Unique Core-Shell Structured Polyaniline Nanofibers Toward Ultrahigh-Rate Flexible All-Solid-State Supercapacitor.

Promoting charge storage and fast charging capability simultaneously is a long-standing challenge for supercapacitors. A facile flowing seed polymerization is adopted to prepare polyaniline (PANI) nanofibers, in which phytic acid (PA) doped oligomers are first produced as the seeds for promoting the highly oriented growth of PANI nanofibers accompanying with the copolymerization of m-aminobenzene sulfonic acid (ASA) and aniline occurred on the surface of PANI nanofibers, as a result, unique core-shell structured PANI nanofibers are continuously fabricated. Benefitting from compact nanofiber structure, excellent dispersion, and self-doping effect, as-prepared PANI nanofibers exhibit a specific capacitance of 671.2 F g-1 at 2 A g-1 and ultrahigh rate capability of 93.1% from 2 to 100 A g-1. Then assembled all-solid-state supercapacitor can deliver the highest energy density of 28.3 Wh kg-1 at a power density of 320.2 W kg-1 with remarkable rate capability (81.2% from 1 to 20 A g-1), cycle stability (77.5% after 5000 cycles) as well as light weight and flexibility. It is highly desirable that the present green and scalable approach can be further applied to fabricate other unique core-shell structured PANI nanofibers with appealing potentials in energy storage devices.

Surface modifications of short quartz fibers and their influence on the physicochemical properties and in vitro cell viability of dental composites.

OBJECTIVE: Although glass fibers are more common, quartz fibers (QFs) are also considered as the ideal reinforcing material in dentistry, due to their superior mechanical strength, high purity, and good photoconductive properties. However, the relatively inert surfaces limit their further applications. Therefore, the aim of this study is to modify the fiber surface properties to improve the interfacial interactions with polymeric resins. METHODS: In this study, we systematically introduced four different surface modification strategies onto short quartz fibers (SQFs) for the preparation of dental composites. Particularly, the acid etching was a facile way to create mechanical interlocking structures. In addition, the silanization process, the sol-gel treatment, and the polymer grafting were further proposed to increase the surface roughness and the reactive sites. The effect of surface modifications on the fiber surface morphological changes, mechanical properties, water stability, and in vitro cell viability of dental composites were investigated. RESULTS: Among all surface-modified SQFs, SQFs-POSS (SQFs modified with methacrylate-POSS) exhibited the roughest surface morphology and highest grafting rates compared with other three materials. Furthermore, all these SQFs were applied as reinforcements to make dimethacrylate-based dental resin composites. Of all fillers, SQFs-POSS demonstrated the best reinforcing effect, providing significantly higher improvements of 55.7 %, 114.3 %, and 164.7 % for flexural strength, flexural modulus, and breaking energy, respectively, over those of SQFs-filled composite. The related reinforcing mechanism was further investigated. The SQFs-POSS-filled composite also exhibited the best water stability performance and in vitro cell viability. SIGNIFICANCE: This work provided valuable insights into the optimization of filler-matrix interaction through fiber surface modifications. Specifically, SQFs-POSS markedly outperformed other formulations in terms of the physicochemical performance and in vitro cytotoxicity, which offers possibilities for developing high-performance dental composites for clinical applications in restorative dentistry.

Facile and rapid one-step extraction of carboxylated cellulose nanocrystals by H2SO4/HNO3 mixed acid hydrolysis.

A facile and rapid approach was designed to extract carboxylated cellulose nanocrystals (CCNCs) through a one-step hydrolysis process by using mixed acid system of sulfuric acid and nitric acid (H2SO4/HNO3). It is found that the surface hydroxyl groups on CNCs could be converted into carboxyl groups efficiently after 0.5 h treatment by introducing HNO3 as oxidant. The degree of oxidation could reach a maximum value of 0.11 at the reaction temperature of 80 °C, which was consistent with those prepared by the conventional TEMPO or APS oxidation method. Meanwhile, the as-prepared CCNCs presented a rod-like morphology with the length and diameter of 186 ±â€¯13 and 9 ±â€¯3 nm, respectively. More importantly, the CCNCs showed excellent dispersibility in water and some organic solvents due to the existence of negative carboxyl groups, which was benefit for their reinforcing applications and developing new applications by further surface functionalization.

