Epitaxial crystal growth and solid-state polymerization of piperonyl muconate on the {001} surface of KCl crystal for controlling polymer chain alignment.

We investigated the crystal growth of piperonyl (E,E)-muconate [bis(3,4-methylenedioxybenzyl) (E,E)-muconate, MDO] on inorganic crystalline substrates during vapor deposition for the control of polymer chain alignment by the subsequent solid-state photopolymerization of the MDO monomer thin films deposited on the substrate. We controlled the arrangement of the MDO molecules and the polymer chains produced on the substrate, depending on the lattice parameters of the substrate surfaces used. The epitaxial crystal growth of MDO on the {001} plane of a KCl single crystal was observed under the condition that the crystal lattice lengths of MDO agreed well with the specific space distance of the substrate; i.e., the KCl cubic crystal resulted in a d(110) value of 4.45 Å, which was very close to the value of the monomer stacking distance in the MDO crystal (d(s) = 4.43 Å). On the other hand, slightly large and too small d(110) values for KBr and NaCl, respectively, resulted in the less controlled and no epitaxial crystal growth of MDO. The irradiation of polarized UV light on the MDO thin-film crystal produced highly regulated polymer alignment in a specific direction on the KCl substrate.