Measurements and theoretical analysis of excess enthalpies and excess volumes of methyl methacrylate+ n-alkanes ( n-pentane, n-hexane, n-heptane, n-decane and n-dodecane)

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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 χ 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 χ 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).