Sandwich-Structured Ordered Mesoporous Polydopamine/MXene Hybrids as High-Performance Anodes for Lithium-Ion Batteries.

Organic polymers have attracted significant interest as electrodes for energy storage devices because of their advantages, including molecular flexibility, cost-effectiveness, and environmentally friendly nature. Nevertheless, the real implementation of polymer-based electrodes is restricted by their poor stability, low capacity, and slow electron-transfer/ion diffusion kinetics. In this work, a sandwich-structured composite of ordered mesoporous polydopamine (OMPDA)/Ti3C2Tx has been fabricated by in situ polymerization of dopamine on the surface of Ti3C2Tx via employing the PS-b-PEO block polymer as a soft template. The OMPDA layers with vertically oriented, accessible nanopores (∼20 nm) provide a continuous pore channel for ion diffusion, while the Ti3C2Tx layers guarantee a fast electron-transfer path. The OMPDA/Ti3C2Tx composite anode exhibits high reversible capacity, good rate performance, and excellent cyclability for lithium-ion batteries. The in situ transmission electron microscopy analysis reveals that the OMPDA in the composite only shows a small volume expansion and almost preserves the initial morphology during lithiation. Moreover, these in situ experiments also demonstrate the generation of a stable and ultrathin solid electrolyte interphase layer surrounding the active material, which acts as an electrode protective film during cycling. This study demonstrates the method to develop polymer-based electrodes for high-performance rechargeable batteries.

Relaxation times and energy barriers of rubbing-induced birefringence in glass-forming polymers.

The relaxations of rubbing-induced birefringence (RIB) in several glass-forming polymers, including polycarbonate and polystyrene (PS) derivatives with various modifications to the phenyl ring side group, are studied. Significant relaxations of RIB are observed at temperatures well below the glass transition temperature T (g) . The relaxation times span a wide range from approximately 10 s to probably geological time scale. Physical aging effects are absent in the RIB relaxations. The model proposed for the interpretation of RIB in PS describes well the RIB relaxations in all the polymers investigated here. The energy barriers are of the order of a few hundred kJ/mol and decrease with decreasing temperature, in opposition to the trend of Vogel-Fulcher form for polymer segmental relaxations above T (g) . The relaxation behaviors of different polymers are qualitatively similar but somewhat different in quantitative details, such as in the values of the saturated birefringence, the shape of the initial barrier density distribution functions, the rates of barrier decrease with decreasing temperature, and the dependence of relaxation times on temperature and parameter xi , etc. The RIB relaxations are different from any of the other relaxations below T (g) that have been reported in the literature, such as dielectric relaxations or optical probe relaxations. A microscopic model for the relaxations of RIB is much desired.

Achieving Long-Term Sustained Drug Delivery for Electrospun Biopolyester Nanofibrous Membranes by Introducing Cellulose Nanocrystals.

Electrospun nanofibrous membranes of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) seems not to be ideal for biomedical applications because of their hydrophobicity, and high crystallinity, as well as weak mechanical properties. It is found that hydrophilic drug such as tetracycline hydrochloride (TH) generally is located on the hydrophobic surface of electrospun PHBV nanofibrous membranes, leading to fast drug release. Therefore, we used cellulose nanocrystals (CNCs) as rigid organic nanofillers for PHBV nanofibrous membranes to enhance their mechanical, thermal, and hydrophilic properties. The influences of the CNC contents on microstructures and properties of composite nanofibrous membranes were studied. It is found that at 6 wt % CNC content, the increase of tensile strength by 125%, Young's modulus by 110%, and maximum decomposition temperature (Tmax) by 24.3 °C could be achieved, which could be contributed to strong hydrogen bonding between PHBV and CNCs. Moreover, with the introducing of the hydrophilic CNCs, the hydrophilicity of composite nanofibrous membranes was improved gradually. More importantly, good cytocompatibility, high drug loading and long-term sustained release property of composite nanofibrous membranes could be achieved. The maximum drug loading and drug loading efficiency were 25 and 98.8%, respectively, and more than 86% drug content was delivered within 540 h for the nanofibrous composite membranes with 6 wt % CNC content.

