Chinese Journal of Polymer Science最新文献

Polydimethylsiloxane (PDMS) is an electron-withdrawing material that is widely used in triboelectric nanogenerators (TENGs). However, PDMS has poor mechanical properties after curing and is easily damaged when subjected to long-term workloads. Thus, the long-term stable operation of TENGs under mechanical deformation cannot be guaranteed. In this work, multiple hydrogen bonds and aromatic disulfide bonds were introduced into PDMS elastomers. These elastomers exhibited high toughness (a tensile strength of 1.91 MPa and an elongation at break of 340%), good recyclability, and room-temperature self-healing properties (healing efficiency of 96.4% in 24 h). Recyclable sandwich-like triboelectric nanogenerators with excellent electrical output performance (13.5 V) and room-temperature self-healing performance (24 h, 98% recovery of self-generating performance) were prepared by utilizing the hydrogen bonding between the PDMS elastomer and MXene. The work reported herein offers theoretical guidance and a compelling strategy for developing high-performance TENG negative friction layers.

The development of physically crosslinked hydrogels with excellent mechanical and sensing properties is of importance for expanding the practical applications of intelligent soft hydrogel materials. Herein, after copolymerization of hydroxyl-containing amino acid derivative N-acryloyl serine (ASer) with acrylamide (AM), we introduce Zr⁴⁺ through an immersion strategy to construct metal ion-toughened non-covalent crosslinked hydrogels (with tensile strength of up to 5.73 MPa). It is found that the synergistic coordination of hydroxyl and carboxyl groups with Zr⁴⁺ substantially increases the crosslinking density of the hydrogels, thereby imparting markedly superior mechanical properties compared to hydroxyl-free Zr⁴⁺-crosslinked hydrogels, such as N-acryloyl alanine (AAla) copolymerized with AM hydrogels (with tensile strength of 2.98 MPa). Through the adjustment of the composition of the copolymer and the density of coordination bonds, the mechanical properties of the hydrogels can be modulated over a wide range. Additionally, due to the introduction of metal ions and the dynamic nature of coordination bonds, the hydrogels also exhibit excellent sensing performance and good self-recovery properties, paving the way for the development of flexible electronic substrates with outstanding comprehensive performances.

Crystal polymers or liquid crystal elastomers undergo a phase transition that results in a change in the corresponding optical properties, which has the potential to be applied in areas such as information encryption and anti-counterfeiting. The utilization of these materials for patterning purposes requires different phase transition temperatures. However, once prepared, altering the phase transition temperature of them presents significant challenges. Herein, a poly(oxime-ester) (POE) network is developed to achieve high-resolution and multilevel patterning by photo-induced isomerization. The as-prepared POE exhibits the ability to transition from an opaque state to a transparent state under temperature stimuli, with the transition temperature and kinetics dependent on UV light exposure time. Thus, complex patterns and information can be encrypted through different selective regional exposure time and decrypted under specific temperature or cooling time. Furthermore, we illustrate an example of temporal communication, where cooling time or temperature serves as the encoded information. This research expands the application scope of advanced encryption materials, showcasing the potential of POE in dynamic information encryption and decryption processes.

Adhesives play an important role in modern society’s production and daily life. Developing robust and sustainable adhesives remains a great challenge. Here we report a sustainable epoxy-vitrimer adhesive with high adhesive strength (about 10 MPa) and reusability (82% strength after 3 times). This adhesive can be fabricated from commercially available products through a straightforward hot-pressing method without the need of solvents. The adhesive process is also simple, requiring only 30 min at 180 °C. In addition, the vitrimer adhesive has the advantages of both erasability for reuse and excellent water resistance. This work provides a facile strategy to fabricate high-strength adhesive that ensures reusability, recyclability, low cost of raw materials, and simple processing technology. Simultaneously, it expands the range of potential applications for epoxy vitrimers.

Covalent adaptive networks (CANs) are capable of undergoing segment rearrangement after being heated, which endows the materials with excellent self-healing and reprocessing performance, providing an efficient solution to the environment pollution caused by the plastic wastes. The main challenge remains in developing CANs with both excellent reprocessing performance and creep-resistance property. In this study, a series of CANs containing dynamic covalent benzopyrazole-urea bonds were developed based on the addition reaction between benzopyrazole and isocyanate groups. DFT calculation confirmed that relatively low dissociation energy is obtained through undergoing a five-member ring transition state, confirming excellent dynamic property of the benzopyrazole-urea bonds. As verified by the FTIR results, this nice dynamic property can be well maintained after incorporating the benzopyrazole-urea bonds into polymer networks. Excellent self-healing and reprocessing performance is observed by the 3-ABP/PDMS elastomers owing to the dynamic benzopyrazole-urea bonds. Phase separation induced by the aggregation of the hard segments locked the benzopyrazole-urea bonds, which also makes the elastomers display excellent creep-resistance performance. This hard phase locking strategy provides an efficient approach to design CANs materials with both excellent reprocessing and creep-resistance performance.

