Sharif Digital Repository

Gels are composed of crosslinked polymer network and solvent molecules. When the main chain network is incorporated with functional groups that can undergo photo-chemical reaction upon light irradiation, the gel becomes light-responsive. Under irradiation, the photosensitive groups may undergo photo-ionization process and generate charges that are attached to the main chain or diffuse into the solvent. The newly generated ions disturb the osmotic balance of the gel medium. As a result, water molecules and mobile ions are driven into or out of the network to compensate the osmotic imbalance, which eventually leads to macroscopic swelling or shrinking of the gel. In this work, we develop a... 

Three versions of zirconium-based metal organic frameworks, NH2-UiO-66, GMA-UiO-66, and EDA-UiO-66, were synthesized and employed as adsorbent for CO2/CH4 separation. GMA-UiO-66 was synthesized via a ring opening reaction between the amine species in the framework and epoxy groups in glycidyl methacrylate (GMA), while the green aza-Michael addition reaction was used for the first time to functionalize GMA-UiO-66 with ethylenediamine (EDA). The products were characterized by BET, XRD, TGA, FESEM, ICP-OES, 1H NMR, mass spectroscopy, and FTIR-ATR methods to monitor their textural properties before and after functionalization. The results indicated that GMA was successfully grafted to the... 

Actin is known as the most abundant essentially protein in eukaryotic cells. Actin plays a crucial role in many cellular processes involving mechanical forces such as cell motility, adhesion, muscle contraction, and intracellular transport. However, little is known about the mechanical properties of this protein when subjected to mechanical forces in cellular processes. In this article, a series of large-scale molecular dynamics simulations are carried out to elucidate nanomechanical behavior such as elastic and viscoelastic properties of a single actin filament. Here, we used two individual methods namely, all-atoms and coarse-grained molecular dynamics, to evaluate elastic properties of a... 

The purpose of this study was to produce an intelligent superabsorbent polymer (SAP) to be used as a pH sensitive matrix for the controlled delivery of drugs. Novel types of highly swelling SAPs were prepared by grafting crosslinked acrylic acid-co-acrylamide (AA-co-AAm) chains onto pectin by free-radical polymerization. The superabsorbent formation was confirmed by Fourier transform infrared spectroscopic (FT-IR) and scanning electron microscopy (SEM). The controlled release behavior of ibuprofen (IBU) from the superabsorbent polymer was investigated. SAP structural-property relationships that affect its controlled release behavior were determined. Analysis of the results indicated that it... 

We demonstrated a novel mixed-matrix composite membrane (MMCM) based on acrylated polyurethane (APU) and UiO-66 nanoparticles to separate CO 2 /N 2 mixture. UiO-66 and functionalized UiO-66 including NH 2 -UiO-66 and glycidyl methacrylate (GMA)-UiO-66 were loaded into APU/2-hydroxyethyl methacrylate (APUH) matrix at variable concentrations between 3 and 30 wt %. APUH/GMA-UiO-66 MMCMs exhibited strong adhesion with a support layer of polyester/polysulfone, which was not deteriorated after immersion in water for a long time (20 days). Incorporation of UiO-66 and its functionalized forms increased simultaneously permeability and CO 2 /N 2 selectivity, which were indeed superior in comparison... 

In the past few years, laser-assisted methods have greatly influenced biomedical studies due to less invasive ways of treatment and higher precision. New stimuli-responsive drug carriers are still explored by scientists to achieve a better spatiotemporal control of drug carriers by using visible to NIR light instead of phototoxic ultra-violet irradiation. Due to their biocompatibility and high loading capacity of hydrophilic drugs, hydrogels have been used extensively in this area. However, poor cellular uptake and restricted loading of hydrophobic drugs are challenges that should be addressed. In this study, a previously known nanogel system based on chitosan and poly(N-isopropylacrylamide)... 

In this study a novel alginate-g-poly(acrylic acid)/alumina composite was synthesized and characterized. Preparation of the composite hydrogels involved free radical polymerization of a combination of alginate, acrylic acid (AA) and distilled water, in appropriate amounts and N,N-methylene bisacrylamide (MBA) as crosslinking agent. The composite formation was confirmed by Fourier transform infrared spectroscopic (FTIR). The surface morphologies of the synthesized hydrogels were assessed by scanning electron microscopy. Systematically, the different variables of the graft copolymerization were optimized to achieve maximum swelling capacity. The swelling of superabsorbent hydrogels was... 

