l‑Citrulline-Modified Ti₃C₂T_<i>x</i> MXene Nanosheets Embedded in Polyacrylamide/Sodium Alginate Hydrogels for Electromagnetic Interference Shielding

In this work, a robust and mechanically composite hydrogel with an efficient electromagnetic interference shielding performance was successfully fabricated via the incorporation of l-citrulline-modified Ti3C2Tx MXene nanosheets into the polyacrylamide/sodium alginate hydrogels by using ferrous chloride as the adhesive. A l-citrulline-modified Ti3C2Tx MXene nanosheet was the main shielding medium; ferrous chloride could not only enhance the mechanical property of the resultant hydrogels but also slightly improve the EMI shielding efficiency. The optimal tensile strength (3.42 MPa) and the EMI shielding effectiveness (26.8 dB) were achieved for the composite hydrogels with 6.5 wt % l-citrulline-modified Ti3C2Tx MXene nanosheets and 0.6 mol/L ferrous chloride, and the high ductility (780% elongation at break) of the composite hydrogel was reached with 0.5 wt % l-citrulline-modified Ti3C2Tx MXene and 0.8 mol/L ferrous chlorides. With outstanding mechanical and EMI shielding performances, the prepared composite hydrogels could apply in the electronic skin field

Fabrication of dopamine modified polylactide-poly(ethylene glycol) scaffolds with adjustable properties

<p>Bio-based polymers have been widely used to be as scaffolds for repairing the bone defects. However, the polymer scaffolds are generally lack of bioactivity and cell recognition site. Seeking effective ways to improve the bioactivity and interaction between materials and tissue or cells is clinically important for long-term performance of bone repair materials. In this work, polylactide-<i>b</i>-poly(ethylene glycol)-<i>b</i>-polylactide (PLA-PEG-PLA, PLEL) tri-block copolymers were firstly synthesized by ring-opening polymerization of lactide using PEG with various molecular weights. Inspired by excellent adhesion of dopamine (DA), a facile and effective method was developed to fabricate polydopamine (PDA) and polydopamine/nano-hydroxyapatite (PDA/n-HA) modified PLEL scaffolds by deposition of PDA and PDA/n-HA coating. The surface structure, degradation rates and mineralization of the modified PLEL scaffolds were investigated, and obviously improved after immobilization of PDA and PDA/n-HA coatings. Moreover, the biocompatible results showed a significant increase in cells viability and adhesion. Therefore, the surface modification with PDA and PDA/n-HA could not only adjust the properties of scaffolds, but also reinforce the interfacial adhesion between the PLEL and cells.</p

High-Sensitivity Flexible Sensor Based on Biomimetic Strain-Stiffening Hydrogel

Recently, flexible wearable and implantable electronic devices have attracted enormous interest in biomedical applications. However, current bioelectronic systems have not solved the problem of mechanical mismatch of tissue–electrode interfaces. Therefore, the biomimetic hydrogel with tissue-like mechanical properties is highly desirable for flexible electronic devices. Herein, we propose a strategy to fabricate a biomimetic hydrogel with strain-stiffening property via regional chain entanglements. The strain-stiffening property of the biomimetic hydrogel is realized by embedding highly swollen poly(acrylate sodium) microgels to act as the microregions of dense entanglement in the soft polyacrylamide matrix. In addition, poly(acrylate sodium) microgels can release Na+ ions, endowing hydrogel with electrical signals to serve as strain sensors for detecting different human movements. The resultant sensors own a low Young’s modulus (22.61–112.45 kPa), high nominal tensile strength (0.99 MPa), and high sensitivity with a gauge factor up to 6.77 at strain of 300%. Based on its simple manufacture process, well mechanical matching suitability, and high sensitivity, the as-prepared sensor might have great potential for a wide range of large-scale applications such as wearable and implantable electronic devices

Green Antibacterial Nanocomposites from Poly(lactide)/Poly(butylene adipate-<i>co</i>-terephthalate)/Nanocrystal Cellulose–Silver Nanohybrids

