Elmira Khaksar; Marzieh Golshan; Hossein Roghani-Mamaqani; Mehdi Salami-Kalajahi
Abstract
In this study, reversible addition-fragmentation chain transfer (RAFT) polymerization was used to synthesize hydrophobic polystyrene (PS), poly(methyl acrylate) (PMA), and poly(methyl acrylate-b-styrene) (PMA-b-PS) block copolymers with three distinct molecular weights. Polyaniline (PANI) was synthesized ...
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In this study, reversible addition-fragmentation chain transfer (RAFT) polymerization was used to synthesize hydrophobic polystyrene (PS), poly(methyl acrylate) (PMA), and poly(methyl acrylate-b-styrene) (PMA-b-PS) block copolymers with three distinct molecular weights. Polyaniline (PANI) was synthesized by electrochemical method. Proton nuclear magnetic resonance (1H NMR) and gel permeation chromatography (GPC) have both been used to examine the properties of the polymers synthesized. In aqueous media at room temperature, PANI has been co-assembled with PS, PMA, and PMA-b-PS. The size and morphology of the co-assembled structures have been examined using transmission electron microscopy (TEM), dynamic light scattering (DLS), and field emission scanning electron microscopy (FE-SEM). According to the findings, polymers hydrophobicity increased with increasing molecular weight, causing faster precipitation in aqueous solution and a reduction in particle size. The results demonstrated that adding conductive polymer produced core-shell morphologies, while the core morphologies are different. Thermodynamic principles governed morphology, and the most likely morphology to develop was the one that minimized the total surface free energy. The polymers caused the surface tension between the polymers with water and the surface tension between the primary polymer and the secondary polymer to be reduced by overlapping each other and precipitation.
Olefin polymerization and copolymerization
Ahmad-Ali Shokri; Saeid Talebi; Mehdi Salami-Kalajahi
Abstract
Laboratory runs can be minimized via experimental design which yields the optimum and best data regarding the independent parameters. In this research work, response surface methodology (RSM) based on a threelevel central composite design (CCD) was utilized to optimize and evaluate the interactive effects ...
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Laboratory runs can be minimized via experimental design which yields the optimum and best data regarding the independent parameters. In this research work, response surface methodology (RSM) based on a threelevel central composite design (CCD) was utilized to optimize and evaluate the interactive effects of processing conditions for polymerization of 1,3-butadiene (Bd) diene monomer using Ziegler-Natta catalyst. The polybutadiene rubber (PBR) having different cis content and molecular weight was obtained. The catalyst components included neodymium versatate (NdV3) as catalyst, triethyl aluminum (TEAL) as cocatalyst or activator, and ethylaluminum sesquichloride (EASC) as chloride donor. For the modeling, three independent variables, namely monomer concentration (8-28 wt%), reaction time (1.5-2.5 h), and reaction temperature (45-75ºC) at three levels were selected to optimize the dependent variables or responses including monomer conversion, viscosity-average molecular weight and the cis isomer content of the obtained polymer. The interaction between three crucial parameters was studied and modeled. Quadratic models were obtained to relate process conditions to dependent variables. It was observed that the optimal conditions predicted by RSM were consistent with the experimental data. Statistical analysis demonstrated that concentration of the monomer and the time of reaction significantly affected cis content. Moreover, processing conditions to achieve the desired response variables were predicted and experimentally approved. The optimal reaction conditions derived from RSM are monomer concentration = 19 wt%, polymerization time = 2 hours, and polymerization temperature = 50ºC. Polymerization was carried out at optimum conditions. The appropriate level of dependent variables including 94.2% monomer conversion, 151812 g/mol viscosity-average molecular weight and 98.8% cis content was acquired.
