Structural Analysis of Ethylene/Propylene Copolymers Synthesized with a Constrained Geometry Catalyst

The chain structures of five ethylene/propylene copolymer samples with propylene mole fractions of 0.277, 0.308, 0.321, 0.583, and 0.587 were analyzed and reported in this paper. These polymers were synthesized in a solution continuous stirred-tank reactor (CSTR) at 130−150 °C using a constrained geometry catalyst (CGC). The copolymers had polydispersities close to 2. Inverted propylene units were present. A large number of long runs of polyethylene and polypropylene units were also observed. Increasing the propylene composition significantly increased the sequences of one and two methylene units and decreased those of six and more consecutive methylene units. However, the uninterrupted methylene sequence distributions were little influenced by polymerization temperature. The meso and racemic contents in the continuous and inverted propylene units were approximately equal, indicating that the CGC did not have much control over the stereoregularity of the propylene insertion. Compared to the vanadium ethylene propylene elastomers (EPM), the CGC EP copolymers had fewer alternating comonomer sequences and more consecutive ethylene and propylene units.