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In this study, reduced graphene oxide (rGO)/boron nitride (BN) anisotropic aerogels (CGAs) used as the heat conduction network were prepared by one-step heat flow method to improve the low thermal conductivity and low heat transfer efficiency of phase change materials. Composite phase change materials (CPCMs) were obtained after vacuum adsorption of paraffin. The structure and thermal properties of the samples were then characterized. The results showed that the anisotropic aerogel was successfully prepared and the corresponding CPCM axial thermal conductivity was 1.68 W/(m K) when the graphene oxide (GO)/BN used to prepare the CGA was 1:20, which was 504% higher than pure paraffin. After 50 cycles, the paraffin leakage rate was 3.1%, and the enthalpy loss rate was 2.7%. When simulating the actual temperature change, the paraffin phase change time could be advanced by approximately 1210 s, and the paraffin phase change efficiency could be improved by approximately 47%. CPCMs have high thermal conductivity, high heat transfer efficiency, and high thermal conduction network stability. They exhibit high heat transfer efficiency and can be used in the fields of thermal energy storage and solar energy conversion and so on.

In view of their advantages (plasticity, low density, adjustable pore size, high porosity of >99.9%), three-dimensional graphene aerogels (GAs) are widely used for energy storage and adsorption separation, which has inspired the development and optimization of the corresponding synthetic techniques. In particular, self-assembly in the liquid phase features the benefits of tunability and sustainability and is viewed as a promising strategy of GA synthesis. During hydrothermal GA preparation, hydrophilic graphene oxide (GO) gradually turns lipophilic upon reduction, and the resulting phase transition separation and polarity change induce self-assembly into an aerogel. However, the effect of solution polarity on the structure or state of dispersed GO nanosheets, which affects the final property-determining process of automatic assembly, is still unclear. Herein, we prepared a series of GAs by hydrothermal reduction of unwashed GO with vitamin C in liquid-phase systems of different polarity and investigated the effects of polarity on the self-assembly process and aerogel properties using a range of instrumental techniques. The results showed that GO reduction is slowed down in weakly polar systems and further demonstrated that the shape of partially reduced graphene oxide (rGO) flakes depends on solution polarity. Flaky, layered, and stacked rGO particles obtained in strongly polar media self-assembled into anisotropic gully aerogels that were brittle and almost completely inelastic. Conversely, in weakly polar media, the prepared rGO sheets were twisted, which increased the number of contact points and modes between sheets and resulted in self-assembly into uniform-pore-structure honeycomb aerogels that showed good elasticity and could be repeatedly compressed.

Phased energy storage technologies are highly advantageous and feasible for storing and utilizing clean renewable energy resources, for instance, solar energy and waste heat, and it is an effective method to improve energy efficiency and save energy. However, phase change energy storage has some problems, for example, low thermal conductivity and phase change leakage, which lead to limited application. In this paper, anisotropic graphene aerogels were prepared by ice crystal template method with high thermal conductivity of graphene, and silver was attached to the pore wall graphene sheets and the graphene sheet boundaries of the aerogels. The results show that anisotropic graphene aerogels were successfully prepared, and SEM and EDS indicate that up to 9.14 at % silver was successfully attached to the graphene sheets and boundaries. The anisotropic thermal conductivity of the PArGO phase change composites after adsorption of the paraffin is significant, with a maximum axial thermal conductivity of PArGO of 1.20 W/(mK) and radial thermal conductivity of 0.54 W/(mK), compared to the pure paraffin (0.26 W/(mK)) increased by 362% and 108%, respectively. The enthalpy of the composite has been reduced to 149.6 J/g due to the silver particles attached, but the thermal properties have been greatly improved. In experiments simulating real temperature changes, PArGO achieves phase transitions very fast, with a 74% improvement on thermal efficiency of storage and discharge over the pure paraffin.

In this study, we investigated the directional heating of graphene oxide (GO) dispersion to generate a temperature gradient and form a simulated &ldquo, ocean current&rdquo, inside the dispersion so that GO sheets could be aligned in a directional manner and then reduced and self-assembled into anisotropic reduced graphene oxide (rGO) gel. After freeze-drying and varying degrees of vacuum microwave treatment, anisotropic chemically derived graphene aerogels (AGAs) were obtained. Through performance detection and the analysis of the results, it was verified that the AGAs with certain characteristics of &ldquo, were prepared in this experiment, and its axial direction has obvious directional arrangement. After being treated by vacuum microwave for a short time (1 min.), the axial thermal conductivity of the composite materials (AGA-adsorbed paraffin) was observed to be 1.074 W/mK, and the thermal conductivity enhancement efficiency was 995%, as compared with similar thermal conductivity enhancement composites that were found in previous studies, the proposed method in this paper has the advantages of simple processing, high efficiency, and energy conservation.

