Self-healing materials as an important class of intelligent materials show an intrinsic ability to repair themselves without requiring human participation. One of the exclusive properties of living tissues that makes them resistant to different damages is their self-healing property. The use of polymeric materials has significantly increased in recent decades and it is impossible to imagine the today's world without polymers. During the regular use of polymeric materials, cracks and micro-cracks can occur. Macrocracks are formed as a result of the propagation and development of microcracks which can cause a decrease in mechanical properties and ultimately the breakdown of polymeric materials. Self-healing polymers, which can repair spontaneously after cracks, provide a longer lifetime of materials, and offer an interesting direction in material science.
Photochromism involves the reversible transformation of a chemical species between two isomeric forms induced by the absorption of light which results in a change in absorption spectra. The mechanisms include pericyclic reactions, cis–trans isomerizations, dissociation processes, intramolecular hydrogen transfers or group transfers, and electron transfers (oxidation–reduction). In addition to a color change, these transformations are accompanied by changes in the physical and chemical properties of the species involved, such as alterations to in the dipole moment, refractive index and geometrical structure. Importantly, these dynamic transformations can generate coincident changes in the optical, chemical, electrical and bulk properties of the system that incorporates them. Photochromic molecules therefore play a pivotal role within photo-responsive systems, being able to capture an optical signal and then convert this, via their isomerization, to a useful property change. Photochromic molecules have usually been incorporated into polymer matrices by binding them covalently to polymer backbones or by dissolving or suspending them in polymer solids. The photochemical as well as thermal behavior of organic photochromic molecules is influenced in various ways by the characteristics of the polymeric media so that photochromic polymers have attracted extensive interest, leading to interdisciplinary research.
The nanofiltration membrane was first introduced during late 1980s possessing properties between reverse osmosis and ultrafiltration membrane. Nanofiltration membranes have been used for applications including food industry, pharmaceutical, wastewater treatment, and desalination. Various methods were reported for nanofiltration membrane preparation particularly through electron beam irradiation, UV/photo grafting, layer by layer, plasma treatment, interfacial polymerization, and nanoparticle incorporation. Nanofiltration membranes were reported to remove microorganisms, turbidity, dissolved salts, and hardness. Major problem in application is nanofiltration membrane fouling, thus efforts regarding fouling mitigation are focused.
Crude oil demulsification
The problem of water-in-crude-oil emulsions accompanies with the dawn of petroleum industry. In most cases, the presence of water droplets in crude oil is highly undesirable as it can lead to several problems, among which the oilfield surface qualification treatment (dehydration) and refinery plant upgrading process (desalting) have been mostly concerned. Therefore, the removal of entrained or emulsified water droplets from continuous oil phase has attracted much attention consistently during the past decades, and it will become more and more challenging with the pressure of limited source and unlimited control of processing cost. Nowadays, possible separation methods of water-in-oil (W/O) emulsions include gravity or centrifugal settling, thermal treatment, chemical demulsification, pH adjustment, electrostatic demulsification, freeze/thaw method, filtration, membrane separation, microwave radiation and ultrasonic energy etc.
A polymer brush is a polymer system consisting of a high density of short chains grafted onto a surface to form a special topological structure, which appears as a stretched conformation. It resembles a brush between the short and main chains, influenced by a steric effect. Along with the rapid development of polymer science, the structure and length of polymer brush molecules may be controlled precisely; therefore, it presents an attractive applicability in many fields, including drug delivery, lubrication, altering the conductivity of a material's surface, and controlling the transport of small particles. In recent years, investigation into the stimulus-response polymer brush has involved biochemical, environmental biology and biomedical applications. This is owing to its ability to reversibly switch between adaptation and responsiveness via external stimulation, including temperature, pH value, ionic strength of the solvent and light.
Oligomerization of ethylene to α‐olefins
Linear alpha olefins (LAOs) are primarily prepared through the industrial process of ethylene oligomerization. These linear α-olefins have a broad range of applications to produce plasticizers, detergents, lubricants, and as a comonomer in the production of polyethylene. Comonomers such as 1-hexene and 1-octene as are specially used for the production of the linear low-density polyethylene (LLDPE). So, the selective production of LAOs particularly by the ethylene trimerization, in the laboratory and large scales has been carried out by many researchers and companies. Chromium and titanium-based complexes are the appropriate choices for both selective and non-selective catalytic oligomerization of ethylene among all coordination complexes.