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'-C6H4C6H4OCH2CH(CH3)CH2CH3] were linke d to the skeletal phosphorus atoms of the small-molecule phosphazene c yclic trimers and high polymers through -O(CH2CH2O)(m)- spacer linkage s, where m = 2 or 3. Of the cyclic trimers synthesized, with the formu la P3[O(CH(2)CH2O)(m)C6H4C6H4OCH2CH(CH3)CH2CH3](.)(6) where m = 2 (4) or 3 (5), only 5 was liquid crystalline, as determined by differential scanning calorimetry (DSC). Single-substituent high-polymeric poly(or ganophosphazenes) were synthesized that contained the chiral biphenyl unit linked to the backbone through spacer units m = 2 (6) and 3 (8). Cosubstituent polymers were also synthesized which contained both the chiral biphenyl derivative linked to the backbone through varying spac er lengths and with nonmesogenic cosubstituents, OCH2CH2OCH2CH2OCH3 an d OCH2CF3. The liquid crystalline behavior of these polymers was studi ed with respect to spacer length and nonmesogenic cosubstituents. All the polymers synthesized showed enantiotropic liquid crystallinity. Mo rphologies and thermal behavior of these compounds were investigated w ith the use of DSC, X-ray diffraction, and optical hot stage microscop y.