The mechanical properties of the copolymers were evaluated in a quasi-static tensile tests. Figure shows the stress-strain curves of the copolymers in quasi-static conditions, and the numerical data are also presented in Table . The copolymers showed stress-strain curves typical for thermoplastic elastomers with yield point and rubber-like elasticity. The tensile strength of copolymers with higher hard segments content, i.e. PBS-DL 70-30 showed an increase by 7 MPafrom 17 MPa to 25 MPa when compared to PBS-DLS 60-40. The reason is that the hard segments are responsible for load transfer through crystalline domains, and thus the higher degree of crystallinity of PBS-DLS 70-30 contributed to higher toughness. The incorporation of PEG into PBS copolymer containing 70 wt.% of hard segments content did not affect tensile strength but contributed to enhanced extensibility reaching 820% elongation at break. One explanation of this behaviour is the presence of PEG 6000 crystallites and these crystallites might absorb strain energy upon deformation similar to segmented polyurethanes containing crystallizing soft segments and thus indicating synergistic effect of both PBS and PEG 6000 building blocks. In case of copolymer with lower hard segments content (60 wt.%), incorporation of PEG 6000 reduced both tensile strength (from about 17 MPa to 10 MPa) and elongation at break (from around 830% to 310%). The reason of the loss of elasticity might be triggered by phase separation of hard and soft domains in these copolymers thus losing an effective load transfer ability . The mechanical properties of synthesized copolymers are generally promising for biomedical applications, especially for soft tissue engineering, since for example, mammary artery shows tensile strength of 4.3-10 MPa.