Self-healing Polyurethane Elastomer Research Articles

A robust self-healing polyurethane elastomer: From H-bonds and stacking interactions to well-defined microphase morphology

Self-healing materials have attracted considerable attention because of their improved safety, lifetime, energy efficiency and environmental impact. Supramolecular interactions have been extensively considered in the field of self-healing materials due to their excellent reversibility and sensitive responsiveness to environmental stimuli. However, development of a polymeric material with good mechanical performance as well as self-healing capacity is very challenging. In this study, we report a robust self-healing polyurethane (PU) elastomer polypropylene glycol-2-amino-5-(2-hydroxyethyl)-6-methylpyrimidin-4-ol (PPG-mUPy) by integrating ureidopyrimidone (UPy) motifs with a PPG segment with a well-defined architecture and microphase morphology. To balance the self-healing capacity and mechanical performance, a thermal-triggered switch of H-bonding is introduced. The quadruple H-bonded UPy dimeric moieties in the backbone induce phase separation to form a hard domain as well as enable further aggregation into microcrystals by virtue of the stacking interactions, which are stable in ambient temperature. This feature endows the PU with high mechanical strength. Meanwhile, a high healing efficiency can be realized, when the reversibility of the H-bond was unlocked from the stacking at higher temperature. An optimized sample PPG1000-mUPy50% with a good balance of mechanical performance ( 20.62 MPa of tensile strength) and healing efficiency (93% in tensile strength) was achieved. This strategy will provide a new idea for developing robust self-healing polymers.

Thermal- and mechanical-responsive polyurethane elastomers with self-healing, mechanical-reinforced, and thermal-stable capabilities

Previous studies have shown that the commonly used Diels-Alder (DA) bonds (furan and maleimide) cleaved at low temperatures (about 100 °C), which limits further application of these self-healing materials at higher temperatures. Hence, a series of thermo stable self-healing polyurethane elastomers (PUAn-DA-x) have been developed by using the reversible DA/retro-DA reactions initiated by thermal and mechanical stimuli between anthryl and maleimide functions. The synthesized linear polyurethane bearing pendant anthryl groups (PUAn-0) was effectively toward DA reactions with a bismaleimide crosslinker (BMI) to get covalently crosslinked PUAn-DA-x networks. Tensile test showed that the stress at break of PUAn-DA-1/1 was increased by more than 261% after the PUAn-0 was effectively networked by DA bonds. At the same time, with the aid of hydrogen bonds and chains’ rearrangement, the healing efficiency of PUAn-DA-1/1 could reach as high as 91.28% via the recombination of mechanically decoupled anthracene and maleimide without causing deformation of bulk specimens. In addition, the thermal stabilities of the DA bonds and PUAn-DA-x were studied.

Synthesis and properties of room-temperature self-healing polyurethane elastomers

ABSTRACTTwo kinds of polyurethane elastomers were synthesized. One containing acylhydrazone bonds was named TPIA. The other containing both acylhydrazone and disulfide bonds was named TPID. Self-repairable ability and reprocessability of these two elastomers were studied. The results show that: The polyurethane elastomer TPIA can automatically repair damage to it under acidic conditions. After self-healing for 24 h, the strength and the elongation value at break recovered to 32% and 55% of the originality, respectively. The polyurethane elastomer TPID can automatically repair damage to it under visible light at room temperature. After 24 h of self-healing time, 75% of the original strength and 100% of the original elongation values at break were obtained. These two polyurethane elastomers can be reprocessed in their cured state by just applying temperature and pressure.