Reactivity of Poly(amic acid) Isomers in Thermal Imidization

Abstract

ABSTRACT:The reactivity of isomers ofpoly(amic acid) prepared from 4,4'-oxydianiline and pyromellitic dianhydride in thermal imidization was investigated both in solution and in solid state at l 30°C. FT-NMR was the main tool used to measure the mole fraction of various species formed in partial imidization, using diphenyl pyromellitamic acid as a model compound to verify its applicability. The results were modeled by kinetic equations. It showed that the terephthalamide isomer reacted 4.14 times faster than isophthalamide isomer when imidized in solution. On the other hand, the isophthalamide isomer reacted 3.25 times faster than the terephthalamide isomer when reacted in solid state.KEY WORDS Poly(amic acid) / Imidization / Kinetics / Aromatic polyimides have outstanding thermal, electrical and mechanical properties. They are an important class of high-performance polymers, applied extensively in insulation film for electrical equipment and electronic devices, such as flexible printed circuit board and multilevel metallization of LSis.Polyimides, in general, show a lack in thermoplasticity and solubility for processing. These marterials are unsually processed in the form of their precursors, the poly(amic acid)s, in solution, followed by thermal imidization. The reaction kinetics of imidization have been studied extensively.

Effect of the solvent type and polymerization conditions on the curing kinetics, thermal and viscoelastic performance of poly(amide-imide) resins

“…The high-temperature peaks on the DSC-traces at 180°C and ~260°C were assigned to the imidization reactions of the different conformers of PAAc (reactions 3 and 4 in Figure 4) [19]. The last high temperature exothermal peak (peak 5 in Figure 3) was assigned to the post-curing reactions of sterically hindered reactive centers.…”

Solvent-Free Reactive Extrusion As an Innovative and Efficient Process for the Synthesis of Polyimides

“…The kinetics of the thermal imidization have been widely studied with various techniques 47 , such as Fourier-transform infrared spectroscopy (FT-IR) 48 , carbon-13 nuclear magnetic resonance ( 13 C-NMR) 49 and ultraviolet-visible spectroscopy (UV-vis) 38 . The imidization of PAA is an endothermic process that can be also monitored by differential scanning calorimetry (DSC) 39 .…”

“…The imidization reaction involves an amide and a carboxylic acid group. As these two groups belong to the same chemical species, the authors 38,49 classically consider the kinetics as a first order law expressed with the following rate expression (Equation 3): where k is the rate constant, α the imidization reaction conversion and t the reaction time.…”

Effect of imidization conditions on the morphology of polyimide

“…There have been some attempts to describe the morphology of polyimide. [12][13][14][15][16][17] In a previous article, 18 we reported the reactivities of PAA isomers in solution and in the solid state. This article describes the morphology of polyimide produced by imidization under different conditions.…”