فصلنامه بسپارش
سال ششم شماره 3 (پیاپی 20، پاییز 1395)

The ability to inject a drug-incorporated polymer to a localized site in which the drug transforms from a solution to a semi-solid drug depot has a number of advantages. Most notable among these advantages are ease of application and localized, prolonged drug delivery. In the area of parenteral controlled release formulations, in-situ forming formulations are attractive alternatives to preformed implants and microparticles. Biodegradable in-situ forming implants can be manufactured in simple steps with minimum equipments and uncomplicated processes. They are injected as low viscous solutions or suspensions and transform in the body to a gel or solid depot. Different ways can be used to stimulate this transformation: crosslinking, solidification or precipitation of polymer solution which the former produces in situ crosslinking systems, and the next one produces in situ solidifying organogels and the last one produces in situ polymer precipitation systems with phase separation .In this article we introduce the various strategies that are used to prepare in situ setting systems, and outline their advantages and disadvantages as localized drug delivery systems.

Absorption of electromagnetic radiation in the microwave region is one of the most important cases which, today, is used in commercial purposes and many application fields including communications equipment, civil, military and various electronic systems and technologies. Therefore, with development of wireless electronic devices, we need to have knowledge on some devices that should absorb harmful radiation. According to the nature and position of the wave absorbing materials, the synthesis of these materials and study of their properties are considered important. Since waves constitute both electric field and magnetic field, an ideal wave absorption material should be able to absorb electrical and magnetic waves simultaneously. The nanocomposites containing an electrically conductive material are best candidates as waves absorbents. In using these nanocomposites the wave electric part can be absorbed and converted into heat, in order to dampen the waves. The magnetic property of waves is also another aspect which constitutes waves. Magnetic nanoparticles can absorb the waves by creating small magnetic fields. Therefore, those nanocomposites containing inorganic magnetic nanoparticles as well as conjugated polymers with semi-conductive properties are recently considered as new wave absorbing materials. These light-weight composites can be synthesized easily. Because of the special position of wave absorbent composites in today’s life, study on their varieties, method of preparation and specific features is considered as the topic of this article.

Polymers are commonly applied in construction of rechargeable lithium-ion batteries (LiBs). The role of polymer on LiB electrochemical performance is discussed in detail. Literature reviews show that the use of various polymers in construction of LiBs is growing especially as electrolyte, electrode binder, current collector and separator. The polymer type significantly affects the electrochemical performance of LiBs including the capacity, cycle life, and thermal and mechanical stability of battery components. Our literature research indicates that the polymer electrolytes are going to be widely used in LiBs due to their safety and good electrochemical performance. Recently, the major studies have focused on finding appropriate alternatives amongst hydrophilic polymers as electrode binders in LiBs with aqueous electrolytes to enhance ion diffusion through developed hydrophilic properties.

An organic-inorganic hybrid composite includes a silane coupling agent, an organic polymer and inorganic particles on nano or microscales. These compounds are prepared due to their potential applications in different industries. Silane coupling agents are organo-silicon compounds which act as a binder and are widely used to bond organic materials such as rubbers, plastics, adhesives and coatings to inorganic materials like glass fibers, adhesives, minerals and fillers. For preparation of organic-inorganic hybrid composites, first: the surface of inorganic substrates such as metal powders, inorganic particles and fillers in nano or micro dimensions is modified by applying coupling agents of different functional groups through sol-gel method in an aqueous media under acidic condition. In the next step, the surface of modified particles is polymerized with vinyl monomers or monomers with one or more different functional groups by grafting-to or grafting-from methods. In this way, different nano and micro particles such as silicon dioxide, iron oxide, aluminum oxide, titanium dioxide, silver oxide, bismuth oxide and etc are widely used. As a result, silane coupling agents are extensively used to improve the interfacial adhesion in composites and other material systems and to enhance the performance of composites such as their mechanical strength, moisture or chemical resistance and electrical properties to a desirable level. This typically includes the modification of resins, organic compounds and inorganic surfaces, accomplished by adding one or more specific functional groups of one or more organo-silane coupling agents.

