Interactions of hexamethylenetetramine ligand in atom transfer radical polymerization initiated by activator generated by electron transfer were studied. Polymerization of methyl methacrylate was done using two‐step experimental procedure in 2 L emulsion batch reactor at 50, 60, and 80°C. The selection of reactant ratios was quite challenging for a reactor of this size. Replicate runs were conducted for data reproducibility purpose. Gravimetry method and gel permeation chromatography were used to determine monomer conversion, Mn, and PDI of polymer samples. PMMA produced was also characterized by means of dynamic light scattering, Fourier‐transform infrared spectroscopy and nuclear Magnetic Resonance spectroscopy. Results showed high monomer conversion up to 93% and Mn ranging 243–274 kg/mol with PDI from 1.45 to 1.60. Besides, combining HMTA with sodium dodecyl sulfate, an anionic surfactant, a well‐controlled polymer with a lower Mn of 201 kg/mol and PDI of 1.56 was obtained in 3 hr reaction time.

Surface modification of nanoscale zero-valent iron (nZVI) using polymer stabilizers (e.g., sodium carboxymethyl cellulose, CMC) is usually used to minimize aggregation, increase stability, and enhance transport of nZVI. We investigated the stability and dynamic aggregation of bare and CMC–nZVI as affected by variations in pH, ionic strength (IS), and nZVI particle concentration. CMC coating of nZVI resulted in smaller hydrodynamic size and larger zeta potential. The largest hydrodynamic size of nZVI was associated with bare nZVI at high IS (100 mM), pH close to the point of zero charge (PZC, 7.3–7.6), and larger particle concentration (1.0 g L−1). The increase in the zeta potential of CMC–nZVI reached one- to four-fold of that for bare nZVI, and was greater at pH values close to PZC, high IS, and larger particle concentration. The stability of CMC–nZVI was increased by 61.8, 93.1, and 57.5% as compared to that of bare nZVI at IS of 1, 50 and 100 mM, respectively. Calculations of Derjaguin, Landau, Verwey and Overbeek (DLVO) interaction energy were in agreement with stability results, and showed the formation of substantial energy barriers at low IS indicating greater nZVI stability. Our results suggest that at IS above 50 mM and nZVI particle concentration larger than 0.1 g L−1, the likelihood of nZVI aggregation is high. Nevertheless, CMC polymer stabilizer would enhance the stability and transport of nZVI even under these unfavorable solution chemistry conditions.

Efficient application of nanoscale zero-valent iron (nZVI) particles in remediation processes relies heavily on the ability to modify the surfaces of nZVI particles to enhance their stability and mobility in subsurface layers. We investigated the effect of sodium carboxy-methyl-cellulose (CMC) polymer stabilizer, pH, particle concentration, and flow rate on the transport of nZVI particles in sand columns. Breakthrough curves (BTCs) of nZVI particles indicated that the transport of nZVI particles was increased by the presence of CMC and by increasing the flow rate. The relative concentration (RC) of the eluted CMC-nZVI nanoparticles was larger at pH 9 as compared to RC at pH 7. This is mainly attributed to the increased nZVI particle stability at higher pH due to the increase in the electrostatic repulsion forces and the formation of larger energy barriers. nZVI particle deposition was larger at 0.1 cm min −1 flow due to the increased residence time, which increases the aggregation and settlement of particles. The amount of CMC-nZVI particles eluted from the sand columns was increased by 52% at the maximum flow rate of 1.0 cm min −1 . Bare nZVI were mostly retained in the first millimeters of the soil column, and the amount eluted did not exceed 1.2% of the total amount added. Our results suggest that surface modification of nZVI particles was necessary to increase stability and enhance transport in sandy soil. Nevertheless, a proper flow rate, suitable for the intended remediation efforts, must be considered to minimize nZVI particle deposition and increase remediation efficiency.

