Hetero-Interface Engineering on 9.0 wt% CoOx -Doped CeO2 Nanorods as Electromagnetic Wave Absorber and Integrated into Multifunctional Aerogel.

Ceria (CeO2 ) becomes a promising candidate as electromagnetic wave absorbing materials (EWAMs) for their abundant natural source, rich oxygen vacancy, charge conversion, and electron transfer abilities. However, it remains challenging to regulate its nanoscale and atom-scale composition to optimize the absorbing performance and develop high-performance commercial devices. Herein, a facile method to large-scale synthesis CeO2 @Co-x% (x = 5, 7, 9, 11, 13) series EWAMs with diverse amounts of decorated CoOx is presented. By modulating the ratio of doped CoOx , a rational hetero-interface is created in CeO2 @Co-9% to enhance natural and exchange resonances, improving magnetic loss capability and optimizing impedance matching. Doped CoOx promotes the charge accumulation, interfacial polarization, and multiple scattering of the CeO2 for strengthening the EW absorption and attenuation, which display superb minimum reflective loss (RLmin ) of -74.4 dB with a wide effective absorbing bandwidth (EAB) of 5.26 GHz. Furthermore, a dual crosslinking strategy is employed to fabricate CeO2 @Co-9% into an aerogel device with integrated lightweight, heat insulation, compression resistance, and fame-retardant functions. This work presents an excellent example of large-scale fast synthesis of high-performance CeO2 -based EWAMs and multiplication 3D devices.

Structure-activity strategies for mechanically responsive fluorescent materials: a molecular perspective.

Mechanical response luminescence (MRL) describes the photophysical properties triggered by mechanical stimulation. Usually, MRL can be regulated by intermolecular interactions, molecular conformation or molecular packing, to achieve the desirable optical properties. Herein, at the molecular level, this review covers the factors that influence mechanically responsive fluorescent materials, involving the single- or multifactorial modulation of aliphatic chains, donor-receptor switch, substituent adjustment, and position isomerism. According to these factors, the structure-activity strategies can be summarized as: (i) the self-recovery of optical properties, from the final to initial state, can be regulated by introducing long alkyl chains to a fluorophore. (ii) The sensitivity of MRL materials can be controlled by modifying the donor-acceptor structure via the changed ICT (intramolecular charge transfer) and intramolecular interaction. (iii) The electronic and steric effects of substituents can affect ICT and intermolecular interactions, thereby resulting in high quantum yield and high-contrast MRL materials via changing the molecular stacking of crystalline states. (iv) Intermolecular interaction is modulated by the position isomerism of the substituents, which results in switched molecular packing for the extended response toward a wide range of stimuli. It is anticipated that the molecular mechanisms of these structure-activity relationships will serve as a significant reference for developing novel, high contrast, recyclable mechanical response luminous materials.

Transferring and Retaining of Different Polyaniline Nanofeatures via Electrophoretic Deposition for Enhanced Sensing Performance.

Nanofeatured polyaniline (PANI) electrodes have demonstrated impressive sensing performance due to the enhanced electrolyte diffusion and ion transport. However, the retaining of these nanostructures on substrates via electrophoretic deposition (EPD) faces an insurmountable challenge from the involved dedoping process. Here, camphorsulfonic acid is utilized with high steric effects to dope PANI (PANI-CSA) that can be directly used EPD without involving a dedoping process. Five different nanofeatures (sea cucumber-like, nanofiber, amorphous, nanotube, and nanorod) are synthesized, and they have been all successfully transferred onto indium tin oxide substrate in a formic acid/acetonitrile system, namely a morphology memory effect. The mechanism of retaining these nanofeatures is revealed, which is realized via the processes of dissolution of PANI-CSA, codoping and solvation, and reassembly of basic units into the original nanofeature. The enhanced protonation level by the codoping of formic acid and solvation of acetonitrile plays the key role in retaining these nanofeatures. This method is also applicable to transfer PANI/gold nanorod composites (PANI-CSA/AuNRs). The PANI-CSA/AuNRs electrode as an ascorbic acid sensor has shown an excellent sensing performance with a sensitivity up to 872.7 µA mm-1 cm-2 and a detection limit of as low as 0.18 × 10-6 m.

