Thermochimica Acta, Vol.359, No.2, 169-180, 2000
Measurements and theoretical analysis of excess enthalpies and excess volumes of methyl methacrylate plus n-alkanes (n-pentane, n-hexane, n-heptane, n-decane and n-dodecane)
Excess molar enthalpies (H-m(E)) and excess molar volumes (V-m(E)) have been measured for liquid binary mixtures of methyl methacrylate (MMA)+n-alkanes (n-pentane, n-hexane, n-heptane, n-decane and n-dodecane). The H-m(E) and V-m(E) values are positive over the whole composition range and vary quasi-regularly with the increase in carbon chain length of n-alkanes. The Flory (F) and Prigogine-Flory-Patterson (PFP) theories of solution thermodynamics have been used to analyze the H-m(E) and V-m(E) data. The key parameter needed for the analysis is the interaction parameter chi(12) and has been treated as an adjustable parameter to be fitted to the H-m(E) and V-m(E) values of the binary mixtures. We have applied Flory as well as Patterson models to evaluate the single value for chi(12) over 50 data points. The H-m(E) and V-m(E) values are split into interactional, free volume and P* contributions by using PFP theory. The free volume contributions to H-m(E) and V-m(E) data are found to be smaller and mostly negative. The interactional contribution calculated from PFP theory is not only in sign agreement but also close to measured H-m(E) values. The interactional contribution to V-m(E) values are always large and positive. The free volume and P* effects are found to be dominant and balance the over estimation of interactional term in MMA+n-pentane, +n-hexane and +n-heptane. The P* contribution, however, becomes positive in MMA+higher n-alkanes (>n-heptane).