to increase as the linker spacer length
increased. Experimental apparent molar vol urnes of the binary aqueous
surfactant systems were measured in the post-micelle region and an additivity
scheme was used to estimate the infinite dilution apparent molar volumes.
These data provided estimates of the volumes of micellization for these salts.
The micellization volumes of the c12-s-c12 surfactant series are typically small,
indicating no micelles or very small micelles are produced by these surfactants
in aqueous medium. Mean aggregation numbers, Ns, obtained from time
resolved fluorescence quenching (TRFQ) show that N, increases with increasing
chain length for the m-3-m gemini surfactants. In contrast, low mean
aggregation numbers were obtained for the c12-s-c12 salt series.
Distribution coefficients, Kd, of mixed micelle systems consisting of
sodium alkylcarboxylate salts, CnNa (where n = 10, 12), alkyltrimethyl-
ammonium bromide salts. RNMe3Br (where R = 10, 12), and ethoxylated
alcohols, C EO (where EO = ethylene oxide and n = 0, 1,3) were studied using 4 n
an runr T} relaxation method. Results were compared against a thermodynamic
method for determining Kd and found to be in agreement with this data. The
presence of EO groups on the alcohol favors its solubility in anionic micelles,
indicating that the interaction between the anionic micelle and the alcohol
involves the EO groups of the alcohol. For the cationic systems, an increase in
the number of EO groups has no effect on K, implying that the EO groups do not
contribute to the interactions occurring in mixed micelles of cationic surfactants
and alcohol's containing EO groups.
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Degree
Master of Science (M.Sc.)
Department
Chemistry
Program
Master of Science