A series of liquid crystalline block copolymers (LC BCPs), poly(pentadecafluorooctyl methacrylate)-block-poly(6-(4-(4-methoxyphenylazo)phenoxy)hexyl methacrylate) (PPDFMA-b-P6AzOMe), poly(pentadecafluorooctyl methacrylate)-block-poly(10-(4-(4- n- pentylphenylazo) phenoxy) decyl methacrylate (PPDFMA-b-P10AzC(5)H(11)), and poly(heptafluorobutyl methacrylate)-block-poly(10-(4-(4-n-pentylphenylazo)phenoxy)decyl methacrylate) (PHFBMA-b-P10AzC(5)H(11)), were synthesized by reversible addition-fragmentation chain transfer polymerization. Two opposing trends of domain size shrinkage with molecular weight increase were observed in the two azobenzene LC BCPs. Domain sizes decreased with the increase of molecular weight of the two BCPs containing the P10AzC(5)H(11) block, while the BCPs containing P6AzOMe had the opposite trend. Well-ordered lamellar and cylindrical morphologies could be obtained by altering the length of the LC block, among which the smallest domain feature size was 3.9 nm, half of the 7.8 nm domain spacing. Thin films of the methacrylic BCPs with the azobenzene LC and the fluorinated ester side chains self-assembled to form sub-5 nm domains after 1 min of thermal annealing at 110 degrees C.