Polymer最新文献

The electromechanical properties of PVDF-based polymers, namely converting electrical into mechanical energy, are mainly decided by the crystal structure and domain size of the target product. Thus, we prepare the poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)), its terpolymer poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)), and tetrapolymer poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene -hexafluoropropylene) (P(VDF-TrFE-CFE-HFP)) films for comparison, respectively, where the role of the introduction of third and fourth monomers in the electromechanical properties of P(VDF-TrFE) is completely disclosed. Because of introducing CFE and HFP monomers, P(VDF-TrFE) with the ferroelectricity has converted into the relaxor ferroelectric P(VDF-TrFE-CFE-HFP) with a slimmer P-E loop while maintaining good maximum polarization (P_m). Since the nano ferroelectric domains in the relaxor ferroelectric material are easy to reverse along the polarizing electric field, The P(VDF-TrFE-CFE-HFP) sample achieved a dielectric constant (ε_r) of ∼29 and a strain in the thickness direction (S₃₃) of ∼ -5%, respectively, while the ε_r and S₃₃ of P(VDF-TrFE) sample are ∼11 and ∼-0.8 %, respectively. This research indicates the availability of the third and fourth monomers for improving the electromechanical effect of such electrostrictive polymers, having wide applications in flexible actuators, transformers, sensors, and so forth.

Epoxy vitrimers are a novel type of environmentally friendly materials that possess exceptional properties, including self-healing, recyclability, and reprocessability. They offer a solution to the issue of traditional thermosetting epoxy resins, which are not recyclable. However, the incorporation of dynamic bonds typically results in a decrease in mechanical properties. Therefore, achieving a balance between the mechanical properties and dynamic exchange capability is crucial. In this work, a series of epoxy resin systems with various topological network characteristics were prepared by adjusting the proportions of bisphenol A epoxy resin (E51) and polyethylene glycol diglycidyl ether (EGDGE) epoxy resins in combination with a curing agent containing vinylogous urethane (VU) dynamic bonds. Through further study, we found that with the increase of E51 content, the cross-linking density of the network gradually increased, and the flexibility of the macromolecular chains decreased (favorable for enhancing the material's mechanical performance). Simultaneously, the free volume of the network gradually increased, and the tightness of the macromolecular chains decreased (favorable for improving the material's dynamic exchange ability). These two effects combined to make E51-40 exhibit the lowest activation energy for dynamic covalent bond exchange and the lowest topological transition temperature. Compared to E51-0, the tensile strength and glass transition temperature of E51-40 were improved by 22.23 % and 25.30 %, respectively. After remoulding experiment at 140 °C for 1h, the material exhibited a high tensile strength recovery of 91.34 %. Therefore, starting from the design of molecular structure, adjusting the network topology is an effective means to balance the mechanical and dynamic exchange properties of epoxy vitrimers. This provides experimental guidance and theoretical insights for designing high-performance epoxy vitrimer materials.

The recent advent of the radical thiocarbonyl addition–ring-opening (TARO) copolymerization of thionolactones with vinyl monomers enables the production of degradable thioester backbone-functional vinyl copolymers promising for recycling and biomedical applications. To better understand the copolymerization behaviour of the prototypical thionolactone, dibenzo [c,e]oxepin-5(7H)-thione (DOT), copolymers with three S- and P-vinyl comonomers, phenyl vinyl sulfide (PVS), phenyl vinyl sulfone (PVSO), and diethyl vinylphosphonate (DEVP) were prepared through free and RAFT radical polymerizations. In all cases, DOT was incorporated faster than the vinyl comonomers which led to copolymers with up to 89 mol-% DOT content—surprising in light of past reports of significant retardation for high DOT feeds. All copolymers proved readily degradable. A postpolymerization oxidation enabled the conversion of a DOT–PVS copolymer into a corresponding DOT–PVSO species that remained degradable and offered a synthetic strategy to prepare copolymers with compositions not accessible through a direct copolymerization.

