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)

Excess molar enthalpies (HmE) and excess molar volumes (VmE) 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 HmE and VmE 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 HmE and VmE data. The key parameter needed for the analysis is the interaction parameter χ12 and has been treated as an adjustable parameter to be fitted to the HmE and VmE values of the binary mixtures. We have applied Flory as well as Patterson models to evaluate the single value for χ12 over 50 data points. The HmE and VmE values are split into interactional, free volume and P* contributions by using PFP theory. The free volume contributions to HmE and VmE 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 HmE values. The interactional contribution to VmE 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).