A novel hydrolyzed collagen-based hydrogel has been prepared by grafting the binary mixture of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid onto the collagen backbone in the presence of a cross-linking agent. Its physicochemical properties in aqueous solution were studied. The effect of reaction variables on both gel content and swelling capacity was investigated to achieve a hydrogel with improved absorbency and gel content. The absorbency under load of optimized hydrogel was also investigated by using an absorbency under load tester at various applied pressures. The swelling ratio in various salt solutions was also determined and additionally, the swelling of hydrogels was... 

The chemical modification of isotactic polypropylene was performed by the free-radical-promoted grafting of 1,1,1-trimethylolpropane trimethacrylate (TMPTMA) in the presence of dicumyl peroxide (DCP) as the initiator. The reaction was carried out both in a batch internal mixer and in a corotating twin-screw extruder; the effects of the peroxide and monomer concentrations on the extent of modification in terms of the grafting efficiency and polymer chain structure variations were investigated. The modified samples were characterized with Fourier transform infrared to determine the structure of the grafted groups and the degree of functionalization, with gel permeation chromatography and the... 

Multistimuli-responsive hyperbranched polymers were synthesized in one-step polymerization using reversible addition-fragmentation chain transfer self-condensing vinyl polymerization (RAFT-SCVP). These hyperbranched polymers responded to UV-vis or sunlight, pH changes, and temperature changes. 2-(dodecylthiocarbonothioylthio)-2-methylpropionic acid known as DDMAT participated in esterification with 2-hydroxyethyl methacrylate to obtain a chain transfer monomer in the name of 2-((2-(((dodecylthio)carbonothioyl)thio)-2-methylpropanoyl)oxy)ethylmethacrylate (MACDT). For the first time, smart hyperbranched polymers were produced with the RAFT-SCVP method in one step by using... 

Superhydrophobic surfaces have been used for reducing friction in micro- and nanochannels. In the present work, water flow between two carbon walls with nanostructures made of poly(N-isopropylacrylamide) via the molecular dynamics method has been studied. The structure of this polymer can change based on the temperature of the environment, so that by increasing the temperature the structure becomes hydrophobic. This property has been studied and the effect of multiple factors on the slip length is presented. The effects of the number of monomers in the polymer, the distance between the polymers, and the temperature on the flow field are investigated. The results reveal that the slip length... 

Considering the microstructure-processing-properties relationship, the attempt was made to distinguish the main structural features of drip irrigation tape grades. In this regards, two different commercial polyethylene grades using for irrigation tape application (DB and MD samples) with various microstructural features were fully characterized by means of thermal, rheological and mechanical measurements and microscopic observations. A set of DSC techniques revealed that DB sample has faster crystallization kinetic probably due to its high crystallizable segments in chains and broad molecular weight distribution. It was found, the type of co-monomer used in DB sample is 1-hexene and in MD... 

In this study, the synthesis and characterization of a novel nano-porous superabsorbent hydrogel with high water swelling capacity is described. A nano-porous hydrogel was prepared by employing (2-dimethylaminoethyl) methacrylate (PDMAEMA) as a pH sensitive monomer and sodium alginate (SA) as a water soluble polysaccharide under γ-ray irradiation. The polymerization reaction was performed at room temperature in the absence of chemically toxic crosslinking agent and initiators. The interactive parameters including biopolymer backbone concentration, monomer concentration and γ-irradiation dose were selected as major factors in the synthesis of superabsorbent and three levels for each factor... 

A series of superabsorbent composites were synthesized through graft copolymerization of acrylic acid (AA) onto carboxymethyl cellulose (CMC) in the presence of celite powder using N,N'-methylenebisacrylamide (MBA) as a cross-linking agent and ammonium persulphate (APS) as an initiator. The chemical structure and thermal properties of the composite hydrogels were characterized by FTIR spectroscopy and TGA methods, respectively. Morphology of the samples was examined by scanning electron microscopy (SEM). In free-state, the swelling conditions and hence the related data are not real, because in all their applications the swelling particles of superabsorbent must absorb aqueous solutions while... 

