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 (T_trans = T_m,PPDO or T_m,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,A–B = 99.1 ± 0.1%, R_f,B–C = 81.7 ± 2.6%, R_r,C–B = 59.2 ± 1.2%, and R_r,C–A = 91.8 ± 6.3%.