Subject Number : S-16-CT-0082
Support Type : Collaborative Research
Proposal Title (English) : Synthesis of polyimides using ionic liquids
Username (English) : Christoph Gruber1
Affiliation(English) : 1Friedrich-Alexander Universität Erlangen-Nürnberg, Germany
1. Summary
Polyimides are a class of well-known highly resistant polymers. Their excellent thermal and solvent stability makes them ideal materials for applications in the electronics industry. They are prepared via an amic-acid intermediate from a diamine and a dianhydride. The amic-acid is soluble and can be characterized by conventional analytical methods. Films can be spin-cast and condensation at higher temperature then leads to imidization and the formation of an insoluble polymer film.
The topic of this research is to study the formation of polyimide particles using ionic liquids (IL) instead of organic solvents. (1)
The reaction conditions used were similar to a published method (2) that described the reaction by heating an ethylene glycol solution of the various diamines and dianhydrides for 24 h. Instead of ethylene glycol different ionic liquids such as 1-Ethyl-3-methylimidazolium Tetrafluoroborate were used.

2. Experimental
A general synthesis method is shown in Figure 1. Both monomers were dissolved in ionic liquid and kept at elevated temperature for several hours.

Fig. 1: Synthesis scheme of polyimides

3. Results and Discussion
Fig. 2: TGA spectra of a polyimide synthesized by different IL

Figure 2 shows the TGA spectra of a polyimide successfully synthesized by three different ionic liquids. The ionic liquid does not have a considerable impact on the spectra of the synthesized polyimide particles.

Fig. 3: IR spectra of a polyimide synthesized by different IL

The IR spectra (Figure 3) do not show any correlation between the used ionic liquids either.
The SEM image of a 2 µm microparticle synthesized by this method shows a very fine nanoscale surface decoration (Figure 4).

Fig. 4: SEM images of the synthesized polyimide particles

4. Literature
1) A.N. Vygodskii et al., Macromol. Rapid Commun., 23, 676-680 (2002)
2) T. Namikoshi et al., High Performance Polymers, 1-8 (2014)

Acknowledgment
I am grateful to Prof. Olaf Karthaus for advice and collaboration on the every stage of this work and his hospitality during my visit to CIST, Japan.

5. Publication
none