Silver nanoparticles (AgNPs) with a diameter of 3–6 nm were uniformly reacted onto the surface of nanocrystal cellulose (NCC) via complexation leading to NCC–Ag nanohybrids with an AgNP content of 8 wt %. Subsequently, antibacterial green nanocomposites containing renewable and biodegradable poly­(lactide) (PLA), poly­(butylene adipate-<i>co</i>-terephthalate) (PBAT) and NCC–Ag nanohybrids were synthesized and investigated. The PBAT as flexibilizer improved the toughness of the PLA matrix while the uniformly dispersed NCC–Ag nanohybrids enhanced the compatibility, thermal stability, crystallization, and antibacterial properties of the PLA/PBAT blends. The crystallization rate and the storage modulus (<i>E</i>′) of the green nanocomposites were increased obviously with increasing content of CNC–Ag nanohybrids. Meanwhile, notably the antibacterial activity of the PLA/PBAT/NCC–Ag nanocomposites was achieved against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus cells. The antibacterial performance was mainly related to the antibacterial nature of the finely dispersed NCC–Ag nanohybrids. The study demonstrates great potential of the green nanocomposites in functional packaging and antibacterial textile applications

Biobased Poly(lactide)/ethylene-<i>co</i>-vinyl Acetate Thermoplastic Vulcanizates: Morphology Evolution, Superior Properties, and Partial Degradability

Partially biobased thermoplastic vulcanizates (TPV) with novel morphology, superior properties and partial degradability were prepared by dynamic cross-link of saturated poly­(lactide) and ethylene-<i>co</i>-vinyl acetate (PLA/EVA) blends using 2,5-dimethyl-2,5-di­(<i>tert</i>-butylperoxy)­hexane (AD) as a free radical initiator. EVA showed higher reactivity with free radicals in comparison with PLA, leading to much higher gel content of the EVA phase (<i>G</i>_f‑EVA) than that of the PLA phase (<i>G</i>_f‑PLA). However, the <i>G</i>_f‑PLA increased more steeply at AD content larger than 1 wt % where the reaction of EVA approached to a saturation point. The competing reaction changed the viscosity ratio of the two components (η_PLA/η_EVA) that resulted in a novel morphology evolution of the TPV, i.e., from sea–island-type morphology to phase inversion via a dual-continuous network-like transition and finally cocontinuity again with increasing the AD content. The cross-link and phase inversion considerably enhanced the melt viscosity (η*), elasticity (<i>G</i>′) and the solid-like behavior of the PLA/EVA-based TPV. Meanwhile, superior tensile strength (σ_t = 21 MPa), low tensile set (<i>T</i>_s = 30%), moderate elongation (ε_b = 200%) and suitable stiffness (<i>E</i>′ = 350 MPa, 25 °C) were successfully achieved by tailoring the cross-link structure and phase morphology. In addition, the TPV are partially degradable in aqueous alkali. A degradation rate of approximately 5 wt % was achieved within 10 weeks at 25 °C and the degradation mechanism was investigated from both molecular and macroscopic levels. Therefore, this work provides a new type of partially biobased and degradable materials for substitution of traditional TPV

Facile Synthesis of Hyperbranched Polymers by Sequential Polycondensation

Hyperbranched polymers are an important class of soft nanomaterial, but the synthesis of hyperbranched polymers with well-defined dendritic structure from readily available monomers remains a challenge in polymer chemistry. We herein report a sequential polycondensation method for the one-pot synthesis of hyperbranched polymers with tunable structure and high degree of branching from commercial available monomers. Specifically, in the polycondensation process of equimolar difunctional haloalkane (A₂-type monomers) and trifunctional dihydroxybenzoic acid (CB₂-type monomers) using K₂CO₃ as the base, the aliphatic nucleophilic substitution reactivity sequence of the functional groups derived from CB₂ monomers is C > second B > first B ≫ original B, thereby producing hyperbranched poly­(ester ether)­s with high degree of branching (DB > 0.6). Moreover, the surface functionality of the hyperbranched poly­(ester ether)­s could be facilely tailored by just introducing A-type monofunctional reagents into the one-pot A₂ + CB₂ polymerization system

Porphyrin Derivative Conjugated with Gold Nanoparticles for Dual-Modality Photodynamic and Photothermal Therapies In Vitro

