Polymer International Polym Int 52:1487–1492 (2003) DOI: 10.1002/pi.1262 Synthesis and characterization of novel diimide–dinaphthols and resulting poly(urethane – imide)s Shahram Mehdipour-Ataei 1∗ and Shahriar Keshavarz 2 1 Polyurethane Group, Iran Polymer and Petrochemical Institute, PO Box 14965/115, Tehran, Iran 2 Department of Chemistry, Lorestan University, Khoram Abad, Iran Abstract: Novel diols containing imide groups were prepared via condensation of aromatic dianhydrides with 5-amino-1-naphthol. The diimide–dinaphthols prepared were characterized by conventional methods and used to synthesize new poly(urethane–imide)s (PUIs). All the polymers were characterized and their physical properties, such as solubility, solution viscosity, thermal stability, and thermal behaviour were studied. The polymers obtained showed more thermal stability than typical polyurethanes because of the presence of the imide groups.  2003 Society of Chemical Industry Keywords: poly(urethane–imide)s; thermal stability; dianhydride; diisocyanate INTRODUCTION Polyurethanes (PUs) comprise a class of versatile materials that can easily be prepared by polyaddition of diols with diisocyanates. Their tailormade properties extend from super soft flexible foam to tough elastomers and to longwear coatings, and have resulted in many end uses. 1–3 A major drawback of polyurethanes is their poor heat resistance. Their acceptable mechanical properties (strength, module, etc) vanish above 80 ◦ C, and thermal degradation takes place above 200 ◦ C. 4 Attempts to improve the thermal stability of polyurethanes have been made over a long period. The thermal stability of polyurethanes can be improved by chemical modification of their structure by blending or copolymerization with more thermally stable polymers. Particular attention has been paid to modifications of these polymers by heterocyclic groups. This can be achieved by incorporation of an imide moiety into the polyurethane chain. Polyimides are an important class of heterocyclic polymers that have remarkable high temperature resistance and superior mechanical, electrical properties and durability. 5–7 Various attempts have been made to incorporate polyimide units into polyurethane. In the method most often used, isocyanate terminated polyurethane prepolymer is reacted with acid anhydride. 8 A modified method is the reaction of an isocyanate terminated polyurethane prepolymer with aromatic diamines and dianhydrides to prepare polyurethanes with imide groups. 9 Diels–Alder reaction using various bismaleimides has been reported to prepare PUIs. 10 In our previous publications we reported the preparation and characterization of polyimides; 11 – 17 here, we wish to describe the synthesis of PUIs via reaction of diols containing imide units with diisocyanates. The presence of both urethane and imide linkages in the polymer chain may alter the properties of polymers to an even greater extent. Hence it was thought interesting (especially in view of processing) to synthesize and characterize PUIs. In this way, novel diols containing preformed imide structure were prepared. Reactions of these diimide – dinaphthols with different aromatic and aliphatic diisocyanates resulted in six fully aromatic and two semi-aromatic PUIs with improved thermal stability in comparison with common polyurethanes. EXPERIMENTAL Materials All chemicals were purchased either from Merck or Aldrich Chemical Co. Pyromellitic dianhydride (PMDA), benzophenonetetracarboxylic dianhydride (BTDA), and hexafluoroisopropylidene diphthalic anhydride (6FDA) were dried in a vacuum oven at 110 ◦ C for 5 h. N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), and N-methyl-2- pyrrolidone (NMP) were purified by distillation over calcium hydride under reduced pressure. ∗ Correspondence to: Shahram Mehdipour-Ataei, Polyurethane Group, Iran Polymer and Petrochemical Institute, PO Box 14965/115, Tehran, Iran E-mail: s.mehdipour@proxy.ipi.ac.ir (Received 16 August 2002; revised version received 3 February 2003; accepted 4 April 2003) Published online 7 August 2003  2003 Society of Chemical Industry. Polym Int 0959–8103/2003/$30.00 1487