Effect of chemical structure and preparation process on the aggregation structure and properties of polyimide film

Abstract

In this article, polyimide (PI) films were fabricated via the three-step method including the reactions of condensation polymerization, chemical imidization, and thermal imidization. In comparison with the conventional two-step method to produce PI films, there was an additional step in the present method, i.e., chemical imidization. The aim of chemical imidization was to get PI intermediates with different pre-imidization degree (pre-ID). And PI component in PI intermediates acted as in-situ rigid-rod segments and induced orientation in the films of PI intermediates. Then the orientations of molecular chains were preserved in the following thermal imidization, and caused the difference in aggregation structure and property of the final PI films. The test results indicated that the orderly degree of molecular chains and mechanical properties of PI films increased with pre-ID increasing. Furthermore, this tendency was much more obvious for more rigid backbone structure.

Polyimide fibers prepared by a dry‐spinning process: Enhanced mechanical properties of fibers containing biphenyl units

“…13 When it was heated to 300 8C, the characteristic peaks of the sample at 1370 and 1770 cm 21 were attributed to the CAN stretching and C@O symmetric stretching of the imide ring, respectively; these peaks illustrated the formation of fully imidized PI-1 fibers. 14,15 In our last work, 16 we reported that the peak at 1370 cm 21 could be used to quantitatively calculate the ID by the following equation because of its very strong characteristic features:…”

“…At 100 °C, the precursor PAA fiber vibrations included three bands: the carbonyl stretching of the carboxylic acid at 1726 cm −1 , the carbonyl stretching of the amide I mode at 1670 cm −1 (CO, CONH), and the CNH stretching of the amide II mode at 1540 cm −1 . When it was heated to 300 °C, the characteristic peaks of the sample at 1370 and 1770 cm −1 were attributed to the CN stretching and CO symmetric stretching of the imide ring, respectively; these peaks illustrated the formation of fully imidized PI‐1 fibers …”

Enhancing the Toughness of Free-Standing Polyimide Films for Advanced Electronics Applications: A Study on the Impact of Film-Forming Processes

“…However, the design and synthesis of monomer structures are often complex and time-consuming, which greatly limits the efficiency of PI film preparation. Recently, there has been a growing interest in studying the effect of the imidization process on enhancing the performance of PI materials, as the cost of novel diamines and dianhydride monomers is high and limits their commercial feasibility [18][19][20]. Ji et al [21] traced and studied the structure changes from poly(amic acid) (PAA) fibers to polyimide fibers during ramp-heating and isothermal treatments.…”

Synthesis and characterization of novel fluorosilicone polyimides with high optical transparency

“…Aromatic polyimides (PIs) are well known as a class of high-performance polymers because of their outstanding properties, such as high thermal stability, high mechanical performance, good chemical resistance, and excellent electrical properties. 1 –6 Therefore, they have been widely used in aerospace and electrical and electronic applications. 7 At the same time, optical transparency of PI films is of special importance in some applications, such as flexible solar radiation protectors, orientation films in liquid-crystal display devices, optical waveguides for communication interconnects, and optical half-wave plates for planar lightwave circuits.…”