A novel direct method for preparation of aromatic polyimides via microwave-assisted polycondensation of aromatic dianhydrides and diisocyanates

Improved synthesis and properties of BTDA-TDI/MDI ternary copolyimides via microwave-assisted polycondensation

Polyimides are usually synthesized over a long period of time, and the process is complex. In order to shorten the synthesis time and simplify the process, we developed an improved synthesis method, namely, microwave-assisted polycondensation. The 3,3′-4,4′-benzophenone tetracarboxylic dianhydride (BTDA)–2,4-tolylene diisocyanate (TDI)/1,1′-methylenebis(4-isocyanatobenzene) (MDI) ternary copolyimides prepared in this work have been synthesized using microwave heating at rather short reaction times (15 min), without the need for either the once-off addition of TDI/MDI or the drop-wise addition of that mixture. The structure of the desired ternary copolyimide was confirmed by proton nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy. Its glass-transition temperature is above 400°C, and the temperature for 5% thermal loss under nitrogen atmosphere is 508.8°C. The tensile strength is 141 MPa, which shows that the microwave-assisted copolyimide has excellent heat resistance and mechanical properties.

Synthesis of inorganic polymers under ionizing and super high frequency irradiation: role of reaction media

This article provides a general overview of the results of research on the influence of the reaction media and various types of electromagnetic radiation on the polymerization of inorganic monomers, carried out during the last decade at UNESCO Chair in Green Chemistry for Sustainable Development of Dmitry Mendeleev University of Chemical Technology of Russia.

Enhancement of the Mechanical Properties of Polyimide Film by Microwave Irradiation

Polyimide films have conventionally been prepared by thermal imidization of poly(amic acid)s (PAAs). Here we report that the improvement of tensile strength while increasing (or maintaining) film flexibility of polyimide films was accomplished by simple microwave (MW) irradiation of the PAAs. This improvement in mechanical properties can be attributed to the increase in molecular weight of the polyimides by MW irradiation. Our results show that the mechanical properties of polyimide films can be improved by MW irradiation, which is a green approach that requires relatively low MW power, very short irradiation time, and no incorporation of any additional inorganic substance.

Preparation of polyimide films via microwave-assisted thermal imidization

A series of polyimide (PI) films based on aromatic heterocyclic monomers of 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), p-phenylenediamine (p-PDA) and 4,4′-oxydianiline (ODA) were prepared via a microwave-assisted thermal imidization and conventional thermal imidization method at different temperatures. The effects of microwave irradiation on the imidization degree, microstructures, mechanical and thermal properties of PI films were investigated. The imidization degree of the PI films treated with microwave-assisted heating reached a relatively high value at 250 °C, which was twice as much as those treated with traditional thermal imidization. The tensile strength and modulus of PI films treated with microwave-assisted imidization at 300 °C were 187.61 MPa and 2.71 GPa respectively, which were 30% higher than those of PI films treated with thermal imidization. Moreover, the order degree of polymer chains was improved by the microwave-assisted imidization method. The PI films prepared by the microwave-assisted imidization method showed excellent thermal stability with a 5% weight loss temperature of 573 °C under N₂. The microwave-assisted thermal imidization proved to be a rapid and efficient way to prepare high-performance polyimide materials.

A series of polyimide films were prepared via a microwave-assisted thermal imidization and conventional thermal imidization method at different temperatures.

Microwave-assisted Diels–Alder polycondensation of proton conducting poly(phenylene)s

A 24-fold reduction in reaction time is achieved in the preparation of sulfonated poly(polyphenylene)s using microwave synthesis.

Microwave-assisted ionic liquid phase synthesis of phthalonitrile polymers

A novel, efficient methodology for the synthesis of phthalonitrile derivatives was investigated, using ionic liquid (IL) and microwave media as well as both simultaneously. Phthalonitrile monomers containing imide linkages were prepared from the reaction between aromatic dianhydrides, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BPTA), pyromellitic dianhydride (PMDA), 4,4′-(hexafluroisopropylidene) diphthalic anhydride (6FDA), 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BTDA) and the end-capping agent 4-(3-aminophenoxy)phthalonitrile through the imidization reaction. The use of the IL1-butyl-3-methyl imidazoliumchloride as a solvent significantly increased the rate and yield of the reaction. The use of microwave irradiation and reaction parameters significantly shortened the reaction time while enhancing the purity. The polymerization of the prepared phthalonitrile monomers was carried out with 3 wt% of aromatic diamine 4,4′-oxydianiline (ODA) curing agent under microwave irradiation. It is shown that condensation was successfully carried out using the recyclable IL medium under microwave irradiation.