Emulsion Polymerization Of Acrylamide Research Articles

Tough, Self-Recoverable, Spiropyran (SP3) Bearing Polymer Beads Incorporated PAM Hydrogels with Sole Mechanochromic Behavior.

Spiropyran-containing hydrogels that can respond to external stimuli such as temperature, light, and stress have attracted extensive attention in recent years. However, most of them are generally dual or multiple stimuli-responsive to external stimuli, and the interplay of different stimulus responses is harmful to their sensitivity. Herein, spiropyran bearing polymer beads incorporated PAM (poly(AM–co–MA/DMSP3)) hydrogels with sole mechanochromic properties were synthesized by emulsion polymerization of acrylamide (AM) and methyl acrylate (MA) in the presence of spiropyran dimethacrylate mechanophore (DMSP3) crosslinker. Due to the hydrophobic nature of MA and DMSP3, the resultant hydrogel afforded a rosary structure with DMSP3 bearing polymer beads incorporated in the PAM network. It is found that the chemical component (e.g., AM, MA, and DMSP3 concentrations) significantly affect the mechanical and mechanoresponsive properties of the as-obtained poly(AM–co–MA/DMSP3) hydrogel. Under optimal conditions, poly(AM–co–MA/DMSP3) hydrogel displayed high mechanical properties (tensile stress of 1.91 MPa, a tensile strain of 815%, an elastic modulus of 0.67 MPa, and tearing energy of 3920 J/m2), and a good self-recovery feature. Owing to the mechanoresponsive of SP3, the hydrogels exhibited reversible color changes under force-induced deformation and relaxed recovery states. More impressive, the poly(AM–co–MA/DMSP3) hydrogel showed a linear correlation between tensile strain and chromaticity (x, y) as well as a stain and resting time-dependent color recovery rate. This kind of hydrogel is believed to have great potential in the application of outdoor strain sensors.

Preparation and characterization of polyacrylamide / sodium alginate microspheres and its adsorption of MB dye

A novel polyacrylamide (PAM) / sodium alginate (SA) adsorbent with double network structure was prepared by emulsion polymerization of acrylamide (AM) and SA. The chemical structure, thermal stability, crystallinity, pore size and distribution, surface area, surface morphology and energy dispersive spectrum of PAM/SA microspheres were determined by FTIR, TGA, XRD, BET, SEM and EDS. In addition, the effects of pH, temperature and adsorbent dosage on the adsorption capacity of Methylene blue (MB) were evaluated. The adsorption isotherms and kinetics as well as the thermodynamics of adsorption process were also studied. The results show that due to the entanglements between PAM and SA molecular chains. A double network structure is formed. The introduction of SA leads to the decrease of thermal stability and crystallization ability of PAM. The pore size is in the range of 0–200 nm, and the mesoporous structure is uniform. The particle size of is in the range of 1–10 u m. The surface of PAM/SA composite microspheres is smooth, and the ion crosslinking point is uniformly distributed. The results show that when pH=6, temperature is 25℃ and adsorbent dosage is 0.1g, the maximum adsorption capacity of PAM/SA composite microspheres is 75 mg/g. Langmuir isothermal model has better correlation with MB adsorption, and the maximum capacity obtained by simulation is 1070.54 mg/g. The pseudo-first-order kinetics and adsorption thermodynamics are better. The adsorption process is a physical adsorption rather than the chemical interation. The adsorption force decreases with the increase of temperature. The obtained PAM / SA composite microspheres have excellent adsorption capacity for dye removal from wastewater.

