The basic features of the mechanism of the solid state radiolysis of the title polyethers have been elucidated with an ESR study using the matrix isolation and spin-trapping techniques. The species identified at 77 K are α-alkoxy radicals arising from hydrogen abstractions probably involving the primary ether cation-radicals; chain scission radicals are formed on warming as a consequence of the thermal decomposition of the α-alkoxy radical precursors. The formation of acyl and α-keto radicals, which is observed on warming near room temperature, is identified with cage hydrogen abstraction reactions taking place between the products of the β-scission of the α-alkoxy radicals. Direct information on the stability and ESR properties of the polymeric ether cation-radicals, which are thought to be important intermediates in the radiolysis mechanism, have been obtained by irradiation in the CFCl3 matrix.