Ar represents a monocyclic or polycyclic aromatic group having from 6 to 20 carbon atoms which can be selected from the group consisting of phenylene, naphthylene, fluorenylene, benzofluorenylene, anthracenylene, and substituted derivatives thereof, wherein the substituted groups can be alkyl having 1 to 10 carbon atoms and fluorinated derivatives thereof, and halogen such as F or Cl; and moieties