فهرست مطالب samal babanzadeh

Membrane processes are among the common methods for water sweetening and desalination, however, due to the cost and energy consumption, membrane processes are more suitable and have more practical applications. Designing of membranes in different shapes and dimensions, performing of separation process at room temperature, minimum consumption of chemical materials including solvents, and other additives are among the advantages of membrane process in respect to classical and common separation processes. Different membrane processes are used for water sweetening including reverse osmosis, electrodialysis, microfiltration, ultrafiltration, and nanofiltration membrane processes in which the reverse osmosis and electrodialysis methods are more important. Polymers are commonly used as membranes for the water sweetening industry, and due to their versatile structures and properties have a specific position in such a way that their applications are growing steadily. The most suitable and efficient polymeric membranes applied in the country are cellulose acetate, polyamide composite membranes, polysulfone, polyethylene, polypropylene, polycarbonate, polytetrafluoroethylene, polyvinylidene fluoride, and polydimethylsiloxane. There are different methods for improving the efficiency of polymeric membranes in the water desalination process in which preparation of copolymers and polymer blends, chemical modifications on the polymeric structure or their chemical functionalization, preparation of composites, and physical or chemical modifications on the surface of some polymers are more important that should be resulted in a suitable collection of physical, hydrophobic, chemical, thermal, and hydrolytic stability of the polymer and also led to remarkable flux and salt rejection. In this article, different membrane processes, and polymers that are applying in this industry is briefly introduced.

Aromatic polyamides are well known as a main group of high performance and heat-resistant polymers. One of the drawbacks to utilize these polymers is the difficulty in processing due to their insoluble nature in aprotic organic solvents in addition to their high melting point or glass transition temperature. One way of overcoming the main problem of heat-resistant polymers - i.e., enhancing solubility without too much scarifying of the thermal stability is designing new monomers.

Firstly, bis(4-oxybenzoic acid)-1,5-anthraquinone (DA1) and bis(3-oxybenzoic acid)-1,5-anthraquinone (DA2) were prepared through aromatic nucleophilic substitution reaction of 4-hydroxybenzoic acid and 3-hydroxybenzoic acid with 1,5-dichloro anthraquinone, respectively. In the next step, the Yamazaki method was applied for synthesis of novel polyamides by polycondensation reaction of the obtained new diacids with commercial aromatic diamines such as oxydianiline (ODA), p-phenylene diamine (PPDA), 2,6-diaminopyridine (DAP), and diaminodiphenyl methane (DADPM) in presence of triphenylphosphite and pyridine as the activating agents and N-methyl-2-pyrolidone (NMP) as a solvent.

The structures of prepared novel monomers and polymers were characterized using different spectroscopy methods. The thermal and physical properties of novel polymers such as thermal stability and behavior, solubility, viscosity and ultra violet absorption were studied and the structure-property relationship of these polymers was investigated. The prepared polymers showed defined UV-Vis absorption bands at the range of 344-370 nm. Inclusion of an aromatic and bulky anthraquinone unit to the main chain of polymers led to high thermal stability while their solubility was improved in polar aprotic solvents.

Periodontitis is one of the most widespread oral and dental diseases which results in damaging the periodontal tissues and finally may lead to healthy teeth losses. Recent surveys show that most adult in USA are suffering from chronic periodontits. In recent years, different methods have been used to reconstruct periodontal defects. Guided tissue regeneration (GTR) is a surgical procedure that uses barrier membranes to protect physically the periodontal defect to hinder gingival epithelium and connective tissue cells invasion and promote the proliferation of cells with slow migration rate such as periodontal ligament and bone cells. Generally, the membranes used in GTR are divided into two types: resorbable and non-resorbable. In this review, various GTR membranes based on natural and synthetic polymers are introduced. Natural polymers include polysaccharides and polypeptides and synthetic polymers are usually based on polyesters. Both polymeric membranes have pros and cons. Although natural polymers exhibit appropriate biocompatibility and biodegradability, they usually suffer from inferior mechanical properties. In contrast, membranes based on synthetic polymers have appropriate mechanical strength. However, their biocompatibility is not comparable with natural polymers and their degradation products may lead to foreign body reactions.