Emulsion Polymerization In Presence Research Articles

Multifunctional polyaniline hybrid nanofiber with YVO4 (Er2%;Yb8%)

We synthesized electrospun nanofibers based on polyaniline (PAni) and orthovanadate from Yttrium co-doped with Erbium and Ytterbium [YVO4 (Er2%, Yb8%)]. We evaluated the association of the electrical and thermal properties of PAni with the upconversion (UC) effect due to the orthovanadate. We characterized the material by UV–Vis Spectroscopy, Fourier transform infrared (FTIR), Impedance Spectroscopy and Photoluminescence. Initially, we obtained polyaniline by emulsion polymerization in presence of surfactant, sodium dodecyl sulfate, yttrium orthovanadate and polyvinyl alcohol, resulting in a homogeneous dark green color solution. When we subjected the solution to a 14 kV constant electric potential difference applied between a 12 mm diameter needle (cathode) and a collecting plate (anode) 12 cm apart, the material deposited in the form of fibers. SEM results show that these fibers presented an average diameter of (89 ± 40) nm. On the other hand, when excited with radiation of wavelength λ = 980 nm (2.5 W) the material emitted radiation in the visible region with characteristic peaks at 525, 543 and 553 nm. The emission of intense green light is characteristic of UC effect. Due to photothermal characteristic of PAni the sample was heated, reaching temperatures close to 100 °C without suffering degradation. Measurements of photoluminescence showed that when exposed to HCl vapor, the material presented an increase of almost 100% in the intensity of light emitted in the UC effect, as well as a reduction of its electrical impedance from the order of GΩ to 900 KΩ, in a reversible process. These results are suggestive that these composite fibers appear as a promising active material for the sensing of acid vapors.

Synthesis of starch functionalized sulfonic acid co-imidazolium/silica composite for improving oil recovery through chemical flooding technologies

Polymer flooding in HPHT reservoirs using modified biopolymers and their composites acquire incremental attention nowadays. Some literature reported about limitations of native starch through enhanced oil recovery applications regarding bacterial degradation, thermal and ionic stability under severe reservoir environment. In the present study, functionalization of the starch biopolymer with thiol derivative then oxidation of thiol to sulfonic acid by environmentally friendly oxidants has been prepared and confirmed, after that starch derivative copolymerized with vinyl-containing monomers by free radical/redox emulsion polymerization in presence of silica seeds. Spectroscopic characterization and structure determination carried out by different spectroscopic techniques comprising FTIR, 1H NMR, while particles size measured through DLS and TEM, and thermal analysis determined by TGA analysis. Evaluation of the prepared composite as a novel enhanced oil recovery (EOR) candidate as well as the precursors conducted at simulated reservoir condition, where the oil recovery factor and water cut percentage calculated relevant to injected pore volume. The flooding data indicate that the prepared starch functionalized sulfonic acid co-imidazolium/silica composite is favorable for enhanced oil recovery applications as it can withstand high temperature and salinity conditions and the recovery factor reaches 39% of residual oil saturation.

Investigations in two-step ultrasonic synthesis of PMMA/ZnO nanocomposites by in–situ emulsion polymerization

Abstract This paper reports two-step ultrasonic method for in-situ synthesis of PMMA/ZnO nanocomposites. First step comprises nanoscale ZnO synthesis through ultrasound-assisted in-situ hydrolysis of zinc acetate. In second step, PMMA/ZnO nanocomposites have been synthesized via ultrasound-assisted in-situ emulsion polymerization in presence of native ZnO particles (1–5 wt%, without surface modification). Approx. 10 × -enhancement in polymerization kinetics is obtained. Properties of nanocomposites for different ZnO loadings are: particle size = 77.7–109.7 nm, maximum degradation temperature = 386.4 °C, maximum glass transition temperature = 122.5 °C, UV–visible absorption band width = 350–375 nm, electrical conductivity = 0.028–0.207 μS/cm, tensile strength = 25.8–36.57 MPa, Young's modulus = 1.09–1.47 GPa, percentage elongation = 10.98–17.56%. These enhanced properties (as compared to previous literature) are essentially attributed to uniform dispersion of ZnO in polymer matrix due to intense micro-convection generated by sonication. This results in strong interfacial interactions and adhesion between phases with increased crystallinity.

The Counterbalanced Effect of Size and Surface Properties of Chitosan-Coated poly(isobutylcyanoacrylate) Nanoparticles on Mucoadhesion Due to Pluronic F68 Addition

To evaluate of the effect of size and surface characteristics of poly(isobutylcyanoacrylate) nanoparticles coated with pluronic F68 and thiolated chitosan on mucoadhesion. Nanoparticles were obtained by radical emulsion polymerization in presence of different amounts of F68 (0-4%w/v). Mucoadhesion was ex vivo evaluated by applying nanoparticle suspension on rat intestinal mucosa and quantifying the amount of attached nanoparticles after incubation. F68 unimers added in the polymerization medium allowed decreasing nanoparticle size from 251 to 83nm, but resulted in nanoparticle surface modification. The amount of thiolated chitosan onto nanoparticle surface was decreased resulting in lower thiol groups and zeta potential. Consequently, the decrease of nanoparticle hydrodynamic diameter resulted in eight-fold-increase of the number of nanoparticles attached to the mucosa but a significant decrease of the weight of attached nanoparticles was observed. This unexpected result was due to a decrease of the amount of chitosan and thiolated chitosan available to interact with mucus upon addition of F68 in the polymerization medium. Addition of F68 should not be recommended to improve the amount of mucoadherent nanoparticles. Further studies could allow understanding if the low amount of small size nanoparticles could be able to improve oral bioavailability.

