Micellization in Block Polyelectrolyte Solutions. 2. Fluorescence Study of the Critical Micelle Concentration as a Function of Soluble Block Length and Salt Concentration

Abstract

Critical micelle concentrations (cmcs) of block polyelectrolyte micelles formed from poly-(styrene-6-sodium acrylate) in aqueous and NaCl salt solutions were investigated by fluorescence measurements of solubilized pyrene. The measurements were made for a range of PS block lengths (6 to 110 units) and of PANa block lengths (15-2400 units). For the series consisting of 11 and 23 units of PS, which had been prepared with a wide range of PANa lengths, the cmc was found to pass through a maximum as a function of the soluble (PANa) block length. It was observed that as the length of the PS block increased, the dependence of the log cmc versus the PANa block length decreased. For all samples except the PS(6) series at low salt concentrations, the log cmc values were found to decrease linearly as a function of the square root of the NaCl concentration (VCa) which was varied from 0.10-2.5 M. The shape of the gradient d(log cmc)/d(VCa) versus the log of the number of PANa units was found to follow a curve of the same shape for the block polyelectrolyte micelles consisting of 6, 11, and 23 units of PS. The behavior of the curve was explained on the basis of polyelectrolyte conformations.

Phase Behavior of Amphiphilic Diblock Co-oligomers with Nonionic and Ionic Hydrophilic Groups

“…21 They found that all of these co-oligomers form micelles at this low concentration, and that the diameter of the self-assembled micelles increases as the length of the hydrophobic block increases, as expected. Braun et al have studied low molecular weight poly(ethylene oxide) 23 -bpoly(γ-methyl-ε-caprolactone) y = 2 5 , 3 2 , 4 4 , 5 4 (PEO 2 3 -b-PMCL y=25,32,44,54 ) over the entire polymer concentration range in aqueous solutions. 22 These studies showed that the most prevalent self-assembled nanostructures for all of the diblock copolymer compositions are lamellar bilayers and vesicles.…”

Self-Assembly of Triblock Copolymers in Aqueous Solution

“…There are many factors that affect the above three terms. For example, the block length of the copolymer 8 , the concentration of the precipitant, the initial concentration of polymer 9 , the presence of additives 10 , the common solvent used 11 . The type of micelle, formed in aqueous solution, depends on the relative proportion of the soluble and insoluble block in the polymer.…”

Synthesis and micellization of polydimethylsiloxane– carboxy-terminated poly(ethylene oxide) graft copolymer in aqueous and organic media and its application for the synthesis of core-shell magnetite particles

“…The CMC 1 determined from the equilibrium surface tension measurements is about two orders of magnitude lower as compared to the corresponding value calculated from the variation of I 1 /I 3 ratio, while the CMC 2 values are in good agreement. A discrepancy between CMC values obtained by different methods was already reported [2] and is not fully understood. The values are in good agreement with those reported in the literature for PDMS-PEO diblocks (from 0.04 to 0.33 g\L) and triblocks (from 0.02 to 0.09 g/L) [30].…”

“…At this pH, the interchain aggregation is registered for higher copolymer concentration (CMC = 5.25 g/L) as compared to that evidenced at pH = 4 (CMC 1 = 1.01 g/L, CMC 2 = 1.73 g/L). At high concentrations the value of I 1 /I 3 ratio (1.1) indicates a more hydrophobic environment of pyrene probe (close to that corresponding to pyrene in a polystyrene film or in PS-PEO water solutions [28]) and lower than that corresponding to pyrene in a nonionic detergent such as Triton X-100 [2]). The increasing of the I E /I M ratio with concentration confirms the location of pyrene in less polar microdomains, demonstrating that a region of high polymer density exists despite the presence of the dissociated carboxylic groups attached to the copolymer chain.…”

“…Self-assembling of amphiphilic copolymers consisting of hydrophobic and hydrophilic sequences has attracted much attention due to its potential in controlling the solution properties and in the detailed investigation of the driving forces that determine aggregation [1][2][3][4][5][6]. Such macromolecular compounds can be used to build models and to anticipate the behavior of the more complex biological systems.…”