Novel triple-shape PCU/PPDO interpenetrating polymer networks constructed by self-complementary quadruple hydrogen bonding and covalent bonding

Abstract

Novel 2-ureido-4-pyrimidinone-functionalized poly(ε-caprolactone)/poly(p-dioxanone) interpenetrating polymer networks (PCU/PPDO IPNs) are developed via cross-linking star-shaped 4PCU and 4PPDO by self-complementary quadruple hydrogen bonding and covalent bonding in one-pot, respectively. PCL–PPDO co-networks (PCL–PPDO-CN) were also prepared for comparison. The structures of all the precursors were determined by 1H NMR, and all networks and IPNs were evaluated by swelling tests. The results of differential scanning calorimetry (DSC) analysis indicates that most of the PCU/PPDO IPNs and PCL–PPDO-CN have two well-separated melting peaks, which is the essential property for triple-shape effects (TSE). Nevertheless, the crystalline abilities of the PCL and PPDO segments in the IPNs are much better than that in the co-networks. Moreover, the composition of the IPNs has no obvious effect on the two transition temperatures (Ttrans = Tm,PPDO or Tm,PCU). Dynamic mechanical analysis (DMA) reveals that PCU/PPDO IPNs show pronounced differences in the storage modulus below and above the two Ttrans than that of PCL–PPDO-CN with the same compositions. The cyclic TSE tests demonstrate that the unique structures of PCU/PPDO IPNs with low interference of each segment endows the material with excellent triple-shape properties. For a typical sample PCU30/PPDO70 IPNs the average R of cycles 2–4: Rf,A–B = 99.1 ± 0.1%, Rf,B–C = 81.7 ± 2.6%, Rr,C–B = 59.2 ± 1.2%, and Rr,C–A = 91.8 ± 6.3%.