Graphene Composite via Bacterial Cellulose Assisted Liquid Phase Exfoliation for Sodium-Ion Batteries.

One of the most critical challenges for commercialization of sodium-ion battery (SIB) is to develop carbon anodes with high capacity and good rate performance. Graphene would be an excellent SIB anode candidate due to its success in various kinds of batteries. Liquid-phase exfoliation (LPE) method is an inexpensive, facile and potentially scalable method to produce less-defected graphene sheets. In this work, we developed an improved, dispersant-assisted LPE method to produce graphene composite materials from raw graphite with high yield and better quality for SIB anode. Here, bacterial cellulose (BC) was used as a green dispersant/stabilizer for LPE, a "spacer" for anti-restacking, as well as a carbon precursor in the composite. As a result, the carbonized BC (CBC)/LPE graphene (LEGr) presented improved performance compared to composite with graphene prepared by Hummers method. It exhibited a specific capacity of 233 mAh g-1 at a current density of 20 mA g-1, and 157 mAh g-1 after 200 cycles at a high current density of 100 mA g-1 with capacity retention rate of 87.73%. This method not only provides new insight in graphene composites preparation, but also takes a new step in the exploration of anode materials for sodium-ion batteriesSIBs.

Ultraflexible and Mechanically Strong Polymer/Polyaniline Conductive Interpenetrating Nanocomposite via In Situ Polymerization of Vinyl Monomer.

Simultaneous enhancement of conductivity and mechanical properties for polyaniline/polymer nanocomposite still remains a big challenge. Here, a reverse approach via in situ polymerization (RIP) of vinyl monomers in waterborne polyaniline dispersion was raised to prepare conductive polyaniline (GPANI)/polyacrylate (PMB) interpenetrating polymer (GPANI-PMB) nanocomposite. GPANI/PMB physical blend was simultaneously prepared as reference. The conductive GPANI-PMB nanocomposite film with compact pomegranate-shape morphology is homogeneous, ultraflexible and mechanically strong. With incorporating a considerable amount of PMB into GPANI via the RIP method, only a slight decrease from 3.21 to 2.80 S/cm was detected for the conductivity of GPANI-PMB, while the tensile strength significantly increased from 25 to 43.5 MPa, and the elongation at break increased from 40% to 234%. The water absorption of GPANI-PMB3 after 72 h immersion decreased from 24.68% to 10.35% in comparison with GPANI, which is also higher than that of GPANI/PMB. The conductivity and tensile strength of GPANI-PMB were also much higher than that of GPANI/PMB (0.006 S/cm vs. 5.59 MPa). Moreover, the conductivity of GPANI-PMB remained almost invariable after folding 200 times, while that of GPANI/PMB decreased by almost half. This RIP approach should be applicable for preparing conventional conductive polymer nanocomposite with high conductivity, high strength and high flexibility.

Optimization of Waterborne Poly(Urethane-Acrylate) Nanoemulsions Based on Cationic Polymerizable Macrosurfactants with Different Hydrophobic Side Chain Length.

In situ surfactant-free emulsion polymerization can help avoid the utilization of harmful co-solvents and surfactants in the preparation of waterborne poly(urethane-acrylate) (WPUA) nanoemulsion, but the solid content is extremely limited, which will affect the drying rate and film-forming properties. The utilization of polymerizable macrosurfactants can overcome the above problems. However, the research on cationic polymerizable macrosurfactants is extremely scarce. In this work, cationic dimethylaminoethyl methacrylate-b-alkyl methacrylates block copolymers (PDM-b-PRMA) with terminal double bonds and different hydrophobic side chain (HSC) lengths were fabricated via catalytic chain transfer polymerization (CCTP). HSC length of PDM-b-PRMA played an important role in the phase inversion, morphology, rheological behavior of WPUA nanoemulsions, as well as the comprehensive performance of WPUA/PDM-b-PRMA films. Polymerizable PDM-b-PBMA macrosurfactant had smaller molecular weight, lower surface tension and colloidal size than the random copolymer (PDM-co-PBMA) by traditional free radical polymerization. It was easy for PDM-b-PRMA to orientedly assemble at the oil/water interface and provide better emulsifying ability when the carbon number of HSC was four. Compared with WPUA/PDM-co-PBMA, WPUA/PDM-b-PBMA had a smaller particle size, stability and better film-forming properties. This work elucidated the mechanisms of HSC length in the fabrication of cationic PDM-b-PRMA and provides a novel strategy to prepare cationic WPUA of high performance.

