ISSN:
1435-1536
Schlagwort(e):
Scaling theory
;
micelle formation
;
polyoyethylene dodecyl ethers
;
coil-globule transition
;
surface tension
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Chemie und Pharmazie
,
Maschinenbau
Notizen:
Abstract The micelle formation and adsorption phenomena at the airwater interface of four long-chain polyoxyethylene dodecyl ethers, C12H25O(C2H5O) n H abbreviated as C12E n (n=6, 7, 10, 20, 30, and 40), which have newly been synthesized to have more narrow polyoxyethylene chain-length distribution than previously used, have been investigated in aqueous solution by surface tension measurements over a concentration range of the surfactants (10−5−10−3 m) at different temperatures (25, 35, 40, and 45 °C). The critical micelle concentration (CMC), the area (A) per surfactant molecule, and the standard Gibbs free-energy change of micellization (ΔG m) were determined from the surface-tension data of the solutions and the Gibbs adsorption equation at the various temperatures. It has been found that theCMC values of C12E n increase with increasing chain length of polyoxyethylene but decrease with increasing temperature. The area per moleculeA increases with elevating temperature, their increment from 25 °C to 45 °C being 3.3, 12.2, 20.5, and 36.9 Å2 for the C12E n (n=10, 20, 30, and 40). respectively. Application of a scaling rule in polymer science to parametersA andΔG m has suggested that a coil-globule transition takes place between 35 and 45 °C both at the micellar surface and at the air-water interface for the C12E30 and C12E40 around 40 °C
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF01189494
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