A mild degradation approach applicable to diverse polyacrylates and polymethacrylates without resorting to cyclic monomers and expensive catalysts is proposed.

Stereoisomerism exerts critical influence on the physicochemical properties and biofunctionality. Precise regulation of stereoisomeric composition enables programmable manipulation of polymeric aggregation states and macroscopic properties. Herein, the trans-cis isomerization mechanism inherent to alicyclic PA10C was comprehensively deciphered through an integrated experimental and computational methodology. Primarily, regulated polymerization was conducted under varied thermal regimes within a reactor environment to strategically manipulate the stereoisomeric ratio. Experimental results demonstrated that isomerization transpires at temperatures as low as 170 degrees C, with trans-PA10C as the predominant configuration. Subsequently, the energy barrier of trans-to-cis isomerization of PA10C was calculated using Density Functional Theory (DFT) to be 72.9 kcal/mol. This suggests that configurational inversion necessitates thermal activation exceeding 300 degrees C, exhibiting a substantial discrepancy with experimental observations at 170 degrees C. Theoretical simulations further corroborated that H2O markedly reduced the activation energy to 29.2 kcal/mol, as water cluster facilitate rapid proton transfer through dynamic hydrogen bond during polymerization. Furthermore, trans-PA10C macromolecules adopt a centrosymmetric structure, which facilitates dense packing into crystalline regions with an energy barrier of 7.6 kcal/mol. Therefore, trans-to-cis isomerization requires overcoming the hydrogen bond energy, thereby resulting in the thermodynamic predominance of the trans-configuration. Ultimately, stereoisomerism dynamics of cis/trans-PA10C was carried out, and their characteristic critical isomerization temperature were determined to be 204 degrees C and 300 degrees C, respectively.

Metal halide perovskite nanocrystals (PNCs) are widely employed to photo-catalyze homogeneous reversible deactivation radical polymerization owing to their excellent photophysical properties. However, the structural vulnerability fundamentally impedes their further application in polymerization involving polar solvents, water in particular. Photoinduced reversible addition-fragmentation chain transfer (RAFT) dispersion polymerization, frequently utilizing water as the dispersion medium, facilitates the one-pot fabrication of well-defined nano/microstructured polymers. It is of significance to extend the utilization of PNCs in this heterogeneous polymerization. Herein, water-stable CsPbBr3 NCs are judiciously crafted, exhibiting aqueous structural integrity while maintaining charge transportation capability. Consequently, highly uniform polymethyl methacrylate microspheres could be prepared by photoinduced PNC-catalyzed RAFT dispersion polymerization. This photo-RAFT dispersion polymerization could be readily extended to synthesize various polyvinyl microspheres. Moreover, photo-RAFT dispersion polymerization could be accomplished under near-infrared light owing to the two-photon absorption ability of PNCs, which is inaccessible to conventional photo-RAFT dispersion polymerization.

4D printing of shape memory polymers (SMPs) allows the 3D-printed structures to have adjustable shapes, properties, and functionalities, paving the way for intelligent devices and multifunctional applications. However, 4D-printed SMPs face challenges due to mechanical anisotropy and mediocre shape memory performance hampered by weak interlayer adhesion. This study innovatively integrates shape memory polyamide elastomer with 4D printing technology to develop a multifunctional intelligent orthosis. Here, a dynamic bonds (DBs) reinforced shape memory polyamide elastomer is developed using a twin-screw extruder through reactive extrusion. Dynamic covalent networks are introduced into polyamide elastomer, which enhances interlayer adhesion in 4D-printed objects by utilizing combined effects of multiple dynamic covalent bonds (DCBs) and hierarchical hydrogen bonds (DHBs), leading to the reduction of mechanical anisotropy and improvement of the mechanical and shape memory properties of the 4D printouts. 4D-printed objects demonstrated excellent macroscopic shape memory and reconfiguration, showcasing the versatility of this material, and the application for spinal orthosis is also demonstrated.