A series of biopolymer-based superabsorbent hydrogels based on carboxymethyl cellulose has been prepared by free-radical graft copolymerization of acrylamide and 2-acrylamido-2-methylpropan sulfonic acid (AMPS) in aqueous solution using methylenebisacrylamide as a crosslinking agent and ammonium persulfate as an initiator. The effect of variables on the swelling capacity such as: acrylamide/AMPS weight ratio, reaction temperature, and concentration of the initiator and crosslinker were systematically optimized. The results indicated that with increasing the amount of AMPS, the swelling capacity is increased. FT-IR spectroscopy and scanning electron microscope analysis were used to confirm... 

The incorporation of modified β-cyclodextrin (β-CD) into a poly(N-isopropylacrylamide) (PNIPAAm)/chitosan (PNCS) nanohydrogel was studied. β-CD was functionalized with acrylic groups, with different numbers of vinyl bonds added per β-CD molecule. The surfactant-free dispersion polymerization (SFDP) semi-batch method was used to synthesize the nanohydrogel. Increasing the number of vinyl groups per β-CDAC (β-CD acrylate) molecule induced the formation of smaller nanogels with diameters ranging from 142 to 68 nm. The cyclodextrin-modified dual-responsive nanogels obtained presented an LCST (lower critical solution temperature) in aqueous medium at around 31 C. The incorporation of β-CDAC into... 

This article reports the first oil-absorbent cross-linked copolymer consisting of modified multiwalled carbon nanotube (MWCNT) and showing high oil absorbency. Also, to investigate and evaluate the effective parameters on oil absorbency, cross-linked dodecyl methacrylate (DDMA)-diphenylacrylamide (DPAA) and DDMA-butyl acrylate (BA) copolymers were synthesized. DDMA was copolymerized with different mol% of DPAA or BA and cross-linked using azobisisobutyronitrile as the initiator and various weight percentages of 1,4-butandiol dimethacrylate, methylene bisacrylamide, or vinyl group-modified MWCNT cross-linkers. The effects of monomer feed composition, cross-linker concentration, and the... 

A dual acidic heterogeneous organocatalyst was synthesized by copolymerization of acidic ionic liquid monomer (vinyl-3-(3-sulfopropyl) imidazolium hydrogen sulfate [VSim][HSO 4]) and ionic liquid crosslinker (1,4-butanediyl-3,3′-bis-l-vinyl imidazolium dihydrogen sulfate). The resulting ionic heterogeneous catalyst is shown to be an efficient dual acidic organocatalyst for synthesis of dihydropyrimidines using the Biginelli synthetic route under mild reaction conditions in high yields. Since monomers make the catalyst bed, crosslinked poly(ionic liquid) will have high loading level of acidic groups comparing to other heterogeneous acid catalysts. Despite of conventional heterogeneous ionic... 

Salep phosphate modified biopolymers with different phosphate contents were prepared via reacting salep (a multi-component polysaccharide obtained from dried tubers of certain natural terrestrial orchids) with a solution of primary and secondary sodium phosphates under basic conditions in a semidry process. Structural characterization of salep phosphates were carried out by 31P NMR, FT-IR spectra and TGA curves. Determination of the phosphate content in samples was done by a standard spectrophotometric method. Then, novel (salep phosphate)-based hydrogels were synthesized by graft copolymerization of acrylic acid (AA) monomer onto salep phosphate backbones. Effect of the phosphate contents... 

In this work, a fundamental kinetic model based upon the Hougen-Watson non-porosity formalism was derived and used to simulate dehydrogenation and oxidation axial flow reactors. In addition, partial pressure profiles of components during styrene production process inside porous catalyst were obtained using Dusty-Gas model. The preservation equations are adopted to calculate temperature and flow profiles in the reactors filled with iron-potassium promoted catalyst pellets. The presented mathematical model for ethylbenzene dehydrogenation consists of nonlinear simultaneous differential equations with multiple dependent variables. Simulation results such as selectivity and operating temperature...