Controlled Radical Polymerization of Styrene by Reverse Iodine Transfer Polymerization (RITP) in Miniemulsion:  Use of Hydrogen Peroxide as Oxidant

Abstract

The use of molecular iodine I 2 in controlled radical polymerization, called reverse iodine transfer polymerization, represents a new, straightforward way to prepare controlled macromolecular architectures. Herein, miniemulsion polymerization of styrene in the presence of molecular iodine has been successfully performed. The polymerization of styrene was initiated by bis(4-tert-butylcyclohexyl) peroxydicarbonate at T ) 60 °C with dodecyl sulfate sodium salt as surfactant and hexadecane as hydrophobe, yielding a stable and uncolored latex. A certain amount of iodine reacted with water to form hydroiodic acid, leading to an upward deviation of the experimental molecular weight from the theoretical value. However, when the iodine lost by hydrolysis was regenerated by continuous addition of hydrogen peroxide in acidic conditions, it led to the expected molecular weight (e.g., M n,SEC ) 7900 g mol -1 , M w /M n ) 1.46, styrene conversion ) 78%, M n,theoretical ) 7900 g mol -1 ). Hence, the molecular weight of the polymer chains could be accurately controlled by changing the concentration of iodine. Last, a chain extension was successfully performed in seeded emulsion polymerization, proving the living character of the polymerization.

Molecular iodine in monomer and polymer designing

“…[91] One of their attractive works resides in conducting polymerization in emulsion [92] and miniemulsion of some vinyl monomers such as styrene. [93] The latter polymerization was induced by bis(4-tert-butylcyclohexyl) peroxydicarbonate as radical initiator at a temperature of 60°C with sodium dodecylsulfate salt (SDS) as surfactant and hexadecane as hydrophobe, giving a stable and uncolored latex. Loss of some amount of iodine in form HI, resulting from the reaction of I 2 with water, did occur.…”

Synthesis of diblock and triblock copolymers from butyl acrylate and styrene by reverse iodine transfer polymerization

“…Equally important, the I 2 (or a precursor such as NaI 11,12 ) is low cost when compared with thiocarbonyl derivatives, organometallic complexes, or nitroxide derivatives. Moreover, controlled polymerization of styrene and (meth)acrylic monomers has been carried out successfully by RITP in homogeneous 8,9,13 and heterogeneous 14,15 systems demonstrating the versatility of the process. The growing interest to synthesize poly(styrene)-poly(acrylate) block copolymers is due to their potential use as impact modifiers and/or as thermoplastic elastomers.…”

Controlled/Living Radical Polymerization in Aqueous Miniemulsion

“…Moreover, as expected with ITP method, the polydispersity indexes were high, around 1.7-1.8 at the end of the reaction. In a recent article, Lacroix-Desmazes and co-workers [187] reported for the first time the RITP of styrene in miniemulsion with SDS as a surfactant and hexadecane as a hydrophobe. To counterbalance the hydrolysis of iodine into HOI, I 3 ", Γ and I0 3 ", hydrogen peroxide was continuously added into the reaction medium under acidic conditions.…”