The increasing demand for transparent and flexible materials to protect foldable smartphones and curved displays has revealed the limitations of traditional transparent polymer materials such as polycarbonate (PC) and polymethyl methacrylate (PMMA). These materials are prone to cracking after bending or folding and becoming opaque after scratch, thereby compromising the using feeling of flexible screens. As a result, they struggle to simultaneously possess both transparent and flexible characteristics for a long using time. To meet the diverse requirements of various applications, transparent polyamide elastomer was successfully synthesized by one-step polycondensation of isophthalic acid (IPA) adipic acid (ADA), 4,4'-diaminodcoiicyclohexylmethane (PACM), hexamethylenediamine (HMD) and polyether amine (ED900). The polyamide hard segments confer excellent strength, toughness, wear resistance, chemical stability, low-temperature impact resistance and self-lubrication to the material. Simultaneously, the polyether soft segments enhance the material's ductility and flexibility. The elastomers exhibited outstanding thermal stability, transparency of similar to 91% and mechanical properties with tensile strength of 26-29 MPa and elongation at break of 300% - 600%. Among them, two elastomers with broad glass transition temperature possessed multiple shape memory behavior, and showed no crease after cyclic folding up to 10,000 times demonstrating excellent bending fatigue resistance to long-time and repeated deformation. Therefore, the novel transparent polyamide elastomer with the advantages of good transparency, flexibility, wear and fatigue resistance can be sprayed or daubed in solution on the surface as a smart and peelable protective coating, holding vast potential for widespread applications in the fields of electronic devices, flexible display and optical devices.

Thermoplastic polyamide elastomer (TPAE) is usually synthesized by polycondensation of polyamide and polyether or polyester through esterification/amidation in a stainless steel reactor, which requires harsh reaction conditions and a long reaction time. Unfortunately, this synthetic method cannot produce a high-viscosity sample or a micro-cross-linked sample. In the present work, a kind of TPAE named poly(urethane-urea-amide) (PUUA) was prepared by amino-terminated long carbon chain polyamide 1212 (PA1212) and diisocyanate-terminated polytetramethylene ether glycol (PTMG) through reactive extrusion, which simplified the reaction conditions and shortened the reaction time. Through combining different PA1212 hard segments and PTMG soft segments, PUUAs showed excellent and adjustable mechanical and thermal properties. And the tensile strength and elongation at break could vary in the range of 6-38 MPa and 180-490%, respectively. With the aid of melting/crystallization temperature or glass transition temperature, PUUA exhibited an outstanding one-way shape memory effect (1W-SME) with a shape fixation ratio (R f) of similar to 97.5% and two-way shape memory effect (2W-SME) with a response strain (epsilon res) of 3.8-14.3% for quasi 2W-SME and similar to 2.9% for reversible 2W-SME. Furthermore, PUUA was processed into the wire for fused deposition modeling (FDM), followed by optimization of printing parameters, and then printed into a "swan" possessing a 2W-SME achieving 4D printing. The reactive extrusion production technology not only offers a simple way for synthesizing TPAE industrially but also broadens the application range of TPAE.

A well-defined multidentate polycationic diblock copolymer with multiple quaternary ammonium and sulfonium groups is judiciously synthesized via living radical polymerization. This polymer can serve as a strong passivating ligand to replace the short ligand on a perovskite nanorod, thereby significantly enhancing its colloidal stability, moisture stability, photostability and thermal stability.

Polymerization regulated via photocatalysts offers unprecedented spatiotemporal control over reversible deactivation radical polymerization, enabling the preparation of macromolecules with precise molecular weight control and well-defined architectures. Photoinduced electron/energy transfer reversible addition-fragmentation chain transfer (PET-RAFT) polymerization is highly adaptable owing to its wide range of monomer applicability, oxygen tolerance, and mild polymerization conditions. There has been a push to develop innovative photocatalysts with extended light harvesting ability and enhanced photoactivity for the purpose of potential green chemistry. Herein, judiciously designed potassium poly(heptazine imide) (K-PHI) is proposed as a highly effective photocatalyst for oxygen-tolerant PET-RAFT polymerization under visible light. K-PHI is crafted via post-treatment of graphitic carbon nitride (g-C3N4) in molten salts, which facilitates the mass transfer and polymerization of melon-based structure. Such post-treatment substantially boosts the crystallinity of K-PHI and imposes a profound impact on photophysical properties and carrier transport efficiency of K-PHI. As a result, structurally optimized K-PHI enables a 16.6-fold increase in photopolymerization rate compared to traditional g-C3N4 while maintaining excellent control features (i.e., low dispersity, high chain-end fidelity, etc.). Furthermore, universal monomer adaptation, general chain transfer agent, and recycle capability are scrutinized to demonstrate the robustness and versatility of K-PHI in the oxygen-tolerant PET-RAFT polymerization.

