Étude comparative de quelques systèmes ternaires polystyrène/solvant 1/solvant 2

Abstract

Etude comparative de quelques syst&mes ternaires polystyr&ne/solvant l/solvant 2 Jaques Scornaux et Robert Van Leemput') (Date de reception: 18 septembre 1975) RGSUME:Nous avons Ctudie les proprietes de solutions diluees de polystyrkne dans des melanges binaires composes de benzkne ou de cyclohexane, d'une part, et de methanol, ethanol ou 1 -propanol, d'autre part, ainsi que dans le melange cyclohexane/cyclohexanol et dans le cyclohexanol pur, par les techniques de turbidimetrie, de viscosimetrie et de diffusion de la lumibre. Nos rksultats confirment que les dimensions non perturbkes ne sont pas uniques et sont influencees par divers facteurs. Elles sont tantbt nettement au-dessus de la moyenne (benzkne/alcool), tantbt nettement en dessous (cyclohexane/cyclohexanol). Souvent, l'etat theta se scinde, en solvant mixte, en deux points distincts. Les systkmes cyclohexane/alcool lineaire presentent un caractkre cosolvant, qui s'accompagne d'une adsorption preferentielle du precipitant. Les principaux facteurs qui influencent tant la qualit6 du solvant que les dimensions non perturbkes apparaissent Ctre la non-idea-lit6 du melange et l'association de I'un des liquides. La cosolubilite ne peut pas &tre Ctablie uniquement par des mesures de dimensions moleculaires relatives. SUMMARY:Turbidimetry, viscometry and light scattering measurements have been carried out on polystyrene fractions dissolved in several binary solvents, including benzene or cyclohexane on the one hand, and methanol, ethanol or I-propanol on the other, as well as in cyclohexaneicyclohexanol mixtures and in pure cyclohexanol. Our results confirm that unperturbed dimensions are not single-valued and are influenced by various factors. In some solvents, they are definitely higher (benzene/alcohol), in other cases, lower (cyclohexaneicyclohexanol) than the mean value. In binary solvents, the theta state often divides into two distinct points. The cyclohexane/linear alcohol systems exhibit cosolvency, along with selective adsorption of the precipitant. The most important factors acting on the solvent quality and on the unperturbed dimensions are the non-ideality of the solvent mixture and the association of one of its components. Cosolvency may not be established solely by measurements of relative molecular dimensions.*) A qui la correspondance doit &tre adressee.

Coil dimensions in the powerful cosolvent system poly(methyl methacrylate)/acetonitrile + chlorobutane

“…The same conclusion regarding the large magnitude of the excluded volume present in the cosolvent mixtures is reached by looking at the coil expansion coefficient, calculated through a,3 = [V]/KqMwV* (7) The values of a, thus calculated for sample IV are, for example, 0.87 (MeCN), 0.91 (CIBu), and 1.23 (MeCN + CIBu, = 0.42). We see that this powerful cosolvent system allows us to cover an extended range of a, values (all at the same fixed temperature of 25 °C) by simply changing the composition of the liquid mixture.…”

“…The combination cyclohexane + alcohols also gives cosolvent mixtures for polystyrene in which dimensions have been studied. 7 For the polymer poly (methyl methacrylate) (PMMA), a whole series of cosolvents has been reported recently.8"11 Several of these cosolvents are formed by mixing acetonitrile with other liquids. The purpose of the present paper is to report on the variation of coil dimensions as a function of solvent composition in one of those cosolvents, namely, acetonitrile (MeCN) + 1-chlorobutane (CIBu).…”