e) were 506-31 °C in nitrogen and 509-36 °C in air, respectively. The isomeric PTIs (b-strong class="EmphasisTypeBold ">d) films exhibited good mechanical properties with tensile strength of about 90 MPa, elongation at break of more than 6.0 %, and tensile moduli of more than 2.2 GPa. The storage moduli of PTIs (b-strong class="EmphasisTypeBold ">d) almost completely maintained at about 2.0 GPa before reaching the corresponding glass transition temperatures. It is noted that the minimum melt viscosity of these polymers decreased with increasing the content of unsymmetrical 3- and 4-substituted phthalimide unit. Keywords Isomeric AB-type monomers Self-condensation Isomeric poly(thioether imide)s Aromatic nucleophilic substitution reaction" />