Cloud-point pressure curves of ethene/poly[ethylene-co-((meth)acrylic acid)] mixtures

Ethene-methacrylic acid (MAA) and etheneacrylic acid (AA) copolymers of narrow polydispersity and high chemical homogeneity have been synthesized at acid, unit copolymer contents up to 9 mol-% within a continuously operated stirred tank reactor at overall monomer conversions of about 2%. Cloud-point pressures (CPPs) of mixtures of 3 wt.-% copolymer in ethene (E) have been measured in an optical high-pressure cell at pressures and temperatures up to 3 000 bar and 260degreesC, respectively. The CPP weakly, increases with acid copolymer content up to about 3.5 mol-%. Toward higher Acid contents, the CPP is strongly enhanced, in particular at the tower edge of the experimental temperature range at around 200degreesC. This increase in CPP is more pronounced for the AA than for the MAA systems. The data suggest that hydrogen-bonding interactions are operative in the pressurized E/poly(E-co-(M)AA) mixtures at temperatures of 260degreesC and perhaps even above. E-AA and E-MAA copolymers with acid contents of about 5.6 mol-% have also been completely methyl-esterified to yield the associated methyl esters. The CPPs of the resulting E-methyl acrylate and E-methyl methacrylate copolymers in mixtures with E are significantly below the CPPs of the corresponding E/poly(E-co-(M)AA) systems.