Kinetics and monomer partitioning during polymerization of vinyl acetate in microemulsions stabilized with AOT and n-butanol

Abstract

Vinyl acetate (VAc) was polymerized in microemulsion using sodium bis(2-ethylhexyl) sulfosuccinate (AOT) as surfactant and n-butanol (n-BuOH) as the cosurfactant (1:1, wt/wt) with potassium persulfate (KPS) as initiator. The effects of monomer, surfactant, and initiator concentration, as well as the temperature on the kinetics, particle size, and molar masses were studied. It was observed that polymerization rate increases as monomer, initiator, and temperature increases; however, the opposite was observed as surfactant concentration increases. Average particle diameters (Dp)< 50 nm and polymers with weight average molar masses (Mw) between 2.7×10 5 and 7.5×10 5 g/mol were obtained. For low amounts of stabilizing agents (AOT and n-BuOH), a bimodal molar mass distribution (MMD) was obtained. As nbutanol concentration increased, Mw decreases and a monomodal MMD was observed, which can be explained because chain transfer events are promoted by the presence of n-BuOH. A thermodynamic model was implemented to simulate the partitioning of VAc in the presence of n-BuOH between the phases throughout polymerization. It was found from simulations that microemulsion droplets are depleted fast at 5 % conversion and, due to the high water solubility of VAc, most of the monomer (70 %) and n-BuOH (97 %) reside in the aqueous phase at the beginning of polymerization, which indicates that both homogeneous and micellar nucleation are present.

Self-Organization Induced by Self-Assembly in Microheterogeneous Reaction-Diffusion System

“…Note that no dissipative patterns are observed at [AA] > 100 mM. Polydispersity of latex particles (nanogels) formed due to microemulsion polymerization of other monomers was found elsewhere …”

“…Polydispersity of latex particles (nanogels) formed due to microemulsion polymerization of other monomers was found elsewhere. 28 We have also measured the electrical conductivity of the BZ-AA-AOT microemulsion as a function of [AA] (see Figure 4). Figure 4 demonstrates that the increase in [AA] (starting at [AA] ≅ 100 mM) drastically elevates the conductivity, which indicates the percolation transition to the interconnected bicontinuous structure.…”

Three dimensional PEDOT nanowires network

“…There are several methods to produce polymer nanostructures. The most commonly used are: electron beam lithography and optical lithography [5], soft template [4,[6][7][8] and finally hard template [9,10]. The last two methods have become very important in the development of many strategies to nanostructure polymeric materials.…”

“…The typical synthesis is carried out in two different phases, both immiscible. This method includes micro-emulsion [6], mini-emulsion [7] and emulsion polymerization [8]. The hard template procedure uses a rigid material as a template to produce the nanostructures.…”