The effect of hydrogen bonding on the phase behavior of poly(ethylene-co-acrylic acid)-ethylene-cosolvent mixtures at high pressures

Experimental cloud-point data to 260 °C and 2,500 bar are reported to demonstrate the impact of two cosolvents, acetone and methanol, on the phase behavior of polyethylene, poly(ethylene-co-2.4 mol% acrylic acid) (EAA_2.4), poly(ethylene-co-3.9 mol% acrylic acid) (EAA_3.9), poly(ethylene-co-6.9 mol% acrylic acid) (EAA_6.9), and poly(ethylene-co-9.2 mol% acrylic acid) (EAA_9.2) in ethylene. In pressure-temperature (P-T) space, the miscibility of EAA copolymers in ethylene decreases significantly with temperature and with increasing acrylic acid content of EAA due to self-association of the acrylic acid segments. Acetone and methanol, both dramatically enlarge the solubility of EAA copolymers due to the hydrogen bonding with acrylic acids in the EAA. At low concentrations, methanol is a better cosolvent than acetone. However, the impact of methanol diminishes rapidly with increasing methanol concentration once all the acrylic acids in the EAA are hydrogen bond with methanol molecules.