Achieving versatile room temperature phosphorescence (RTP) materials, especially with tunable mechanical properties and shape memory is attractive and essential but rarely reported. Here, a strategy was reported to realize multi-functional RTP films with multicolor fluorescence, ultralong afterglow, adjustable mechanical properties, and shape memory through the synergistic dynamic interaction of lanthanide (Ln^III)-terpyridine coordination, borate ester bonds, and hydrogen bondings in a poly(vinyl alcohol) (PVA) matrix. By varying the amount of borax, the mechanical properties of the films could be finely controlled due to the change of crosslinking degree of dynamic borate ester bonds in PVA. The assembly and disassembly of borate ester bonds upon the trigger of borax and acid were applied as reversible linkage to achieve programmable shape memory behavior. In addition, the films displayed both fascinating multicolor fluorescence and ultralong afterglow characteristics due to the presence of Ln^III doping and confinement of terpyridine in PVA. This study provides a new avenue to impart modulable mechanical strength and shape memory to RTP materials.

Elastomers with high strength and toughness, excellent self-healing properties, and biocompatibility have broad application prospects in wearable electronics and other fields, but preparing it remains a challenge. In this work, we propose a highly adaptable strategy by introducing the small molecule crosslinking agent of triethanolamine (TEA) to the poly thioctic acid (PTA) chains and preparing the PA_xE_y elastomers using a simple synthesis step. This strategy stabilizes the PTA chains by constructing multiple non-covalent cross-linked dynamic networks, endowing materials with excellent strength and toughness (tensile strength of 288 kPa, toughness of 278.2 kJ/m³), admirable self-healing properties (self-healing efficiency of 121.6% within 7 h at 70 °C), and good biocompatibility. The PA_xE_y elastomers can also be combined with MWNTs to become flexible strain sensors, which can be used to monitor human joint movements with high sensitivity, repeatable responses, and stability.

Sulfur-containing dynamic polymers had attracted significant attention due to their unique chemical structures with high reversibility. Utilizating sulfur, an inexpensive industrial waste product, to synthesize dynamic polysulfide polymers through reverse vulcanization has been a notable approach. However, this method required high temperatures and resulted in the release of unpleasant oders. In this study, we presented a robust method for the preparation of sulfur-rich polymers with dynamic polysulfide bonds from elemental sulfur and inexpensive epoxide monomers via a one-pot strategy at the mild room temperature. Different types of polysulfide molecules and polymers were synthesized by reacting various epoxide compounds with sulfur, along with the investigation of their structures and dynamic behaviors. It was noteworthy that the obatined polymers prepared from m-(2,3-epoxypropoxy)-N,N-bis(2,3-epoxypropyl)aniline and elemental sulfur exhibit multiple dynamic behaviors, including polysulfide metathesis and polysulfide-thiol exchange, enabling their rapid stress relaxation, self-healing, reprocessing and degradable properties of the cross-linked polymer. More importantly, the hydroxyl groups at the side chains from epoxide ring opening exhibited potential transesterification. This work provided a facile strategy for designing dynamic sulfur-rich polymers via a mild synthesis route.

The incorporation of molecular switches into polymer networks has been a powerful approach for the development of functional polymer materials that display macroscopic actuation and function enabled directly by molecular changes. However, such materials sometimes require harsh conditions to perform their functions, and the design of new molecular photoswitches that can function under physiological conditions is highly needed. Here, we report the design and synthesis of a spiropyridine-based photoswitchable hydrogel that exhibits light-driven actuation at physiological pH. Owing to its high pK_a, spiropyridine maintains its ring-open protonated form at neutral pH, and the resulting hydrogel remains in a swollen state. Upon irradiation with visible light, the ring closure of spiropyridine leads to a decrease in the charge and a reduction in the volume of the hydrogel. The contracted gel could spontaneously recover to its expanding state in the dark, and this process is highly dynamic and reversible when the light is switched on and off. Furthermore, the hydrogel shows switchable fluorescence in response to visible light. Bending deformation is observed in the hydrogel thin films upon irradiation from one side. Importantly, the independence of this spiropyridine hydrogel from the acidic environment makes it biotolerant and shows excellent biocompatibility. This biocompatible spiropyridine hydrogel might have important biorelated applications in the future.