only a limited number of studies were done in aqueous media, [4] even though, conducting polymerization in dispersed media is more convenient for economic and environmental reasons, and industrial settings. [5][6][7] However, ATRP behavior in emulsion medium may present few concerns including wide particle size distribution, loss of control of the polymerization, and low initiation efficiency. [8] A number of ATRP studies [5,6,9] have applied new initiation techniques called activators generated by electron transfer (AGET) which not only demands a relatively low amount of catalyst complex but can also use ecofriendly reducing agents such as vitamin C or sugar. Besides, the AGET ATRP technique can be performed in emulsion medium by incorporating stable and oxidative copper (CuBr 2 ) complex in the initiation step. It is important to highlight that an in-depth understanding of chemical kinetic features of ATRP in emulsion systems is not quite well documented in open literature. In fact, ATRP is still largely unstudied in dispersed systems. [6] Oh et al. [7] conducted a very interesting review of controlled radical polymerization (CRP) techniques in emulsion and dispersion systems.At theoretical level, several studies have reported different mathematical methods to understand the behavior of ATRP in dispersed medium. [10][11][12][13][14][15][16][17][18][19] Assumptions were made in order to simplify the ATRP reaction mechanism. For instance, these ATRP systems were conducted in miniemulsion or dispersion mediums and have polymer particle diameters from 35 to 70 nm with low conversion. [19,20] It is clear that ATRP is different from free radical polymerization in a few aspects such as thermodynamic and chemical equilibriums of the system. Moreover, deactivating species along with propagating radicals were assumed to transfer radicals between monomer droplets and polymerizing particles. Besides, there is a lack of a sufficient experimental data over a reasonable range of reaction conditions in order to gain a better understanding of ATRP kinetic mechanism in emulsion medium. For instance, Peng et al. [21] carried out an experimental investigation of n-butyl methacrylate (BMA) ATRP in emulsion polymerization. They investigated the effects of several factors including the Ab initio emulsion atom transfer radical polymerization (ATRP) differs from regular emulsion polymerization because the kinetic and thermodynamic aspects of each process are very unlikely alike. This paper presents a kinetic analysis of activator generated by electron transfer (AGET) ATRP of methyl methacrylate (MMA) in a stirred emulsion reactor. The focus of the study is to assess the variation of the monomer content in the organic phase and the rate polymerization for different reaction temperatures, as well as the impact of surfactant content and stirring speed on latex stability. Poly(methyl methacrylate) (PMMA) polymer samples are analyzed by means of gravimetry, dynamic light scattering, gel permeation chromatography, and HNMR techniques to dete...

Atom Transfer Radical Polymerization (ATRP) in a 2L emulsion batch reactor system was initiated by using the Activator Generated by Electron Transfer (AGET) technique to produce Poly (Methyl Methacrylate) (PMMA). The reactants were composed of Ethyl-2-bromoisobutyrate (EBiB) as the initiator, polyoxyethylene (20) oleyl ether (Brij98) as nonionic surfactant and ascorbic acid as the reducing agent. In addition, the catalyst complex consists of copper bromide (CuBr2) and different ligands such as Triphenylphosphine (PPh3), 1, 10-Phenanthroline (Phenol), and Vitamin D. The effect of using PPh3, Phenol and Vitamin D as novel ligands was investigated to produce PMMA polymers having the features obtained through controlled polymerization. The reaction follows a two-step experimental procedure, during which a transition from microemulsion to emulsion takes place. The mixing process between the organic phase and the aqueous phase was carried out under sufficient amount of air for simplification purposes. However, the reaction is usually sensitive to air and therefore a particular precaution was taken when purging the system inside the reactor. Gravimetric method was used to measure the monomer conversion. Characterization of PMMA samples was done by means of GPC to measure the molecular weight and the polydispersity of the product. FTIR analysis was performed to characterize the polymer product. After 5h of reaction, high monomer conversion was obtained using Phenol and gradually increasing up to 93% with low number average molecular weight of 10,158 g/mol and a relatively narrow PDI of 1.58. A narrower PDi was obtained with Phenol compared with PPh3 and Vitamin D.