Polymer nanoparticles by reversible addition-fragmentation chain transfer microemulsion polymerization

Microemulsion polymerization produces small latex nanoparticles (D < 50 nm) of high molecular weight (M_N = 10⁶ to 10⁷ g/mol) polymer, and provides several advantages relative to other types of heterogeneous polymeri- zations, such as rapid reaction times and a product that is colloidally stable. Since the introduction of microemulsion polymerization by Stoffer and Bone [1] and Atik and Thomas [2] in the early 1980s, this technique has been widely studied because of the dramatic benefits the high surface area-to-volume ratio of the polymer particles provides for many applications including sensors [3], fluorescence markers [4], and conductive films [5]. Control of the microstructural properties (such as molecular weight, polydispersity, monomer sequences, chain ends, and degree of branching) in a microemulsion polymerization could lead to enhanced chemical and mechanical properties and an even broader range of applications. Of the many controlled free radical polymerization techniques that have been developed to control these microstructural properties, including nitroxide-mediated polymeriza- tion (NMP) [6-9], atom transfer radical polymerization (ATRP) [10-13], and degenerative transfer (DT) [14,15], reversible addition-fragmentation chain transfer (RAFT) polymerization has emerged as the most promising due to its versatility and simplicity [16,17]. Also, in a RAFT polymerization the resulting polymer is free from the contamination of metal catalysts.