425 Grafting reactions and heparin adsorption of poly(amidoamine)-grafted poly(urethane amide)s MC. Tanzi, B. Barzaghi and R. Anouchinsky Dept. Bioingegneria, Politecnico di Milano, Italy S. Bile&s, A. Penhasi and D. Cohn Casali Institute of Applied Chemistry, Hebrew University, Jerusalem, Israel Differently terminated poly(amidoamine) (PAA) oligomers were grafted on the surface of poly(ether urethane amide)s (PEUAm), with fumaric or maleic acid moieties. The grafting reaction was Michael-type addition of amino groups to activated double bonds in the PEUAm backbone. PAAs having primary amino, or secondary amino end-groups were directly grafted on the surface of PEUAm sheets. For vinyl-terminated chains an a, 52 amino-polyether spacer was introduced initially, following the same addition mechanism. Ungrafted and grafted materials were characterized, besides other analytical techniques, by ATR FT-IR spectroscopy. The heparin adsorption on PEAUm films was analysed after its elution from heparinized samples, quantified by coagulation tests (aPTT), and related to the presence of the PAAs chains grafted’ on to the surface. Results indicate that PAA-grafted PEUAm elastomeric biomaterials, display enhanced heparin adsorption abilities. Keywords: Poly(ether urethane amide@, poly(amidoamine)s, polymer-grafting, heparin Received 24 April 1991; revised 35 July 1991; accepted 4 November 1991 Segmented polyurethanes are among the most promising biomedical elastomers. These segmented, microphase segregated polymers comprising, alternatively, hard and soft blocks, exhibit superior physical and mechanical propertieslq ‘. Nevertheless, some fundamental aspects of their performance in biological systems, such as surface thrombogenicity, calcification and degradation, still pose serious problems. A novel family of segmented polyurethanes has recently been developed3v4, using dicarboxylic acids instead of traditional chain extenders (diamines and diols)5s 6 , The ability shown by the amide groups, produced by the reaction between the isocyanate and carboxyl functionalities, to form strong intermolecular hydrogen bonds, results in well-developed hard domains and, in turn, in polymeric materials displaying improved mechanical properties. The enhanced stiffness and planarity associated with the amide group, is an additional advantageous feature of these chain extenders, contri- buting to develop enhanced microphase segregation and improved mechanical properties. The resulting poly(ether urethane amide)s (PEUAm) show excellent Correspondence to Dr M.C. Tanzi, Dept. Bioingegneria, Politecnico di Milano, P.zza L.da Vinci, 32, 20133 Milano, Italy. @ 1992 Butterworth-Heinemann zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Ltd 0142-9612/92/070425-07 properties, their behaviour being a function of the dicarboxylic acid incorporated into the polymeric backbone. Clearly, the length and molecular symmetry of the chain extender play a central role7*“. When fumaric (FA) or maleic acid (MA) were used, the resulting ‘poly(urethene amide)s’ (PEUFA and PEUMA, respectively] still have reactive double bonds. These can perform as grafting sites for further derivatization, thus allowing specific tailoring of the base polymers. By grafting hydrophilic vinyl monomers such as hydroxy- ethyl methacrylate (HEMA) or acrylamide (AAm] via a radical-initiated reaction, or amino-terminated polyether glycols via a Michael-type addition mechanism, the hydrophilicity of these matrices was gradually increased, as previously described3. The ability of PAAs to create stable complexes with heparin has been extensively reportedg-‘2, and has been attributed to the strong ionic and electrostatic interactions, generated between the negatively charged heparin and the protonated tertiary amino nitrogens present in the PAA chain. This introductory study focusses on the grafting of poly(amidoamine) chains (PAA), aiming at developing heparinizable surfaces, and thus providing enhanced blood compatibility to the resulting polymers. Biomaterials 1992, Vol. 13 No. 7