Effect of EO Chain Length of Dodecanol Ethoxylates (C12En) on the Complexation of C12En/SDS Mixed Micelles with an Oppositely Charged Polyelectrolyte
✍ Scribed by H. Zhang; Y. Li; P. Dubin; T. Kato
- Publisher
- Elsevier Science
- Year
- 1996
- Tongue
- English
- Weight
- 144 KB
- Volume
- 183
- Category
- Article
- ISSN
- 0021-9797
No coin nor oath required. For personal study only.
✦ Synopsis
The surface charge density of micelle, s, is therefore Turbidimetry, dynamic light scattering, and capillary electroa particularly important variable, which may be conveniently phoresis were used to study the complexation of polydiallyldimethcontrolled by adjusting the mole fraction (Y ) of the ionic ylammonium chloride (PDADMAC) with mixed micelles of socomponent in mixed micelles. Upon increasing Y, one obdium dodecyl sulfate (SDS) and dodecanol ethoxylates (C 12 E n ). serves a transitional point (Y c ) corresponding to the onset The effect of EO chain length and its distribution was examined of polyelectrolyte binding followed by bulk phase separation using various combinations of C 12 E n (n Å 4, 6, 8, 12). The results with further increase of Y (Y p ). Many polyelectrolyte-mixed show that the onset of the complexation of PDADMAC with the micelle systems have been studied in this manner by monimixed micelles is affected by the EO chain length of C 12 E n : the toring the dependence of the turbidity or mean particle size mole fraction (Y ) of SDS in the mixed micelle required to form on Y (4, 5). Some of these include mixtures of dodecanol the complex (Y c ) increases with n. The effect of EO chain length on the onset of bulk phase separation shows the same trend. Al-hexaoxyethylene ether (C 12 E 6 ) with sodium dodecyl sulfate though Y c varies with n, the electrophoretic mobility of mixed (SDS), or TX-100 with SDS, in combination with polymicelles with composition corresponding to Y c is independent of cations such as polydiallyldimethylammonium chloride n. We propose that the effect of EO chain length has two aspects: (PDADMAC), polymethacrylamidopropyltrimethylam-(1) an increase in the average distance between bound polycation monium chloride (PMAPTAC), etc. (5); or mixed posisegments and the SDS sulfate groups, and (2) an increase in the tively charged mixed micelles, such as TX-100/dodecyl tridistance between SDS head groups, which causes a decrease in the methylammonium bromide (DTMAB) in combination with surface charge density (s) of the micelle. Therefore, the electrical polyanions, such as sodium polystyrene sulfonate and sopotential at the mean locus of bound polymer segments, c 0 , dedium polyvinyl sulfate (NaPVS) (3).
creases with increasing n; in order for complexation to occur, this
There is substantial evidence to show that the significant effect must be compensated for by a larger value of Y. Broader interaction is between polyelectrolyte and mixed micelle, distributions of EO chain length lead to an increase in the range not between polyelectrolyte and ionic monomeric surfactant.
of Y over which the soluble complex is stable. We suggest that polycations initially bind to micelles which are rich in shorter EO (i) There is no effect of the concentration of anionic surfacchains and thus have higher ''surface'' potential, c 0 . However, tant per se: no complexation is observed, regardless of anadditional SDS may go preferentially into micelles rich in longer ionic surfactant concentration, as long as nonionic surfactant chains with lower c 0 . This delays the formation of micelles which is in suitable excess. (ii) Many studies (1-3) have shown have sufficiently large c 0 to cause phase separation. ᭧ 1996 Academic that complex formation occurs only when some critical mi-Press, Inc.
celle surface charge density is attained, an unlikely scenario if complex formation involved nonmicellar surfactant. (iii) The mixed micelle cmc is typically on the order of 0.1