R-ATRP of Acrylamide under the Action of Iron Complex System in Inverse Emulsion

Reaction of acrylamide in inverse emulsion, adding Fe (EDTA)2-, with ammonium persulfate (APS) to form complex initiation system, Fe (EDTA)2 -is oxidized to Fe (EDTA)-, the control effect of the Fe (EDTA)-in the inverse emulsion polymerization of acrylamide was discussed. The results showed that acrylamide in inverse emulsion polymerization reaction by adding Fe (EDTA)2-, When the complex concentration is 2.8×10-4mol/L, n [(NH4)2S2O8]::n (FeSO4):n (Na2EDTA)=1:1:1.10, the reaction time was 6 hours, the amount of emulsifier is 3%,the reaction temperature is 40°C , The rate of conversion of monomer Increased in linear relationship with molecular weight, the final rate of conversion of monomer was 93.16%;a kinetic curve showed a good linear relationship, the coefficient of linear correlation was 0.997,Therefore, the Fe (EDTA)2 -have dual role firstly as a reducing agent of an oxidation - reduction initiator system and secondly as potential catalyst in reverse atom transfer radical polymerization (RATRP) .

On the Kinetics of Inverse Emulsion Polymerization of Acrylamide

The inverse emulsion polymerization of acrylamide (AAm) initiated by a water-soluble initiator (ammonium peroxodisulfate, APS) was investigated. The rate of inverse emulsion polymerization increased with both increasing initiator and emulsifier concentrations. The molecular weight of polyacrylamide decreased with increasing the initiator concentration and slightly rose with increasing the emulsifier concentration. With increasing APS concentration the curves are broader. This indicates widening of molecular weight distribution. The decrease in M¯ w with increasing APS concentration results from the increased termination of growing radicals mainly by primary or oligomeric radicals. The number of radicals per particle was inversely proportional to the APS concentration. The increased deactivation of primary and monomeric radicals decreased their desorption rate and re-entry rates as well. The desorption rate of radicals was interpreted using three models: the Nomura model (Nmodel, k′ des, N), the Gilbert model (Gmodel, k′ des, G) and the Ugelstadt model (Tmodel, k′ des, T). The desorption rate constant (k′ des) for the different models differs by up to two orders of magnitude. The value of k des increases in the following order: Nmodel < Gmodel < Tmodel. The radical entry rate decreases with rising emulsifier concentration and increases with rising initiator concentration.

The inverse emulsion polymerization of acrylamide using polystyrene-graft-polyoxyethylene as the stabilizer

Inverse emulsion polymerization of aqueous solution of acrylamide (AM) in toluene is carried out using polystyrene-graft-polyoxyethylene (PSt-g-PEO) as an emulsifier. The kinetics of polymerization, morphology of the particle, and particle size of the inverse emulsion have been investigated. The rates of polymerization are found to be proportional to the initiator concentration, the monomer concentration, and the emulsifier concentration. The morphology of the particle shows a spherical structure. The effects of amphipathic graft copolymer structure on the average molecular weight of polyacrylamide are studied. The mechanism of the inverse emulsion polymerization using amphipathic graft copolymer as emulsifier is proposed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2719–2725, 1999

Synthesis and kinetics of microgel in inverse emulsion polymerization of acrylamide

The kinetic behavior is studied in inverse emulsion polymerization of acrylamide. The polymerization rate in a micelle is proportional to the monomer concentration and the effective average radical concentration. When concentrations of monomer and radical are too low to proceed the polymerization only, some finite final conversion is obtained. The micelles of various sizes have different effective average radical concentrations at the same monomer concentration. Therefore, the polymerization rate and the final conversion are different for various sized micelles. The minimum amounts of emulsifier required to get stable state during reaction is 10 and 7 wt% (based on oil phase) in toluene and n-heptane systems, respectively. Phase inversion is observed with the increase of viscosity during polymerization. The final latex coagulates obviously in the toluene system even with 10 wt% of emulsifier, however, it can be improved more in the n-heptane system with 10 wt% of emulsifier. The crosslinking agent which copolymerizes with the monomer was supposed to remain in the interface of micelles. Such interfacial copolymerization not only hardens particles but improves the stability of the system also, therefore avoiding coagulation among particles. An increase in the content of crosslinking agent leads to a more uniform size of final particles. The microgel added in the alkyd resin decreases the drying time. The greater the amount of microgel added, the shorter the drying time.