Ordering of Poly( p -phenylene ethynylene)s in Liquid Crystals

Poly(phenylene ethynylene)s were designed and synthesized that are completely sol. in nematic liq. cryst. solvents at mol. wts. (GPC, relative to PS) of more than 100,000. These materials experience a chain extended rod conformation under these conditions with the polymer chains highly aligned with the liq. crystal director and an enhanced conjugation length detd. by optical spectroscopy. Structure-property relationships are investigated that reveal the role of steric congestion about the polymer mainchain in detg. the order parameter of the polymers. It was also found that the order polymer parameters increased with increasing mol. wts. [on SciFinder(R)]