Gold nanoparticles (Au NPs) have been confirmed to show excellent photothermal conversion property for tumor theranostic applications. To improve the antitumor efficacy, a novel nanoplatform system composed of porphyrin derivative and Au NPs was fabricated to study the dual-modality photodynamic and photothermal therapy with laser irradiation. Modified chitosan was coated on the Au NPs surface via ligand exchange between thiol groups and Au. The chitosan-coated Au NPs (QCS-SH/Au NPs) were further conjugated with meso-tetrakis­(4-sulphonatophenyl)­porphyrin (TPPS) via electrostatic interaction to obtain the porphyrin-conjugated Au hybrid nanoparticles (TPPS/QCS-SH/Au NPs). Size, morphology, and properties of the prepared nanoparticles were confirmed by Zeta potential, nanoparticle size analyzer, transmission electron microscopy (TEM), and UV–vis spectroscopy. Moreover, both photothermal therapy (PTT) and photodynamic therapy (PDT) were investigated. Compared with alone Au NPs or TPPS, the hybrid TPPS/QCS-SH/Au NPs with lower cytotoxicity showed durable elevated temperature to around 56 °C and large amount of singlet oxygen (¹O₂) produced from TPPS. Thus, the hybrid nanoparticles showed a more significant synergistic therapy effect of hyperthermia from PTT as well as ¹O₂ from PDT, which has potential applications in the tumor therapy fields

Rapid Stereocomplexation between Enantiomeric Comb-Shaped Cellulose‑<i>g</i>‑poly(l‑lactide) Nanohybrids and Poly(d‑lactide) from the Melt

In this work we report the in situ preparation of fully biobased stereocomplex poly­(lactide) (SC-PLA) nanocomposites grafted onto nanocrystalline cellulose (NCC). The stereocomplexation rate by compounding high-molar-mass poly­(d-lactide) (PDLA) with comb-like NCC grafted poly­(l-lactide) is rather high in comparison with mixtures of PDLA and PLLA. The rapid stereocomplexation was evidenced by a high stereocomplexation temperature (<i>T</i>_c‑sc = 145 °C) and a high SC crystallinity (<i>X</i>_c‑sc = 38%) upon fast cooling (50 °C/min) from the melt (250 °C for 2 min), which are higher than currently reported values. Moreover, the half-life crystallization time (175–190 °C) of the SC-PLA was shortened by 84–92% in comparison with the PDLA/PLLA blends. The high­(er) stereocomplexation rate and the melt stability of the SC in the nanocomposites were ascribed to the nucleation effect of the chemically bonded NCC and the “memory effect” of molecular pairs in the stereocomplex melt because of the confined freedom of the grafted PLLA chains

Efficient Toughening of Epoxy–Anhydride Thermosets with a Biobased Tannic Acid Derivative

Research into toughening an epoxy resin using biobased modifiers without trade-offs in its modulus, mechanical strength, and other properties still remains a challenge. In this article, an approach to toughen epoxy resin with tannic acid, a common polyphenolic compound extracted from plants and microorganisms, is presented. First, dodecane functionalized tannic acid (TA-DD) is prepared and subsequently incorporated into epoxy/anhydride curing system. Owing to the modification of long aliphatic chain, TA-DD can induce epoxy matrix yielding phase separation, forming microscaled separated phases. In the meantime, the terminal hydroxyl groups of TA-DD can participate in the curing process, which offers a good interfacial interaction between TA-DD and epoxy matrix. With such a mechanism, the results show that TA-DD can significantly toughen the epoxy resin without trade-offs in its strength, modulus, and <i>T</i>_g. The thermoset with only 0.5 wt % TA-DD reaches highest impact strength, which is 196% increase of that of neat epoxy. This article opens up the possibility of utilizing the renewable tannic acid as an effective modifier for epoxy resin with good mechanical and thermal properties

High-Performance PEBA2533-Functional MMT Mixed Matrix Membrane Containing High-Speed Facilitated Transport Channels for CO₂/N₂ Separation

A novel mixed matrix membrane was fabricated by establishing montmorillonite (MMT) functionalized with poly­(ethylene glycol) methyl ether (PEG) and aminosilane coupling agents in a PEBA membrane. The functional MMT played multiple roles in enhancing membrane performance. First, the MMT channels could be used as high-speed facilitated transport channels, in which the movable metal cations acted as carriers of CO₂ to increase the CO₂ permeability. Second, due to mobility of long-chain aminos and reversible reactions between CO₂ and amine groups, the functional MMT could actively catch the CO₂, not passively wait for arrival of CO₂, which can facilitate the CO₂ transport. At last, PEG consisting of EO groups had excellent affinity for CO₂ to enhance the CO₂/N₂ selectivity. Thus, the as-prepared functional MMMs exhibited good CO₂ permeability and CO₂/N₂ selectivity. The functional MMM doped with 40 wt % of MMT-HD702-PEG5000 displayed optimal gas separation with a CO₂ permeability of 448.45 Barrer and a CO₂/N₂ selectivity of 70.73, surpassing the upper bound lines of the Robeson study of 2008