Abstract: The present invention provides novel heat stable polyamide-imide polymers having excellent flow properties which render them more readily processible into fibers, films, sheets and other molded articles. The polymers are prepared by forming the polycondensation product of one or more aromatic diamines and one or more trifunctional acid anhydride monomers, wherein at least one of said diamine monomers is a 12F-Diamine or 12F-Oxydiamine containing at least two CF.sub.3 ##STR1## R groups linking two aromatic moieties, wherein R is CF.sub.3 or phenyl. In addition to improved flow properties, the polyamide-imide polymers of this invention also exhibit improved solubility properties in most organic solvents, improved resistance to attack by chlorinated solvents such as trichloroethylene as compared with polyimides, improved hydrophobic properties as well as excellent thermal properties including resistance to thermooxidative degredation.