Polar ordering of linear rod-like polyamide with different linking structure of nonlinear optical chromophores

We have investigated the correlation between the macroscopic physical properties and the microscopic molecular structure for linear rod-like polyamides with different linking structure of nonlinear optical chromophores by in situ corona poling and optical second harmonic generation. These polymers consist of a wholly aromatic rigid backbone poly(p-phenylene terephthalamide), PPTA and nonlinear optical chromophores of various sizes. Though all polymers with different linking structure of chromophores possess similar α- and β-glass transition temperatures, their bulk physical properties greatly depend on the microscopic linking structure. Especially the polyamide F-DCVA with a flexibly linked bulky chromophore exhibits a high internal stress due to a thermal contraction of the rigid polyamide backbone, which at room temperature can overcome the orientational force of the externally applied electric field.