Two-photon polymerization of diacrylate mesogen for producing polymer with patterned orientation structures

摘要

Two-photon absorption initiating crosslinking of diacrylate mesogen RM257 has been studied. Two-photon absorption process in the diacrylate mesogen is trigged by a low-power continuous laser irradiation at 632.8 nm wavelength. In order to manipulate the diacrylate mesogen to contain local structures, a thin layer of RM257 was exposed to a holographic irradiation produced by means of two-beam interferometry, in which the two coherent beams were provided by a HeNe laser. The holography irradiation acts double as the optical source that provides energy to produce free-radicals for initiating the crosslinking of the acrylate units and the driving force for the alignment of mesogenic groups in the diacrylate mesogen. The regions in the resultant diacrylate polymer exposed to the constructive fringes are found to contain ordered polymer network whose mesogenic groups orient perpendicular to the polarization of the holographic field, whereas those regions exposed to the destructive fringes present isotropic polymer networks.