Nitroxide-mediated living free radical miniemulsion polymerization of styrene

Living free-radical bulk polymerization using a stable free r; initiator sy stem based on nitroxide stable radicals such as TEMPO (2,2 tetramethyl-l -p iperidynyloxy) has permitted the synthesis of polymers molecular weight dis tributions only slightly broader than those obtained via ar polymerization (PDI < 1.3). Most recently we were able to successfully appl living free-ra dical polymerization in a miniemulsion polymerization process: prepare stab le latexes with 20% solids and having relatively narrow mole weight distrib utions (1.14 - 1.6). Styrene miniemulsions were prepared using anionic surf actant Dowfax 8390 with hexadecane as costabilizer. The miniemu polymerizat ions were carried out at 125 degrees C in pressure bottles using be peroxid e (BPO) and TEMPO. The kinetics of the living free radical miniemu polymeri zation were followed as a function of the [TEMPO]/[BPO] ratio in ore develo p a mechanistic understanding of the nucleation and growth processes in dis perse system. The development of particle number and the total numb polymer chains (through the molecular weight analysis) during the cour polymerizat ions in the presence and absence of TEMPO are used to deve comprehensive pi cture of the process.