Nitroxide-mediated living free radical miniemulsion polymerization of styrene (vol 155, pg 1, 2000)

摘要

Living free-radical bulk polymerization using a stable free radical initiator system based on nitroxide stable radicals such as TEMPO (2,2,6,6,-tetramethyl-1 -piperidynyloxy) has permitted the synthesis of polymers with molecular weight distributions only slightly broader than those obtained via anionic polymerization (PDI < 1.3). Most recently we were able to successfully apply the living free-radical polymerization in a miniemulsion polymerization process and prepare stable latexes with 20% solids and having relatively narrow molecular weight distributions (1.14 - 1.6). Styrene miniemulsions were prepared using an anionic surfactant Dowfax 8390 with hexadecane as costabilizer. The miniemulsion polymerizations were carried out at 125C in pressure bottles using benzoyl peroxide (BPO) and TEMPO. The kinetics of the living free radical miniemulsion polymerization were followed as a function of the [TEMPO]/[BPO] ratio in order to develop a mechanistic understanding of the nucleation and growth processes in this disperse system. The development of particle number and the total number of polymer chains (through the molecular weight analysis) during the course of polymerizations in the presence and absence of TEMPO are used to develop a comprehensive picture of the process. [References: 1]