Stilbene-based liquid crystalline and photocrosslinkable polynaphthylphosphate esters

A series of liquid crystalline and photocrosslinkable polymers were synthesized from 4,4'-bis(m-hydroxyalkyloxy)stilbene (m = 2, 4, 6, 8, 10) with naphthylphosphorodichloridate. The synthesized polymers were characterized by spectroscopic techniques. Thermogravimetric analysis revealed that the polymers were stable between 283 and 341 A degrees C, then underwent two-stage decomposition, and char yield increased with decreasing spacer length. DSC and HOPM analysis disclosed that the polymers III-V (m = 6, 8, 10) exhibited LC phases wherein flexible methylene spacer separates mesogenic alignment and reduces overall rigidity of polymers, while polymers I and II are unable to show LC phase. The photolysis was studied by UV-visible and fluorescence spectroscopy. The rate of photocrosslinking increases with increase in methylene chain. The fluorescence property decreased with successive UV irradiation in the polymers.