Macromolecular Rapid Communications最新文献

Intelligent-responsive temporary plugging agents (TPAs) have great potential in the field of oil and gas resource extraction due to their self-adaptability to the environment. However, the transport mechanism of oil and gas molecules, such as aqueous methane solution in intelligent-responsive TPA-modified nano-channels and the blocking behavior of TPA, have not been verified yet. In this work, dissipative particle dynamics simulations (DPD) are conducted to investigate the velocity distribution and the force characteristics of aqueous methane solutions under different driving velocities, as well as the blocking effect of TPA to the flow of solution. Simulation results indicate that aqueous methane solution primarily concentrates in the uncovered area of the TPA and diffuses into the TPA-covered area when the nano-channel is closed. The velocity distribution of the flowing solution in the open nano-channel follows a subparabolic pattern. Methane molecules in the closed nano-channel show sharp oscillations in velocity and force profiles, which can be mitigated by increasing the methane concentration. The designed TPA effectively blocks fluid flow but its head and tail are vulnerable to the shear forces from the fluid. This study enhances the understanding of the nanoflows in the wellbores during the extraction of oil and natural gas resources.

Modified polyvinylidene chloride (PVDC) resin was prepared using octafluoropentyl methacrylate and trimethylolpropane trimethacrylate as modifying monomers through seeded emulsion polymerization. The successful incorporation of octafluoropentyl methacrylate into the PVDC resin was confirmed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and XPS were utilized to investigate the element distribution in the modified monomer emulsion and the mechanism of monomer modification. The results demonstrated that the fluorine monomer was reacted in the resin, and mainly concentrated on the surface of the resin. The addition of octafluoropentyl methacrylate and trimethylolpropane trimethacrylate improved the water resistance of the resin. Compared to unmodified PVDC resin, the contact angle of the modified PVDC resin increased from 89.46° to 109.51°, and the water resistance at room temperature increased from 120 to 500 h. Furthermore, the modified resin exhibited excellent mechanical properties, thermal stability, and storage stability.

Polymer-metal complexes (PMCs) based on poly(2,2'-bipyridine-4,4'-dicarboxamide-co-polydimethylsiloxanes) with cyclometalated di(2-phenylpyridinato-C²,N')iridium(III) fragments and cross-linked by Zn²⁺ (Zn[Ir]-BipyPDMSs) or Ir³⁺ (Ir[Ir]-BipyPDMSs) represent flexible, stretchable, phosphorescent, and self-healing molecular oxygen sensors. PMCs provide strong phosphorescence at λ_em = 595-605 nm. Zn[Ir]-BipyPDMS with PDMS chain length of M_n = 5000 has the highest quantum yield of 9.3% and is a molecular oxygen sensor at different O₂ concentrations (0-100 vol%) compared to Ir[Ir]-BipyPDMSs. A Stern-Volmer constant is determined for Zn[Ir]-BipyPDMS as K_SV = 0.014%^-1, which is similar to the reported oxygen-sensitive iridium(III) complexes. All synthesized PMCs exhibit high elongation at break (up to 1100%) and self-healing efficiency (up to 99%).

The swelling and collapse of responsive nanogels on a planar lipid bilayer are studied by means of mesoscopic computer simulations. The effects of molecular weight, cross-linking density, and adhesion strength are examined. The conditions for collapse-mediated engulfing by the bilayer are found. In particular, the results show that at low hydrophobicity level the increase in the nanogel softness decreases the engulfing rate. On the contrary, for stronger hydrophobicity level the trend changes to the opposite one. At the same time, when the cross-linking density is too low or the adhesion strength is too high the nanogel deformation at the membrane suppresses the engulfing regardless of the network swelling ratio. Finally, for comparative reasons, the behavior of the nanogels is also studied at the solid surface. These results may be useful in the design of soft particles capable of tuning of their elasticity and porosity for successful intracellular drug delivery.

The need for eco-friendly cooling materials and material recycling are two urgent challenges to address. In this paper, the role of the ground tyre rubber treatment (cryo-grinding and devulcanization) is investigated on the tensile and elastocaloric properties of Natural rubber (NR)/ ground tyre rubber (GTR). The GTR particles that are sieved (<63µm) and devulcanized by microwave irradiation (1 min at 800Watts) exhibit a low network chain density (0.53 × 10^-4 mol.cm^-3) resulting from crosslinks breakage and rubber chains scission, as supported by FTIR showing a decrease of S─S, C─S, and C─C bonds. The NR/GTR blends show a high elastocaloric effect as compared to the pristine NR, which can be ascribed to the high content of carbon black in the GTR (52 wt.%) and also the high level of devulcanization of the GTR. NR/GTR blends reach a heating of +8 °C and a cooling of >-6 °C, resulting in a material's coefficient of performance COP_mat = 2.8-3 compared to 2.6 for the pristine NR. The concomitant effect of cryogrinding and microwave devulcanization is proposed as a way to improve the tensile and elastocaloric properties of natural rubber/waste rubber blends for their possible integration into elastocaloric devices for heating/cooling applications.

