Preparation and Properties of Flame Retardant Poly(urethane-imide)s Containing Phosphine Oxide Moiety O ¨ zdemir O ¨ zarslan, Mustafa Kemal Bayazıt, Efkan C ¸ atıker Department of Chemistry, Faculty of Science & Letters, Abant Izzet Baysal University, Bolu 14280, Turkey Received 12 July 2008; accepted 16 April 2009 DOI 10.1002/app.30601 Published online 18 June 2009 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: The preparation of new poly(urethane- imide)s (PUIs) having acceptable thermal stability and higher flame resistance was aimed. Two new aromatic diisocyanate-containing methyldiphenylphosphine oxide and triphenylphosphine oxide moieties were synthesized via Curtius rearrangement in situ and polymerized by various prepared diols. Four aliphatic hydroxy termi- nated aromatic based diols were synthesized by the reac- tion between ethylene carbonate and various diphenolic substances. Chemical structures of monomers and poly- mers were characterized by FTIR, 1 H NMR, 13 C NMR, and 31 P NMR spectroscopy. Thermal stabilities and decomposition behaviors of the PUIs were tested by DSC and TGA. Thermal measurements indicate that the poly- mers have high thermal stability and produce high char. Polymers exhibit quite high fire resistance, evaluated by fire test UL-94. The films of the polymers were prepared by casting the solution. Inherent viscosities, solubilities, and water absorbtion behaviors of the polymers were reported in. V V C 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 1329–1338, 2009 Key words: fire retardant polymers; phosphorus- containing polymers; poly(urethane-imide)s INTRODUCTION Polyurethanes have been extensively applied in vari- ous areas of industry, such as construction, automo- tive, vehicles, upholstery, medicine etc., and in many household appliances because of their excellent phys- ical and mechanical properties. Low solvent and heat resistance are their major disadvantages. Their ac- ceptable mechanical properties vanish above 70–80  C and thermal degradation takes place above 180  C. To overcome this disadvantages, chemically modified and thermally more stable polyurethanes have been synthesized by either blending or copolymerization. Polyurethane copolymers are commonly prepared, such as poly(urethane-imide)s (PUIs), poly(urethane- epoxie)s, poly(urethane-diacetylene)s, and poly(ur- ethane-amide)s. 1 Polyimides are one of high- performance engineering plastics with their high thermal stability, excellent mechanical strength, high thermooxidative stability and superior electrical insu- lation, and chemical properties. 2,3 The polyimide materials can be processed into various material forms, such as thin films, fibers, foams, adhesive film, coatings, dry powders, and fiber-coated pre- preg, however, they have also two major shortcom- ings for wide application. 4 Unless carefully designed, they have inferior solubility in most organic solvents and processing difficulties due to the high melting points and/or glass transition temperatures. 5,6 To overcome these shortcomings, various attempts have been made with the aim of synthetic modifications of the rigid-chain structure by the introduction of flexi- ble bridging linkages, 7 the distortion of molecular symmetry by meta- or ortho-oriented phenylene link- ages and the introduction of bulky groups into the polymer chain without sacrificing their high thermal stability. Copolymerization is a method used to over- come these limitations. Poly(ester-imide)s, 8–10 poly (siloxane-imide)s, 11,12 PUIs, 13–15 poly(ether-imide)s, 16–19 and poly(amide-imide)s 20–23 are the well-known copolymers of polyimides. As a result, by the intro- duction of imide groups into the polyurethane struc- ture, it is possible to obtain a thermally more stable and easily processable polyurethanes. Moreover, polyurethanes are easily flammable materials, widely used in construction of vehicles, such as automotive, marine, and aircraft. To improve flame resistance of polyurethanes, two approaches have been used (1) copolymerization with comonomers containing ele- ments or groups such as P, Si, S, or X; (2) additive method, where additives containing such groups. The first method is more preferable for high- performance polymers. 24–28 Journal of Applied Polymer Science, Vol. 114, 1329–1338 (2009) V V C 2009 Wiley Periodicals, Inc. Correspondence to: O ¨ .O ¨ zarslan (ozarslan_o@ibu.edu.tr). Contract grant sponsor: The Scientific and Technological Research Council of Turkey; contract grant number: MAG- 104M117.