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

Novel 2-ureido-4-pyrimidinone-functionalized poly(3-caprolactone)/poly(p-dioxanone) interpenetrating polymer networks (PCU/PPDO IPNs) are developed via cross-linking star-shaped (PCU)-P-4 and (PPDO)-P-4 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 H-1 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 (T-trans = T-m,T-PPDO or T-m,T-PCU). Dynamic mechanical analysis (DMA) reveals that PCU/PPDO IPNs show pronounced differences in the storage modulus below and above the two T-trans 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: R-f,R-A-B = 99.1 +/- 0.1%, R-f,R-B-C = 81.7 +/- 2.6%, R-r,R-C-B = 59.2 +/- 1.2%, and R-r,R-C-A = 91.8 +/- 6.3%.