Polypyrrole-encapsulated iron tungstate nanocomposites: a versatile platform for multimodal tumor imaging and photothermal therapy.

A versatile nanoplatform of FeWO4@Polypyrrole (PPy) core/shell nanocomposites, which was facilely fabricated by first hydrothermal synthesis of FeWO4 nanoparticles and subsequent surface-coating of polypyrrole shell, was developed as an effective nanotheranostic agent of cancer. The as-prepared nanocomposites demonstrated excellent dispersion in saline, long-term colloidal storage, outstanding photo-stability and high photothermal efficiency in solution. In particular, FeWO4@PPy exhibited efficient performance for hyperthermia-killing of cancer cells under the irradiation of an 808 nm laser, accompanied with multimodal contrast capabilities for magnetic resonance imaging, X-ray computed tomography and infrared thermal imaging in vitro and in vivo. Furthermore, the nanocomposites presented impactful tumor growth inhibition and good biocompability in animal experiments. Blood circulation and biodistribution of the nanocomposites were also investigated to understand their in vivo behaviours. Our results verified the platform of FeWO4@PPy nanocomposites as a promising photothermal agent for imaging-guided cancer theranostics.

Hydrous RuO2 nanoparticles as an efficient NIR-light induced photothermal agent for ablation of cancer cells in vitro and in vivo.

Metal oxides are receiving an incremental attention in recent years for their potential applications in ablation of cancer cells due to their efficient photothermal conversion and good biocompatibility, but the large sizes and poor photo-stability will seriously limit their practical application. Herein, hydrous RuO2 nanoparticles were synthesized by a facile hydrothermal treatment and surface-modified with polyvinylpyrrolidone (PVP) coating. PVP-coated RuO2 nanoparticles exhibit a well dispertion in saline solution, strong characteristic plasmonic absorption in NIR region, enhanced photothermal conversion efficiency of 54.8% and remarkable photo-stability under the irridation of an 808 nm laser. The nanoparticles were further employed as a new photothermal ablation agent for cancer cells which led rapidly to cellular deaths both in vitro and in vivo.

Surface grafting of cellulose nanocrystals with poly(3-hydroxybutyrate-co-3-hydroxyvalerate).

Chemically modified cellulose nanocrystals (CNCs) were synthesized by grafting poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) onto CNCs via homogeneous acylation reaction between N,N-dimethyl formamide (DMF) by using toluene diisocyanate (TDI) as coupling agent and dibutyltin dilaurate as catalyst. The resulting copolymers were studied by using (1)HNMR, FT-IR, WAXD, DSC, TGA and contact angle measurements. Results showed that the copolymers kept their initial morphological integrity. Moreover, it is found that with the increase of the TDI/PHBV fractions, two transition exhibitions occurred in their thermal and hydrophobic properties, which could be modulated through controlling the lengths and grafting densities of PHBV side chains. Compared with those of neat PHBV, the crystallization of PHCN7 became easy while the crystallinity slightly decreased to 55.5%, the maximum decomposition temperature increased by 48.5°C, meanwhile the contact angle increased to 58° as compared to neat CNCs (30°).

Hydrophilic molybdenum oxide nanomaterials with controlled morphology and strong plasmonic absorption for photothermal ablation of cancer cells.

