Effect of polydimethylsiloxane incorporation on the properties of polyimides synthesized from newly designed α,α'-bis(2-aminophenoxy)-p-xylene

Abstract

The advances in the field of high performance materials demand a unique combination of properties i.e. good oxidative and thermal stability, high glass transition temperature, excellent mechanical properties, good adhesion along with chemical, wear, fire and radiation resistance for diverse range of applications including aerospace, automotive and microelectronic industries, as films, adhesives, sealants, coatings, insulators, gas separation membranes etc. In this regard, large number of polymeric materials such as polyamides, polyimides, poly(amide-imide)s polybenzimidazoles, polyethers, polyketones, polysulphones, and polyesters have been developed in order to replace metal, ceramic or glass and reduce the cost of present day industrial processes [1][2][3][4][5][6][7]. Polyimides especially aromatic polyimides have attracted the attention of scientists and engineers more than any other polymer as they have great potential to serve this purpose due to favorable combination of aforementioned sought properties [8]. Abstract. A novel diamine monomer !,!"-bis(2-aminophenoxy)-p-xylene (2APX) was synthesized and condensed with four different dianhydrides to prepare a series of polyimides. Aminopropyl terminated polydimethylsiloxane (PDMS) was incorporated within the backbone of polyimides for the preparation of poly(imide siloxane) copolymers. Fourier transform infrared (FTIR), 1 H and 13 C nuclear magnetic resonance (NMR) spectroscopic studies accompanied by elemental and single crystal X-ray analysis were performed for structure elucidation of 2NPX and 2APX. The crystal system of the 2NPX was found to be monoclinic, belonging to space group P2 1 /n while 2APX was triclinic with space group P1. The structural elucidation of polymers was carried out by FTIR and 1 H NMR spectroscopy and their properties were studied by solubility testing, wide angle X-ray diffraction (WAXRD), thermogravimetric analysis (TGA) and viscosity measurement along with laser light scattering technique (LLS). WAXRD pattern showed the semicrystalline nature of polyimides which was decreased in case of copolymers. The poly(imide siloxane) copolymers displayed slightly lower temperature resistance but improved solubility as compared to polyimides. Maximum degradation temperature (T max. ) of polyimides was in the range of 523-570°C while that of copolyimides, ranged between 483-525°C. Similarly, a decline in inherent viscosities and increase in molecular weight was noticed while moving from polyimides to copolyimides.