Unusual activation by solvent of the ethylene free radical polymerization

Abstract

Ethylene polymerization is performed industrially either by radical polymerization under severe conditions (1000–4000 bar, 200–300 °C) or by a catalytic mechanism at lower temperatures (usually less than 100 °C) and pressures (below 50 bar). Standard radical polymerization conditions are too severe to permit a fine control of the macromolecular architecture. Under milder conditions (100 bar, 70 °C), radical ethylene polymerization is assumed ineffective which has been confirmed in bulk (supercritical ethylene). However, we have shown that the efficiency of this polymerization is strongly dependent on the solvent. This unusual activation by solvent has been rationalized using theoretical considerations. A second effect investigated is the influence of solvent on PE molecular weight. Indeed PE with either low molecular weight and high chain-end functionality or higher molecular weight can be synthesized according to the solvent used.