The disclosure describes a monomer having the general formula (I): in which R1 and R2 stand, independently of one another, for hydrogen, for an optionally substituted C1-C20-alkyl group or C1-C20-oxyalkyl group, optionally interrupted by 1 to 5 oxygen atoms and/or sulfur atoms, or jointly for an optionally substituted C1-C20-dioxyalkylene group or C6-C20-dioxyarylene group. The monomer has a color in a range of a Hazen color number determined according to test method described herein of at least 20 to a Gardner color number determined according to test method described herein of not more than 5. The present invention also relates to a method for the manufacture of a capacitor, a capacitor obtained by this method and to the use of a monomer.