Blends of L-tyrosine based polyurethanes for biomaterial applications

Abstract

Abstract. Three polyurethane blends were made from segmented polyurethanes synthesized from desaminotyrosyl tyrosine hexyl ester (DTH), an L-tyrosine based diphenolic dipeptide, as chain extender. The soft segment of these polyurethanes is either polyethylene glycol (PEG) or polycaprolactone diol (PCL) and the diisocyanate is hexamethylene diisocyanate (HDI). The blends were developed to investigate the effect of varying composition on the overall physical, thermal, mechanical, surface and degradation properties of the material. The characterization results show that the properties of these blended materials can be controlled by adjusting the composition. Blends with increased PEG based polyurethane exhibited more water absorption and higher degradation characteristics. With increasing PCL based polyurethane, the mechanical properties of the blends were improved although the blends were relatively more amorphous in nature. The L-tyrosine based polyurethane blends hold the potential for use in different biomaterial applications.Keywords: polymer blends and alloys, L-tyrosine, polyurethane, poly(caprolactone), poly(ethylene glycol) eXPRESS Polymer Letters Vol.1, No.11 (2007) [724][725][726][727][728][729][730][731][732][733] Available online at www.expresspolymlett.com DOI: 10.3144/expresspolymlett.2007.100 urethanes are either PEG or PCL and the diisocyanate is hexamethylene diisocyanate (HDI). These polyurethanes have a wide range of physicomechanical properties that are suitable for tissue engineering applications. The structures of the polyurethanes are shown in Figure 1. The polyurethanes synthesized from PEG exhibit poor mechanical properties and a high rate of degradation whereas PCL based polyurethanes have better mechanical properties but very slow degradation rates. In this work, three blends of L-tyrosine based polyurethanes were fabricated by using different compositions of the two polyurethanes. Structural and morphological characterization of the blends was carried out by spectroscopic, thermal and microscopic techniques. In addition, contact angle, water absorption and hydrolytic degradation studies were done to investigate the applicability of the systems for biomaterial applications. Experimental MaterialsL-tyrosine, desaminotyrosine, Ethyl-N'-dimethylaminopropyl carbodiimide (EDC.HCl), polyethylene glycol(PEG), poly caprolactone diol(PCL), hexamethylene diisocyanate (HDI) were obtained from Sigma Aldrich, St. Louis(MO) USA. n-Hexanol, tetrahydrofuran, N-N'dimethylformamide (DMF), and chloroform were obtained from Fisher Scientific, Pittsburgh(PA) USA. The solvents were analytical grade and were used as received, unless otherwise mentioned. De-ionized water was used for all purposes. Two different L-tyrosine based polyurethanes were synthesized from either polycaprolactone diol (PCL, M w = 1250 g/mol) or polyethylene glycol (PEG, M w = 1000 g/mol), as the polyol and hexamethylene diisocyanate (HDI) as the diisocyanate. The chain extender was desaminotyrosyl tyrosine hexyl ester (DTH), a di...

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