Block copolymers by combination of cationic and radical routes: 4. Cationic polymerization of tetrahydrofuran initiated by difunctional azo-oxocarbenium initiator

Abstract

Abstract The kinetics of the bulk polymerization of tetrahydrofuran initiated by 4,4-azobis(4-cyanopentanoyl chloride) in conjunction with silver salts have been studied at −20, 0 and 10°C. Propagation rate constants increase with increasing temperature ( k p = 4.7 × 10 −4 at −20°C, 3.7 × 10 −3 at 0°C and 1.2 × 10 −2 l mol −1 s −1 at 10°C) and an Arrhenius plot gives an activation energy of 57.6 kJ mol −1 . The enthalpy and entropy changes were estimated to be ΔH p = −24 kJ mol −1 and ΔS ° p = −86.7 JK −1 mol −1 respectively. Spectroscopic and degradation studies showed that polymers obtained via this initiation method contained one azo linkage per macromolecule chain.