Sharif Digital Repository

Background: Kinetic andmorphological aspects of slurry propylene polymerization using a MgCl2-supported Ziegler-Natta catalyst synthesized from a Mg(OEt)2 precursor are investigated in comparison with a ball-milled Ziegler-Natta catalyst. Results: The two types of catalyst show completely different polymerization profiles: mild activation and long-standing activity with good replication of the catalyst particles for the Mg(OEt)2-based catalyst, and rapid activation and deactivation with severe fragmentation of the catalyst particles for the ball-milled catalyst. The observed differences are discussed in relation to spatial distribution of TiCl4 on the outermost part and inside of the... 

In this report, the synthesis of a novel superabsorbent hydrogel via γ-irradiation graft copolymerization of acrylamide onto sodium alginate and kappa-carrageenan hybrid backbones in a homogeneous solution is described. The Taguchi method was used as a powerful experimental design tool for synthesis optimization. A series of superabsorbent hydrogels was synthesized by proposed conditions of Qualitek-4 software. Considering the results of nine trials according to analysis of variance, optimum conditions were proposed. The swelling behavior of optimum superabsorbent hydrogels was studied in various solutions, with pH values ranging from 1 to 13. In addition, swelling kinetics, swelling in... 

Due to the weak performance of commercially affordable natural and synthetic polymeric thickeners in high temperatures and salinity, they fail to use in many applications especially in saline conditions with high temperatures. In this work, a new salt and temperature resistance acrylamide/styrene/maleic anhydride terpolymer (PASM-t) with self-associative properties was synthesized via a one-step inverse emulsion polymerization and its applicability as a rheological modifier and thickener was investigated. The characteristics of synthesized PASM-t (s-PASM-t) and its aqueous solutions were investigated using FT-IR, FE-SEM, GPC and rheometric mechanical spectrometry (RMS) analyses. The... 

In this research, polysulfone (PSf) ultrafiltration (UF) membranes were prepared by a phase inversion method. Surface modification of the PSf membranes was carried out via grafting of acrylic acid as a hydrophilic monomer by free radical graft polymerization initiated by redox reaction. A central composite design (CCD) of response surface methodology (RSM) was applied to design the experiments. The process variables were acrylic acid concentration (CAA), redox system contact time (T1), and acrylic acid polymerization time (T2), while the contact angle (CA), pure water flux (PWF), and flux recovery ratio (FRR) were considered as the responses. Analysis of variance (ANOVA) demonstrated that... 

Smart bio-based shape memory polymers with high performance and fast response have the exciting potential to meet the growing need in biomedical applications. In this study, novel fast response UV-curable shape memory polyurethane acrylates (SMPUAs) comprising polycaprolactone diols (PCL-Diol), hexamethylene diisocyanate (HDI) and hydroxy-methyl methacrylate (HEMA) were synthesized by two-step bulk polymerization. Two series of PUAs with almost the same amount of hard segment content (HSC) were prepared with varying soft-segment molecular weight (2000, 3000, and 4000 g/mol) and different molar ratios of constituents. A mono-functional reactive diluent was used to control HSC and reduce the... 

Transdermal drug delivery systems have overcome many limitations of other drug administration routes, such as injection pain and first-pass metabolism following oral route, although transdermal drug delivery systems are limited to drugs with low molecular weight. Hence, new emerging technology allowing high molecular weight drug delivery across the skin—known as ‘microneedles’—has been developed, which creates microchannels that facilitate drug delivery. In this report, drug-loaded degradable conic microneedles are modeled to characterize the degradation rate and drug release profile. Since a lot of data are available for polylactic acid-co-glycolic acid (PLGA) degradation in the literature,... 

