Polymers comprising at least one unit of formula (1) wherein n is 0 or 1, m and p are independently from each other 0,1,2,3,4,5 or 6, provided that the sum of n, m and p is at least 2, and n and p are not 0 at the same time, Ar 1 and Ar 2 are independently from each other C 6-14 -arylene or C 6-14 -aryl,which may be substituted with 1 to 4 substituents independently selected from the group consisting of C 1-30 -alkyl, C 2-30 -alkenyl, C 2-30 -alkynyl, C 5-8 -cycloalkyl, C 6-14 -aryl and 5 to 14 membered heteroaryl, and X 1 ,X 2 and X 3 are independently from each other and at each occurrence O or S, compositions comprising these polymers, and electronic devices comprising a layer formed from the compositions. Preferably, the electronic device is an organic field effect transistor and the layer is the dielectric layer.