Piezoelectric polymer textiles offer distinct advantages in the fabrication of wearable nanogenerators (NGs). One effective strategy to enhance the output capacity of NGs is to modulate the piezoelectric performance of the textiles. This paper focuses on further improving the piezoelectric properties of nylon-11,11 textiles through post-drawing and annealing treatments. We elucidate the evolution of morphology and the ferroelectric phase in the submicron/nanoscale fibers during post processing as well as the corresponding changes in performance. The drawing process primarily enhances the orientation of the crystalline phase and reduces the fiber diameter, while the annealing process more effectively promotes the crystal size and crystallinity. Afterward, we propose an optimal postdrawing and annealing assisted-electrostatic spinning process. Under the synergistic effects of these post-treatments, the remanent polarization (Pr) of nylon-11,11 textile increased to 4.7 times that of the untreated textile, resulting in amplified piezoelectric outputs. The output voltage, current, and power density of the prepared PENG reached 21.5 V, 800 nA, and 1.88 mW·m-2 (80 MΩ), respectively. Notably, at pressures exceeding 8 kPa, the mechano-voltage and current sensitivity reached as high as 266 mV/kPa and 13.99 nA/kPa, respectively, which is extraordinary compared to other piezoelectric NGs and comparable to the performance of nylon-based triboelectric NGs. Furthermore, we investigated the potential application of the prepared PENG in biomechanical energy harvesting and human movement monitoring. Experiments demonstrated its effectiveness in powering light bulbs, tracking walking status, and monitoring finger/hand/wrist gestures.

In the field of self-powered sensing, the need for wearing comfort and flexibility of the material is increasing. Although piezoelectric ceramics have excellent piezoelectric properties, their poor flexibility limits their application range. In the quest for better wearing comfort, nanocomposite polymers using elastomers as polymer matrices are rapidly emerging. However, there still exists a challenge to achieve uniform dispersion of nanofillers in the polymer matrix due to their significant difference in surface energy. In this work, a novel thermoplastic polyamide elastomer (TPAE) based nanocomposite with strong interfacial strength and uniform dispersion was proposed, which was achieved through incorporating γ-aminopropyltriethoxysilane (KH550)-functionalized BaTiO3 nanoparticles (KH550@BTO) into in situ polycondensation of TPAE for flexible piezoelectric nanogenerators (PENGs) with sensing capability. The PENGs not only possessed excellent mechanical properties (elongation at break ∼ 400%) but also exhibited good piezoelectric behavior (VOC ∼ 19 V, ISC ∼ 121 nA). Moreover, the PENGs exhibited excellent durability, stability (6000 cycles without degradation), and rapid response time (∼21 ms), which was superior to those of most reported BTO-based nanocomposites. Based on the performance, the PENG could be used to monitor human motions after the assembly of wireless wearable devices, and different badminton serving postures were further recognized by the assistance of machine learning. This work provides an innovative approach for the preparation of soft piezoelectric nanocomposites, which is helpful for self-powered and wireless flexible sensors with better performance and more comfortable use in human motion monitoring and recognition.

Polyamide 66 (PA66) with less entangled structure, high crystallinity and excellent mechanical properties was fabricated in this work by direct solid-state polymerization (DSSP) method. The polymerization process and mechanism of DSSP were systematically investigated. Results demonstrate that DSSP is a transition process from salt crystal directly to polymer crystal, enabling the production of PA66 with a less entangled and highly crystalline structure. DSSP sample exhibits a crystallinity of 51.8 % as tested by WAXD, and 59.7 % when measured via DSC, surpassing the crystallinity of the majority of PA66 fibers. Furthermore, the sample achieves a maximum melting point of 271.7 degrees C. Correspondingly, mechanical properties and heat distortion temperature of DSSP sample are also improved. Therefore, this work enhances the in-depth understanding of polymerization mechanism of DSSP, and provides an efficient, scalable approach for fabricating polymers with less entanglement, high crystallinity, and exceptional performance characteristics.

