1. Introduction Recently, there has been renewed interest in apply- ing biodegradable thermoplastic elastomers (TPEs) for biomedical implants. TPEs are favored over chem- ically crosslinked networks because of their remold- ability and easy processability. Unlike crosslinked elastomeric networks, TPE demonstrates elastomeric properties due to physical crosslinks that are formed as a result of microphase separation between hard and soft segments. Typically, soft segments can pro- vide elasticity and flexibility while hard segments offer the necessary physical crosslink sites. Polyurethanes (PU) and poly(urethane urea) (PUU) have been intensively studied for several decades for mainly tissue engineering scaffolds and vascular implants because of their compatibility, elasticity and ease of surface modification. The hard segment in PUs typically contains diisocyanate, and their modification is an accepted way to alter properties of thermoplastic PU and PUU. One can enhance elasticity of PU by using an aliphatic diisocyanate instead of aromatic diisocyanate; and improve ten- sile strength and Young’s modulus by increasing hard segments content [1]. However, increasing the 897 Enhancing mechanical properties of thermoplastic polyurethane elastomers with 1,3-trimethylene carbonate, epsilon-caprolactone and L-lactide copolymers via soft segment crystallization S. S. Liow 1* , V. T. Lipik 1 , L. K. Widjaja 1 , S. S. Venkatraman 1 , M. J. M. Abadie 1,2 1 School of Materials Science and Engineering, Nanyang Technological University, 50, Nanyang Avenue, Singapore 639798, Singapore 2 Laboratory of Polymer Science and Advanced Organic Materials, LEMP/MAO, Université Montpellier 2, Place Bataillon, 34095 Montpellier Cedex 05, France Received 11 February 2011; accepted in revised form 13 April 2011 Abstract. Multiblock thermoplastic polyurethane elastomers based on random and triblock copolymers were synthesized and studied. Dihydroxyl-terminated random copolymers were prepared by ring opening copolymerization of !-caprolac- tone (CL) and 1,3-trimethylene carbonate (TMC). The triblock copolymers were synthesized by using these random copolymers as macro-initiator for the L-lactide (L-LA) blocks. These random and triblock copolymers were further reacted with 1,6-hexamethylene diisocyanate (HMDI) and chain extended by 1,4-butanediol (BDO). The polymer structure and chemical composition were characterized by 1 H NMR 13 C NMR and SEC. Their thermal and mechanical properties were studied by using DSC and Instron microtester. Multiblock polyurethanes based on random PCL-co-PTMC copolymers showed strain recovery improvement with increasing PCL content. However, these polyurethanes were unable to sustain deformation at body temperature due to the melting of PCL crystals and low hard segments content. With the presence of crystallizable PLLA blocks, mechanical properties were improved at body temperature without compromising their good strain recovery. Keywords: biodegradable polymers, thermoplastic polyurethanes, soft segment crystallinity, strain recovery, elastomers eXPRESS Polymer Letters Vol.5, No.10 (2011) 897–910 Available online at www.expresspolymlett.com DOI: 10.3144/expresspolymlett.2011.88 * Corresponding author, e-mail: Liow0019@e.ntu.edu.sg © BME-PT