odonnejm@che.udel.edu

B.S. Chemical Engineering, 2001                                Bucknell University

Macromolecular design via interchange of xanthates in microemulsion polymerization

Millions of tons of polymer latexes are produced annually by heterogeneous polymerization for applications such as coatings, adhesives, flocculants and rheological modifiers.  Industrially produced polymer latexes often suffer from poor control of molecular weight and high polydispersity.  The goal of this research is to produce stable latex nanoparticles containing high molecular weight, monodisperse polymer chains, while maintaining molecular weight control and exerting control over the microstructural properties.  To address this goal we are currently investigating the application of Macromolecular Design via Interchange of Xanthates (MADIX) to microemulsion polymerization.

Microemulsion polymerization is known to produce stable latex nanoparticles of very high molecular weight (10⁶ to 10⁷ Daltons) polymer chains and provides several advantages relative to other forms of heterogeneous polymerization including optical transparency, fast reaction times and smaller latex particle size (less than 50 nm).  In addition, microemulsion polymerization provides a model system by which to study the reaction mechanism and resulting latex and polymer properties of MADIX due to the segregation of the radicals into the micelles such that termination reactions are negligible.

MADIX is a type of reversible addition-fragmentation chain transfer (RAFT) polymerization that refers specifically to the use of xanthates as the chain transfer agents.  RAFT has proven to be a successful means of controlled/living polymerization for a wide range of monomers and reaction conditions in homogeneous polymerizations.  However, the mechanism of RAFT in a heterogeneous polymerization is not well understood.