Photochemical Transformations in Bis-Methacrylic Polymers for Liquid Crystal Photoalignment: IR Spectroscopy Studies

Abstract

Fourier transform infrared spectroscopy (FTIR) is applied to study photochemical transformations in poly(p-methacryloylaminophenyl methacrylate), a material with pronounced liquid crystal photoalignment capability. The characteristic bands corresponding to photosensitive groups of this polymer are identified by comparing its FTIR spectra with the spectra of model compounds having a reduced number of photochemical transformations. The changes in FTIR spectra of this material under ultraviolet illumination give evidence of two Fries rearrangements (in arylamide and arylester groups) and a conversion of C˭CH₂ methacrylic bonds. This allows one to refine the microscopic model of photoinduced ordering in this class of polymers.

Keywords:

• Arylmethacrylate
• crosslinking
• Fries rearrangement
• FTIR spectroscopy
• liquid crystal photoalignment

Acknowledgment

These studies were partially supported by the “Dnipro” program of the French-Ukrainian scientific collaboration. We thank Dr. O. Fesenko and Ms. O. Litsis for the kind assistance in FTIR measurements.

Notes

*Due to the presence of free methacrylic groups capable to crosslink in a course of DSC measurements it was not possible to obtain correct T_g values.

*Corresponding group is absent.

Note: ν - stretching, δ - deformational vibrations.