Interpenetrating polymer networks of polyurethane and polytriazole: Effect of the composition and number average molecular weight of glycidyl azide polymer on the mechanical properties and morphology

Abstract

AbstractOn account of some special advantages of interpenetrating polymer networks (IPNs), the preparation of IPNs with excellent properties may be a promising way to strengthen the polyurethanes (PUs) and toughen the glycidyl azide polymer (GAP) based polytriazoles (PTAs). This work provides the effect of composition and number average molecular weight (Mn) of GAP on the mechanical properties and morphology of full‐IPNs. A series of IPNs based on the crosslinked Ace‐terminated GAP (Ace‐GAP) as polytriazole phase and crosslinked hydroxy‐terminated liquid fluorinated polymer (HTLF‐1500) as polyurethane phase (namely, GAP‐HTLF‐X full‐IPNs) were successfully fabricated via in situ polymerization without any catalysts at 80°C by azide–alkynyl click chemistry and hydroxyl‐isocyanate urethane reaction. These IPNs were characterized using attenuated total reflectance/Fourier‐transform infrared spectroscopy (ATR/FTIR), uniaxial tensile testing, swelling measurement, and scanning electron microscopy (SEM). The tensile strength of GAP‐HTLF full‐IPNs gradually increased by increasing the weight ratio of Ace‐GAP, but the breaking elongation dramatically decreased compared with elongation at break of HTLF polyurethane. In addition, a small Mn of GAP is beneficial in enhancing the tensile strength, elongation at break and toughness of the IPNs. However, a small Mn of GAP corresponds to increased difficulty of preparing GAP‐HTLF full‐IPNs. GAP1k‐HTLF full‐IPN was not successfully prepared. When the Mn of GAP was 2000 g/mol, the GAP2k‐HTLF‐80 full‐IPN exhibited prominent mechanical performance with a tensile strength of 83.1 MPa, elongation at break of 28.5% and fracture energy of 99.1 kJ/m3. Swelling measurement showed that when the weight ratio of GAP with larger Mn (5, 3, and 2 k) increased to more than 70%, the molecular interpenetration existed in the IPNs, demonstrating the presence of additional physical crosslinks and entanglement for full‐IPNs. SEM studies revealed that highly formed interpenetration and few microphase separations can be observed on the fracture surface of the IPNs with optimal mechanical properties. Combined with the results of mechanical properties, swelling measurement, and SEM studies, the degree of molecular interpenetration and microphase separation were beneficial to improve the mechanical properties of elastomers. This work can provide a certain guiding significance for the preparation of IPN with excellent properties.