Effects of Continuous Phase and Crosslinking Agent on the Rheological Behaviors and Properties of Cationic Poly(urethane-acrylate) Emulsifier-Free Microemulsions.

Cationic poly(urethane-acrylate) emulsifier-free microemulsions are prepared by seeded emulsion polymerization (SPUA) or in-situ emulsion polymerization (IPUA) with (a) or without (b) crosslinking agent hydroxyethyl acrylate (HEA). Furthermore, no surfactant is introduced into the reaction system. The effect of continuous phase and HEA on the rheological behavior and properties of microemulsions are studied. The results show that IPUA using vinylmonomers as the continuous phase and with HEA (IPUAMB-b) has the highest ζ value, lowest coagulation ratio, smallest particle size of 48 nm and apparent core-shell structures. Rheological research has concluded that the zero-shear viscosity of IPUAB-b and IPUAM-b emulsion is 6.03×102 and 7.89 Pa·s, respectively, and presents pseudoplastic behavior. However, IPUAMB-b and SPUA-b display Newtonian behavior with η0 of 0.136 Pa·s and 0.0823 Pa·s, respectively. PUA emulsions display similar rheological behavior when NMP is replaced by the mixture of MMA and BA.

Facile approach to fabricate waterborne polyaniline nanocomposites with environmental benignity and high physical properties.

Waterborne polyaniline (PANI) dispersion has got extensive attention due to its environmental friendliness and good processability, whereas the storage stability and mechanical property have been the challenge for the waterborne PANI composites. Here we prepare for waterborne PANI dispersion through the chemical graft polymerisation of PANI into epichlorohydrin modified poly (vinyl alcohol) (EPVA). In comparison with waterborne PANI dispersion prepared through physical blend and in situ polymerisation, the storage stability of PANI-g-EPVA dispersion is greatly improved and the dispersion keeps stable for one year. In addition, the as-prepared PANI-g-EPVA film displays more uniform and smooth morphology, as well as enhanced phase compatibility. PANI is homogeneously distributed in the EPVA matrix on the nanoscale. PANI-g-EPVA displays different morphology at different aniline content. The electrical conductivity corresponds to 7.3 S/cm when only 30% PANI is incorporated into the composites, and then increases up to 20.83 S/cm with further increase in the aniline content. Simultaneously, the tensile strength increases from 35 MPa to 64 MPa. The as-prepared PANI-g-EPVA dispersion can be directly used as the conductive ink or coatings for cellulose fibre paper to prepare flexible conductive paper with high conductivity and mechanical property, which is also suitable for large scalable production.

Micromorphology and phase behavior of cationic polyurethane segmented copolymer modified with hydroxysilane.

A series of cationic waterborne polyurethane dispersions (SiPU) modified with hydroxysilane (HPMS) were successfully synthesized based on poly(oxytetramethylene) glycols (PTMG) and isophorone isocyanate (IPDI), and the films were obtained by casting the dispersions on tetrafluoroethylene (TFE) plates. Effects of HPMS content on micromorphology, particle size of the dispersions were studied, as well as thermal properties, phase behavior and surface structure of the films. The particles had the morphology of a solid sphere, with particle size varying from 17.1 nm to 114.4 nm corresponding to the increase of HPMS concentration, which can be attributed to the increase of interfacial tension. XPS spectra indicated the surface migration of Si element in the process of film forming, and the SiPU surface was mainly composed of soft segments. DSC analysis, together with TG-DTG-DTA results demonstrated the HPMS soft segment merged with the transition region of PU matrix, forming part of polyurethane backbone, but an improved microphase separation was observed when HPMS concentration greater than 15%. It was also found that incorporation of flexible HPMS prevented the degradation of polyurethane backbone, resulting in the increase of thermal stability in ultimate copolymer.