Synthesis and characterization of biodegradable acrylated polyurethane based on poly(ε-caprolactone) and 1,6-hexamethylene diisocyanate

• We synthesized biodegradable acrylated polyurethanes (PUA) based on PCL and HDI.
• Morphological and mechanical properties were investigated experimentally.
• Increasing crystallinity and hard segment content enhances the mechanical properties.
• Hydrolytic degradation was associated with surface tension and amorphous structure.

A series of biodegradable acrylic terminated polyurethanes (APUs) based on poly(ε-caprolactone) diol (PCL), aliphatic 1,6-hexamethylene diisocyanate (HDI) and hydroxyethyl methyl acrylate (HEMA) was synthesized as potential materials for hard tissue biomedical applications. PCLs with low molecular weights of 1000 and 2000 g/mol were employed to provide different amounts of end capped urethane acrylate in APUs. To control crosslink density, a mixture of two different reactive diluents including mono-functional HEMA and bi-functional ethylene glycol dimethacrylate (EGDMA) with different weight ratios was incorporated into the APUs, called here PUAs. Morphological characteristics and mechanical properties were investigated using X-ray diffraction (XRD), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). DMA results indicated some degree of microphase separation between hard and soft segments; however, the microphase separation is more prominent for PUAs with higher molecular weight PCL. It was also found that the degree of crosslinking dominated greatly the formation of crystalline structure. PUAs with low crosslink density exhibited crystalline microstructure. The results also indicated that the mechanical properties of PUAs were governed considerably by crystalline microstructure, and hard segment content. All PUAs demonstrated hydrophobic behavior and were able to be degraded hydrolytically. The degradation process was closely related to the microstructure and surface tension of PUAs.