José Ramón Ochoa

Excitonic treatment and bonding of aggregates of Rhodamine 6G in ethanol

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.

Kinetics of acenaphthylene bulk polymerization by DTA

Abstract The kinetics of acenaphthylene bulk polymerization in the temperature range 413–473 K were determined by DTA. The polymerization reaction of this compound was found to be zero order with respect to the monomer.

Polymer + cosolvent systems. Part 6.—Influence of preferential solvation on unperturbed dimensions of the poly(methyl methacrylate) chain

The thermodynamic behaviour of syndiotactic poly(methyl methacrylate)(PMMA) has been studied in CCl4(1)+ methanol(2), CCl4(1)+ propan-1-ol(2) and CCl4(1)+ butan-1-ol(2) cosolvent mixtures. When the preferential sorption coefficient, λ, is negative, the best cosolvent mixture is CCl4(1)+ butan-1-ol(2), but when λ is positive the CCl4(1)+ methanol(2) cosolvent mixture is best. The results obtained are discussed as a function of the local solvent composition, x2.

Thermodynamic properties of the PMMA–acetonitrile–1,4-dioxane system

Thermodynamic properties of atactic poly(methylmethacrylate) in an acetonitrile–1,4-dioxane binary mixture have been studied at 298 K by viscometry and laser light scattering. Both techniques make evident a strong synergistic effect with its maximum close to U2= 70% 1,4-dioxane. The preferential sorption parameter λ as obtained by laser light scattering is practically equal to zero over the whole composition range. The experimental values compare favourably with those obtained theoretically from several ternary solution theories.

Polymer Cosolvent Systems 3. PMMA(3)/CCl4 (1)/n-Butyl Chloride(2)

SummaryIn this paper we have studied the behaviour of PMMA in the binary mixture CCl4/n-butyl chloride by viscometry, light scattering and dyalisis. We have found that the CCl4/n-butyl chloride mixture behaves as cosolvent in the range 10 < u2 < 90% n-butyl chloride. The n-butyl chloride is preferentially adsorbed in the whole composition range. The obtained results are discussed attending to GE and the liquid order.

Thermodynamic magnitudes of l-menthol/-acetonitrile and l-menthol/carbon tetrachloride binary mixture by VPO

Abstract In this paper we have studied the thermodynamic behaviour of l -menthol in acetonitrile and carbon tetrachloride by vapour pressure osmometry (VPO) in the temperature range 303–323 K. We have found that l -menthol behaves in a different way in both solvents. From osmotic coefficients we have calculated the excess functions of the system. In l -menthol/carbon tetrachloride we have found a great deviation from ideal behaviour, on the contrary, the deviation is very slight in the other system. This circumstance hinders the study of this system with VPO. The behaviour of l -menthol in carbon tetrachloride has been discussed as a function of molecular interactions. Finally, self-association phenomena have been detected. By means of theoretical models the association number has been calculated.

Viscometric behaviour of PMMA(3)/THF(1)water(2) system

SummaryWe have studied the PMMA viscometric behaviour in the polar binary mixture THF(1)/water(2). The results obtained point out that this mixture presents a synergistic effect in the composition interval 0 < u2<12% (w/w) water. We have found also a sharp variation of the PMMA unperturbed dimensions, kΘ, which can be due to a conformational change. Starting from the evaluation of the intermolecular interaction parameter, B, and the Mark-Houwink-Sakurada exponent, the theta composition of the system has been determined.