Lower Critical Solution Temperatures, Part I Polymethylene in n-alkanes

Lower critical solution temperatures (LCST's) of three linear polyethylenes of differing molecular weights were measured visually in various n‐alkanes ranging from n‐hexane to n‐tridecane. The LCST observed increases with decreasing molecular weight of polyethyline and with increasing the chain length of the n‐alkanes. The limiting LCST's, θL for polyethylene/n‐alkane systems were obtained by extrapolating to the infinite molecular weight of polyethylene using a Shultz‐Flory plot. Flory's equation of state theory is discussed in conjunction with the conventional Flory‐Huggins theory and the equation of state parameters for the pure solvents are obtained according to the Flory theory. The θL temperatures for polyethylene in n‐hexane, n‐heptane, and n‐octane are calculated in accordance with Flory's and Patterson's equations and compared with the experimental values. The θL temperatures are found to be well predicted by one version of the Flory theory.