There is disclosed a compound having Formula I or Formula I′: In Formula I and Formula I′: Ar1 and Ar2 are the same or different and are aryl groups; R1 through R5 are independently the same or different at each occurrence and are D, F, alkyl groups, aryl groups, alkoxy groups, silyl groups, or crosslinkable groups; R6 is H, D, or halogen; a through e are independently an integer from 0 to 4; f is 1 or 2; g is 0, 1 or 2; h is 1 or 2; and n is an integer greater than 0.