Reversible Vesicle–Spherical Micelle Transition in a Polyion Complex Micellar System Induced by Changing the Mixing Ratio of Copolymer Components

Abstract

The mixing ratio dependence of the morphology of a polyion complex micelle formed of an anionic–neutral double-hydrophilic block copolymer (AP) and a cationic–neutral double-hydrophilic block copolymer (MP) in 0.1 M aqueous NaCl solution was investigated by using small-angle X-ray scattering (SAXS), electrophoretic light scattering (ELS), and isothermal titration calorimetry (ITC), under the condition that the anionic and cationic block chains are much longer than the neutral block chains. When the anionic and cationic monomer units in the solution are nearly equimolar, the net charge of the polyion complex micelle is close to zero, and the bilayer vesicle is formed. However, when the anionic or cationic monomer units in the solution are richer than the other, the polyion complex micelle is charged by including the excess block copolymer component to form the smaller spherical micelle. The morphology transition between the vesicle and spherical micelle can take place reversibly by simply adding AP or MP into the micellar solutions. The electrostatic energy of the micelle may induce the morphology transition.

Colloidal Dispersion of a Perfluorosulfonated Ionomer in Water–Methanol Mixtures

“…Then, the particle scattering function P ( k ) is given by MwPfalse(kfalse)=(1−wlarge)Mnormalw,smallPnormalz,smallfalse(kfalse)+wlargeMnormalw,largePnormalz,largefalse(kfalse) where w large is the weight fraction of the large spherical component in the total spherical components, M w, i and P z ,i ( k ) ( i = small and large) are the weight average molar mass and z-average particle scattering function of the spherical component i , respectively. The particle scattering function P z,i ( k ) may be written as [16,19,20,21] Pnormalz,normalifalse(kfalse)=true∫9[sin(kRnormalM)−kRnormalMcos(kRnormalM)(kRnormalM)3]2Mnormalwnormali(M)dM where R M is the radius of the fraction with the molar mass M , which is calculated by RM=(3M4πNA…”

“…Here, F is the instrument constant (which was determined by the comparison with the SLS results; see below), I θsoln ( I θ,solv ) and I mon,soln ( I mon,solv ) are the scattering intensity at the scattering angle θ and the monitor value of the incident SAXS intensity, respectively, of the solution (of the solvent), N A is the Avogadro constant, a e is the classical radius of electron, and γ is the SAXS contrast factor of the polymer. Values of γ for PFSI in water–MeOH mixtures with w H 2 O were calculated by [16] γ=(1−x)nnormale,TEF+xnnormale,normalS(1−x)MTFE+xMS−υfalse¯υsolv[nnormale,normalH2normalOMH2normalOwH2normalO+nnormale,MeOHMMeOH(1−wH2normalO)] where the subscripts TFE and S denote the monomer units of tetrafluoroethylene and sulfonated-side-chain substituted TFE, respectively, x is the mole fraction of S in the copolymer, n e, i and M i ( i = TFE, S, H 2 O, and MeOH) are numbers of electrons and molar masses of i , respectively, υfalse¯ is the partial specific volume of PFSI, and ν solv is the specific volume of the solvent. The value of υfalse¯ was determined in water by densitometry and assumed to be independent of w H 2 O .…”

Dehydration, Micellization, and Phase Separation of Thermosensitive Polyoxazoline Star Block Copolymers in Aqueous Solution

“…Yield 4.0 g, 80%. 1 The SAXS excess Rayleigh ratio RX, at the scattering angle  and the optical constant Ke of SAXS were calculated by 16,17…”

Macro- and Microphase Separated Protein-Polyelectrolyte Complexes: Design Parameters and Current Progress

“…A variety of morphologies have been reported, including spherical micelles [17,24,25,106,107,108,109], worm-like micelles [106,110,111,112], vesicles [32,113,114,115,116,117], and lamellae [106,118,119,120,121]. Micelle morphology is influenced by a variety of factors, depending on the particular polymers, including salt concentration [106,112], mixing ratio [107,110], temperature [119,122], and relative size of each component of the system [119] (Figure 4).…”