Atom transfer radical emulsion polymerization (emulsion ATRP) of styrene with water-soluble initiator

Selective copper-catalysed atom transfer radical addition (ATRA) in water under environmentally benign conditions

Simple and green conditions for copper-catalysed ATRA reactions in water have been developed. Firstly, [Cu(ADPA)(H2O)(ClO4)2] (1b, ADPA = 9-[(2,2'-dipicolylamino)methyl]anthracene) was demonstrated to be capable of selectively catalysing the ATRA of CCl4 to styrene using L-ascorbic acid (AsH2) as a reducing agent in organic solvent mixtures under ambient atmosphere. Mechanistic investigation suggested that our ATRA reaction proceeded via a single-electron transfer (SET) mechanism through an inner-sphere complex, which is consistent with the widely accepted mechanism for copper-catalysed ATRA. To perform the reaction in water as a sole solvent, a biocompatible surfactant (2 wt% Tween 20 or Tween 80) was added to improve solubility and increase the local concentration of organic reagents and the copper catalyst. Without the need for a complicated oxygen-free set-up, the ATRA reaction catalysed by this simple aqueous-dispersed system can be performed at a mild temperature (60 °C) and a relatively short reaction time (6 h) using 1 mol% of the catalyst. Furthermore, this facile protocol is also applicable for other alkene substrates demonstrated in this work, resulting in satisfactory to excellent substrate conversion and product yields.

Mini Monomer Encapsulated Emulsion Polymerization of PMMA Using Aqueous ARGET ATRP

A new emulsion polymerization based on Activators Regenerated by Electron Transfer Atom Transfer Radical Polymerization (ARGET ATRP) has been developed to produce poly(methyl methacrylate) (PMMA). The critical components of single-pot synthesis via a mini Monomer Encapsulated ARGET ATRP emulsion polymerization will be discussed. In this method, monomer is isolated in a micelle by pre-emulsification in a nonionic surfactant through high power stirring while acetone is introduced to the polymerization to aid in reactant transport and tetrabutylammonium salts are used as phase transfer agents. Polymerizations using tetrabutylammonium bromide (TBAB) were more controlled and demonstrated low Đ (M_w/M_n < 1.17), where those using tetrabutylammonium chloride (TBAC) exhibited higher Đ (M_w/M_n > 1.50). First-order linear kinetics for MMA polymerizations at 100 mM TBAB was demonstrated, while the reactions deviated from linearity at higher concentrations of TBAB and all concentrations of TBAC.