Enhanced mechanical properties of linear segmented shape memory poly(urethane-urea) by incorporating flexible PEG400 and rigid piperazine

The goal of this study is to design and synthesize a linear segmented shape memory poly(urethane-urea) (SMPUU) that possesses near-body-temperature shape memory temperature (T_tran) and enhanced mechanical properties by incorporating flexible poly(ethylene glycol) 400 (PEG400) to form poly(D,L-lactic acid)-based macrodiols (PDLLA--PEG400--PDLLA) and then rigid piperazine (PPZ) as a chain extender to form the desired SMPUUs (PEG400--PUU--PPZ). PEG400 increased M_n while maintaining a lower T_g of PDLLA--PEG400--PDLLA, which together with PPZ improved the mechanical properties of PEG400--PUU--PPZ. The obtained optimum SMPUU with enhanced mechanical properties (σ_y = 24.28 MPa; ?_f = 698%; U_f = 181.5 MJ/m³) and a T_g of 40.62°C exhibited sound shape memory properties as well, suggesting a promising SMPUU for in vivo biomedical applications.