Analysis of Molecular Aggregation Structures of Fully Aromatic and Semialiphatic Polyimide Films with Synchrotron Grazing Incidence Wide-Angle X-ray Scattering

Abstract

The intermolecular aggregation structures of fully aromatic polyimides (Ar-PIs) prepared from pyromillitic dianhydride (PMDA) and those of semialiphatic polyimides (Al-PIs) from 4,4′-diaminocyclohexylmethane (DCHM) were characterized by a grazing incidence wide-angle X-ray scattering (GIWAXS) technique. The aggregation structures of both Ar- and Al-PI thin films formed on Si substrates were identified as a mixture of a liquid-crystalline-like ordered domain and an amorphous matrix. For Ar-PIs whose glass transition temperatures (T g) are higher than the imidization temperature (T i), the aggregation structures are significantly influenced by the three-dimensional structures of the PI chain. Rodlike molecular structures with high planarity are prerequisites for the growth of ordered domains of Ar-PIs, whereas an Ar-PI having a bent and nonplanar structure displays the highest intensities of an amorphous halo. In addition, the bulky −CF3 groups in the diamine moiety increase the interchain distance in the ordered domains. On the other hand, for Al-PIs whose T gs are lower than T i, the degrees of interchain ordering in the ordered domains were higher than those of Ar-PIs, but the orientation of the ordered domains was decreased significantly by decreasing their T gs. This is due to the vigorous motion of PI chains during thermal imidization.

Intrinsically Microporous Soluble Polyimides Incorporating Tröger’s Base for Membrane Gas Separation

“…This implies that the aggregation structure of the PI-TB-1 membrane was mainly amorphous morphology, but was combined with some ordered chain packing domains. 57,58 Then, the calculated d-spacing values of 6.74, 5.72, and 3.46 Å from the peaks located at 2θ = 13.12°, 15.49°, and 25.75°for the PI-TB-1 polymer membrane can be assigned to the main interchain distance in the amorphous domain, the interchain distance in the ordered domain and π−π stacking of aromatic rings, respectively. Obviously, the chain packing of macromolecules in the ordered domains is closer than that in amorphous domains.…”

Influence of Confined Polymer Structure on Proton Transport Property in Sulfonated Polyimide Thin Films

“…34,35 Mostly, the rigid and planar PI molecular structures can be responsible for the higher degrees of in-plane orientation than those having bent and three dimensional molecular structures. 33 This study reveals that the organized structure in SPI thin film significantly exhibit the high proton conduction. The chemical stability also plays an essential role in obtaining the high proton conduction, which derived from the spacing between the sulfonic acid group and polyimide main chain.…”

“…Furthermore, the lyotropic lamella structure parallel to the substrate plane formed the longrange proton transport path when the SPI confined into film. As mentioned in the previous studies, 14,33,36 the planar PI molecular structure mostly orients the polymer chain in the in-plane direction, which possibly enhances the proton conductivity in such thin film system.…”

“…This implies that the degree of crystallinity improved by RH and causes the aggregated structures such as liquid-crystal-like and ordered crystalline structures. 33 The increase in humidity results the remarkable interaction between the aggregated lamellar structures and water molecules, which possibly rearranged the crystalline order. Understanding of this structural property well correlates with our earlier finding of the expansion of lamellar structure in the out-of-plane direction when the PMDA/SPI system hydrated fully.…”

Effect of Casting Solvent on Interfacial Molecular Structure and Proton Transport Characteristics of Sulfonated Polyimide Thin Films

“…[14][15][16][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] In thin films, aromatic polyimides (PIs) possessing a rigid and planar backbone exhibit a highly ordered lamella structure oriented parallel to the substrate plane with in-plane orientated backbones. 36 Notably, the molecular structure and ch-packing of imide and phenyl groups in PIs significantly vary depending on the aggregation structures, such as crystalline, liquid crystalline-like and amorphous. In our previous studies, we have found the lyotropic liquid crystalline (LC) lamellar behavior in the SPI thin film and existence of high relative humidity (RH) induces the expansion of the LC structure to the out-of-plane direction.…”