SIDE-CHAIN LIQUID-CRYSTALLINE IONOMERS .2. ORIENTATION IN A MAGNETIC-FIELD

Orientation behavior in a 5.9-T magnetic field was investigated through infrared dichroism of a nematic side-chain liquid crystalline polyacrylate and two of its ionomers containing around 10 mol % of the units of sodium salt of acrylic acid, prepared through partial alkaline hydrolysis. On the basis of a comparative study, it was found that the magnetic alignment of the nematic domains was severely limited by the presence of the ionic aggregates mainly due to their effect of reducing the polymer chains mobility, which increases the elastic constraints and effectively hinders the orientation of the mesogenic groups. Further, the maximum achievable orientation, which was lowered as the ion content increased, was found to be obtained at temperatures closer to the nematic to isotropic transition temperature. The orientation of the flexible spacer linking the mesogenic groups to the chain backbone was also determined, and on the basis of a large number of data a coupling constant of ca 0.54 was obtained between the orientations of the two constituents for all the samples.