Journal of Physical Chemistry B, Vol.114, No.8, 2607-2616, 2010
Alternating Oligo[(2,3-O-isopropylidene-L-threitol)]-co-[(E,E)-1,4-bis(styryl)benzen e]s: The Linear Chirality Transmisson Additivity Relationship in Nematic Liquid Crystals
Alternating oligo[2,3-O-isopropylidene-L-threitol]-co-[(E,E)-1,4-bis(styryl)benzene] s (denoted as 2-6 in the article) show helical twisting power (HTP), in 4-pentoxyl-4'-biphenylcarbonitrile (5OCB), linearly proportional to the number of the chiral cores in the oligomers. The HTP per chiral core of -1.75 mu m(-1) was recorded in the correlation plot with a correlation coefficient of R = 0.99. These results suggested that the C, chiral L-threitol cores are aligned along the same axis. The comparable linear dichroism (LD) of 0.42 +/- 0.02 obtained for (rac)-2-5 at 405 rim, and of 0.52 +/- 0.03 for E7, a commercially available room temperature nematic solvent, at 347 nm in a parallel rubbed cell indicated that the long axis of the bis(styryl)benzene segments is more or less parallel to the director of the E7 in the LC matrix. This observation is highly exciting because the HTP per core Could still be maintained, no matter whether the cores are evenly spread in a form of monomer in the LC matrix or tightly confined in a polymer. Theoretical treatments about the conformations of the dopant in the nematic matrix are discussed.