Sequenced Ethylene−Propylene Copolymers:  Effects of Short Ethylene Run Lengths

Abstract

Two sequenced ethylene-propylene (EP) copolymers possessing methyl groups every fifth (EP5) or seventh (EP7) carbon have been prepared using an olefin metathesis polycondensation/hydrogenation strategy, thus generating methyl branched polyolefins with short ethylene run lengths of 4 or 6 carbons, respectively. Precise spacing of methyl branches along both copolymer backbones imparts pristine microstructure and targeted comonomer ratios in the copolymer. Extensive NMR spectral data are presented detailing polymer microstructure, branching analysis, and end-group identification. Thermal analysis using differential scanning calorimetry revealed multiple low-temperature relaxations for EP7 and glass transition temperature of -63 °C for EP5, and FT-IR analysis suggests no crystallinity under ambient conditions. A new ADMET monomer synthesis is also reported for the development of highly functionalized polyolefins or sequenced ethylene copolymers.

Systematic Studies of Morphological Changes of Precision Polyethylene

“…PE with precisely spaced methyl branches on every 9th carbon ( Me‐9 ) organizes into a hexagonal crystal, and polyethylenes bearing methyl branches on every 5th ( Me‐5 ) and 7th carbon ( Me‐7 ) lead to completely amorphous materials . These results are in agreement with previously published models …”

A mechanistic study on the synthesis of branched functional polyethylene through reactive co‐polymer approach

“…Therefore, a broad melting peak is associated with the DSC thermogram of poly(1‐hexene) made by the Brookhart‐type catalysts. As demonstrated by Wagener and co‐workers, a polyethylene chain with about eight methylene sequence between two adjacent methyl branches shows a melting temperature of −14°C, while the melting temperature increases to 39°C for the same structure with 14 methylenes . Consequently, the broad melting peak between 0 and 30°C, in the thermogram of Run 1, can be attributed to the methylene sequences with 8−14 carbon atoms that have been created by one or two successive 1,6‐enchainments of the 1‐hexene, respectively.…”

Facile synthesis of ethylene–propylene fully alternating copolymer and comparison with random copolymer of similar composition

“…Wagener and coworkers have done a lot of work on the synthesis and characterization of ethylene–propylene copolymer models using step polymerization namely acyclic diene metathesis (ADMET) polymerization rather than chain polymerization techniques . ADMET polymerization of symmetric α,ω‐diolefin monomers followed by exhaustive hydrogenation offers a new viable method to synthesize PE backbone with precisely distributed methyl branches, for instance, PEs containing methyl on every 5, 7, 9, 15, 21, and 39 carbons along the backbone respectively were successfully prepared.…”