The polarization dependence of a diacetylene polymn. was studied. For this purpose, peptide amphiphile fibers with a diacetylene moiety, which could only polymerize in the direction of the fiber, were employed. If nonaligned samples were illuminated with polarized light, only the fibers parallel to the polarization direction of the light were polymd. With magnetically aligned fibers, spatially selective polymn. was accomplished using polarization holog.