Branched and curved nanotubular polyaniline synthesized by emulsion polymerization in presence of zinc salts of n-dodecylbenzenesulfonic acid

The presence of zinc salts of DBSA (n-dodecylbenzenesulfonic acid), designated as Zn(DBSA) 2, induced some branches and curvature of the resultant polyaniline nanotubes. These branched or curved nanotubes can be clearly seen from their SEM and TEM micrographs taken for various polyaniline nanotubes prepared in the presence of Zn(DBSA) 2. For branched or curved polyaniline nanotubes, the conjugation chain length can be monitored by the position of their λ maxs in the UV–Vis–NIR spectra.

Synthesis of Modified Poly(vinyl acetate) Adhesives

Modified poly(vinyl acetate) copolymers with drying oils as comonomers have been prepared. The unsaturated triglycerides can produce cross-linking and give a waterproof effect due to their hydrophobicity. The new copolymers synthesized by solution polymerization in an organic medium have been submitted to analytical characterization in order to investigate the role of the drying oils in the polymerization reaction. NMR spectroscopy has been used to obtain information on the structure of the polymerization products and to confirm the eventual C–C bond formation between vinyl acetate and triglycerides. Spectroscopic data are found to be in agreement with copolymer formation. Copolymers as water dispersion have also been synthesized by emulsion polymerization in presence of poly(vinyl alcohol) as protective colloid and evaluated as wood adhesives. The corresponding polymer films have been subjected to mechanical characterization. An improvement in the water and solvent resistance has been observed due to the presence of drying oils. The cobalt acetate, if present as catalyst in the adhesive formulation, promotes cross-linking and produces a positive effect on the adhesive performance.

Characterization of some poly(methyl methacrylate)s prepared by emulsifier‐free emulsion polymerization in presence of some organic ligands and their nickel complexes

AbstractThe aqueous polymerization of methyl methacrylate (MMA) was studied using sodium bisulfite as initiator in absence and presence of tetraoxalyl urea (TOU), tetraoxalyl thiourea (TOthioU) and tetraoxalyl paraphenylene diamine (TOp‐phD). The effect of their nickel complexes on the polymerization rate has also been studied. Ligands with free carboxyl groups have a retarding effect on the polymerization reaction, while their nickel complexes have a catalytic effect. The polymers obtained in presence of nickel complexes were found to have wider molecular weight distribution than those obtained in their absence; this was deduced by thin layer chromatographic analysis in a binary mixture (benzene/methanol). The apparent energy of activation was found to be 5.83 × 104 J/mol, 1.87 × 104 J/mol, 2.11 × 104 J/mol, and 3.95 × 104 J/mol in absence and in presence of 0.5 g of Ni complex of TOp‐phD, TOthioU and TOU, respectively.

Characterization of poly(methyl methacrylate) prepared by emulsifier free emulsion polymerization in presence of carborundum

AbstractThe emulsifier free emulsion polymerization of methyl methacrylate was studied using sodium bisulfite as initiator in absence and in presence of carborundum. It was found that the carborundum has a catalytic effect on the polymerization reaction. The viscosity average molecular masses were determined. The polymers obtained in presence of carborundum have a broader molecular mass distribution.

Characterization of some poly(methyl methacrylate) prepared by emulsion polymerization in presence of egyptian delta titano magnetite ore (EDTMO)

AbstractThe emulsion polymerization of methyl methacrylate was studied in water using potassium persulphate as initiator and dedocyl–benzene sodium sulphonate as emulsifying agent at 85°C. The effect of Egyptian delta titano magnetite ore (EDTMO) upon the activation energy and on the mean average molecular weights of the obtained polymers was studied. It was found that the viscosity average molecular weights increase with decrease of reaction temperature and initiator concentration but increase with increase of monomer concentration in the reaction medium. Some of the polymer samples prepared in absence and in presence of some (EDTMO) were separated on tlc plates according to molecular weight in binary mixture, benzene:methanol (1:1.4 by volume) at 30°C. The tlc techniques were performed to give an idea about the molecular weight distribution of the polymer samples obtained.

A contribution to the theory of emulsion polymerization

AbstractThe polymerization curve in emulsion polymerization in presence of retarding substance was determined. The active concentration of the monomer in the vicinity of the growing radical was assumed constant, while the number of reacting particles was varied. The active concentration of the retardant in the vicinity of the reacting radical was assumed constant during the polymerization.The following relationship was derived for the decrease in monomer concentration: where −m, is the decrease in monomer concentration, k2 is the kinetic constant of the chain growth, (M) is the active concentration of the monomer in the vicinity of the growing radical, n is the concentration of all particles in the emulsion, V′t is the velocity of penetration of the initiator radical into the particles; the initiation velocity V′i(n – n1)/n, n1 is the concentration of reacting particles, i.e., of particles containing the growing polymer radical, V′r = nk3[R]; k3 is the constant of chain termination by a retardant molecule; V′in1/n is the velocity of termination by a primary radical, and t is polymerization time. For the polymerization with a constant number of particles we have where −m2 is the decrease in monomer concentration during the period of constant polymerization rate. In the presence of a large amount of retardant, when V′r ≫ 2V′i the decrease in monomer concentration is given by This equation shows that for these conditions the decrease in monomer concentration is independent of the number of polymerizing particles, but it is directly proportional to the initiation velocity, and inversely proportional to k3[R]. For the final period at the end of the polymerization, when it can no longer be assumed that the active concentration of the monomer in the vicinity of reacting radical is constant, the following formula was derived: where −m3 is the total decrease in monomer concentration during the period of (M) ≠ const.; N is the number of particles in unit volume of the aqueous phase, NA is Avogadro's number; (M0) is the active concentration of the monomer in the period of constant polymerization rate; and t3 is the time elapsed from the beginning of this period, i.e., total polymerization time minus time of constant (M).