-Ar(Lng-Ar)w wherein w is an integer of 1 to about 10, preferably 1 to about 8, more preferably 1, 2 or 3; Ar is a divalent aromatic moiety as described above, and each Lng is a bridging linkage individually chosen from the group consisting of carbon-to-carbon single bonds, ether linkages (e.g. -O-), keto linkages (e.g., ##STR37## sulfide linkages (e.g., -S-), polysulfide linkages of 2 to 6 sulfur