Nitroxide‐Mediated Radical Polymerization in Microemulsion

Abstract

Nitroxide‐mediated polymerizations of styrene in microemulsion have been carried out at 125 °C using the cationic surfactant tetradecyltrimethylammonium bromide and the nitroxides 2,2,6,6‐tetramethylpiperidinyl‐1‐oxy (TEMPO) and N‐tert‐butyl‐N‐[1‐diethylphosphono‐(2,2‐dimethylpropyl)] nitroxide (SG1). TEMPO‐mediated polymerizations were extremely slow, with large particles (dn = 39–129 nm) and broad molecular weight distributions (MWDs). The origin of the broad MWDs was likely significant alkoxyamine decomposition and differing diffusion rates of monomer and low MW alkoxyamines (and nitroxide) between monomer‐swollen micelles and polymer particles. SG1‐mediated polymerizations proceeded at higher rates, resulting in nanoparticles (dn = 21–37 nm) and lower $\overline M _{\rm w} /\overline M _{\rm n}$ than for TEMPO.magnified image

Compartmentalization in NMP in Dispersed Systems: Relative Contributions of Confined Space Effect and Segregation Effect Depending on Nitroxide Type

“…[11][12][13] Recent years have seen increasing experimental evidence of compartmentalization in both NMP [14,15] and ATRP [16,17] in support of the theoretical predictions. Previous theoretical investigations of compartmentalization effects in NMP in dispersed systems have dealt with the systems 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO)/ styrene (S)/125 8C [3,4,8] and N-tert-butyl-N-(1-diethylphosphono-2,2-dimethylpropyl) SG1/S/90 8C.…”

“…The simulations reveal that [T ] is proportional to d 3 (i.e., slope ¼ 3 in Figure 2b for small particles), but it is not trivial to derive the corresponding analytical expression from Equation (14). are higher for TIPNO because of the higher K. However, in a compartmentalized system, the segregation effect on termination is stronger for TIPNO than for TEMPO, and thus the extent of reduction of the termination rate is greater for TIPNO than TEMPO.…”

Recent advances in controlled/living radical polymerization in emulsion and dispersion

“…3) proceeded at higher conversion, allowing for the preparation of nanoparticles with d ¼ 21-37 nm, and lower M w /M n than for TEMPO. 189 …”

Compartmentalization Effects on Bimolecular Termination in Atom Transfer Radical Polymerization in Nanoreactors

“…In many cases, these theoretical predictions have now been verified experimentally. [31][32][33][34] In CLRP systems based on the persistent radical effect [35][36][37] (e.g., NMP and ATRP), compartmentalization may manifest itself via the segregation effect and/or the confined space effect. [14] The segregation effect refers to The factors that determine the magnitude of the segregation effect in atom transfer radical polymerization (ATRP) in a dispersed system (miniemulsion, emulsion, etc.)…”