title: Precipitate-Coacervate Transformation in Polyelectrolyte-Mixed Micelle Systems.
abstract: The polycation/anionic-nonionic mixed micelle, poly(diallyldimethylammonium chloride)-sodium dodecyl sulfate/Triton X-100 (PDADMAC-SDS/TX100), is a model polyelectrolyte-colloid system in that the micellar mole fraction of SDS (Y) controls the micelle surface charge density, thus modulating the polyelectrolyte-colloid interaction. The exquisite temperature dependence of this system provides an important additional variable, controlling both liquid-liquid (L-L) and liquid-solid (L-S) phase separation, both of which are driven by the entropy of small ion release. In order to elucidate these transitions, we applied high-precision turbidimetry (±0.1 %), isothermal titration calorimetry, and epifluorescence microscopy which demonstrates preservation of micelle structure under all conditions. The L-S region at large Y including precipitation displays a remarkable linear, inverse Y-dependence of the L-S transition temperature Ts. In sharp contrast, the critical temperature for L-L coacervation Tφ, shows nearly symmetrical effects of positive and negative deviations in Y from the point of soluble complex neutrality, which is controlled in solution by the micelle charge and the number of micelles bound per polymer chain n (Zcomplex= Zpolymer+ nZmicelle). In solid-like states, n no longer signifies the number of micelles bound per polymer chain, since the proximity of micelles inverts the host-guest relationship with each micelle binding multiple PE chains. This intimate binding goes hand-in-hand with the entropy of release of micelle-localized charge-compensating ions whose concentration depends on Y. These ions need not be released in L-L coacervation, but during L-S transition their displacement by PE accounts for the inverse dependence of Tson micelle charge, Y.
authors.affiliation: Department of Chemistry, University of Massachusetts Amherst , 710 North Pleasant Street, Amherst, Massachusetts 01003, United States.
authors.forename: Fatih
authors.identifier: 0000-0001-8494-1104
authors.initials: F
authors.lastname: Comert
authors.affiliation: Department of Chemistry, University of Massachusetts Amherst , 710 North Pleasant Street, Amherst, Massachusetts 01003, United States.
authors.forename: Duy
authors.initials: D
authors.lastname: Nguyen
authors.affiliation: Department of Chemistry, University of Massachusetts Amherst , 710 North Pleasant Street, Amherst, Massachusetts 01003, United States.
authors.forename: Marguerite
authors.initials: M
authors.lastname: Rushanan
authors.affiliation: Department of Physics, University of Massachusetts Amherst , 666 North Pleasant Street, Amherst, Massachusetts 01003, United States.
authors.forename: Peker
authors.initials: P
authors.lastname: Milas
authors.affiliation: Department of Chemistry, University of Massachusetts Amherst , 710 North Pleasant Street, Amherst, Massachusetts 01003, United States.
authors.forename: Amy Y
authors.initials: AY
authors.lastname: Xu
authors.affiliation: Department of Chemistry, University of Massachusetts Amherst , 710 North Pleasant Street, Amherst, Massachusetts 01003, United States.
authors.forename: Paul L
authors.identifier: 0000-0002-4643-8169
authors.initials: PL
authors.lastname: Dubin