Solar cells are devices that directly convert the sunlight into electricity by photovoltaic effect. Photovoltaic effect was discovered in 1839 by Bequerel. In recent years, different generations of solar cells have been developed. There are different types of solar cells including silicone solar cells, dye-sensitized solar cells, quantum dot solar cells, organic solar cells and new generations. Among different kinds of solar cells, polymer solar cells have attracted a lot of attention because of their flexibility, light weight, possibility of designing of materials for their construction, high absorption coefficient, solution processability and production by low-cost technologies. In this review, polymer solar cells and conjugated conductive polymers as applied in active layers and their characteristics as conjugated polymers are introduced. In recent times advances are made on active layer architecture in order to increase power conversion efficiency. Finally, their corresponding characterization methods and their most important parameters are discussed.

Polymers usually have high resistance to electricity flow. Electrical conductivity of polymers could be changed utilizing fillers. One of these fillers, indium tin oxide (ITO), has many different applications in various fields due to its relatively low electrical resistance and its ability to impart transparency and clear coatings. Electrically conductive transparent coatings containing ITO nanoparticles can be prepared via sol-gel technique (low temperature) and cured by UV irradiation and/or by post curing at low temperature and reduction under a passage of gas (such as N2) on polymeric substrates. Fluence of UV irradiation is an effective parameter on surface morphology of polymeric samples. Photo-degradation of coatings may occur at high irradiation fluence due to the photons leaked from polymeric substrates surface. The difference in surface topography (surface roughness) of polymeric substrates results in samples with different electrical resistance. A polymeric substrate with the lowest surface roughness shows the highest electrical conductivity.

As a new and practical bio-engineering phenomenon, adding drag reducing polymers (DRPs) to blood has paramount effect on improving blood circulation in both in-vitro and in-vivo systems. It is proved that these agents could be employed for better resuscitation and revival of a disturbed blood flow and oxygen shortage in animal models. A minute concentration of DRPs was successfully applied in some animal models to improve blood flow and to increase tissue perfusion. Although there is not any report on human, yet the scientists vigorously extend their application to the living body. In the current study, apart from the introduction given on drag reduction effect and various drag reducing agents, some useful applications are presented on DRPs effect on blood circulation and the potential mechanisms to support them. The main studies which are carried out in vitro do reveal that by adding DRP, thickness of the cell free layer is reduced near the blood vessel wall.

Nowadays in worldwide competitive markets, the development of product by shortening the cycle time from design to production process in order to increase the rate of production is a remarkable success for manufacturing organizations. Therefore, fast prototyping and manufacturing methods are developed and grown at a fast rate. The fused deposition modeling (FDM) using polymeric filaments can be classified as one of the fast prototyping methods. Several works have been carried out to evaluate the effect of FDM processing parameters on mechanical properties. The results showed that the parameters such as raster orientation, air gap and build plane were the most important factors on mechanical properties, also the fill pattern and design precision were the ones which had significant impacts on the surface quality. By reviewing the related published papers, our aim in this article has been to provide some information on the above-mentioned manufacturing process to include the important parameters that should be controlled in order to acquire a product with optimum mechanical properties.

Fluorescence is an interesting phenomenon emanated in photo-electrical characteirstics of polymers. This feature is used in making highly sensitive polymer sensors. In this study, as part of the introduction given on luminescence and its different types there is a discussion on the production of chemical sensors based on conjugated polymers (CP). This discussion focuses on polymer sensors based on fluorescence polymers, their detection mechanisms, various kinds, pros and cons, different systems of media and future trends. It has been asserted that the chemical sensors based on amplifying fluorescent polymers (AFPs) have suitable semi-conductivity and processability at the same time. Amplifying fluorescent polymers through shifting the excitons in three dimensions and formation of molecular wire show high sensitivity in detection of explosives. The field tests performed by these devices have proved that this technology can be successfully used for high-sensitive detection of explosives, land mines and under-water mines based on nitro-aromatic compounds.

Expert of Petrochemical group/Standard Research center