فصلنامه بسپارش
سال دوازدهم شماره 1 (پیاپی 42، بهار 1401)

The tissues in the human body comprise complex assemblages of several different types of cells that are dispersed on an extracellular matrix (ECM). In addition to biochemical and chemophysical factors, dynamic changes in the mechanical-structural properties of ECM lead to changes in cell behavior such as proliferation, differentiation, and its nature. Since any activity of the cells takes place on a dynamic substrate in the body, it is necessary to provide conditions in which the dynamic environment inside the body can be simulated. Therefore, researchers need intelligent biomaterials that can act as a powerful substrate to design smart cell culture platforms and tissue engineering scaffolds, as well as to simulate this complex environment. Shape memory polymers (SMPs) and shape-changing polymers (SCPs) are the new generations of intelligent materials that can be converted from shape A to shape B in a response to a stimulus, creating new mechanical and structural properties. Although tissue engineering studies on static substrates have been performed so far, it is now clear that the fate of cells in proliferation and differentiation is influenced by the dynamic conditions of the environment. However, recent studies have been focused on designing new substrates to mimic the dynamic microenvironment. In this review article, a brief definition of cell mechanobiology is introduced and then the recent advances in the design of SMPs and SCPs used in fundamental cell mechanobiology studies were highlighted. A survey of the current review can create a more innovative perspective for researchers in this field.

Only 10% of Iran's oil reservoirs have a sandy structure and the rest have a carbonate structure. Therefore, a relatively large part of the oil in these reservoirs is heavy and can not be extracted by conventional methods. For this reason, methods called enhanced recovery are used to increase the recovery factor of oil reservoirs. Enhanced recovery is performed by secondary and tertiary methods, which include thermal and chemical methods and gas injection are among the tertiary methods. One of the chemical methods is polymer flooding. For many years, polymers have been used to control the mobility of injected water and to enhanced recovery of oil reservoirs. By increasing the viscosity of polymers, they reduce the mobility of water, increase the stability of the kinematic profile, reduce the phenomenon of finger injection of the injected fluid, and finally increase the oil production from the reservoir. In this paper, first the application of polymers in oil reservoirs, then the types of polymers used in the discussion of enhanced oil recovery, including polyacrylamides, alkali-surfactant-polymer, xanthanes, polysaccharides, and hydroxyethyl cellulose have been investigated. In addition, destructive factors of polymer structure, factors affecting polymer flooding, different injection patterns, screening criteria, and in general parameters affecting the succesful operation and its general dimensions, as well as, simulation of polymer flooding in one of the Iranian oil fields are investigated.

Today, almost all polymer researchers use rheological methods to identify the microstructure of various polymer systems. One of the most popular and widely used methods is the small amplitude oscillatory shear (SAOS) test. SAOS provides a set of valuable information about the microstructure of polymeric materials. Various materials in this test are examined only in the linear viscoelastic region (LVR). However, polymer melts (raw, alloy, composite, etc.) are exposed to a much higher shear rate in processing methods. Therefore, the study of the non-linear behavior of polymers is of particular importance. Fourier transform rheology (FT rheology) is one of the most advanced methods for identifying the microstructure of polymers. The use of large amplitude oscillatory shear (LAOS), which leads to departure from the LVR, is the basis of the method. The stress response to this large deformation has the basic harmonies and involves higher odd harmonies that complicate the response form. In this method, the Fourier transform technique is used to convert a complex response in the time domain to a simple response in the frequency domain. The mentioned response contains valuable information about the microstructure of materials, which is impossible to extract (with this high accuracy) from the output responses in the LVR.

Electrospinning is an easy and efficient method for preparing nanofibers on laboratory and industrial scales. In recent years, various studies have been done with special attentions to specific structures, increasing the application and eliminating the shortcomings of previous methods. Janus structure is one of the new and widely used structures that due to the limitations and challenges in achieving this structure, such as nozzle design, phase separation of two polymer solutions during electrospinning, flow rate control, optimal voltage and other parameters, the published reports in this field, are limited. Side-by-side electrospinning is one of the common ways to achieve this special structure. In this method, with appropriate nozzle design, two polymer solutions can be electrospun simultaneously. In addition, the nozzle design and the related parameters such as needle diameter, angle, and distance between the nozzles are of special importance. Also, parameters related to the rheological behavior of the polymer, especially viscosity, are crucial in achieving this particular structure. In this paper, the methods of preparation of Janus nanofibers by side-by-side electrospinning method, new structures based on these nanofibers, including the study of structure and production methods through side-by-side electrospinning, are briefly reviewed.

Pressure vessels are one of the most widely used and high-risk equipment in various industries. Pressure vessels are divided into four types based on material and structure. Weakness in design, construction and production, service and especially incorrect choice of materials are the causes of pressure vessel failure. With the introduction of composites into the world of these vessels, many design weaknesses and their mechanical properties have been improved. By using high density polymers such as polyethylene, the weight of the pressure vessel is reduced. Type IV pressure vessels with the simultaneous use of composite structure and polymer liner are able to reduce weight by up to one-fifth and double the useful life compared to the type I of vessels. The advantages of the fourth type of pressure vessels are corrosion resistance, no fatigue in consecutive loads, lightness and portability, high operating pressure (700 bar) and lack of complexity of the production method, and their disadvantage is the high production cost due to the use of carbon fibers. These pressure vessels are used to store alternative fuels such as hydrogen and portable individual oxygen capsules. In this article, the pressure vessels types are briefly reviewed and the fourth type is compared with other types.

Polyurea has drawn the attention of construction activists and engineers as a modern building material due to its unique structure, unique properties, and relatively easy application even in hard-to-reach places. A wide range of excellent properties such as durability and high resistance against the atmospheric, chemical, and biological factors have made this polymer a superb option for the construction industry. The ability to reinforce the building materials and structures coupled with excellent resistance against corrosion and abrasion has dramatically increased the popularity of polyurea as a protective coating in the construction industry. In these industries, sealing and insulating the different floors and surfaces have also been considered using the polyurea coating. Polyurea coating technology is a green technology without pollution and toxicity to the environment, which is an essential advantage over many competing technologies in the construction industry. The use of polyurea composite systems to optimize various properties such as mechanical and thermal properties in addition to reducing the costs and economic burden is increasing. In the present paper, multiple applications of polyurea-based materials in the construction industry are discussed.