Important Factors Controlling Synthesis of Imides in Water

Abstract

Four amine/anhydride models have been studied in order to understand the critical factors which control the synthesis of imides and polyimides in water. This synthesis method has been proposed recently as a convenient, environmentally friendly method of producing both thermosetting and thermoplastic polyimides. The key starting step in the synthesis is the formation of a salt/complex between the hydrolysed anhydride and the amine. The results from a combination of quantitative 1 H NMR, HPLC and DSC analysis have shown that the reactions are reversible, and that the important factor in driving the reaction to completion in water is the insolubility of the imide product. Analysis of the precipitated imides shows them to be free of significant amounts of the considerably more water soluble amic acids (i.e. the uncyclized amide acids), which often contaminate imides made in conventional aprotic solvents. Of the models investigated, only the imidization of the second amino group in 2,4,6-trimethyl-1,3-phenylene diamine (TMPDA) was subject to kinetic control.A general conclusion from these experiments is that where a different result is observed in water synthesis of imides compared with conventional aprotic solvent synthesis, it is likely to reflect the vastly different solvation powers of the two solvents rather than a difference in reaction mechanism.

Geomimetics for green polymer synthesis: highly ordered polyimides via hydrothermal techniques

“…12,15 Previous attempts to obtain polyimides hydrothermally did not achieve the target of high crystallinity. 16,17 In this contribution, we introduce a simultaneous polymerization and crystallization approach, which gives direct access to the thermodynamically favored, highly crystalline product. Our approach yields PPPI, a 1D high-performance polymer, of impressive crystallinity that cannot be achieved by classical procedures.…”

Water as Solvent in Polyimide Synthesis II: Processable Aromatic Polyimides

“…The mechanical and thermal properties of this material are detailed in table 1 and indicate that it is possible to form thick thermally stable items containing high percentages of cyclized Kapton-type polyimides. The T g as determined by the peak in tan 1 at 1 Hz is 274 2 C and is clearly dominated by the PETI-5 component with T g of 262 2 C. An alternative technique commonly used to make polyimides more processable without affecting the thermal stability significantly is by copolymerization [5]. A Kaptonlike copolyimide using PMDA with a 1 : 1 mixture of 3,4 4 -oxydianiline (ODA) and 4,4 4 -ODA was produced using the water synthesis method again in high yield, as a fine yellow powder.…”

“…Although the many environmental and economic benefits of the technology were stressed there is one potentially significant disadvantage of this method. This drawback results from the fact that the process is complete in one step from the diamine and tetra acid monomers (in their salt form) to a final fully cyclized product [2]. This means that, if the resulting polyimide is insoluble and infusible, the aqueous polyimide synthesis method would be at a disadvantage when attempting to produce a commercially viable product.…”

Preparation of Polyimide Powders via Hydrothermal Polymerization and Post-Heat Treatment for Application to Compression-Molding Materials

“…However, conventional synthesis of PMDA-ODA PI powder is performed using organic solvents such as N -methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), and cresol. − The use of the toxic high-boiling-temperature solvents presents economic and environmental disadvantages. In addition, the high degree of complexity of the manufacturing process prevents the application of compression-molding in various fields. ,− …”