DOI 10.1515/htmp-2012-0059 High Temp. Mater. Proc. 2013; 32(1): 51 –57 Khalil Faghihi*, Mohsen Hajibeygi Heat Resistant Poly(amide-imide)s Derived from N,N′-(4,4′-Pyromellitoyl)-bis-L-phenyl Acetic Acid and Aromatic Diamines: Synthesis and Properties Abstract: Six new heat resistant and optically active poly(amide-imide)s 5a–f were prepared by the direct poly- condensation reaction of N,N′-(4,4′-pyromellitoyl)-bis-L- phenyl acetic acid 3 with various different diamines 4a–f in a medium consisting of triphenyl phosphite, N-methyl- 2-pyrrolidone, pyridine and calcium chloride. These poly- mers were obtained in high yields and had inherent vis- cosities between 0.35–0.50 dL/g. The resulting polymers were characterized by viscosity measurements, thermal gravimetric analysis (TGA and DTG), differential scanning calorimeter (DSC), solubility test, specific rotation, FT-IR and 1 H NMR spectroscopy. N,N′-(4,4′-pyromellitoyl)-bis- L-phenyl acetic acid 3 was prepared by an one-stop reac- tion of pyromellitic anhydride 1 with L-phenyl acetic acid 3 in acetic acid solution in quantitative yield. Keywords: heat resistant, optically active, poly(amide- imide), aromatic diamines *Corresponding author: Khalil Faghihi: Department of Chemistry, Arak Branch, Islamic Azad University, Arak, Iran E-mail: k-faghihi@araku.ac.ir Mohsen Hajibeygi: Department of Chemistry, Varamin Pishva Branch, Islamic Azad University, Varamin, Iran Introduction Aromatic polyimides are one of the most important class of thermally stable polymers [1–3], which are well known for their high-performance properties but they have one major disadvantage of typically being insoluble and un- processable after conversion from the poly(amic-acid) to the polyimide form. Replacement of polyimides by copoly- imides such as poly(amide-imide)s (PAIs) may be useful in modifying the intractable nature of polyimides. PAIs contain both amide and cyclic imide units along the polymer chain and hence constitute a polymer class with average properties between aromatic polyamides and polyimides. These classes of polymers seem to provide a favorable balance between processability and perfor- mance [4–7]. PAIs can be synthesized readily by general synthetic methods similar to those for both aromatic poly- amides and polyimides. Various approaches have been carried out successfully in the synthesis of PAIs [8]. One of most convenient and efficient synthesis of high- molecular-weight PAIs is the direct polycondensation of imide-containing dicarboxylic acids with aromatic di- amines by means of the Yamazaki–Higashi phosphoryla- tion technique [9]. The direct polycondensation route is a very useful laboratory method and avoids using moisture- sensitive acid chlorides, or isocyanates [10–12]. Also the properties of PAIs can be readily modified by the incorpo- ration of different segments such as flexible linkages [-O-, -SO 2 -, -(CH 2 ) n -, -C(CF 3 -) 2 ], bulky pendent groups (such as t-butyl, adamantyle and naphtyl), large pendent groups or polar constituents such as heterocyclic segments into the polymer backbone due to the altering crystallinity and intermolecular interactions. If the flexible segments are carefully chosen, it is possible to promote solubil- ity without affecting thermal and mechanical properties to any great extent [13–21]. In our pervious papers we described synthesis of different polyamides and poly(amide-imide)s containing heterocyclic moieties in the main chain such as hydantoin derivatives and pyridyl moiety with improved solubility and thermal properties [22–25]. This paper reports the synthesis and characterization of a new series of new optically active poly(amide-imide)s 5a–f containing N,N′-(4,4′-pyromellitoyl)-bis-L-phenyl acetic acid moieties in the main chain in a medium con- sisting of triphenyl phosphite, N-methyl-2-pyrrolidone, pyridine and calcium chloride. The synthesis and applica- tion of optically active polymers are the newly consider- able topics, which have been paid more attention recently. Because polymers with chiral structures are biologically very important. Most of the natural polymers are optically active and have special chemical activities such as cata- lytic properties that exist in genes, proteins and enzymes [26–29].