The self-association of Rhodamine 6G in ethanol has been studied by determining the dimerization and trimerization constants at different temperatures. The excitonic interpretation of the absorption spectra suggests a linear structure for the aggregates. The nature of the bonding has been also studied.

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The inverse microemulsion polymerization of acrylamide in a paraffinic solvent, Rolling-M-245, stabilized by a mixture of nonionic surfactants (Emulan-ELP-11 and Brij-92), was studied. Pseudoternary phase diagrams of this system were determined, and a range of hydrophilic-lipophilic balance (HLB) values, from 8.98 to 9.2, were selected as the most favorable for acrylamide polymerization. The influence of factors such as the initiator composition, HLB, percentage of the aqueous phase, and addition of the monomer by steps on the final conversion and polyacrylamide molar masses were investigated. High conversions and molar masses were generally obtained with the different formulations. The polyacrylamide molar masses were influenced by the HLB and content in the aqueous phase. The addition of the aqueous phase by steps led to a progressive diminution of the molar masses as the number of stages increased.

SynopsisSeveral polymer-metal complexes were prepared by reacting poly(viny1 carbazole) (PNVC) with copper(I1) chloride, CuC1,.2H,O, in refluxing tetrahydrofurane (THF) for mole ratios of CuC1,.2H2O to monomeric unit (Cu:PNVC ratio) ranging between 0.086 and 4.98. Complexes were characterized by infrared (IR) and elemental analysis. Thermal behavior of complexes was studied by differential thermal analysis (DTA). It appears that THF behaves as a specific solvent for complexation of PNVC with copper(I1) chloride.

Usually, the temperature dependence of the absolute viscosity q can be written as where RTis the thermal energy and Q is the apparent activation energy of viscous flow which is constant over a limited temperature range. The meaning of the preexponential term A is related to a n activation entropy. This expression is of the Arrhenius form and has been called the Guzman-Andrade equation, which was theoretically derived by Eyring.' Thus, the absolute viscosity of a liquid is given by where N a n d h are, respectively, the Avogadro number and the Planck's constant, V is the molar volume of the liquid, and S is the entropy of activation of viscous flow.From eqs.(1) and (2) we obtainMeasurements of absolute viscosities of dilute polymer solutions and their thermal variation are often employed as a way to characterize properties of macromolecules in solution.',2Moore et a1.4-6 have related the A and Q parameters of the Guzman-Andrade equation to the polymer flexibility and thermodynamic properties of polymer-solvent systems.In this article, we have used eq. (1) to study the behavior of the poly(cyclohexy1 methacrylate) (PCHM) in methyl isobutyl ketone on the temperature range 283-313 K. EXPERIMENTALCyclohexyl methacrylate (Fluka purum) was washed three times with sodium hydroxide followed by distilled water; it was dried over anhydrous NazSO, and distilled ( < 25 mm Hg) in pure dried nitrogen.A sample of poly(cyclohexy1 methacrylate) was obtained by radical polymerization using 1,2-azobisisobutyronitrile (Fluka puriss) as initiator in benzene, at 328 K. The polymer obtained was fractionated by solubility in the system pdioxanelmethanol. All fractions were purified by dissolving in benzene and reprecipitation with methanol. They were freeze-dried.All solvents were analytical grade froE Fluka.Number average molecular weights M, and weight average molecular weights z,, were determined by membrane osmometry and laser light scattering, respectively. In Table I, it can be seen the molecular weights and polydispersity index of the five fractions employed in this work. Viscosities of both pure solvent and polymer solutions were measured, at several temperatures (283-313 K), by means of an modified Ubbelohde viscometer. The kinetic energy corrections were less than 0.2%. The bath temperature was regulated to k0.02 K. Intrinsic viscosities were obtained by graphical extrapolation of both q,,/c and In q,/c to zero concentration of polymer.