Aligning polymer main chain by pendent chromophore alignment: Optical and electrical methods

We have studied whether the main chain can be aligned by alignment of attached chromophores using two types of polymethacrylates carrying side-on attached and end-on attached chromophores. To align chromophores, nonpolar alignment by optical pumping and polar alignment by the corona poling method were used. To verify the alignment of the polymer main chain, we measured infrared wave absorption for the characteristic vibration mode. The photoalignment of side-on attached chromophore gave better aligning of the main chains. The degree of photoalignment of main chains depended on the main chain conformation as well as on the temperature at which samples were aligned. The degrees of alignment for main chains and that for the chromophores show maximum values at a temperature a little lower than the glass transition temperature. We could understand these behaviors with the free volume concept. Also, the degree of alignment for the side-on type was 2 times larger than that for the end-on type. This shows that, in the solid solution, cooperative interaction between polymer main chains and chromophores increases the rigidity and alignment of the polymer main chain. For the end-on attached chromophore, the alignments of chromophores and polymer main chains by corona poling were similar to those by optical pumping. But for the side-on attached chromophore, optical pumping was more efficient compared to the corona poling.