Preparation, characterization, and properties of poly(thioether ether imide)s from isomeric bis(chlorophthalimide)s and bis(4-mercaptophenyl) ether

A series of isomeric poly(thioether ether imide)s (PTEIs) containing both thioether and ether linkages were prepared by aromatic nucleophilic substitution reaction of isomeric bis(chlorophthalimide)s (BCPIs) with bis(4-mercaptophenyl) ether (BMPE). The inherent viscosities of synthesized polymers were found in the range of 0.41–0.86 dL g−1 in N-methyl-2-pyrrolidone at 30°C. The glass transition temperature (Tg) of the isomeric PTEIs were 210–242°C and increased by increasing the content of 3-substituted phthalimide unit in the polymer backbone. The 5% weight loss temperature values reached up to 525–539°C under nitrogen and 523–534°C in air atmospheres, respectively, which indicated this kind of polyimide possessed excellent thermal stability. Flexible films could be cast from the polymer solution. The PTEI films exhibited moderate mechanical properties with tensile strengths of 106–127 MPa, elongations at break of 8.6–11.5%, and tensile moduli of 2.2–2.8 GPa, respectively. Dynamic mechanical thermal analysis results illustrated that the storage moduli (E′) of PTEI (a–e) almost completely maintained at about 2.3 GPa before reaching the corresponding Tg. It is noted that the minimum melt viscosity of isomeric PTEIs (a′–e′) decreased by increasing the content of unsymmetrical 3,4′-substituted phthalimide unit in the polymer main chain.