Mechanically Robust Fluorinated Graphene/Poly(<i>p</i>‑Phenylene Benzobisoxazole) Nanofiber Films with Low Dielectric Constant and Enhanced Thermal Conductivity: Implications for Thermal Management Applications

Low-dielectric materials have found broad applications in microelectronics but are limited by poor mechanical properties and thermal conductivity. In this study, a class of nanocomposite films based on fluorinated graphene (FG) was developed by replacing the traditional polymer matrix with a 3D interconnected poly(p-phenylene benzobisoxazole) (PBO) nanofiber network. The FG nanosheets are uniformly distributed in the porous network of PBO nanofibers (PBONF) and stacked orderly to form a nacre-like layered structure while paving effective thermal conduction paths. Ultimately, the strong interfacial bonding and efficient synergy between FG and PBONF endow the composite films with unparalleled tensile properties (strength and modulus up to 295.4 MPa and 7.79 GPa, respectively) and folding endurance (no drop in tensile properties after 1000 folds), ultralow dielectric constant (as low as 1.71), and excellent thermal conductivity (12.13 W m–1 K–1). In addition, these FG/PBONF composite films also exhibit an ultrahigh thermal stability (5% weight loss temperature higher than 540 °C), which makes them promising for the heat dissipation of high-power electronic devices in extreme environments

Data measured in dust concentration environments.

Measurement data of material height in dusty environments.</p

Inhibition of Heterogeneous Ice Nucleation by Bioinspired Coatings of Polyampholytes

Control of heterogeneous ice nucleation (HIN) on foreign surfaces is of great importance for anti-ice-nucleation material design. In this work, we studied the HIN behaviors on various ion-modified poly­(butylene succinate) (PBS) surfaces via chain-extension reaction. Inspired by antifreeze proteins (AFPs), the PBS-based polyampholytes, containing both negative and positive charge groups on a single chain, show excellent performance of ice nucleation inhibition and freezing delay. Unlike the extremely high price and low availability of AFPs, these PBS-based polyampholytes can be commercially synthesized under mild reaction conditions. Through water freezing tests on a wide range of substrates at different temperatures, these PBS-based polyampholytes have shown application value of tuning ice nucleation via a simple spin-coating method

Novel Biodegradable and Double Crystalline Multiblock Copolymers Comprising of Poly(butylene succinate) and Poly(ε-caprolactone): Synthesis, Characterization, and Properties

A series of double crystalline multiblock copolymers composed of poly­(butylene succinate) (PBS) and poly­(ε-caprolactone) (PCL) have been successfully synthesized with hexamethylene diisocyanate (HDI) as a chain extender. The copolymers were systematically characterized by ¹H NMR, GPC, TGA, DSC, WAXD, and mechanical testing. The results indicate that the PBS segment is immiscible with the PCL segment in the amorphous region. The copolymers follow a two-stage degradation behavior, and thermal stability increases with increasing PBS content. PBS and PCL in the copolymers crystallize and melt separately. The mechanical properties of the copolymers can be conveniently adjusted from rigid plastics to flexible elastomers by changing the feed composition. The impact strength is substantially improved by the incorporation of the PCL segment

Double Crystalline Multiblock Copolymers with Controlling Microstructure for High Shape Memory Fixity and Recovery

The shape memory performance of double crystalline poly­(butylene succinate)-<i>co</i>-poly­(ε-caprolactone) (PBS-<i>co</i>-PCL) multiblock copolymers with controlling microstructure was studied, and the corresponding microstructure origin was further quantitatively analyzed by wide and small-angle X-ray scattering (WAXS and SAXS) experiments. It was found that the multiblock copolymer with higher PCL content, proper deformation strain, and inhibited crystallization of PBS (lower crystallinity and smaller crystal size, which could be realized by quenching from the melt) would exhibit better shape memory fixity and recovery performance. WAXS and SAXS results revealed that the shape fixity ratio (<i>R</i>_f) was closely related with the relative crystallinity of the PCL component, while the shape recovery ratio (<i>R</i>_r) strongly relied on the deformation and recovery behavior of the PBS and PCL components that changed along with compositions and deformation strains. For the copolymer with higher PCL content (BS₃₀CL₇₀), at the lower deformation strain (0% ∼ 90%), both the PBS and PCL components after recovery had no orientation (labeled as stage I), resulting in almost complete recovery; with the deformation strain increasing (90% ∼ 200%), it was the irreversible deformation of the PCL component that largely took responsibility for the decreased <i>R</i>_r (stage II). On the contrary, when the PCL content decreased to 50 <i>wt</i> % (BS₅₀CL₅₀), stage I (0% ∼ 50%) and stage II (50% ∼ 100%) appeared in much lower strains; with the deformation strain increasing (100% ∼ 200%), the irreversible deformation of both PBS and PCL components was mainly responsible for the further reduction of <i>R</i>_r (stage III). It could exhibit excellent shape memory performance for biodegradable double crystalline multiblock copolymers by controlling the composition, deformation strain, and crystallization, which might have wide application prospects in biomedical areas

