Phase separation of micellar solutions at extreme dilution: A study of polystyrene-b-poly(sodium acrylate) micelles in aqueous NaCl solutions

Abstract

Micellar solutions of polystyrene‐b‐poly(sodium acrylate) copolymers in aqueous NaCl were studied by static light scattering (SLS). It was found that micellar solutions of the copolymer, at concentrations of NaCl at, or above, 2.0 mol dm−3, became turbid on dilution at constant salt concentration and at constant temperature. Turbidity arose from highly dilute solutions (typically at a concentration three orders of magnitude lower than the overlap concentration of the micelle, C*), but at concentrations above the expected critical micellization concentrations (c.m.c.s). The observed turbidity was attributed to the phase separation of the micellar phase. A systematic investigation of the phase separation phenomenon was performed. The effects of various parameters on the solution behavior of the micellar solutions were studied, including the effect of the concentration of NaCl, the effect of temperature, and the effect of the length of the hydrophilic, corona‐forming poly(sodium acrylate) block. Phase separation was attributed to the presence of a very large excess of NaCl in the dilute micellar solutions. It was proposed that phase separation arose because of the reduced hydration of the polyion, the decreased electrostatic repulsion between the micelles, and the increase in the amount of ion binding, which occur in highly dilute salt solutions. © 1996 John Wiley & Sons, Inc.

Thermodynamics of Crew-Cut Micelle Formation of Polystyrene-b-Poly(acrylic acid) Diblock Copolymers in DMF/H2O Mixtures

“…40 Several research groups have investigated the asymmetry factor Z as a function of temperature near the onset of the micellization and found that there is a peak that in some cases appears at the same temperature as the peak in the scattering curve (see Figure 1). 20,39,[41][42][43] We also observed a maximum in the plot of Z as a function of temperature. This is shown in Figure 5 for the 0.77 and 0.97 wt % fractionated block copolymer samples in DMF containing 4.50 wt % water.…”

Brain targeting efficiency of intranasal clozapine-loaded mixed micelles following radio labeling with Technetium-99m

“…Turbidity measurements can demonstrate the existence of big aggregates (Kulthe et al, 2011 ). Also, turbidity appearance (low % T ) in the system is usually recognized as the result of temporary detachment of huge particles or insoluble drugs (Barlow et al, 1996 ; Kulthe et al, 2011 ). A significant effect of Tetronic type and concentration was observed on % T values as shown in Table 4 .…”

Triple-stimuli-responsive ferrocene-containing homopolymers by RAFT polymerization

“…One might argue that the addition of FeCl 3 also led to the increase of the concentration of salt, which could affect the self-assembly behavior of amphiphilic block copolymer and micellar morphologies according to previous reports. [49][50][51] In order to make this issue clear, we added different amounts of NaCl into the aqueous solution of the poly(Fc-DEAE-AM) 4a homopolymer instead of FeCl 3 . Noticeable spherical aggregates were observed from the TEM and DLS analysis as the concentration of NaCl was 1.7 and 17 mM, respectively, while large aggregates were formed as the concentration of NaCl increased to 170 mM.…”