In view of their advantages (plasticity, low density, adjustable pore size, high porosity of99.9%), three-dimensional graphene aerogels (GAs) are widely used for energy storage and adsorption separation, which has inspired the development and optimization of the corresponding synthetic techniques. In particular, self-assembly in the liquid phase features the benefits of tunability and sustainability and is viewed as a promising strategy of GA synthesis. During hydrothermal GA preparation, hydrophilic graphene oxide (GO) gradually turns lipophilic upon reduction, and the resulting phase transition separation and polarity change induce self-assembly into an aerogel. However, the effect of solution polarity on the structure or state of dispersed GO nanosheets, which affects the final property-determining process of automatic assembly, is still unclear. Herein, we prepared a series of GAs by hydrothermal reduction of unwashed GO with vitamin C in liquid-phase systems of different polarity and investigated the effects of polarity on the self-assembly process and aerogel properties using a range of instrumental techniques. The results showed that GO reduction is slowed down in weakly polar systems and further demonstrated that the shape of partially reduced graphene oxide (rGO) flakes depends on solution polarity. Flaky, layered, and stacked rGO particles obtained in strongly polar media self-assembled into anisotropic gully aerogels that were brittle and almost completely inelastic. Conversely, in weakly polar media, the prepared rGO sheets were twisted, which increased the number of contact points and modes between sheets and resulted in self-assembly into uniform-pore-structure honeycomb aerogels that showed good elasticity and could be repeatedly compressed.

Feather, as a by-product of the poultry industry, has long been treated as a solid waste, which causes environmental and economic problems. In this work, the hydrolyzed feather keratin (HFK) was extracted from the chicken feather using a cost-effective method of alkali-extraction and acid-precipitation by applying urea and sodium sulfide. The aim was development and characterization of the eco-friendly films based on the HFK with variable glycerol contents by a thermoplastic process. The thermal analysis showed that high temperature and high pressure improved the compatibility between the glycerol and the HFK molecules. Also it was shown that the addition of water is necessary in the hot-pressing process of films. The FT-IR analysis indicated that the formation of the new hydrogen bonds between HFK and glycerol. By increasing the glycerol content, the film tensile strength ( σ b ) decreases from 10.5 MPa to 5.7 MPa and the solubility increases from 15.3% to 20.9%, while the elongation at break ( e b ) achieves the maximum value of 63.8% for the film with 35% glycerol. The swelling was just below 16.9% at 25 °C for 24 h, suggesting a good stability of the films in water. The water vapor permeability (WVP) varied between 3.02 × 10 − 10 g · m − 2 · s − 1 · Pa − 1 and 4.11 × 10 − 10 g · m − 2 · s − 1 · Pa − 1 for the films with 20% and 40% glycerol, respectively. The HFK film was uniform, translucent and tough, which could be used in packaging and agricultural field.

The development of edible films based on the natural biopolymer feather keratin (FK) from poultry feathers is of great interest to food packaging. Edible dialdehyde carboxymethyl cellulose (DCMC) crosslinked FK films plasticized with glycerol were prepared by a casting method. The effect of DCMC crosslinking on the microstructure, light transmission, aggregate structure, tensile properties, water resistance and water vapor barrier were investigated. The results indicated the formation of both covalent and hydrogen bonding between FK and DCMC to form amorphous FK/DCMC films with good UV-barrier properties and transmittance. However, with increasing DCMC content, a decrease in tensile strength of the FK films indicated that plasticization, induced by hydrophilic properties of the DCMC, partly offset the crosslinking effect. Reduction in the moisture content, solubility and water vapor permeability indicated that DCMC crosslinking slightly reduced the moisture sensitivity of the FK films. Thus, DCMC crosslinking increased the potential viability of the FK films for food packaging applications, offering a value-added product.