Non-traditional intrinsic luminescent polymers (NTILPs) have shown great potential in bioimaging and anti-counterfeiting applications. However, the intrinsic luminescence mechanism in these polymers is still under debate, with clustering-triggered emission (CTE) theory being one of the most plausible explanations; yet, further research is needed. In this work, starting from acylamination of tartaric acid, we synthesized a pair of chiral polyamides, PA6LAT and PA6DAT. Circular dichroism spectroscopy confirmed the opposite helical conformations of PA6LAT and PA6DAT, exhibiting pronounced aggregation chirality amplification behavior and demonstrating typical CTE characteristics. The solid-state powders of the polyamides showed finely tunable multicolor fluorescence under different excitation wavelengths. The presence of through-space conjugations in the polyamides was further confirmed through theoretical calculations, revealing the significance of amide clusters and oxygen clusters in their CTE behavior. Interestingly, changing the solvent from HFIP to DMSO enabled single emission behavior in polyamide solutions, with the emission peak precisely tunable from 430 nm to 485 nm. This solvent-dependent shift was attributed to the differential dissociation of amide and oxygen clusters in these two solvents, corresponding to the opposite optical rotation of the polyamides induced by solvents. The fluorescence behavior in solvents also further confirmed the emission mechanism triggered by amide and oxygen clusters in PA6LAT and PA6DAT. This study deepened the understanding of the intrinsic luminescence mechanism of polyamides, reporting for the first time the precise tuning of the fluorescence behavior of NTILPs and the underlying mechanism through solvent-induced effects, contributing to a better understanding of the multicolor luminescence behavior of NTILPs.

Piezoelectric nanogenerators (PENGs) have been attracting considerable attention as an efficient solution for harvesting environmental mechanical energy. Among the piezoelectric materials for the fabrication of PENGs, piezoelectric polymers have shown unique advantages, particularly for self-powered systems in wearable devices. However, the variety of piezoelectric polymers studied for the PENG development has been relatively limited, leaving room for advancements in their performance. In this study, we introduced odd-odd piezoelectric nylon (nylon 11,11) for the first time for PENG fabrication. Electrospinning conditions were studied to yield nylon 11,11 nanofibers with uniform morphology and optimized piezoelectric crystalline states. The influence of concentration of the electrospinning solution on the fiber morphology and piezoelectric-active gamma crystal structure is elucidated, and the applied electric field is found to be critical in controlling the orientation of the ferroelectric crystal domain. Further, the correlation between the outputs of the as-prepared PENG and the characteristics of the nanofiber mats was established. Finally, the piezoelectric output of PENGs fabricated by NF-20 reached the maximum values, an open-circuit voltage of up to 22.0 V and a short-circuit current of approximately 300 nA, when subjected to a compressive force of 20 N at a frequency of 5 Hz on an area of 6.25 cm(2). Also, it enabled the conversion of mechanical energy into electricity with an instantaneous output power density of 9.13 mW m(-2) (60.9 mW m(-3), 0.18 G Omega). Importantly, the as-prepared PENGs consistently exhibit unwavering and reliable piezoelectric performance in a variety of practical applications, including continuous compression, successive daily wear, energy harvesting from routine physical activities, and the transition of sign language into electric signals. Therefore, nylon 11,11 nanofiber PENGs hold substantial potential and advantages for the design of self-powered devices and electromechanical responsive equipment. Piezoelectric nanogenerators based on nylon 11 enable efficient harvesting of environmental energy, serving as a green energy source.

