Conformational characterization of imide compounds and polyimides using far-infrared spectroscopy and DFT calculations

• Published in: Polymer (Guilford) Vol. 86; pp. 83 - 90
• Main Authors: Okada, Tomohiro, Ando, Shinji
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 08.03.2016
• Subjects: Conformational anlysis; Far-infrared; Fourier transforms; Imides; Infrared; Infrared spectroscopy; Mathematical models; Polyimide; Polyimide resins; Spectra; Spectroscopy; Conformational anlysis; Polyimide; Far-infrared
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2016.01.037

A new method to characterize local conformations of aromatic imide compounds and polyimides was established via Fourier transform infrared (IR) spectroscopy at low frequencies (far-IR) and density functional theory (DFT) calculations. The far-IR spectrum of an imide model compound (sBPDA/An) was well reproduced by the DFT calculations in the 650–100 cm−1 range by considering local molecular conformations and the effects of neighboring molecules. The conformations of 3,3′,4,4’-biphenyltetracarboxylic (sBPDA) type polyimide films were subsequently analyzed using their far-IR spectra compared with the calculated spectra of sBPDA/An. The dihedral angle between biphenyldiimide moieties (ϕ) tends to be coplanar in the highly ordered region, whereas that between phthalimide and phenylene (ω) tends to be more twisted. Conformation dependent far-IR is a facile and versatile tool to estimate local conformations of aromatic polymers. [Display omitted] •A novel method to characterize local conformations of polyimides are developed.•Far-IR spectrum of model compound is well reproduced by DFT calculation.•Biphenyldiimide moieties of polyimides are coplanar in highly ordered region.•Dihedral angles between phthalimide−phenyl are more twisted in highly ordered region.