620 Research Article Received: 12 May 2010 Revised: 1 September 2010 Accepted: 14 September 2010 Published online in Wiley Online Library: 14 December 2010 (wileyonlinelibrary.com) DOI 10.1002/pi.2992 Simple and versatile method for the one-pot synthesis of segmented poly(urethane urea)s via in situ-formed AB-type macromonomers Fatemeh Shokrolahi, Hamid Yeganeh * and Hamid Mirzadeh Abstract We present a one-pot method for the synthesis of poly(urethane urea)s (PUUs) with uniform (monodisperse) hard segments that eliminates tedious approaches to control the exothermic nature of isocyanate – amine reaction, is less sensitive to impurities and involves no isolation of intermediates. Reaction of two moles of hexamethylene diisocyanate with one mole of polycaprolactone of various molecular weights under optimum time and temperature led to NCO-terminated polyurethane prepolymers. Addition of an equimolar quantity of benzoic acid and excess dimethylsulfoxide at ambient temperature produced quantitative yields of PUUs with high molecular weight. The structure of the PUUs was fully characterized using spectroscopic methods and a reasonable mechanism for the reaction sequences was determined via preparation and characterization of a model compound. Dynamic mechanical thermal analysis data confirmed the phase-separated structure of the PUUs. Evaluation of stress-strain curves revealed the wide-ranging mechanical properties depending on soft-segment molecular weight. Monitoring the remaining weight and molecular weight of polymers incubated in phosphate-buffered saline showed hydrolytic degradability with rate depending on soft-segment molecular weight. Also, a preliminary investigation of the interaction of L929 fibroblast cells with the prepared polymers confirmed no cytotoxicity and acceptable cytocompatibility for the PUUs. c  2010 Society of Chemical Industry Keywords: polyurethanes; biocompatibility; poly(urethane urea)s; biodegradability INTRODUCTION Poly(urethane urea)s (PUUs) are a class of elastomers exhibiting su- perior extensibility, high flexural endurance, toughness and good biocompatibility in comparison to segmented polyurethanes. Therefore, PUUs are widely employed in various fields includ- ing numerous biomedical applications. 1–10 In particular, the biodegradable analogues of PUUs have been investigated for ap- plications in regenerative medicine. 11–14 In contrast to biostable implants, these biomaterials are designed to undergo controlled degradation in vivo and support cell in-growth both in vitro and in vivo. PUUs are segmented elastomers the properties of which, by variation of their soft component using various diisocyanates, and chain extenders, can be tailored. In fact the superior prop- erties of PUUs are mainly attributed to the well-defined hard segment domain of PUUs, which acts as a physical crosslink (paracrystal-like domain) due to the strong intermolecular hydro- gen bonding between the urea groups. 15–21 Therefore, due to their tunable biological, mechanical and physicochemical proper- ties, biodegradable PUUs present compelling future opportunities as scaffolds for tissue regeneration. There is always a search for more simple methods of synthesizing polymers, especially where the properties can easily be tailored. Generally, a PUU is synthesized by a chain-extending reaction of an isocyanate-terminated polyurethane prepolymer (ITPP). As chain-extending reagents, polyvalent aliphatic, aromatic and alicyclic amines are commonly used. Due to the lower cytotoxicity of degradation products under biological conditions, alkane diamines such as putrescine are the preferred extending reagents for the preparation of PUUs for biomedical applications. 22 However, control of the reaction is difficult due to the extremely high reaction rate and a considerable exothermic nature. To avoid this, the reaction is carried out in such solvents as N,N- dimethylacetamide (DMAc) and N,N-dimethylformamide (DMF). The role of the solvent is to avoid the rapid polymerization reaction due to a diffusion-controlled reaction between the isocyanate groups and amino groups. For controlling the apparent isocyanate–amine reaction rate, the use of aldehyde- or ketone-blocked diamines, capable of un- dergoing a reformation reaction (deblocking), in the polymeriza- tion reactions was reported by Kitahama and co-workers. 23–26 They prepared a segmented PUU film from methylenebis(phenyl iso- cyanate) (MDI), poly(tetramethylene oxide) (PTMO) and ethylene- diamine (EDA) blocked with acetone without using DMAc as solvent. The reaction products from acetone and EDA consisted of mono- and di-ketimines, 2,2-dimethylimidazolidine as main prod- uct, water and the unreacted raw materials. They found that with increasing the masking ratio of acetone to EDA, the concentra- tions of the ketimine groups and water increased while those of the imidazolidine and EDA decreased. The molar fraction of the by-product from the reaction of an isocyanate group with water increased, mainly because of the catalytic effect of the ketimine groups. Use of certain amounts of acetic acid and blocking agent ∗ Correspondence to: Hamid Yeganeh, Iran Polymer and Petrochemical Institute, PO Box 14965/115, Tehran, Iran. E-mail: h.yeganeh@ippi.ac.ir Iran Polymer and Petrochemical Institute, PO Box 14965/115, Tehran, Iran Polym Int 2011; 60: 620–629 www.soci.org c  2010 Society of Chemical Industry