Solvent soluble block copolyesters consisting essentially of units having the formula: ##EQU1## WHEREIN R is an alkylene radical containing at least 3 carbon atoms; R.sup.1 is an alkyl radical and R.sup.2 is an alkyl, alkaryl, aralkyl or aryl radical; A is an alkylene or arylene radical; a is an integer of at least 10; b is an integer of at least 1; c is an integer of at least 2; and d is an integer of at least 2; are formed by first reacting a dihalo-polydiorganosiloxane with a dihydric phenol or other diol and subsequently reacting the resulting reaction product with a dicarboxylic acid halide. These polymers are useful as release agents and leveling agents and find particular utility as abhesive materials for waterless lithographic printing plates.