Synthesis and characterization of high molecular weight poly(1,5-dioxepan-2-one) with narrow molecular weight distribution

Abstract

Ring-opening polymerization of 1,5-dioxepan-2-one (DXO) initiated with aluminium isopropoxide in tetrahydrofuran (THF) solution and in bulk has been investigated. An improved monomer purification procedure is presented which makes it possible to synthesize high molecular weight poly(DXO) with a narrow molecular weight distribution. The kinetic dependence on parameters such as polymerization temperature, the presence of Lewis bases and water impurities is discussed. The activation energies ( E a) of the solution polymerization with and without 1 molar equivalent of pyridine (relative amount of initiator) were found to be 42.2 and 44.0 kJ mol −1, respectively. The addition of a Lewis base (pyridine) did not influence the polymerization kinetics and transesterification reactions to any great extent. Bulk polymerization proceeds rapidly to full conversion and leads to poly(DXO) with a controlled molecular weight and a narrow molecular weight distribution. The Mark-Houwink relationship in THF at 25°C was determined; values of constants were K = 1.1 × 10 −4dl g −1 and a = 0.766.