Synthesis and characterization of poly(amide‐imide)s containing 1,6‐diamantane moieties in the main chain

A series of new poly(amide‐imide)s were synthesized by direct polycondensation of the 1,6‐bis(trimellitimido)diamantane ( 1 ) with various aromatic diamines in N ‐methyl‐2‐pyrrolidone (NMP) containing lithium chloride. The poly(amide‐imide)s had inherent viscosities of 0.33–1.55 dL/g. The new polycyclic monomer 1 was synthesized from 1,6‐diaminodiamantane with trimellitic anhydride. Dynamic mechanical analysis revealed polymers 3a – c to have main transitions at 385°C, 385°C, and 330°C, respectively. Moreover, these polymers were stable at high temperatures and maintained good mechanical properties ( G ′ ≈ 10 8 Pa) up to temperatures close to the main transition well above 350°C. Their 5% weight loss temperatures ranged from 421 to 448°C in nitrogen, and from 417 to 426°C in air. A glass transition of poly(amide‐imide)s 3 was not observed. Poly(amide‐imide)s 3 (except 3e ) were soluble in NMP, pyridine, and o ‐chlorophenol. Some of the polymers ( 3a – c ) could be cast into flexible films. Their cast films had tensile strengths ranging from 35.5 to 46.9 MPa, elongations at break from 5.8 to 7.5%, and initial moduli from 1.8 to 2.1 GPa.