Synthesis of aromatic polyimides from dianhydrides and diamines

Two-Dimensional Raman Correlation Spectroscopy Study of the Pathway for the Thermal Imidization of Poly(amic acid)

“…The pathways of cyclization during thermal imidization suggested by Kreuz et al 17,18 are depicted in Figure 3. In In order to investigate the most plausible pathway for PI formation from PAA in the film state, the powerful 2D Raman correlation method was used to produce 2D Raman contour maps.…”

“…For example, Kreuz et al suggested that the proton attached to the nitrogen is lost either after or before cyclization. 17,18 They also suggested that the film type of PAA follows the former process, while deprotonation occurs first in basic solvents, such as N-methyl-2-pyrrolidone (NMP). Although their results are needed further confirmation, to our best knowledge, no studies have been performed.…”

15N NMR spectroscopy as a method for comparing the rates of imidization of several diamines

“…A number of other researchers have noted and studied the reaction kinetics of imide formation [8][9][10][11][12]. There seems to be some agreement that the imidization reaction from the amide-acid proceeds through an initial fast step and a later slower step, although there are differing views on the cause of this difference.…”

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

“…At the same time, this solvent is known for its catalytic effect among other nucleophilic reactions in acidic conditions [16,22,23]. In addition, there is a direct correlation between the basicity and the nucleophilicity: increase of the basicity increases the nucleophilicity [24] and, accordingly, the reaction rate [10,25]. Taking into account the fact that MI has a higher pH value than NMP (pH NMP = 7.7-8; pH MI = 9.5-10.5) [26,27] it can be supposed that MI could bring more benefits as media for the PAI reaction than NMP.…”

“…On the other hand, the solvent is a media in which the PAI reactions occur. The postcuring reaction is extremely important for the final structure formation and occurs at elevated temperatures, when the solvent is evaporated [7,10]. In the present study, effect of both curing conditions and solvent type on the polymerization kinetics and final properties of PAI resins was investigated.…”