The effects of structure and composition of different montmorillonites on their catalytic performance in the dimerization of unsaturated fatty acids were investigated. The dimerization reaction was performed at 240 ºC for 3 h, with montmorillonite as catalyst, and LiCl as the co-catalyst. The results showed that the specific surface areas of the different montmorillonites did not have a major effect on their catalytic performance, but the interlayer spacing and surface acidity of montmorillonite show significant effects on the product yield. After the organic modification through hexadecyl trimethyl ammonium bromide (CTAB) intercalation, the microenvironment of the montmorillonite layer changes. Moreover, the inner and outer surfaces change from being hydrophilic to lipophilic, which improves the dispersibility of montmorillonite in fatty acids. The xAl/xSi molar ratios of the three samples are similar and lie within the range of 0.4306-0.5010, thus the xAl/xSi molar ratio has little effect on the dimerization reaction.

Feather keratin (FK) extracted from feathers represents a valuable source of biodegradable and biocompatible polymer. The aim of this study was the development and characterization of blended films based on FK and polyvinyl alcohol (PVA) cross-linked by dialdehyde starch (DAS) for a potential drug release application. The compatibility of FK/PVA was improved when cross-linked by DAS: the relative crystallinity of the PVA/FK film slightly decreased, and the enthalpy value for the melting peak decreased by about 50% for the cross-linked films. The total soluble mass of all blend films in water was below 35% at 37 °C, indicating a good stability of the films in water. The results of the Rhodamine B dye (as a model drug) release tests showed that the release rates decreased with increasing DAS content. DAS-induced cross-linking improves several important properties of the FK/PVA films, such as the compactness, the compatibility, and the stability in water. These improvements offer the potential to expand the application of FK films in the biomaterial field.

Feathers, a byproduct of the poultry industry, have long been considered as a solid waste, posing a series of environmental and economic problems. However, feather keratin (FK) extracted from feathers is a valuable source of the biodegradable and biocompatible polymer. The aim of this study was to develop and characterize novel casting films based on feather keratin (FK) crosslinked by dialdehyde starch (DAS) and plasticized with glycerol for applications in biomedicine. The microstructure, crystallization behavior, light transmission, moisture content, solubility, tensile properties, water vapor barrier property, and cytotoxicity of the FK–DAS films were investigated. The fracture surface of the crosslinked film showed a more compact microstructure than that of the control film, and the crosslinked films were completely amorphous and very transparent (transparency value

Feathers, as a by-product of the poultry industry, have long been treated as solid waste disposal which causes a series of environmental and economic problems. Feather keratin (FK) can be extracted from feathers and have very strong stretching resistance. A series blend films based on FK and poly (vinyl alcohol) (PVA) was prepared by solution casting, and dialdehyde starch (DAS) were introduced to achieve better physicochemical properties for the blend films. According to DSC analysis, the single glass transition temperature and single melting temperature of the blend films indicated the good compatibility among FK, PVA and DAS. With increasing PVA content, the tensile strength (σb), elongation at break (ϵb), and decomposition temperature increased, indicated that hydrogen bonds were formed between FK and PVA. With certain PVA content, the increase of DAS caused σb to increase and ϵb, decomposition rates, solubility and water vapor permeability (WVP) to decrease, suggesting the formation of crosslink netw...

Two polymerizable room temperature ionic liquids (RTIL), AMPS-BA and AMPS-DMAEMA, were synthesized by neutralization of 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) with butylamine (BA) and 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA), respectively, in acetone, followed by evaporation of the solvent under a reduced pressure at room temperature. The RTILs were characterized by differential scanning calorimetry to determine their glass transition temperatures (Tg). Co-polymeric gels of the RTILs with 2-hydroxyethylmethacrylate (HEMA) were prepared by aqueous solution polymerization using N,N′-methylenebisacrylamide (MBAm) as a cross-linker and ammonium persulfate as an initiator. The superabsorbency of the gels in water and various organic solvents was gravimetrically investigated. The results showed that the Tg of AMPS-BA and AMPS-DMAEMA was -47.7°C and -45.8°C, respectively. Poly(AMPS-BA-co-HEMA) gels exhibited superabsorbency in both water and various organic solvents, while poly(AMPS-DMAEMA-co-HEMA) gels did not swell in any liquids. The mechanism for the swelling difference between poly(AMPS-BA-co-HEMA) gels and poly(AMPS-DMAEMA-co-HEMA) gels was critically discussed.

