ISSN:
1435-1536
Keywords:
Surface tension
;
conductance
;
tentacle molecule
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract The aggregation and air-water interface properties of a three-legged tentacle molecule tris (11-pyridinium undec-1-yl)benzene-1, 3, 5-tricarboxylate tribromide have been investigated by measurement of the molar conductance, λ, and equilibrium surface tensin,γ, over a wide range of bulk concentration (8×10−6 − 0.3 M). In contrast to the single chain analogue, dodecyl pyridinium bromide, DDPB, the tentacle species shows no evidence for a conventional micellar transition in solutions up to 100 fold more concentrated than the critical micelle concentration of DDPB, though aggregation of small numbers of molecules cannot be excluded. The conductance behaviour suggests the occurrence of ion-pair (or higher) equilibria, which are likely to complicate the interpretation of the data. Also, in contrast to a previous tentacle molecule described in the literature, the present species is significantly surface active, and in the high concentration limit reducesγ to 〈30 mNm−1, significantly lower than the values obtained for simple ionic amphiphiles. In this region the tentacle species seems to stand like a ‘tripod’ at the water-air interface with both its hydrocarbon legs and its aromatic body lifted clear of the water surface. At much lower concentrations two small plateau regions inγ are apparent (∼ 60 and 52 mNm−1). Here, the tentacle molecule occupies a much larger surface area, and seems to adopt a crab-like crouch with its aromatic body and polar ester substituents lowered into the water surface.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01410639
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