Nitroxide‐Mediated Controlled/Living Free Radical Copolymerization of Styrene and Divinylbenzene in Aqueous Miniemulsion

Abstract

Summary: The nitroxide‐mediated controlled/living free radical copolymerization of styrene and divinylbenzene using a polystyrene‐TEMPO macroinitiator in aqueous miniemulsion and in bulk have been investigated. The crosslink densities were estimated based on the content of pendant vinyl groups as determined by 1H NMR. Considerably lower crosslink densities were revealed in the miniemulsion than in the corresponding bulk system. The rate of polymerization in the miniemulsion increased with decreasing particle size, and was significantly higher than in bulk.Crosslink density for the TEMPO‐mediated free radical copolymerization of S(1) and DVB(2) (f = 0.99, f = 0.01) at 125 °C in bulk (□) and in miniemulsions with dn = 585 nm (○) and 53.3 nm (•).magnified imageCrosslink density for the TEMPO‐mediated free radical copolymerization of S(1) and DVB(2) (f = 0.99, f = 0.01) at 125 °C in bulk (□) and in miniemulsions with dn = 585 nm (○) and 53.3 nm (•).

Synthesis of Poly(vinyl acetate) Nanogels by Xanthate‐Mediated Radical Crosslinking Copolymerization

“…[11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] One objective of the use of controlled/living CC is to produce uniformly crosslinked structures, which may offer advantages, for instance, in active delivery applications to improve control over the release of encapsulated agents. In this regard, nitroxide-mediated polymerization (NMP), [11][12][13][14] atom transfer radical polymerization (ATRP), [15][16][17][18][19] and reversible addition-fragmentation chain transfer (RAFT) [20][21][22][23][24][25] polymerization have been recently considered to achieve branched copolymers of a homogeneous structure by radical crosslinking copolymerization (RCC). In a seminal work, [20a] our group reported the synthesis of hydrophilic polymeric nanogels in aqueous solutions by macromolecular design by interchange of xanthates (MADIX), a RAFT-like process that utilizes xanthates as CTAs.…”

Effect of stirring rate on particle formation in emulsifier-free, organotellurium-mediated living radical emulsion polymerization (emulsion TERP) of styrene

“…11,12 Because the control agents used for CLRP thus far have typically been hydrophobic, most of the research efforts in this area have studied miniemulsion polymerization, which ideally proceeds in hydrophobic monomer droplets. [13][14][15][16][17] There has been great interest in the possibility of applying CLRP to emulsion polymerization, but it has been difficult to realize because of problems with the transfer of the control agent. Specifically, the main problem is that the hydrophobic control agent in a monomer droplet does not transfer smoothly into micelles (particles) as polymerization loci via an aqueous medium.…”

Polimerização RAFT em Miniemulsão

“…Conforme já revisado, as técnicas de CLRP [136] permite a síntese de polímeros com arquitetura molecular definida, tendo sido recentemente adaptada para uso em diversos tipos de sistemas dispersos de polimerização, o que torna possível o uso de diversas técnicas de CLRP como rota de síntese de nanogéis com arquitetura molecular complexa e definida [13,[137][138][139][140][141] . De uma forma geral, as técnicas de CLRP em sistemas dispersos são de fato rotas bem atrativas para a síntese de nano-hidrogéis com estrutura molecular bem definida (ex.…”