Synthesis and characterization of polyimides containing naphthalene pendant group and flexible ether linkages

Abstract

A series of novel polyimides containing naphthalene pendant moieties were prepared from various diamines (including bis(4-amino-3,5-dimethylphenyl)naphthylmethane 1, bis(4-aminophenoxy-3,5-dimethylphenyl)naphthylmethane 4, and bis(4-aminophenoxy-3,5-dimethylphenyl)methane 5) with various aromatic tetracarboxylic dianhydrides via both two-step and one-step methods. All polyimides, except 8 5a– d , were readily soluble in common organic solvent, such as chloroform. Differential scanning calorimetry (DSC) revealed that the naphthalene bearing diamine monomers had a low entropy, and formed amorphous polyimides. They retained high moduli even at high temperatures by DMA, and had measured coefficients of thermal expansion (CTEs) in the range of 46.86–67.14 ppm by TMA. The glass transition temperature ( T g) of all polyimides were found to be 268–294°C, 298–326°C and 270–315°C, respectively by DSC, DMA, and TMA. Thermogravimetric analyses indicated that the polymers were fairly stable up to 489–571°C (10 wt% loss in N 2). They had a tensile strength in the range of 56–97 MPa, and elongations to break of around 3%. These polyimide films have dielectric constants ranging from 2.71 to 3.28 with moisture absorptions of less than 0.98%.