RESUMO
Addressing the demand for integrating strength and durability reinforcement in shape memory polyurethane (SMPU) for diverse applications remains a significant challenge. Here a series of SMPUs with ultra-high strength, self-healing and recyclability, and excellent shape memory properties through introducing dynamic boron-urethane bonds are synthesized. The introducing of boric acid (BA) to polyurethane leading to the formation of dynamic covalent bonds (DCB) boron-urethane, that confer a robust cross-linking structure on the SMPUs led to the formation of ordered stable hydrogen-bonding network within the SMPUs. The flexible crosslinking with DCB represents a novel strategy for balancing the trade-off between strength and durability, with their strengths reaching up to 82.2 MPa while also addressing the issue of durability in prolonged usage through the provision of self-healing and recyclability. The self-healing and recyclability of SMPU are demonstrated through rapid dynamic exchange reaction of boron-urethane bonds, systematically investigated by dynamic mechanical analysis (DMA). This study sheds light on the essential role of such PU with self-healing and recyclability, contributing to the extension of the PU's service life. The findings of this work provide a general strategy for overcoming traditional trade-offs in preparing SMPUs with both high strength and good durability.
RESUMO
Shape memory polymer (SMP)-based smart molds, which could provide high-resolution mold shape and morph in response to external stimuli for readily demolding the complex structure, attract extensive attention. However, the suitable SMP for smart molds is usually confined with low stretchability that likely causes damage during demolding. Herein, we present a cyanate ester smart composite (CESC) with a reconfigurable, solvent-processable, and near-infrared (NIR)-triggerable shape memory effect (SME), which enables the 2D sheet with a variety of morphed complex shapes through deformation in a mild situation. Notably, the reconfigurable SME and the recyclability of the shape memory cyanate ester (SMCE) were addressed for the first time, attributed to the dynamic covalent bonds of transesterification and the novel cyanurate exchange. In addition, we found that the mechanism of solvent-processable SME is attributed to the varied cross-linking density and the mobility of the polymer chain. Integrating the multiple responsive SME and reconfigurable SME, the CESC demonstrated versatile applications as a smart mold. The results demonstrate a wide scope of application of the integrated SME and provide a new design strategy for thermoset cyanate materials.
RESUMO
The 4D-printing technology is applied to fabricate a shape memory peripheral stent with good biocompatibility, which sustains long-term drug release. The star polymer s-PCL is prepared by ring opening polymerization of ε-caprolactone with the -OH of ß-cyclodextrin (ßCD) as initiator, and then the s-PCL is modified with acrylate endgroup which allows the polymerization under UV light to form the crosslinking network c-PCL. Attributed to the feature of the high crosslinked structure and chemical nature of polycaprolactone (PCL) and ßCD, the composite exhibits appropriate tensile strength and sufficient elasticity and bursting pressure, and it is comparable with great saphenous vein in human body. The radial support of the 4D-printed stent is 0.56 ± 0.11 N and is equivalent to that of commercial stent. The cell adhesion and proliferation results show a good biocompatibility of the stent with human umbilical vein endothelial cells. Due to the presence of ßCD, the wettability and biocompatibility of the materials are improved, and the sustained paclitaxel release based on the host-guest complexion shows the potential of the drug-loaded stent for long-term release. This study provides a new strategy to solve the urgent need of small-diameter scaffolds to treat critical limb ischemia.