ABSTRACTAzobenzene (Azo) liquid‐crystalline polymers are intriguing due to their unique photo‐induced isomerization and supramolecular chirality. However, clarification on multicomponent chiral induction towards Azo polymers remains ambiguous and challenging. Herein, chiral solvents and amines were employed to control the chiroptical activity of achiral Azo polymers. Methyl L‐/D‐lactate was added as the poor solvent and chiral inducer to achieve the first chiral induction in Azo aggregates. Chiral amines were utilized for the second chiral induction based on the acid–base interactions between the carboxyl groups of polymers and amines. The chiral enhancement and inversion of Azo units could be observed through the synergistic or antagonistic effect between solvents and amines. The impacts of solvent, chemical structures, feed ratio, enantiomeric excess, and temperature on supramolecular chirality were systematically studied. Furthermore, this system displayed the chiroptical switching property and chiral recovery under reversible irradiation.

Liquid metal (LM) and liquid metal alloys (LMs) possess unique physicochemical features, which have become emerging and functionalized materials that are attractive applicants in various fields. Herein, uniform LM nanodroplets armored by carbon dots (LMD@CDs) were prepared and exhibited high colloidal stability in various solvents, as well as water. After optimization, LMD@CDs can be applied as functional additives for the 3D/4D printing of hydrogel and cross-linked resin through digital light processing (DLP). The light absorption of LMD@CDs not only improved the printing accuracy, but also led to the cross-linking density differential during the post-curing process. Base on the cross-linking density differential of soft hydrogel and photothermal performance of the LM, the 3D printed objects can exhibit stimulus responses to both water and laser irradiation. Additionally, the CDs shell and LM core of LMD@CDs provide the printed objects interesting photoluminescence and electric conductivity capabilities, respectively. We deduce this versatile 3D/4D printing system would provide a new platform for the preparation of multi-functional and stimuli-responsive advance materials.

Electro-induced two-way shape memory polymer is a kind of smart material which can realize bidirectional reversible actuation under current stimulation. However, due to the limitation of materials, there are few studies on the electro-induced two-way shape memory effect. Herein, the two-way shape memory effect of a new type of semi-crystalline thermoplastic polyamide elastomer (TPAE, T12) was systematically studied. The response strain (εact) of two-way shape memory effect for T12 under constant stress and stress-free condition could reach 16.4 % and 9.7 %, respectively. The introduction of multi-walled carbon nanotubes (CNTs) endowed the T12 material with good conductivity, and CNTs did not significantly influence the two-way shape memory performance of T12/CNTs composite. Moreover, when the content of CNTs was 5 wt%, the surface temperature of T12/CNTs composite could reach 36 °C–90 °C at a voltage of 90 V–150 V. Then, we realized the electro-induced two-way shape memory behavior of T12/CNTs composite through the construction of bilayer SEBS/T12/CNTs actuator. Therefore, T12 material, as a new two-way shape memory TPAE, has great application potential in aerospace, soft robotics, medical and other fields.

Maintaining uniform dispersion of nano filler under high content is critical for fabricating polymer-based composites with great mechanical and thermally conductive properties. In this work, BNNS/PA12T nanocomposite with the highest boron nitride nanosheet (BNNS) content of 23.1 wt% was successfully prepared by the aqueous solution-assisted in-situ polymerization method. Results demonstrate that the BNNS can be uniformly dispersed in the composite due to the low viscosity during the polymerization process. As a result, when the content of BNNS is 23.1 wt%, the mechanical properties and thermal conductivity of BNNS/PA12T nanocomposite are 62 MPa and 1.55 W/(mK). Furthermore, the composites also possess excellent high-temperature resistance with the coefficient of thermal expansion (CTE) of 60 ppm/degrees C, about one third of pure PA12T, and the thermal deformation temperature also reaches 139.4 degrees C. Therefore, the fabricated BNNS/PA12T nanocomposite can be effectively applied as thermal management and packaging materials for electronic devices.Highlights BNNS/PA12T nanocomposites were prepared by aqueous solution-assisted method. BNNS can be uniformly dispersed at the filling content up to 23 wt%. The thermal conductivity of BNNS/PA12T nanocomposite can reach 1.55 W/(mK). Possessing excellent mechanical properties and dimensional stability. The nanocomposite can be effectively applied for thermal management.