Effect of the Crosslinking Degree on Self-Healing Poly(1,2,3-Triazolium) Adhesive.

Dynamic covalent materials are a class of polymer that could be stress-relaxation, reprocessable, and self-healing due to dynamic crosslinks in network. Dynamic crosslinks play an important role in the typical characteristic of self-healing polymers. It is meaningful to understand the effect of crosslinking degree on the properties of poly(1,2,3-triazolium) (PTAM). In this article, the dynamic covalent network of PTAM adhesive has been used to study the effect of crosslinking degree. A series of PTAM adhesive with different crosslinking degrees have been obtained by changing the amount of crosslinker. Adhesion property can first rise then fall down with the increase of crosslinking degree and the best lap-shear strength is above 20 MPa. Creep resistance and solvent resistance can be enhanced with the increase of crosslinking degree. Self-healing studies have shown that crosslinking degree can enhance the ability of self-healing, but too high crosslinking degree raises the temperature of self-healing and causes side reaction which reduces the self-healing efficiency. These results provide some insights for the influence of the crosslinking degree on the self-healing and the structural design of dynamic covalent materials.

Synthesis and Characterization of Block Copolymers of Poly(silylene diethynylbenzen) and Poly(silylene dipropargyl aryl ether).

Poly(silylene diethynylbenzene)-b-poly(silylene dipropargyloxy diphenyl propane) copolymer (ABA-A), poly(silylene diethynylbenzene)-b-poly(silylene dipropargyloxy diphenyl ether) copolymer (ABA-O), and a contrast poly(silylene diethynylbenzene) with equivalent polymerization degree were synthesized through Grignard reactions. The structures and properties of the copolymers were investigated via hydrogen nuclear magnetic resonance, Fourier transform infrared spectroscopy, Haake torque rheometer, differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis and mechanical tests. The results show that the block copolymers possess comprehensive properties, especially good processability and good mechanical properties. The processing windows of these copolymers are wider than 58 °C. The flexural strength of the cured ABA-A copolymer reaches as high as 40.2 MPa. The degradation temperatures at 5% weight loss (Td5) of the cured copolymers in nitrogen are all above 560 °C.

Automatically Programmable Shape-Memory Polymers Based on Asymmetric Swelling of Bilayer Structures.

Shape-memory polymers (SMPs) possess the capability to change shapes upon stimulation; however, the programming process that determines the temporary shape cannot proceed without external manipulation, which may greatly affect the shape complexity, accuracy, and reproducibility. Here, an automatically programmable SMP (AP-SMP) based on asymmetric swelling of bilayer SMP structures is demonstrated without external manipulation. In the automatic programming process, the AP-SMP can be deformed by the swelling of its hydrophilic hinge film in warm water to a temporary shape, which could be fixed by the glass transition of the two SMP films through cooling and drying in air. Owing to the unique ability, many complex shapes can be easily customized through diverse design strategies. Moreover, the AP-SMPs can reversibly transform between the permanent and temporary shapes, and both shapes are free-standing in normal conditions. The automatic programming of AP-SMPs may greatly expand the potential application range of SMPs.

Novolac-based poly(1,2,3-triazolium)s with good ionic conductivity and enhanced CO2 permeation.

Novolac-based poly(1,2,3-triazolium)s with 1,2,3-triazolium side groups spaced by oligo(ethylene glycol), a new kind of poly(ionic liquid) membrane, was prepared via the well-known Click chemistry (1,3-dipolar cycloaddition reaction). The thermal properties, ionic conductivity and gas permeation performance of these self-standing membranes were investigated. The obtained membranes exhibit glass transition temperatures ranging from -1 °C to -7.5 °C, and a temperature at 10% weight loss above 330 °C. These membranes have good ionic conductivity (σ DC up to 5.1 × 10-7 S cm-1 at 30 °C under anhydrous conditions) as compared with the reported 1,2,3-triazolium-based crosslinked polymers. And they could be potentially used for CO2 separation as they exhibit enhanced CO2 permeability up to 434.5 barrer at 4 atm pressure.