New amphiphilic rodlike polymers with pendent hemicyanine groups. 1. Synthesis and properties

We have synthesized new wholly aromatic polymers containing hemicyanine dyes in the side chain. The polymers are soluble in both protic solvents (methanol, ethanol, phenol) and aprotic solvents (DMSO, NMP, DMAc). However, they could not be processed into good optical quality films by simple casting or spin-coating. These amphiphilic polymers exhibited a polyelectrolyte effect in deionized water. The excessive positive charges along the hydrophobic rigid backbones, which bear two charged groups per repeat unit at the end of the methylene spacers, dramatically affect their dimension in solution, with intramolecular charge repulsions tending to assume an extended conformation. The bulk susceptibility of these materials was determined by the second harmonic generation technique. Significant SHG activity was observed from the spin-coated films without the aid of electric field induced poling. However, the corona-poled polymer films showed smaller d(33) values in the range 70-105 pm/V than expected due to the inefficient electric poling, which we discuss in terms of the domains of the chyomophores that are not well developed by electric poling.