The molybdenum oxide nanosheets have shown strong localized surface plasmon resonance (LSPR) absorption in the near-infrared (NIR) region. However, the long alky chains of ligands made them hydrophobic and less biocompatible. To meet the requirements of molybdenum based nanomaterials for use as a future photothermal therapy, a simple hydrothermal route has been developed for hydrophilic molybdenum oxide nanospheres and nanoribbons using a molybdenum precursor and poly(ethylene glycol) (PEG). First, molybdenum oxide nanomaterials prepared in the presence of PEG exhibit strong localized surface plasmon resonance (LSPR) absorption in near-infrared (NIR) region, compared with that of no PEG. Second, elevation of synthetic temperature leads to a gradual transformation of molybdenum oxide nanospheres into nanoribbons, entailing the evolution of an intense LSPR absorption in the NIR region. Third, as-prepared molybdenum oxide nanomaterials coated with PEG possess a hydrophilic property and thus can be directly used for biological applications without additional post treatments. Moreover, molybdenum oxide nanoribbons as a model of photothermal materials can efficiently convert the 980 nm wavelength laser energy into heat energy, and this localized hyperthermia produces the effective thermal ablation of cancer cells, meaning a potential photothermal material.

Simultaneous improvement of mechanical properties and thermal stability of bacterial polyester by cellulose nanocrystals.

Green nanocomposites were prepared by adding well-dispersed cellulose nanocrystals (CNCs) into bacterial polyester poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) matrix. Simultaneous enhancements on the mechanical property and thermal stability of PHBV after reinforcement of CNCs were achieved. Compared to neat PHBV, a 149% improvement in tensile strength and 250% increase in Young's modulus can be obtained for the resulting nanocomposites with 10 wt.% CNCs, more importantly, the T0, T5%, Tmax and Tf increased by 51.4, 36.5, 47.1 and 52.9°C, respectively. This was due to a combination of CNCs reinforcement in the polymeric matrix, and especially the formation of strong intermolecular hydrogen bonding interactions through achieving the excellent dispersion of CNCs in the PHBV matrix via the solvent exchange procedure, as a result, the formation of six-membered ring ester during the degradation process of PHBV was clearly suppressed.

The absence of physical aging effects on the relaxation of rubbing-induced birefringence in polystyrene.

We found, through extensive experimental studies, that the physical aging effects are absent in the relaxation of rubbing-induced birefringence (RIB) in polystyrene (PS), and the relaxation involves very small length scale. A phenomenological model based on individual birefringence elements is proposed for the RIB relaxation. The relaxation times (RTs) of the elements are found to be independent of the thermal or stress history of the samples, either before or after the formation of the birefringence. The RTs are also independent of the molecular weight, rubbing conditions, and film thickness, while the RTs distribution function does depend on the molecular weight and rubbing conditions. The model provides quantitative interpretations that agree very well with all the reported experimental results, and sheds important light on the novel behaviors of the RIB relaxation. The absence of physical aging effects is probably due to the combined effects of small length scale of the RIB relaxation, and the accelerated aging speed in the near surface region in which the RIB concentrates.

The effects of thermal annealing on the relaxation of rubbing-induced birefringence in polystyrene.

We have conducted a systematic study on the effects of post rubbing annealing on the relaxation of rubbing-induced birefringence of polystyrene. It is found that annealing at T(0) only affects the relaxation up to T(0)+T(Lag), where T(Lag) is proportional to the logarithm of the annealing time t(A). A theoretical model based on the distribution of relaxation times due to the individual birefringence elements is proposed. To remove its contribution to the net birefringence each element must overcome an energy barrier E=(317+1.17xi)x10(3) J/mol, and therefore must have a characteristic relaxation time tau which depends on temperature T and a barrier height which ranges from 340.4 kJ/mol to 445.7 kJ/mol. The relaxation of birefringence is expressed by the equation NB(T, t)=[Formula: see text]N(xi)e(-t/tau(T,xi))dxi, in which both the relaxation time tau(T,xi) and the distribution function N(xi) can be extracted from experimental data. The predictions of the model agree well with all the experimental results presented in this work. The differences and similarities of the relaxation of birefringence with respect to the physical aging of quenched PS are discussed. In particular, similarities in terms of the general temperature lag phenomena are noted.