The purpose of this research is to explain the surface modification of fabricated polyamide reverse osmosis (RO) membranes using UV-initiated graft polymerization at different irradiation times (15, 30, 60, and 90 s) and various acrylamide concentrations (10, 20, and 30 g L−1). Also, coating of membranes surface with various concentrations of TiO2 nanoparticles (10, 20, 30, and 50 ppm) followed by the same UV irradiation times was investigated. After that, the membranes modification was done by grafting of acrylamide blended with TiO2 nanoparticles via UV irradiation. The characterization of membranes surface properties and their performance were systematically carried out. The results... 

A number of synthetic hydrogels suffer from low mechanical strength. Despite of the recent advances in the fabrication of tough hydrogels, it is still a great challenge to simultaneously construct high stretchability, and self-adhesive and self-healing capability in a hydrogel. Herein, a new type of double network hydrogel was prepared based on irreversible cross-linking of polyacrylamide chains and Schiff-base reversible cross-linking between glycidyl methacrylate-grafted ethylenediamine and oxidized sodium alginate (OSA). The combination of both cross-linkings and their synergistic effect provided a novel hydrogel with high strength, stretchable, rapid self-healing, and self-adhesiveness... 

A novel multi stimuli-responsive silica nanocomposite with a core-shell structure is synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization. The SiO2 nanoparticles are chemically modified via 3-(trimethoxylsilyl) propyl methacrylate (MPS) which they are used in the core of nanocomposite. The macro-RAFT agent is prepared by RAFT polymerization of N-isopropylacrylamide (NIPAM), spirooxazine acryloyl monomer (SOM), and 2-(dodecylthiocarbonothioylthio)-2-methylpropionic acid (DDMAT as a RAFT agent). Finally, the smart nanocomposite is prepared by reaction between the macro-RAFT agent and 2-(Dimethylamino) ethyl methacrylate (DMAEMA) as a monomer. SOM as a... 

We consider chaperone-assisted translocation of biopolymers with two distinct monomers or bases A and B, with the size of the chaperones being λα, where α is a monomer's size. The probability that A and B are neighbors in the biopolymer is PAB. A master equation is used, together with the detailed-balanced condition, in order to derive analytical results for the statistics of the first-passage times of the biopolymer as a function of PAB, λ, and the biopolymer's configuration. Monte Carlo simulations have also been carried out in order to compute the same quantities for biopolymers with 100-900 monomers and several λ. The results indicate nontrivial dependence of the variance of the... 

In this paper, preparation of polyethylene/clay nanocomposites (PECNC) by in situ Ziegler-Natta catalyst polymerization was investigated. A Ziegler-Natta catalyst was first supported on montmorillonite (MMT) type clay and subsequently used for polymerizing ethylene. Clay and clay supported catalyst were characterized by Fourier transmission infrared and ICP method. X-ray diffraction (XRD) and transmission electron microscopy results show that silicate layers of the mineral clay in prepared nanocomposites were intercalated and exfoliated in the polymeric matrix. Differential scanning calorimetry results show that the prepared nanocomposites have higher crystallization temperature than pure... 

A study was conducted to report an observation on the effect of nanoclay fillers on the α-relaxation in an epoxy resin. The observation provided useful facts about glass transition processes in nanoclay-filled epoxy composites. The investigation involved the synthesis of intercalated-exfoliated clay-epoxy compounds, by swelling an organophilic montmorillonite in an aromatic epoxy resin and polymerization. The epoxy resin used in the study was a diglycidyl ether of bisphenol A (DGEBA), EPON 828, with an equivalent weight of 184-190 g/eq from Hexion Specialty Chemicals. The epoxy resin was cured with piperidine, obtained from Sigma-Aldrich. Nanomer® 1.30E. An octadecyl amine treated... 

The hybrid-polymer nanocomposite poly(styrene-methyl methacrylate- acrylic acid) /nanoclay was synthesized by miniemulsion polymerization for novel use as a drilling fluid additive. Three low-solid-drilling fluids (bentonite-based; natural polymer-based; nanoclay-based) were formulated using the hybrid nanocomposite as an additive and their rheological performance compared. The polymer/clay hybrid nanoparticles significantly improve rheological and filtration properties of the drilling fluids and they remain stable at high pressure, high temperature and harsh salinity conditions. The fluids’ filtration properties improve as the concentration of the polymer/nanoclay-hybrid-nanoparticles... 