Polyethylene terephthalate (PET) industrial yarn is prone to damage during weaving due to its insufficient flexibility. Therefore, it is worth exploring whether polybutylene terephthalate (PBT) with improved flexibility can be utilized for the production of high strength and low modulus industrial yarn. In this study, a low velocity spinning multi-stage multi-ratio drawing technology route was employed for spinning, but PBT fibers only achieved a break strength of 5.1cN/dtex, which was lower than that of PET fibers (7.2cN/dtex). By comparing the multi-level structure evolution of PET and PBT during spinning, it was found that the core problem limiting the strength improvement of PBT fibers is due to the early formation of folded chain lamellar structure in PBT as-spun fibers during cooling, which hinders conformational transition during hot drawing and limits the drawing ratio. This has important implications for the development of PBT industrial yarn technology by adjusting the crystallization characteristics of PBT as-spun fibers.

The functionalization of native olive wood shell stone for the formation of new active heterogeneous cobalt-based biocatalysts has been conducted. The resulting biocatalysts have been fully characterized using various analytical techniques, including X-ray fluorescence (XRF), elemental analysis, granulometry, X-ray photoelectron spectroscopy (XPS), Fourier-Transform Infrared Spectroscopy (FTIR), thermogravimetry (TGA), moisture content, field-emission scanning electron microscopy (FESEM) and high-angle annular dark-field imaging (HAADF) with energy dispersive X-ray spectroscopy (EDX). The catalytic performance of these new functional heterogeneous materials has been verified by gelation time measurements on a multipurpose unsaturated polyester/styrene/tert-butyl peroxybenzoate system. The results are compared with those obtained using the current workhorse of the industry, which utilizes cobalt-based catalysts, particularly cobalt octoate dissolved in a solvent solution known to have adverse environmental and human health implications.

UV-light curing polyurethane-urea adhesives (PU-urea) were formulated from 4,4′-methylenediphenyl diisocyanate (MDI), 1,5-pentanediol (PD), 1,5-pentanediamine (cadaverine, CAD), and acetone as the adhesive carrier. The UV light-triggered curing process of these PU-urea formulations was controlled by blocking hydroxyl and amine functional groups of PD and CAD, respectively, with 6-nitroveratryloxycarbonyl (NVoc) as a photo-labile protecting group. The adhesive formulation was proven to undergo a dual curing procedure, integrating the UV light-induced polymerization and the release of the volatile adhesive carrier. This study highlights the critical role of the urethane:urea linkage ratio in the synthesis of photo-triggered adhesives to achieve optimal performance. Hence, the formulation with a NCO:OH:NH₂ molar ratio of 2.6:1.0:0.5 and a 96 % acetone content exhibited the most appropriate mechanical response in PETG-adhesive-PETG joints. Upon 60 min of photo-curing process (180 mW cm⁻²) shear strength values of around 6.11 MPa, in combination with the concomitant substrate failure of the adhesive joint, were observed. From this research, the potential implementation of the formulated PU-urea systems as competitive adhesive alternatives was proven. It was shown that the temporally controlled UV-induced functional group release is essential for achieving optimum adhesion performance.

Conductive hydrogels have attracted significant attention as versatile materials for flexible sensors, with potential implementation in wearable technologies, electronic skins, and health diagnostics. However, traditional hydrogel models are frequently limited by their inadequate mechanical strength, poor conductivity, weak adhesion, and low durability, which pose significant barriers to their further application in flexible sensors. In this work, we prepared composite multifunctional hydrogels as flexible sensors, which were synthesized from sulfobetaine methacrylate SBMA) and acrylamide (AM), infused with dodecyl quaternary ammonium salt (Q12), and incorporated with poly(dopamine)-functionalized carbon nanotubes (PDA@CNTs). The PDA modification enhances the compatibility of CNTs with the hydrogel matrix. The incorporation of PDA@CNTs into the hydrogel matrix, along with the establishment of multiple dynamic bonds—such as ionic bonds, hydrogen bonds, cation-π interactions, and π-π stacking between polymer chains and PDA moieties—significantly enhances its tensile strength (53.79 kPa), toughness (134.77 kJ/m³), adhesive capabilities (29.84 kPa to paper), and electrical conductivity (0.2 S/m). Moreover, the composite hydrogel reveals a remarkable mechanical strain response, coupled with impressive stability and durability over prolonged periods. It efficiently differentiates between mild elongations (10%–40 %) and substantial elongations (50%–300 %), thereby showcasing its capability for real-time biomechanical motion monitoring. Additionally, the composite hydrogel displays remarkable photothermal antibacterial efficacy upon exposure to near-infrared (NIR) radiation, along with outstanding biocompatibility under standard conditions, thereby confirming its suitability for safe and long-term biological interactions. The exceptional functionality of these composite hydrogels renders them highly conducive to diverse applications in the realm of wearable sensor technologies.

