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ABBAS ASFADEH,VAHID HADDADI-ASL,MEHDI SALAMI-KALAJAHI,MOHAMMADREZA SARSABILI,HOSSEIN ROGHANI-MAMAQANI 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2013 NANO Vol.8 No.2
Effect of pristine and modified MCM-41 on the kinetics of styrene atom transfer radical polymerization (ATRP) was studied using a double bound containing modifier at 110°C. Conversion, molecular weight and PDI were obtained during the polymerization reactions to study the polymerization kinetics. Addition of the both types of MCM-41 has resulted in inconsiderable variations on the kinetics of polymerization. A similar trend is observed for the molecular weight of the free chains; however, increasing MCM-41 content results in higher PDI values. Also, surface modification of MCM-41 results in lower polymerization rates. In the case of grafted chains, molecular weight and PDI values increase by increasing MCM-41 content.
KHEZROLLAH KHEZRI,VAHID HADDADI-ASL,HOSSEIN ROGHANI-MAMAQANI 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2014 NANO Vol.9 No.2
Mesoporous silica nanoparticles (MCM-41) surface was functionalized with 3-(trimethoxysilyl)propyl methacrylate (MPS). Then, the resultant double bond containing nanoparticles were usedin grafting through simultaneous reverse and normal initiation technique for atom transferradical polymerization (SR&NI ATRP) of styrene to synthesize well-de¯ned polystyrene nano-composites with twofold chains. Nitrogen adsorption/desorption isotherm and X-ray di®ractionanalysis were used to evaluate characteristics of spherical MCM-41 nanoparticles. Morphologicalstudies were also performed by scanning and transmission electron microscopy. Conversion andmolecular weight determinations were carried out using gas and size exclusion chromatographyrespectively. Addition of MCM-41 nanoparticles by 3 wt.% results in a decrease of conversionfrom 93% to 82%. Molecular weight of the free and attached polystyrene chains decreases byadding 3 wt.% MCM-41 nanoparticles; however, PDI values increases from 1.27 to 1.78 for freechains and 1.87 to 2.48 for attached chains. A peak around 4.1 ppm which originates fromhydrogen atom of terminal units of polystyrene chains in proton nuclear magnetic resonancespectra in combination with low PDI values can appropriately demonstrate the living nature ofthe polymerization. Increasing thermal stability of the nanocomposites is demonstrated byThermogravimetric analysis. Di®erential scanning calorimetry also shows a decrease in glasstransition temperature by increasing MCM-41 nanoparticles.
EFFECT OF CARBON NANOTUBES ON THE KINETICS OF IN SITU POLYMERIZATION OF METHYL METHACRYLATE
MEHDI SALAMI-KALAJAHI,VAHID HADDADI-ASL,FARID BEHBOODI-SADABAD,SAEID RAHIMI-RAZIN,HOSSEIN ROGHANI-MAMAQANI,MAHMOUD HEMMATI 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2012 NANO Vol.7 No.1
The effect of carbon nanotubes on the kinetics of free radical polymerization of methyl methacrylate (MMA) was investigated. To do this, pristine, acid treated, alcoholic and methacrylate-modified carbon nanotubes with different loadings were used and Conversion, molecular weight and polydispersity index (PDI) of all samples were monitored during polymerization. The results show that carbon nanotubes induce an induction time to polymerization system which is independent of modification system while decrease in monomer conversion can be improved by developing organic moieties on surface. Molecular weight and polydispersity index for free and attached-on-surface chains were studied separately and different kinetics behaviors were observed for them. Molecular weight of free chains was increased by adding carbon nanotubes while more modified nanotubes resulted in much increased molecular weight. On the other hand, more system stability of more modified nanotubes, which was tested using UV-Visible spectra, resulted in higher molecular weights. Adding more nanotubes in the case of MMA-modified nanotubes caused to determine an optimum loading value to reach maximum molecular weight of free chains which was ascribed to system stability according to UV-Visible results. In this optimum loading value, free chains had minimum PDI value. However, increasing carbon nanotubes content led to decreased molecular weight of attached chains while PDI values increased because of shielding effect as physical phenomenon.
Hanie Ahmadi,Reza Ghamsarizade,VAHID HADDADI-ASL,Hossein Eivaz Mohammadloo,Bahram Ramezanzadeh 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.116 No.-
To overcome the magnesium’s high corrosion rate issue, triple polyvinylalcohol (PVA) coatings containinghydroxyapatite (HA) and 8-hydroxyquinoline (8-HQ) were prepared by two different methods of electrospinningand immersion. The formation of HA and Mg(8-HQ)2 layers during exposure to a corrosive mediumwas indicated by X-ray diffraction (XRD) and fluorescent images, respectively. Results showed thatthe electrospinning coating containing HA and 8-HQ, revealed a significant anti-corrosion performance(Rct = 7891, and 12,680 ohm cm2 in NaCl 3.5 wt.%, and simulated body fluid (SBF), respectively) comparedto the same composition immersion samples (Rct = 3231, and 3727 ohm cm2). The increment in anticorrosionperformance is caused by the release of HA and 8-HQ from the nanofibers. The problem of bacterialinfections in magnesium implants has been improved (reduction in bacterial-growth percentage= 90% in coating prepared by electrospinning method) by cleverly designing the triple coatingcontaining 8-HQ as an anti-bacterial compound.