In this study, anisotropic graphene/graphene oxide (GO) aerogels (AGAs) were obtained by freeze-drying after direct participation of pristine graphene in the self-assembly of anisotropic gel by the heat flow method. After vacuum microwave treatment, the physical, chemical and structural characteristics of the AGAs were investigated. The results show that AGAs, in which the internal graphene sheets are parallel to the heat flow direction, are successfully prepared. After microwave treatment, the amount of oxygen and nitrogen reduces significantly and the sp2 domain increases. However, at the same time, many fragments and holes are generated in the graphene sheets. The effects of AGAs on the phase transition of paraffin is studied, and the results show that the melting enthalpy, solidification enthalpy and initial melting temperature of AGA/paraffin composites decreases as the GO content in the AGAs increases, whereas the melting range, solidifying range and subcooling degree increases. The highest axial thermal conductivity of the AGA/paraffin composite is 1.45 W/(mK), and the thermal conductivity enhancement efficiency is 884% (AGA content was 0.53 vol %). Compared with previously investigated, similar AGA/paraffin composites, the aerogels fabricated in this study have the obvious advantages of a simple fabrication process, a low cost and a high thermal conductivity enhancement efficiency. These aerogels possess the potential for application in phase-change energy storage (PES), thermal energy management and other fields.

Novel copolymeric gels of poly(AMPS–TEA-co-AAm) with superabsorbency in both water and alcohols were synthesized by neutralizing 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) with triethylamine (TEA) followed by copolymerizing the resulted salt with acrylamide (AAm) in aqueous solutions using N,N′-methylenebisacrylamide (MBAm) as a crosslinker, and ammonium persulfate (APS) as an initiator. By swelling the xerogel of poly(AMPS–TEA-co-AAm) in the drug solution followed by removing the solvent to give drug-polymer conjugate, the incorporation of a model drug, chloramphenicol, into the gels was investigated by using water and alcohols as solvent, respectively. The in vitro drug release profile of the drug-polymer conjugate was investigated in PBS. The results showed that poly(AMPS–TEA-co-AAm) gels exhibited superabsorbency in both water and a series of alcohols; and the alcohol-facilitated uploading of chloramphenicol into the gels was much greater than that achieved in water. The poly(AMPS–TEA-co-AAm...

Effective therapy lies in achieving a therapeutic amount of drug to the proper site in the body and then maintaining the desired drug concentration for a sufficient time interval to be clinically effective for treatment. The blood-brain barrier (BBB) hinders most drugs from entering the central nervous system (CNS) from the blood stream, leading to the difficulty of delivering drugs to the brain via the circulatory system for the treatment, diagnosis and prevention of brain diseases. Several brain drug delivery approaches have been developed, such as intracerebral and intracerebroventricular administration, intranasal delivery and blood-to-brain delivery, as a result of transient BBB disruption induced by biological, chemical or physical stimuli such as zonula occludens toxin, mannitol, magnetic heating and ultrasound, but these approaches showed disadvantages of being dangerous, high cost and unsuitability for most brain diseases and drugs. The strategy of vector-mediated blood-to-brain delivery, which involves improving BBB permeability of the drug-carrier conjugate, can minimize side effects, such as being submicrometre objects that behave as a whole unit in terms of their transport and properties, nanomaterials, are promising carrier vehicles for direct drug transport across the intact BBB as a result of their potential to enter the brain capillary endothelial cells by means of normal endocytosis and transcytosis due to their small size, as well as their possibility of being functionalized with multiple copies of the drug molecule of interest. This review provids a concise discussion of nano carriers for drug transport across the intact BBB, various forms of nanomaterials including inorganic/solid lipid/polymeric nanoparticles, nanoemulsions, quantum dots, nanogels, liposomes, micelles, dendrimers, polymersomes and exosomes are critically evaluated, their mechanisms for drug transport across the BBB are reviewed, and the future directions of this area are fully discussed.

The adsorption behaviors of copper and lead ions in aqueous solution by cottonseed protein-poly (acrylic acid) copolymer (CP-PAA) hydrogel composite have been studied in single component sorption systems. The influence of cottonseed protein content in the copolymer composition on the adsorption capacity of the hydrogel is studied and the sorption of copper (II) and lead (II) ions is investigated in aqueous solution with different initial metal ion concentration and pH value, respectively. The results indicate that the hydrogel composite is a suitable sorbent for the two metal ions. The experimental data of the adsorption equilibrium from Cu(II) and Pb(II) solution correlated well with the Langmuir isotherm equation. The adsorption kinetics of the two metal ions has been analyzed and the pseudo–second-order equation provides good fits to experimental data of both metals. By treatment with aqueous HCl solution, the hydrogel can be regenerated and reused again to adsorb heavy metal ions. The characterization...