New potentially biodegradable polyurethanes

New potentially biodegradable, thermoplastic multiblock copolymers from poly(lactic acid), poly (ε‐caprolactone) and/or poly(lactic acid‐ε‐caprolactone) copolymers were synthesized using toluene diisocyanate (TDI) as chain extender and poly(ethylene glycol) as intrinsic plasticizer. The structures of the resulting copolymers were unambiguously confirmed by NMR, IR and matrix assisted laser desorption ionization‐time‐of‐flight mass spectrometry (MALDI‐TOF MS) methods. The effects of the molar ratio of the polymers to TDI on the molar mass and on the mechanical properties of the resulting multiblock copolymers were also investigated. The mechanical properties such as tensile strength, Young's modulus, Shore A hardness and elongation at break of the multiblock copolymers suitable for making foils are compared with those of some relevant commercially available plastics. According to the comparative mechanical tests, some mechanical properties of the new biodegradable copolymers exceed those of the conventional plastics. Copyright © 2006 John Wiley & Sons, Ltd.