Study of Sodium Dodecyl Sulfate−Poly(propylene oxide) Methacrylate Mixed Micelles

Abstract

Sodium dodecyl sulfate (SDS)-poly(propylene oxide) methacrylate (PPOMA) (of molecular weight Mw ) 434 g‚mol -1 ) mixtures have been studied using conductimetry, static light scattering, fluorescence spectroscopy, and 1 H NMR. It has been shown that SDS and PPOMA form mixed micelles, and SDS and PPOMA aggregation numbers, Nag SDS and Nag PPOMA, have been determined. Total aggregation numbers of the micelles (Nag SDS + Nag PPOMA) and those of SDS decrease upon increasing the weight ratio R ) PPOMA/SDS. Localization of PPOMA inside the mixed micelles is considered (i) using 1 H NMR to localize the methacrylate function at the hydrophobic core-water interface and (ii) by studying the SDS-PPO micellar system (whose Mw ) 400 g‚mol -1 ). Both methods have indicated that the PPO chain of the macromonomer is localized at the SDS micelle surface. Models based on the theorical prediction of the critical micellar concentration of mixed micelles and structural model of swollen micelles are used to confirm the particular structure proposed for the SDS-PPOMA system, i.e., the micelle hydrophobic core is primarily composed of the C 12 chains of the sodium dodecyl sulfate, the hydrophobic core-water interface is made up of the SDS polar heads as well as methacrylate functions of the PPOMA, the PPO chains of the macromonomer are adsorbed preferentially on the surface, i.e., on the polar heads of the SDS.

Rapid and quantitative determination of critical micelle concentration by automatic continuous mixing and static light scattering

“…For SDS without salt, the aggregation number is 50, whereas it is 90 in the 0.1 M NaCl solution. These values are almost identical to those previously reported in literature, where N ag = 54 and 89, respectively, as measured with a fluorescence technique [23].…”

“…A comparison with literature data suggests a satisfactory overall performance of this automatic continuous mixing and static light scattering (ACM-SLS) technique. To affirm that the comparison is independent of the purity of surfactant used, the cmc values were determined by independent surface tension and conductimetric measurements of the same solution according to methods described in the literature [21][22][23][24]. All results are reported in Fig.…”

Micellar copolymerization of associative polymers: Study of the effect of acrylamide on sodium dodecyl sulfate–poly(propylene oxide) methacrylate mixed micelles

“…In the first part of this paper, we report a study of the influence of acrylamide on the micellar properties of pure SDS micelle alone, using different techniques to verify if addition of acrylamide perturbs or does not perturb the micellar properties of SDS. In our previous works, we have demonstrated that our hydrophobic monomer PPOMA incorporates into SDS micelles, by significantly decreasing the SDS aggregation number, N ag SDS [31,32]. The various parameters of SDS-PPOMA mixed micelles we obtained in the previous paper are reported in Table 1.…”

“…Such polymers can be prepared by micellar copolymeriza- Note. CMC and α are the critical micellar concentration and the ionization degree; N ag total , N ag SDS , and N ag PPOMA , the total, SDS, and PPOMA aggregation numbers [31]. C SDS = 0.05 mol L −1 .…”

“…The amplitude of the viscosity jump at the LCST of the PPO branch was expected to depend on the length of the PPOMA block in the copolymer and consequently on the weight ratio R = PPOMA/SDS. A systematical study of the SDS-PPOMA micellar system, using many complementary techniques (conductimetry, fluorescence, and light and neutron scattering) [29][30][31][32], has revealed without any ambiguity that the hydrophobic comonomer (PPOMA) strongly modifies the CMC and N ag of SDS. It clearly appeared that the previous assumption expressed by relation (1) could not be valid in this particular case.…”