Vanillyl alcohol has emerged as a widely used building block for the development of biobased monomers. More specifically, the cationic (photo-)polymerization of the respective diglycidyl ether (DGEVA) is known to produce materials of outstanding thermomechanical performance. Generally, chain transfer agents (CTAs) are of interest in cationic resins not only because they lead to more homogeneous polymer networks but also because they strikingly improve the polymerization speed. Herein, the aim is to compare the cationic chain-growth photopolymerization with the thermally initiated anionic step-growth polymerization, with and without the addition of CTAs. Indeed, CTAs lead to faster polymerization reactions as well as the formation of more homogeneous networks, especially in the case of the thermal anionic step-growth polymerization. Resulting from curing above the T_G of the respective anionic step-growth polymer, materials with outstanding tensile toughness (>5 MJ cm^-3) are obtained that result in the manufacture of potential shape-memory polymers.

Passive daytime radiative cooling (PDRC) presents a promising avenue for efficient thermal management without relying on electrical power. In this study, the potential of integrating Hollow Yttrium-Oxide Spheres (HYSs) within a Polydimethylsiloxane (PDMS) matrix to enhance PDRC is investigated. Through a combination of experimental characterization and computational analysis, the optical properties and radiative cooling performance of PDMS films embedded with HYSs are evaluated. These results demonstrate that HYSs significantly improve both solar reflectivity and long-wave infrared (LWIR) emissivity of the PDMS matrix. Finite-Difference Time-Domain (FDTD) simulations confirm the scattering efficiency of HYSs across various wavelength ranges, highlighting their effectiveness as additives for enhancing the radiative properties of passive cooling materials. Experimental validation reveals enhanced reflectivity and emissivity of PDMS films with embedded HYSs, resulting in superior cooling performance compared to non-HYS counterparts. Overall, this study underscores the potential of HYS-infused PDMS films as a promising solution for passive radiative cooling, with broad applicability in diverse domains requiring efficient thermal management solutions. Additionally, these research insights pave the way for establishing an AI database for passive radiative cooling research, offering new avenues for further exploration and application in this field.

Wearable strain transducers are poised to transform the field of healthcare owing to the promise of personalized devices capable of real-time collection of human physiological health indicators. For instance, monitoring patients' progress following injury and/or surgery during physiotherapy is crucial but rarely performed outside clinics. Herein, multifunctional liquid-free ionic elastomers are designed through the volume effect and the formation of dynamic hydrogen bond networks between polyvinyl alcohol (PVA) and weak acids (phosphoric acid, phytic acid, formic acid, citric acid). An ultra-stretchable (4600% strain), highly conducting (10 mS cm^-1), self-repairable (77% of initial strain), and adhesive ionic elastomer is obtained at high loadings of phytic acid (4:1 weight to PVA). Moreover, the elastomer displayed durable performances, with intact mechanical properties after a year of storage. The elastomer is used as a transducer to monitor human motions in a device comprising an ESP32-based development board. The device detected walking and/or running biomechanics and communicated motion-sensing data (i.e., amplitude, frequency) wirelessly. The reported technology can also be applied to other body parts to monitor recovery after injury and/or surgery and inform practitioners of motion biomechanics remotely and in real time to increase convalescence effectiveness, reduce clinic appointments, and prevent injuries.

Fluorosilicone rubber is essential for sealing in extreme temperatures and non-polar environments due to its exceptional adaptability. However, achieving a high yield of fluorosilicone polymers with medium and high fluorine content remains a challenge. Herein, a facile gradient strategy is developed that involves modifying the method of cyclic monomer addition based on the rate of ring-opening polymerization (ROP), to improve yield and adjust fluorine content precisely. The polymerization process is designed and tailored based on the reaction rates of anionic ring-opening polymerization (AROP) and cationic ring-opening polymerization (CROP) via an efficient gradient strategy. The effects of the polymerization process on the viscosity and yield of vinyl fluorosilicone polymers and hydrofluorosilicone polymers are investigated and optimized. Notably, the as-prepared vinyl-terminated fluoromethylsilane with 60% fluorine content (FMS-Vi-60F) has a high yield (86.6%) and high viscosity (150 000 mPa·s) in a short reaction time, which is superior to previous methods. Clearly, the gradient ring-opening method developed in this work provides a facile and efficient synthesis for fabricating fluorosilicone polymers with a high yield and tunable fluorine content.

Covalent Organic Frameworks (COFs) exhibit a range of exceptional attributes, including notable porosity, outstanding stability, and a precisely tuned π-conjugated network, rendering them highly promising candidates for fluorescence sensors applications. In this study, the synthesis of two emissive hydrazone-linked COFs designed for hydrazine detection is presented. The partially conjugated structure of the hydrazone linkage effectively weakens the fluorescence quenching processes induced by aggregation. Additionally, the incorporation of flexible structural components further reduces conjugation, thereby enhancing luminescent efficiency. Remarkably, these COFs possess a significant abundance of heteroatoms, enabling distinctive interactions with hydrazine molecules, which in turn results in exceptional selectivity and sensitivity for hydrazine detection. The detection limit of these COFs reaches the nanomolar range, surpassing all previously reported COFs, thereby underscoring their superior performance in chemical sensing applications.