Second osmotic virial coefficient revisited: Variation with molecular weight and temperature from endothermal to exothermal conditions
| Autor: | H. ‐J. Adam, B. A. Wolf |
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| Rok vydání: | 1981 |
| Předmět: | |
| Zdroj: | The Journal of Chemical Physics. 75:4121-4129 |
| ISSN: | 1089-7690 0021-9606 |
| DOI: | 10.1063/1.442500 |
| Popis: | Light scattering measurements for six samples of polystyrene (M = 20 400 to 2.5×106) were performed in tert‐butylacetate from 0–140 °C. Within this T interval, the second virial coefficients A2 change from negative to positive, pass through a maximum at intermediate temperatures, and get negative again. The M dependence vanishes when A2 = 0 at ϑ+ = 15.5 °C for endothermal, and at ϑ− = 109.5 °C for exothermal conditions. The temperature of athermal behavior increases with M from 42 °C (M = 20 400) to 62 °C (M = 2.5×106). For sufficiently high temperatures A2 grows larger as M is raised, in contrast to the normal situation. There exist strong indications that limM→∞ A2 is generally different from zero, except for theta conditions. The enthalpy part of the second virial coefficient A2,H becomes independent of M at Ξ+ = 31 °C for endothermal solutions and at Ξ− = 90 °C for exothermal. Between these temperatures A2,H decreases as M rises, else it increases. The unperturbed dimensions are the same at ϑ+ and ϑ−.... |
| Databáze: | OpenAIRE |
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