دو ماهنامه علوم و تکنولوژی پلیمر
سال بیست و نهم شماره 3 (پیاپی 143، امرداد و شهریور 1395)

Nanotechnology has a prominent potential in biomedical and biomedicine applications. Especially, owing to their exclusive characteristics, hybrid nanocompounds have been recently considered as promising systems for imaging and therapeutic usages. Study on silica-based mesoporous silica materials as drug delivery systems has been considerably developed over the recent few years due to the excellent versatility and stability of these mesoporous materials. In this review, the advanced developments in synthesis, functionalization and application of mesoporous silica in drug delivery are introduced. The first section consists of three main methods, grafting, co-condensation, and periodic mesoporous organosilicates. In the next part, new approaches for functionalization of mesoporous silica in order to control drug delivery are explained. The superiority of mesoporous nannoparticles for numerous drug delivery applications are also summarized. Different mesoporous silica structures can be designed by various chemical methods to meet the drug delivery requirements. The accessible channels in mesoporous which may act as reservoirs for storing drugs can be opened and closed by different systems and create stimuli-responsive release carriers. This review focuses on intelligent nanomaterials based on mesoporous silica which can be stimulated by chemical or biological signals, such as pH, temperature, light, magnetic field and enzymes.

A great contribution in research activities on carbon dioxide (CO2) separation, as the most important challenge in greenhouse gases control, has been made to develop new polymeric membranes. In this case, mixed matrix membranes (MMMs), comprised of rigid particles dispersed in a continuous polymeric matrix, was proposed as an effective method to improve the separation properties of polymeric membranes. In this research, ethylene vinyl acetate (EVA) copolymer and zeolite 4A powders were applied to prepare MMMs using solution casting/solvent evaporation method and CO2/N2 separation performance of the membranes was examined under different feed pressures (3-8 bar) and operating temperatures (25-50°C). Morphological and structural characterizations of the membranes were evaluated using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), density and solvent-induced swelling measurements. The gas permeability measurements through the constant-volume method showed the permeability of two gases increased in the presence of zeolite 4A nanoparticles in the polymer matrix. Calculation of diffusivity coefficients of gases revealed that improvement in the diffusivity of all gases into membrane matrix was the main reason for permeability enhancement. In addition, the increase in the CO2/N2 ideal selectivity with the presence of zeolite 4A nanoparticles in the polymer matrix was attributed to the increment in CO2/N2 diffusion selectivity. Under optimum condition, with the addition of 10 wt% zeolite 4A nanoparticles into the membrane matrix, the CO2 permeability increased from 20.81 to 35.24 Barrer and its related selectivity increased 20% compared to that of neat EVA membrane. Furthermore, the membrane performances increased upon feed pressure rise, while the selectivity decreased with the increase in temperature.

In order to achieve better mechanical properties of the nanocomposites containing carbon nanotubes, the carbon nanotubes should be oriented in a specific direction in the polymer matrix. This produces nanocomposites with anisotropic properties. Experimental study on the effect of injection direction and carbon nanotubes orientation on the mechanical properties of a multi-walled carbon nanotube (MWCNT)/polymethyl methacrylate (PMMA) anisotropic nanocomposite is the main aim of this article. Therefore, variable input factors including MWCNT concentration (0, 0.5, 1 and 1.5 wt%) and its in-flow and perpendicular directions were studied. First, nanocomposites were produced by co-rotating twin-screw extrusion. After that the nanocomposite sheets were fabricated by injection molding and test samples were cut into standard dimensions by laser cutting. The parameters including elastic module, yield strength, elongation, impact strength and hardness were studied. In addition, the effect of MWCNT on the melt flow index and optical properties was studied. Morphology of nanocomposites was carried out by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Increasing the elastic modulus by about 51%, tensile strength by 19% and elongation by 27% with addition of 1.5 %wt MWCNTs were also found. The results also illustrated that the elastic modulus improved by 10% and tensile strength by 13 % in the direction perpendicular to the flow direction. Yet more elongation was observed in in-flow direction. A little drop in hardness, a slight increase in impact strength and a decrease in luster and transparency by increases in MWCNTs loading were other noticeable results. A reduction in melt flow impact from 11 to 6.3 g/10min was another remarkable finding.

