A Comparative Study between FRP and ATRP of Styrene by Monte Carlo Simulation: Effect of Free Radical Mobility

Styrene polymerization through FRP and ATRP methods was carried out at 110oC, while in-depth studies were performed by Monte Carlo simulation.The changes in monomer conversion, initiator concentration, average molecular weight, and polydispersity index were computed over the course of the polymerization. As the results indicate, compared to ATRP, the FRP reaches higher conversion in a similar reaction time. In addition, the concentration of initiator suddenly drops at the early stages of the ATRP and eventually amounts to zero; chain-length dependent termination rate constant also decreases as the polymerization progresses. However, in case of FRP, the concentration of initiator exponentially falls and termination rate constant rises during the reaction. Furthermore, the average molecular weight increases linearly in the course of ATRP, which testifies the living dynamism of the reaction. Finally, the molecular weight distribution of chains obtained byATRP process is much narrower

Effect of Reactant Concentration Variations on the Kinetics of Atom Transfer Radical Polymerization of Acrylonitrile

Polyacrylontrile synthesis, via atom transfer radical polymerization, is studied in various initiator concentrations, transitional metal catalyst and different concentrations of CuBr2. The variations of monomer conversion and the lin-earity of semi-logarithmic kinetic profile which is the evidence of living polymerization and constant radical concentration in the reaction medium, were revealed by gas chromatography technique (GC). Gel permeation chromatography (GPC) studies revealed that, the number average molecular weight increases linearly against monomer conversion, an indicative of living nature of the polymerization process. Additionally, the conversion, apparent rate constant and number average molecular weight increased with increased initiator concentration as well as the transitional metal complex concentration. However, addition of CuBr2 lowered conversion, kapp, and the number average molecular weight of polyacrylonitrile. Molecular weight distribution of synthesized polymers broadened with increased initiator concentration and also transitional metal complex concentration. However, addition of CuBr2 has resulted in narrower molecular weight distribution polyacrylonitrile. Moreover, all the samples experienced a drop in PDI value from nearly 2 to almost 1.1 as the reaction progressed

Preparation of Polystyrene Nanocomposite by In Situ Atom Transfer Radical Polymerization: Study of Polymerization Kinetics in the Presence of Clay

Styrene nanocomposites were synthesized by in-situ atom transfer radical polymerization at 110oC. The variations of monomer conversion and the linearity of semilogarithmic kinetic plot, some signs of living polymerizationand constant radical concentration in the reaction medium, were revealed by gas chromatography technique (GC). According to the gel permeation chromatography (GPC) results, the number average molecular weight increased linearly against the monomer conversion indicating the living nature of the polymerization. Weight average molecular weight and polydispersity of nanocomposites were also derived from GPC data. In addition, the PDI value was wider for polymers extracted from nanocomposite samples, and still widened as the clay content increased. Moreover, all the samples experienced a fall in PDI value from nearly 2 to almost 1.1 as the reaction progressed. FTIR results are indications of some interactions between clay surface and monomer, which may be attributed to higher rated in polymerization kinetics. XRD displayed no peak in in-situ synthesized nanocomposites indicating an exfoliated structure in the prepared nanocomposites; conversely, a solution blending technique resulted in an intercalated structure. AFM phase images well displayed the dispersion of nanoclay in the polymeric matrix. The delamination of clay platelets in the polymer matrix of in-situ prepared nanocomposite is demonstrated by TEM images; on the other hand, TEM results revealed the intercalated structure of nanocomposites prepared by solution blending technique

Modification of graphene with silica nanoparticles for use in hybrid network formation from epoxy, novolac, and epoxidized novolac resins by sol-gel method: Investigation of thermal properties

Thermal stability of hybrid composites prepared from epoxy, novolac, and epoxidized-novolac resins and also modified graphene oxide (SFGO) was studied. SFGO was prepared by covering graphene oxide with silica nanoparticles and a bifunctional silane modifier. The first hybrid was prepared from SFGO and silane-modified epoxy resin. The second one was prepared from SFGO, and silane-modified epoxy and novolac resins. The third hybrid was formed from SFGO, silane-modified novolac, and epoxidized novolac resins. Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) results showed that modification of graphene oxide was carried out successfully. TGA results show that degradation temperature and char residue of resins were increased through their incorporation into hybrid network with SFGO. In addition, the most increase of char residue was observed for the hybrid composites formed from SFGO and modified novolac and epoxy resins

Poly(styrene-co-butyl acrylate)/Clay Nanocomposite Latexes Synthesized via In Situ Atom Transfer Radical Polymerization in Miniemulsion: Activators Generated by Electron Transfer Approach

W       ater born poly(styrene-butyl acrylate)/clay nanocomposite latexes were synthesized by a novel initiating system of activators generated by   electron transfer (AGET) in a system of atom transfer radical polymerization   (ATRP). Initially, the clay was swelled in a mixture of styrene, butyl acrylate,   and hexadecane. The mixture was then sonicated to obtain a stable miniemulsion. To   synthesize poly(styrene-butyl acrylate)/clay nanocomposite latexes, the reducing   agent (ascorbic acid) was added dropwise to the reactor (to reduce termination reactions).   Particle size and particle size distribution of resulting nanocomposite latexes   were determined by dynamic light scattering (DLS). These latex particles were produced   with diameters in the size range of 138-171 nm. In addition, the increase in   clay content led to increased particles size. Number and weight-average molecular   weights of the resultant copolymer nanocomposites and their molecular weight distributions   were determined by gel permeation chromatography. The narrow molecular   weight distribution of the nanocomposites is an indication of a successful ATRP   which was accomplished in miniemulsion formation. Using         1   H NMR, copolymers were characterized and the mol ratios of monomers in copolymer composition were   calculated. X-Ray diffraction and transmission electron microscopy results showed   the mixed intercalated and exfoliated morphologies of nanocomposites in which   homogeneous distributions of clay layers in the polymer matrix have been achieved