An in Situ Potential-Enhanced Ion Transport System Based on FeHCF–PPy/PSS Membrane for the Removal of Ca²⁺ and Mg²⁺ from Dilute Aqueous Solution

An in situ potential-enhanced ion transport system based on the electrochemically switched ion permselectivity (ESIP) membrane was developed for the effective removal of Ca²⁺ and Mg²⁺ from dilute aqueous solution. In this system, uptake/release of the target ions can be realized by modulating the redox states of the ESIP membrane, and continuously permselective separation of the target ions through the ESIP membrane can be achieved by tactfully applying a pulse potential on the membrane and combining with an external electric field. In this study, iron hexacyanoferrate (FeHCF)–polypyrrole/polystyrenesulfonate (PPy/PSS) ESIP membrane with high conductivity and high flux was prepared by using stainless steel wire mesh (SSWM) as conductive substrate. The driving force for the ion transport was analyzed in detail by the equivalent circuit of the system. It is found that the FeHCF interlayer between the SSWM substrate and the PPy/PSS membrane played an important role in removing Ca²⁺ and Mg²⁺ from aqueous solutions, and markedly enhanced the separation performance of the membrane due to the improvement of the electroactivity as well as the change of the surface morphology. Influences of the applied cell voltage of the external electric field and the pulse (constant) potential across the membrane on the separation of Ca²⁺ and Mg²⁺ were investigated. It is demonstrated that the pulse potential was more beneficial for improving the removal efficiency than the constant potential applied on the membrane. The hardness of the treated water was reduced to 50 ppm (CaCO₃) by applying a pulse potential of ±2.0 V and an cell voltage of 5.0 V when the initial concentration of Ca²⁺ was 10 mM (1000 ppm (CaCO₃)). It is expected that the in situ potential-enhanced ion transport system based on the FeHCF–PPy/PSS membrane could be used as a novel water softening technology

Reversible Lamellar Periodic Structures Induced by Sequential Crystallization/Melting in PBS-<i>co</i>-PCL Multiblock Copolymer

Reversible periodic structures in a symmetric poly­(butylene succinate)-<i>co</i>-poly­(ε-caprolactone) (PBS-<i>co</i>-PCL) multiblock copolymer have been detected for the first time. A phase-segregated structure can be observed under the phase contrast optical microscope at 150 °C, but it has no significant effect on the subsequent crystallization behavior of the PBS component, which can break out at lower temperatures (i.e., 82 °C) forming spherulites that contain the molten PCL component within them. During PBS chains crystallization at 82 °C, two peaks are detected by SAXS experiments. The high-<i>q</i> peak corresponds to a periodic structure formed within PBS-rich domains consisting of PBS lamellae and amorphous regions containing PBS and molten PCL chains. The low-<i>q</i> peak arises from a periodic structure formed within PCL-rich domains consisting of PBS lamellae and thick amorphous layers needed to accommodate the large fraction of molten PCL chains at 82 °C. When the temperature is decreased to 36 °C, the PCL component crystallizes within the PBS spherulitic template, and an alternating double crystalline layer structure of PCL and PBS forms, which leads to a decreased intensity of the low-<i>q</i> peak and an increased intensity of the high-<i>q</i> peak. If the temperature is increased again, the PCL crystals remelt and the high-<i>q</i> peak can still be observed, while the low-<i>q</i> peak becomes stronger again, confirming the reversibility of the periodic structures. Based on the results obtained, a schematic morphological model of the reversible periodic structures in the crystallization/melting process is proposed