Controlled radical polymerization of styrene by iodine transfer polymerization (ITP) in ab initio emulsion polymerization

- Ab initio iodine transfer emulsion polymerization of styrene is performed.
- Colloidally stable and uncoloured monomodal living latex particles are obtained.
- Methyl-2-iodopropionate is used as reversible chain transfer agent.
- A better control of Mn is obtained at 68 °C (VA-057) rather than at 80 °C (V-501).
- Block copolymerization with butyl acrylate is accomplished from a living seed latex.

The use of iodocompounds in radical polymerization presents a straightforward way to prepare controlled macromolecular architectures. Herein, ab initio emulsion polymerization of styrene has been successfully performed by iodine transfer polymerization using methyl-2-iodopropionate as transfer agent, 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]tetrahydrate (VA-057) as initiator and dodecyl sulfate sodium salt (SDS) as surfactant, yielding stable and uncoloured latexes (e.g. styrene conversion = 76%, Mn,theoretical = 7800 g mol−1, Mn,SEC = 8400 g mol−1, Mw/Mn = 1.84, particle diameter dp = 55 nm with a monomodal particle size distribution). Hence, the molecular weight of the polymer chains could be accurately controlled by the concentration of transfer agent. Furthermore, a poly(styrene)-b-poly(styrene-co-butyl acrylate) block copolymer latex was synthesized in seeded emulsion polymerization, proving the living character of the polymerization.