this invention relates the novel diamines , the polyimide oligomers and the polyimides derived therefrom and to the method of preparing the diamines , oligomers and the polyimides . the thermoplastic polyimides derived from the aromatic diamines of this invention are characterized as having a high glass transition temperature , good mechanical properties and improved processability in the manufacture of adhesives , electronic and composite materials for use in the automotive and aerospace industry . the distinction of the novel aromatic diamines of this invention is the 2 , 2 &# 39 ;, 6 , 6 &# 39 ;- substituted biphenyl radicals which exhibit noncoplanar conformation that enhances the solubility of the diamine as well as the processability of the polyimides , while retaining a relatively high glass transition temperature and improved mechanical properties at useful temperature ranges .