فصلنامه بسپارش
سال سیزدهم شماره 4 (پیاپی 49، زمستان 1402)

Due to their high latent heat, phase change materials have can store and release a large amount of thermal energy during phase change. Meanwhile, phase change material nanoemulsions have received much attention due to their suitable heat transfer properties and high heat storage capacity. In addition to the sensible heat capacity of the carrier fluid, these materials also have the ability to store thermal energy by using the latent heat capacity of phase change materials in the form of a dispersed phase. Also, due to the large surface to volume ratio of the dispersed phase on very small scales, heat transfer accelerates in this nanoemulsion system. In the present work, a comprehensive study on the formulation, thermophysical and rheological properties of nanoemulsion phase change materials is presented, in order to provide an insight into the advantages and challenges of using these materials. In addition to the experimental investigations on emulsions stability during storage time, and under thermal cycles and shear mechanical stresses have also been discussed. The effect of droplet size, stabilizer type and dispersed phase concentration on supercooling and other rheological and thermophysical properties of nanoemulsions such as thermal conductivity and density have also been investigated in order to determine the cooling-heating rate and volume required for energy storage, respectively. Finally, the potential of phase change material nanoemulsions for the effective management of thermal energy and promoting the methods of using renewable energy in different fields has been reviewed.

In recent years, research on polymer electrolytes (PEs) has been developed, because these materials can be considered as a suitable alternative to liquid electrolytes in various applications. Using polymer electrolytes solve the problems of solvent leakage, dendrite growth (lithium dendrite in lithium ion batteries), internal short circuit, use of corrosive solvent and production of harmful gases. During the last three decades, the introduction of polymer electrolyte membranes has led to significant progress in expanding and improving the performance of electrochemical devices such as batteries, fuel cells, supercapacitors, sensors, solar cells, etc. In general, PEs are ion-doped structures that have the ability to transfer and exchange ions via ion conducting sites. In various applications, polymer electrolyte membranes should provide properties, such as flexibility and proper filmability, high safety, suitable ionic conductivity for practical applications, low electrical conductivity, good mechanical strength, and thermal and electrochemical stability. In this article, in order to develop a sufficient knowledge of polymer electrolyte membranes, their specific chemical structure, ion transport mechanisms, methods of improving properties, as well as the applications of polymer electrolytes (such as fuel cells, batteries, capacitors, etc.) has been reviewed

Chitosan (CS) as a natural polymer has been widely studied in the field of wound healing due to its useful properties including non-toxicity, excellent biological properties, biodegradability and promotion of collagen deposition. However, low mechanical strength and moderate antibacterial properties are disadvantages that limit its further clinical application. Chitosan is a copolymer with a linear chain of diglucosamine and N-acetyl beta-glucosamine, which is produced by deacetylation of chitin. The deacetylation leads to the formation of cationic amine groups, which is actually a prerequisite for the antibacterial function of chitosan. Many researchers have adopted the use of nanotechnology, especially metal nanoparticles (MNPs), in order to improve the mechanical strength and specific antibacterial properties of chitosan composites with promising results. In addition, chitosan naturally acts as a reducing agent for metal nanoparticles, which can also reduce cytotoxicity. Therefore, chitosan in combination with metal nanoparticles exhibits antibacterial activity, excellent mechanical strength and anti-inflammatory properties and has great potential to accelerate the wound healing process. It is worth mentioning that the mechanism of action of metal nanoparticles is dose-dependent and excessive concentration can cause significant cytotoxicity. The loading efficiency and release rate of metal nanoparticles changes according to the manufacturing process. Hence, further investigation of dosage and preparation methods is a necessary prerequisite for clinical applications.

Solar radiation is a promising source for sustainable energy conversion and storage in many scientific and technological fields. Recently, the use of photothermal absorbers located at the water-air interface to generate steam has attracted a lot of attention, because the heat loss into the bulk water reduces by the localized heat, resulted in an improved solar steam efficiency. The structure of absorbers and salt resistance are two crucial parameters for water transport and desalination stability. As a new member of promising 2D materials, MXene has advantages including metallic conductivity, flexibility, diverse surface chemistry, and favorable optical and mechanical properties. These unique properties have attracted a lot of attention, and research on MXene has been intensively conducted and innovative applications have been reported in various fields. At the same time, various MXene/polymer nanocomposites have been developed and many wonderful results have been reported. In this article, the studies conducted in the field of MXene-polymer nanocomposite synthesis and their application in solar water desalination are reviewed. It should be noted that in recent years, limited studies have been done in this field, and there is a very high potential for further research.

Today, polymer materials are widely used due to their diverse properties, low cost, and easy mass production. Polytetrahydrofuran polyethylene glycol (TPEG) block copolymer is one of the prepolymers and precursors of polyurethanes. Polytetrahydrofuran polyethylene glycol block copolymer binder with its flexibility property increases flexibility and elongation, and as a result improves polyurethane properties. In the present work, the synthesis of polyether by chemical depolymerization method from polymer raw materials has been reviewed. TPEG is a hydroxyl-terminated polyether that is synthesized from the raw materials of polytetrahydrofuran (PTHF) and polyethylene glycol (PEG) in the presence of an acid catalyst (sulfuric acid) by chemical polymerization reaction. The synthesis has two simultaneous stages: polymerization of polytetrahydrofuran with an acid catalyst and then coupling the obtained product with polyethylene glycol. Factors such as reaction time and temperature, molecular weight and molar ratio of the reactants and acid catalyst concentration affect the molecular weight and the yield of production. In this copolymer, tetrahydofuran blocks form the soft segment and ethylene oxide blocks form the hard segment of the copolymer. The ratio of the soft segment to the hard segment of this polymer plays an important role in determining properties such as viscosity, density, and glass transition temperature (Tg). Characterization of this polymer is done using various tests including Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), carbon and proton nuclear magnetic resonance spectroscopy (13C NMR and 1H NMR). Researches show that the resulting copolymer is a random block copolymer. The glass transition temperature and melting point of TPEG are -73.5 ℃ and 8.74 ℃, respectively.