Interaction of Unimolecular Micelles of Hydrophobically-Modified Polyelectrolytes with Nonionic/Ionic Mixed Surfactant Micelles

Abstract

Interactions of random copolymers of sodium 2-(acrylamido)-2-methylpropanesulfonate and N-dodecylmethacrylamide (DodMAm) with n-dodecyl hexaethylene glycol monoether (C12E6) with and without added n-hexadecyltrimethylammonium chloride (CTAC) in 0.2 M NaCl aqueous solutions were investigated by fluorescence and light-scattering techniques. The polymers with the DodMAm contents (f Dod) ranging from 10 to 50 mol % were singly labeled with pyrene (1 mol %) or doubly labeled with pyrene (1 mol %) and naphthalene (4 mol %). These polymers form unimolecular micelles (unimer micelles) owing to intramolecular self-association of polymer-bound dodecyl groups, the compactness of the unimer micelle depending on f Dod. The unimer micelles of the polymers with f Dod ≥ 30 mol % have a particularly compact nanostructure where polymer chains are highly collapsed. In the presence of C12E6/CTAC mixed micelles, the polymer with f Dod = 10 mol % abruptly undergoes bulk phase separation as the mole fraction of CTAC (Y) in the mixed micelle is increased to a certain critical level (Y p) (i.e., Y p ≈ 0.15). With an increase in f Dod, the bulk phase separation becomes significantly less abrupt, accompanying a marked increase in Y p. For the polymers with f Dod ≥ 40 mol %, no such bulk phase separation was observed in a region of 0 ≤ Y ≤ 0.6. Intrapolymer nonradiative energy transfer indicates that the unimer micelles of the polymers with f Dod ≥ 30 mol % are unfolded by interactions with C12E6. The formation of soluble polymer−micelle complexes was manifested by an increase in the hydrodynamic radius (R h) upon addition of C12E6 to polymer solutions. The R h for the unimer micelle with f Dod = 50 mol % increased from 8.2 to 15.8 nm by the addition of 5.0 mM of C12E6 at a polymer concentration of 1.5 g/L. The R h at Y = 0 further increased to 21.5 nm as CTAC was added to Y = 0.07, indicating an interplay of hydrophobic and electrostatic interactions in the complexation between the unimer micelle and C12E6/CTAC mixed micelles.

The Composition of Mixed Micelles Formed by Dodecyl Trimethyl Ammonium Bromide and Benzethonium Chloride in Water

“…The ratio of the first to the third vibrionic peaks (I 1 , at 374 nm and I 3 , at 384 nm, respectively) of pyrene I 1 /I 3 is sensitive to the local environment of pyrene [45][46][47]. This procedure is described in the literature [48] and leads to aggregation numbers in agreement with those evaluated through other experimental techniques.…”

Interactions between gemini surfactant alkanediyl-α,ω-bis(dodecyldimethylammonium bromide) and polyelectrolyte NaPAA

“…Emission spectrum (λ EX = 335 nm) of the mixed solution was recorded with recorded with F4500 (HITACHI) at 25 • C. A typical emission spectrum has five peaks at 373, 379, 384, 390, and 397 nm, respectively. The ratio of the first to the third vibronic peaks I 1 /I 3 is sensitive to the local environment of pyrene [34][35][36].…”

Salt effect on the interactions between gemini surfactant and oppositely charged polyelectrolyte in aqueous solution

“…A typical emission spectrum has five peaks at 373, 379, 384, 390, and 397 nm, respectively. The ratio of the first to the third vibronic peak I 1 /I 3 is sensitive to the local environment of pyrene [23][24][25].…”