Introducing heteroatom groups into benzothiadiazole (BT) unit has proven to be a very effective way to improve the optoelectronic properties of conjugate polymer due to its comprehensive advantages of lowering the HOMO or LUMO energy level, and increasing the interaction force on the polymer backbone. However, at present, little attention was paid to introducing amino groups into the BT unit. Herein, in this work, three D-A-D type aminated monomers (Th–NH₂-BT, Th–2NH₂-BT, and EDOT-2NH₂-BT) with aminated benzothiadiazole as the acceptor unit and thiophene or 3,4-ethylenedioxythiophene (EDOT) as the donor unit were successfully synthesized by Stille coupling reaction, and their corresponding aminated polymers (P(Th–NH₂-BT), P(Th–2NH₂-BT), and P(EDOT-2NH₂-BT)) were facilely achieved by electrochemical polymerization method. The optoelectronic properties of the aminated monomers and their D-A polymers were carefully analyzed, and the electrochemical and electrochromic properties of the resultant aminated polymers were further studied. The finally results show that the absorption and fluorescence spectra of Th–2NH₂-BT and EDOT-2NH₂-BT are both blue-shifted compared to Th–NH₂-BT, and the corresponding optical bandgap are gradually increased (2.41 eV–2.65 eV). EDOT-2NH₂-BT has a relatively lower oxidation potential (0.73 V) and P(EDOT-2NH₂-BT) also has a wide potential window and better redox stability, which was very beneficial for improving its resultant D-A aminated polymers’ optoelectronic properties. As a result, as-formed P(EDOT-2NH₂-BT) shown obvious color change from green in the neutral state to gray in the oxidized state with favorable electrochromic performances, with a high optical contrast (ΔT = 17.17 % at 860 nm) and high coloration efficiency (CE = 223 C⁻¹ cm² at 860 nm), so it is one of the promising materials that can be used in electrochromic devices.

The rapid progression of electronic devices underscores the need for thermal interface materials (TIMs) with superior heat dissipation capabilities to address the overheating issues of high-power density electronic devices. However, the importance of excellent printability in practical automated production for TIMs has often been overlooked. This study introduces poly(2-[[(butylamino)carbonyl]oxy]ethyl acrylate)/liquid metal (Poly (BCOE)/LM) composites, which exhibit excellent printability and heat dissipation properties. The resulting materials, containing 80 wt% LM, display a low total thermal resistance of 0.69 cm² kW⁻¹, a low contact thermal resistance of 0.25 cm² kW⁻¹, a high thermal conductivity of 3.49 W m⁻¹K⁻¹, and effective printing capabilities through material jetting 3D printing onto chip surfaces. In thermal management applications, the composite material prepared in this work was able to reduce the temperature of the chip by a further 17 °C compared to a commercial product (Laird TFlex 300), thus highlighting its practical utility in automated production processes. This novel TIM offers a viable solution for addressing the thermal management needs of modern electronic devices.

General approaches for preparing epoxy vitrimers required lots of catalysts to accelerate transesterification to form the cross-linked network and the residual catalyst not only resulted in toxicity but also poor compatibility with other components. Herein, a green and facile strategy for preparing gallic acid epoxy resin (GA-EP) was developed under catalyst-free condition using renewable gallic acid, xylitol and hexahydro 4-methylphthalic anhydride (MHHPA) as feedstocks. The results indicated that the bio-based epoxy vitrimer had higher glass transition temperature (122 °C), satisfactory mechanical, thermal and degradation properties compared to neat Bisphenol A-based epoxy vitrimer. Furthermore, recycled GA-EP was ground into powder and added to the fresh resin to investigate its reusability. Compared to the original, the recycled epoxy vitrimer system demonstrated comparable performance, except for minor reductions in glass transition temperature (T_g) and modulus, likely stemming from the inherent inhomogeneity of the reprocessed material. This work provides a new approach to the production of high T_g bio-based epoxy vitrimers without adding any catalyst.