Synthesis of Polystyrene-block-poly(butyl acrylate) Copolymers Using Nitroxide-Mediated Living Radical Polymerization in Miniemulsion

Interfacial Mass Transfer in Nitroxide-Mediated Miniemulsion Polymerization

“…As TEMPO, NH 2 -TEMPO, and OH-TEMPO have been employed to mediate polymer growth in different heterogeneous NMP systems, [2,21,22] simulations were performed using the styrene-water partition coefficients corresponding to these nitroxides. At 135 8C the styrene-water partition coefficients of TEMPO, NH 2 -TEMPO, and OH-TEMPO are G j ¼ 98.8, 6.7 and 2.2, [14] respectively, where j corresponds to TEMPO, NH 2 -TEMPO, or OH-TEMPO.…”

“…Such polymers have potential application in the fabrication of commercially valuable block copolymers, [1,2] drug delivery systems, [3] nanotechnology, [4] adhesives, surfactants, and polymer compatibilizers. The distinguishing feature of NMP is the use of a nitroxide, such as 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO), to reversibly deactivate active polymer radicals to give a dormant alkoxyamine molecule (see Scheme 1).…”

“…There is interest in performing NMP in heterogeneous systems, in particular miniemulsion, [1,2,[6][7][8][9][10][11][12][13] because of the benefits gained by operating in a water-based medium (e.g., lower operating viscosities, improved heat transfer, and reduced need for solvents). The mechanisms involved in miniemulsion polymerization are similar to conventional emulsion polymerization, with the primary difference being that submicron monomer droplets (50-300 nm in diameter) act as the primary nucleation and polymerization locus, instead of monomer-swollen micelles.…”

Controlled/Living Radical Polymerization in Aqueous Miniemulsion

“…This result was explained by partition of the TEMPO between the organic and the aqueous phase, which would lead to a significant decrease of the nitroxide concentration in the polymerization locus. While TEMPO-or TEMPO-OH-terminated polystyrene were used as macroinitiators for the miniemulsion polymerization of n-butyl acrylate (nBA) to prepare the corresponding block copolymers by simple chain extension [70,74], when TEMPO was replaced by the more hydrophilic TEMPO-OH during the synthesis of PS homopolymers, significant differences appeared [69,73]. With TEMPO, the initiator efficiency was higher with KPS than with BPO whereas with TEMPO-OH, no such difference was observed.…”

“…nitroxide-terminated oligomers). In the latter case, the macroalkoxyamine is generally a short PS-TEMPO, either synthesized and isolated prior to its use in miniemulsion [70,76,77,79,81,82,95], or synthesized after a first step in bulk stopped at low monomer conversion followed by emulsification of the medium without further purification [74,80].…”