6533b852fe1ef96bd12ab51e

RESEARCH PRODUCT

false

subject

description

Solutions of poly (decyl methacrylate) in isooctane (2,2, 4-trimethylpentane) show lower critical solution temperatures (LCST) that lie well below the thermal degradation of the polymer. The corresponding exothermal theta-temperature (from the Shultz-Flory plot) amounts to 210°C. The increase in solvent quality by pressure turns out to be very pronounced (d Tc/dp ≈ +1 K/bar). With solutions of the polymer in motor oils, high temperature demixing is unlikely to occur below their boiling point. The theoretical evaluation of published experimental data for 11 different systems exhibiting LCSTs demonstrates the following: Under the equilibrium vapour pressure of the solution high temperature demixing is generally observed withing the temperature interval between Tb, the boiling point of the pure solvent (1 bar), and 1,5 Tb. As Tc - Tb increases, the heats of mixing and the pressure influence on Tc increase, too.