Cloud-point data to 270-degrees-C and 2,750 bar are presented for mixt
ures of light hydrocarbons with polyethylene, poly(ethylene-co-methyl
acrylate), and poly(ethylene-co-acrylic acid) copolymers. Adding highl
y structured ethylene to the polymer backbone decreases the number of
chain branches in the backbone, increases DELTAH(fusion), and increase
s the cloud-point pressures. Methyl acrylate added to the backbone dec
reases the crystallinity of the copolymer, but increases its polarity,
thus shifting the cloud point curve to higher temperatures and pressu
res. Adding acrylic acid to the backbone changes the shape of the clou
d point curve and shifts it to high temperatures where intramolecular
hydrogen bonding is reduced. If a polar cosolvent is used the cloud po
int curve shifts to lower temperatures and pressures for mixtures with
polar copolymers especially if the cosolvent hydrogen bonds to the co
polymer. However, once all of the hydrogen bonding sites are occupied,
further additions of cosolvent cause the copolymer to precipitate fro
m solution.