Copolymers of glycidyl azide polymer (GAP) and poly (caprolactone) (PCL) were obtained by introducing PCL molecular chains at both ends or side groups of GAP molecular chains, respectively. GAP/PCL elastomers were prepared via polyurethane curing reaction and compared with GAP/PCL elastomers prepared by physical blending, in order to clarify the relationship between microstructure and macroscopic properties. The results showed that no GAP and PCL phase separation was observed in the chemically bonded GAP/PCL elastomers. The elongation at break of the thermosetting GAP/PCL block copolymer elastomer increased significantly from 268% to 300% due to the increase in molecular weight between crosslinking points. The GAP/PCL graft copolymer, with its longer PCL segment length and higher segment mobility, formed microcrystalline domains within the elastomer, resulting in a significant improvement in tensile strength from 0.32 MPa to 1.07 MPa. In addition, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) revealed that the glass transition temperature of the GAP/PCL elastomer was 2.6 °C lower than that of the pure GAP elastomer, and the thermal stability was also enhanced.
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