Block copolyethers characterised with high impact strengh values (I greater than or equal to 140 kJ/m(2)) and stable physical and chemical properties for long duration under load (at 180-200 degreesC) were obtained from 1,1-dichlor-2,2-di-(4-oxyphenyl)ethylene by acceptor catalytic polycondensation method. The dependence of the tensile and thermal properties of the block copolyethers on the molecular structure was investigated. It is shown that, after heat treatment the heat stability and the mechanical properties improved.