Hydrogels are three-dimensional polymer networks that can absorb and retain a huge amount of aqueous fluids even under certain pressure, but do not dissolve in water. They are responsive to environmental stimulants such as pH and ionic strength of the solution. In this study, a series of novel sodium carboxymethyl cellulose-based hydrogel nanocomposites were synthesized using acrylamide comonomer in the presence of iron magnetic as crosslinker and acrylic acid ammonium persulfate (APS) comonomer as initiator. All reaction variables affecting the water absorbency of the hydrogel nanocomposite including the concentration of crosslinking agent and initiator, and comonomers ratio were optimized in order to achieve the maximum absorption capacity. The experimental data showed that the hydrogel nanocomposite exhibited improved swelling capacity compared to the nanoparticel-free hydrogel. In addition, optimized hydrogel nanocomposite showed a good water uptake ability and the equilibrium swelling capacity was achieved within the initial 10 min. In examining the quality of the synthesized hydrogel nanocomposite, the amount of absorption in saline solutions of different concentrations was measured. Furthermore, the swelling behavior of hydrogel nanocomposite in solutions with different pH values was evaluated. The chemical structure of the hydrogel nanocomposites was characterized by means of transmission electron microscopy (TEM), scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), thermogravimetry analysis (TGA), derivative thermogravimetry (DTG) and Fourier transform infrared spectroscopy (FTIR). In order to study the drug delivery and drug release behavior, the release of sodium diclofenac as a model drug from synthesized hydrogel nanocomposite was examined in two acidic and basic buffer environments. The results indicated that this hydrogel nanocomposite may be an appropriate alternative for drug release processes in human body.

A high quality and high resolution printing can be rapidly created by inkjet printing technology. Inkjet printing is one of the most economic printing methods and ink waste in this technique is very low. Inkjet process provides printing on any type of substrates. The UV curable inks are special types of printing inks that have been widely used in the last decades. The use of UV curable inks is more attractive in inkjet printing technology in comparison to other methods of printing. The most important advantage of UV curable inks in this method is that they are VOC-free and compatible and have good adhesion on many types of substrates. In this research, the effect of hyperbranched polymers on the curing behavior of UV curable inks was investigated. Two types of hyperbranched polymers with hydroxyl and fatty acid chain terminal groups were used in ink formulations. The effect of hyperbranched polymers on the curing behavior of UV curable ink was investigated by real-time FTIR analysis. The results showed that the hyperbranched polymers could improve curing process by increasing the conversion rate of the third curing stage. All ink formulations containing hyperbranched polymers showed higher conversion than a neat sample. The highest conversion was 77 % for the blend containing a hyperbranched polymer with hydroxyl end groups while the neat sample showed a final conversion of 55%. UV curable inks in inkjet process containing hyperbranched polymers with hydroxyl end groups showed a higher final conversion than neat sample.

Poly()ε-caprolactone) ()PCL) has been widely investigated for medical applications because of its good physicochemical properties; however hydrophobic nature of PCL has been a colossal obstacle toward achieving scaffolds which offer satisfactory cell attachment and proliferation. To date, different methods have been proposed to lower the hydrophobicity of PCL. Moreover, molecular dynamic simulation (MD) is an excellent method to predict and study the chemical and physical properties of polymeric systems. To this end, MD study was assigned to evaluate the PCL/Pluronic blend. Moreover, some experimental data on PCL/Pluronic blend were collected and compared with the simulated results. Thermodynamic properties of neat and blended PCL were also calculated using MD simulation. The blend of PCL/Pluronic possessed lower density and higher free volume in comparison with neat PCL because of high mobility and low glass transition temperature of Pluronic chains and due to good molecular interactions between polypropylene oxide blocks of Pluronic and PCL. The ratio of the bulk to shear modulus revealed a toughened PCL blended substrate in comparison to its pure form. Moreover, a high interaction energy between the PCL/Pluronic blend and water molecules was observed due to the thermodynamically favored interactions of polyethylene oxide blocks of Pluronic and water molecules. Mean square displacement of water molecules at the bulk and in the surface of water layer placed in the vicinity of neat and blended PCL was calculated. The results revealed a difference between the behavior of the bulk and interfacial water molecules. Water contact angle measurements were carried out in order to evaluate the simulation results and demonstrated a considerable improvement in hydrophilicity of the PCL thin layers when blended with Pluronic.