Spectroscopic investigation of the one step synthesis of a model polyimide

Date of Completion

January 1994


Chemistry, Polymer|Engineering, Materials Science|Plastics Technology




The objective of this dissertation was to examine the factors affecting acylation and cyclization reactions during solution imidization primarily by spectroscopic techniques. The kinetics of a polyimide synthesized from 1,5-diaminonaphthalene (DAN) and 3,3$\sp\prime$,4,4$\sp\prime$-benzophenonetetracarboxylic dianhydride (BTDA) were studied by a variety of techniques in solution from 25$\sp\circ$C to 45$\sp\circ$C, 100$\sp\circ$C and 210$\sp\circ$C. UV-Visible spectra exhibited blue shifts upon reaction from the diamine to the polyimide. Compositional analysis of the UV-Vis spectra by deconvolution revealed possible intermediates present during the reaction at low temperatures. At higher temperatures such as 100$\sp\circ$C and 210$\sp\circ$C, evidence of three intermediates such as diamic acid, amic acid-imide, and diimide were present. The reaction solvent m-cresol was found to form a complex with the diamine, leading to an equilibrium which was revealed by fluorescence spectroscopy. At low temperatures, dissociation of the imide is possible by hydrolysis. Kinetic analysis revealed activation energies for the acylation and cyclization were between 10 and 28kcal/mol. Infrared spectroscopy was used to provide anhydride compositional data. It also provided independent confirmation of the extent of amide and imide that agreed with compositions obtained by UV-Vis spectroscopy. Overall, the study of polyimide synthesis using m-cresol has revealed that side reactions are possible between the solvent and diamine. The ability of the solvent to act as a catalysis has formed the imide product at relatively low temperatures. At the higher temperatures, a more efficient conversion to the imide was possible because of the minimal hydrolysis and more efficient water removal. The intermediates such as amic acid-amine, diamic acid, amic acid-imide, and diimide were found to exist in the system of DAN and BTDA. Finally, this 'one step' reaction should be considered a multi-step polyimide reaction. ^