Yuri Reyes

Revisiting Chain Transfer to Polymer and Branching in Controlled Radical Polymerization of Butyl Acrylate

Acrylic monomers undergo chain transfer to polymer during polymerization leading to branched and even gelled polymers. It has been experimentally demonstrated that the extent of branching is higher for conventional free radical polymerization than for controlled radical polymerization (ATRP, RAFT, NMP) and this has been qualitatively explained in terms of the differences in the concentrations of highly reactive short-chain radicals between controlled and conventional radical polymerizations. Contrary to this explanation, in this work, it is quantitatively demonstrated that the short transient lifetime of the radicals, i.e., the time between activation and deactivation of the radical in controlled radical polymerization, is the cause for the low level of branching in these polymerizations.

Modeling the equilibrium morphology of nanodroplets in the presence of nanofillers

Waterborne polymer nanocomposites containing carbon nanotubes, clay platelets, laponite disks and other spherical/nonspherical nanofillers have been the focus of many recent investigations. The miniemulsion polymerization has proved to be a powerful technique to create new hybrid waterborne nanocomposites with enhanced properties. It is necessary to understand how the nanofiller shape/size and its compatibility with the phases affects the equilibrium morphology of the polymer nanoparticle to control the morphology and the properties of the resulting polymeric dispersions. With the aid of Monte Carlo simulations, the equilibrium morphology of hybrid monomer nanodroplets in the presence of nanofillers with different characteristics was obtained. A series of morphology maps depending on the nanofiller compatibility with the monomer and water phases and its shape have been obtained. These new maps may help to design and determine the required conditions to synthesize innovative waterborne polymer nanocomposites with specific morphologies through miniemulsion polymerization.