Synthesis of Liquid Crystalline Phosphazenes Containing Chiral Mesogens

Phosphazene cyclic trimers and high polymers containing biphenyl side groups with (S)-2-methyl-1-butoxy as a terminal unit were synthesized. The chiral biphenyl units [4,4'-C sub(6) H sub(4)C sub(6)H sub(4)OCH sub(2)-CH(CH sub(3))CH sub(2)CH sub(3)] were linked to the skeletal phosphorus atoms of the small-molecule phosphazene cyclic trimers and high polymers through -O(CH sub(2)Ch sub(2)O) sub(m) - spacer linkages, where m identical with 2 or 3. Of the cyclic trimers synthesized, with the formula N sub(3)P sub(3)[O(CH sub(2) CH sub(2)O) sub(m)C sub(6)H sub(6)C sub(6)H sub(4)OCH sub(2)CH(CH sub(3)) CH sub(2)CH sub(3)] sub(6) where m identical with 2 (4) or 3 (5), only 5 was liquid crystalline, as determined by differential scanning calorimetry (DSC). Single-substituent high-polymeric poly(organophosphazenes) were synthesizedthat contained the chiral biphenyl unit linked to the backbone through spacer units m identical with 2 (6) and 3 (8). Cosubstituent polymers were also synthesized which contained both the chiral biphenyl derivative linked to the backbone through varying spacer lengths and with nonmesogenic cosubstituents, OCH sub(2)CH sub(2)OCH sub(2)CH sub(2)OCH sub(3) and OCH sub(2)CF sub(3). The liquid crystalline behavior of these polymers was studied with respect to spacer length and nonmesogenic cosubstituents. All the polymers synthesized showed enantiotropic liquid crystallinity. Morphologies and thermal behavior of these compounds were investigated with the use of DSC, X-ray diffraction, and optical hot stage microscopy.