Physicochemical Characterization of Biodegradable Segmented Polyurethanes and Their Blends with Polylactide

Biodegradable segmented poly(urethane)s (SPUs) and poly(urethane-urea)s (SPUUs) were synthesized by a standard two-step prepolymer method using two kinds of diisocyanates (methyl 2,6-diisocyanatohexanoate (LDI) and 1,4-diisocyanatobutane (BDI)) and polycaprolactone diol (PCL) as a soft segment combined with two kinds of chain extenders (1,3-propanediol (PDO) and 1,4-butanediamine (BDA)) as a hard segment. Thermal analysis by differential scanning calorimetry, wide angle X-ray diffraction (WAXD), and small angle X-ray scattering measurements revealed that different kinds of diisocyanates and chain extenders in SPUU affected the crystallinity of PCL segment and the microphase separation structure consisted of soft and hard segments. Diffraction pattern in WAXD due to the crystallization of PCL components inhibited in the cases of two SPUUs with LDI-BDA and BDI-BDA hard segments. Furthermore, these two kinds of SPUU showed good elastic properties because the crystallization of PCL component was inhibited by the strong aggregation of hard segments. The mechanical properties and degradability of poly(L-lactide) (PLLA)/SPUU blends were also investigated. A toughness of PLLA was enhanced by blending with SPUU. Also, this blend shows degradation owing to the hydrolysis. It was revealed that brittleness of PLLA was improved through blending with biodegradable SPUU without sacrificing degradability.