Abstract: In the present paper, an efficient Cu-catalyzed regioselective acylation of indoles with phenylglyoxals was developed which is the first example of indolyl diketones synthesis by a heterogeneous catalyst. The magnetic polyacrylonitrile was synthesized through anchoring acrylonitrile monomers on Fe3O4 nanoparticles surface and then modified with 2-aminopyridine. At the final step, copper nanoparticles were immobilized onto the polymeric support containing stable ligands from functionalized nitrile groups of polyacrylonitrile. The different techniques such as Fourier transmission infrared spectroscopy, X-ray diffraction, Field emission scanning electron microscopy, Transmission... 

For the first time, the UIO-66, NH2-UIO, and NH2-UIO particles covalently functionalized by Glycidyl Methacrylate (GMA@NH2-UIO), were utilized as the novel functional anti-corrosive fillers. The functionality, high surface area, phase composition, excellent thermal properties as well as chemical stability of the Zr-MOFs were proved by FT-IR, BET, XRD, TGA, and water stability tests, respectively. The smart pH-sensitive controlled-release activity of the corrosion inhibitors (i.e., Zr ions and organic compounds) from the prepared Zr-MOFs was proved by the water stability test of the Zr-MOFs particles in the acidic (pH = 2), neutral (pH = 7.5), and alkaline (pH = 12) solutions containing 3.5... 

Water can be pumped in nanochannels by limiting it between the surfaces with different hydrophobicities and exerting a spinning electric field. The asymmetrical hydrophobicity combined with the spinning electric field and the fact that the water molecules have a dipole moment create a situation in which the angular momentum of water molecules is transformed into a linear momentum and the water is pumped into the nanochannel. The hydrophobicity of the surfaces can be manipulated by using nanostructures to reduce friction. In this study, two types of nanostructures have been used which are hierarchical nanostructures and polymer nanostructures made of Poly(N-isopropylacrylamide). The walls of... 

A high sensitive upper critical solution temperature (UCST) copolymer was synthesized through free radical copolymerization with acrylamide (AAm) and vinyl acetate (VA). The UCST behavior is due to a combination of hydrogen bonds and electrostatic potentials between copolymer chains. Turbidimetry, dynamic light scattering, and rheology studies were used to determine the phase transition and aggregation behavior. It is indicated that copolymer with 80% AAm has a phase transition temperature between 38 and 38.2 °C, which is suitable for releasing fever medicine. Also, the temperature gradient for the complete dissolution of the copolymer is 2 °C. The molecular dynamics simulations at a... 

Abstract: In the present paper, an efficient Cu-catalyzed regioselective acylation of indoles with phenylglyoxals was developed which is the first example of indolyl diketones synthesis by a heterogeneous catalyst. The magnetic polyacrylonitrile was synthesized through anchoring acrylonitrile monomers on Fe3O4 nanoparticles surface and then modified with 2-aminopyridine. At the final step, copper nanoparticles were immobilized onto the polymeric support containing stable ligands from functionalized nitrile groups of polyacrylonitrile. The different techniques such as Fourier transmission infrared spectroscopy, X-ray diffraction, Field emission scanning electron microscopy, Transmission... 

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... 

In this study, a new facile and cost effective method is used to modify polysulfone membrane surface in order to improve the hydrophilicity, antifouling, and blood compatibility. This modification was performed by adding two functional monomers on the dialysis membrane. Polysulfone (PSF) membranes containing polyvinylpyrrolidone were prepared via phase inversion technique. In the next step, free radical polymerization combined with surface polymerization was used to introduce acrylic acid (AA) and 2-hydroxyethyl methacrylate (HEMA) onto the polysulfone membrane surface via circulation of initiator and monomer solutions across the membrane surface, respectively. Various monomer concentrations...