Long-chain and short-chain branches in ethene-methyl acrylate copolymers studied by quantitative C-13 NMR spectroscopy

Abstract

The frequency of long-chain branches (LCBs) in ethene (E)-methyl acrylate (MA) copolymers is investigated for material that was synthesized at 150 degrees C and 2,000 bar at different levels of conversion but constant copolymer composition. The copolymers exhibit significantly more LCBs than found in LDPE synthesized under similar conditions. Moreover, it is found that the LCB frequency increases with conversion. At 0.3 mol-% conversion 0.3 LCBs and a 4.0 mol-% conversion 1.1 LCBs per 1,000 C atoms are observed. In addition, the frequency of short-chain branches (SCBs) in the copolymers is investigated. About 9 mol-% of the acrylate units are alkylated, which corresponds to numbers given in literature. As sensors, both LCB and SCB indices provide valuable information for simulation calculations to determine rate coefficients for inter- and intramolecular transfer reactions.