THE EFFECT OF COPOLYMER ARCHITECTURE ON SOLUTION BEHAVIOR

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