Design, synthesis and characterization of novel biodegradable shape memory polymers based on poly(D,L-lactic acid) diol, hexamethylene diisocyanate and piperazine

A novel series of biodegradable shape memory polyurethane ureas (SMPUUs) were designed and synthesized based on poly(D,L-lactic acid) diol, hexamethylene diisocyanate and piperazine. Their structure, degree of crosslinking, thermal properties, shape memory behaviors and mechanical properties were characterized using Fourier transform infrared and 1H NMR spectroscopy, weight analysis, differential scanning calorimetry and tensile testing. The results reveal that successfully introducing the piperazine into the backbone of the SMPUUs gives them excellent shape memory behaviors and good mechanical properties. This, in combination with the ideal shape recovery temperature, which can be designed near human body temperature, could make these biodegradable polyurethanes of great interest as potential biomaterials for medical implantations. On increasing the percentage of hard content of the SMPUUs from 9.00 to 12.12 wt%, the shape fixation rate increases from 95.3 to 98.2%, but the shape recovery ratio decreases from 98.6 to 93.2%; also, both the tensile modulus and tensile strength increase, but elongation at break decreases. To profile the advantages of our SMPUUs, a polyurethane based on poly(D,L-lactic acid) diol, hexamethylene diisocyanate and 1,4-butanediamine was chosen as control. Copyright © 2011 Society of Chemical Industry