~ H I T I C . 4 1I’HENOMEXA ~
I N i i Q U E O L S SOLUTIOES O F
LOXG-CHAIN Q U A T E R N A R Y SALTS
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Critical Phenomena in Aqueous Solutions of Long-chain Quaternary Salts. V.
Temperature Studies of Hyamine 1622-Iodine
Complex Systems
by Irving Cohen and Peter Economoul Department of Chemistry, Polytechnic Institute of Brooklyn, Brooklyn, N e w York (Rrceiued M a r c h 16, 1964)
Thc coaccrvating quaternary ammonium salt, Hyamine 1622, forms a complex with molecular iodine. In a previous study,2 the micellar molecular weights and the charge propcrties of thc homogeneous phase of this cationic soap system as a function of NaCl concentration and Iz concentration at a fixed temperature were characterized from light scattcring measurements. This paper extends this study to temperature effects in the I-Tyamine 1622-iodine complex system. Light scattering dissymmetries provided further evidence, previously deduced from viscosity, diffusion, and micelle molecular measurements, that the homogeneous phase exhibits a narrow electrolyte transition range (e.t.r.) in which, a t low levels of NaC1 concentration, a profound reorganization of the micelle occurs. The e.t.r. is relatively insensitive to small temperature changes in the system. For clectrolyte concentrations in excess of the e.t.r., the micellar growth is an exponential function of the rcciprocal of the absolute temperature of the system. A series of simple empirical equations has been developed which shows the functional relationships between the changes in micelle molecular weight with temperature changes, NaCl concentration changes, and changes in iodine content of the system. I n a noniodinated system, the reduction of the temperature by 1’ produced an increase in the micelle molecular weight equivalent to the increase in the micelle molecular weight produced by the addition of mole of NaCl a t a fixed temperature. Heats of micellization were calculated Fi.7 X from the tempcrature coefficientsof the critical micelle concentrations for selected systems. These calculations were confined to systems of low NaCl concentrations (0.06 M ) where the micellar aggregation number does not change appreciably as a function of NaCl concentration.
Introduction A number of dilute aqueous solutions of protehs12 polyelectrolytes,* and association colloids4 behave as coacervates. The essential feature of coacervation phenomena is the spontaneous separation of a homogeneous macromolecular or macro-ion solution into two solution phases under a variety of conditions depending upon the nature of the solute species. A distinctive feature of dilute, aqueous two-solution-phase coacervate systems, as compared to two-phase systems, involving immiscible solvents or unmixing in a two-component
system with the addition of a third component (ie., alcohol-IW--K2C08)is the following situation. The solvent component of the two phases in an aqueous coacervate system is the same chemical substance, HzO. A colloidal solute particle migrating ~
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(1) This work is submitted in partial fulfillment of t h e requirements for the degree of Dortor of Philosophy in Chemistry from the Polytechnic Institute of Brooklyn. (2) D. G. Dervichian. Trans. Faraday Soc., 18,321 (1954). (3) M.Eisenherg and G. R. Mohan, J . Phys. Chem., 63, 671 (1959). (4) I. Cohen and T. Vassiliades. ibid., 65, 1774 (1961).
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across the interface of a two-phase coacervate system finds itself in essentially the same environment on either side of the interface. From the point of view of composition, the difference between the two phases is a difference in solute concentration. Structurally, the two phases differ in that the colloidal solute of one phase (the equilibrium phase) is randomly oriented and the colloidal solute of the second phase (the coacervate phase) shows a great deal of order.5 In all cases where coacervation has been observed, the solute species are geometrically anisotropic particles. Coacervation is observed in some dilute soap solutions. This paper is one of a series concerned with coacervation in several long-chain quaternary salt solution^^^^ in which two solution phases are formed with the addition of simple electrolytes such as NaC1, NaNOa, and NazS04 to the homogeneous cationic soap solution. This phenomenon is classified as a form of simple coacervation involving a single micellar polyion species. The quaternary ammonium salt, Hyamine 1622 (By), forms a coacervate with the addition of NaCl to a 1% solution of this cationic soap. In the saltfree solution and at low NaCl concentration (
