Molecular structure and thickness dependence of chain orientation in aromatic polyimide films

Abstract

Degrees of orientation of main chains and imide rings were quantitatively estimated for spin‐coated films of six kinds of aromatic polyimides (PIs) using polarized attenuated total reflection (ATR)/Fourier transform infrared (FT‐IR) spectroscopy. The degrees of chain orientation parallel to the film planes are significantly larger for the PIs having rigid structures than those having flexible structures, and the introduction of side groups decrease the degrees of chain orientation. In contrast, the rotational orientations of imide rings are almost isotropic for all PI films. Moreover, the film thickness dependences of the degrees of orientation were investigated for two kinds of rigid‐rod PIs having bulky trifluoromethyl (CF3) side groups in their diamine moieties. The degrees of chain orientation slightly decrease as the film thickness increases, whereas the rotational orientation of imide rings is independent of the film thickness. The degrees of chain orientation on the substrate sides significantly differ from the atmospheric sides of PI films. This difference was generated during thermal imidization because of tensile stress originated from the mismatch in thermal expansion coefficients between the substrates and the PI films. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2109–2120, 2005

Effects of Orientational Relaxation of Polymer Chains Induced by Isotropic Particles on the Enhanced Thermal Conductivity of AlN-filled Polyimide Films

“…A large K p value therefore corresponds to small free volume. The K p values for sBPPD and sBPOD have been reported as 0.6258 and 0.6018, respectively [6]. The densities of Upilex-S and Upilex-R, which are commercial PIs having the same chemical structures as sBPPD and sBPOD, are reported by the manufacturer (Ube Industries) as 1.47 and 1.39, respectively.…”

Novel Poly(benzoxazole-etherimide) Copolymer for Two-Layer Flexible Copper-Clad Laminate

“…[36] Due to the orientation, the low cohesive strength and modulus in the film thickness direction may not be sufficient to stabilize the foam structure and to lead to their collapse. [36] As is known, PI molecular chains are preferentially oriented parallel to the film planes in solid films, [8,12,37] and the degree of chain orientation increases as the rigidity of molecular structure. [37] Therefore, the high rigidity of the PI3 chains resulted in the high degree of molecular chain in-plane orientation and the low cohesive strength and modulus of the film in the film thickness direction, which may be responsible for the formation of the resulting fiber morphology on the peeled PI3 film surface.…”

Effective Reduction of Volumetric Thermal Expansion of Aromatic Polyimide Films by Incorporating Interchain Crosslinking

“…where ∆n 0 is the intrinsic birefringence estimated by DFT calculations, as reported by Terui et al [13,15] P 200 values were thus estimated according to Equation (6). The coefficient of molecular packing, K p , was estimated according to the following equation:…”

“…The procedures for calculating the values of P200 and Kp of the PI films have been described in detail elsewhere [13,15].…”