Reverse Iodine Transfer Polymerization (RITP) of Methyl Methacrylate

Abstract

The polymerization of methyl methacrylate (MMA) initiated by 2,2‘-azobis(isobutyronitrile) (AIBN) as radical initiator in the presence of iodine (I2) was studied at different temperatures (T = 70 °C and 80 °C). This process, called reverse iodine transfer polymerization (RITP), is based on the direct reaction of radicals with molecular iodine. RITP efficiently controls the molecular weight (determined by size exclusion chromatography, SEC) and the structure of the polymer chains (confirmed by 1H and 13C NMR spectroscopy). For instance, PMMA samples of M n,SEC = 2300 g mol-1 and polydispersity index PDI = M w/M n = 1.5 (M n,theoretical = 2300 g mol-1), M n,SEC = 4600 g mol-1 and PDI = 1.6 (M n,theoretical = 4700 g mol-1), M n,SEC = 9600 g mol-1 and PDI = 1.6 (M n,theoretical = 10 000 g mol-1), and M n,SEC = 19 200 g mol-1 and PDI = 1.5 (M n,theoretical = 18400 g mol-1) were successfully prepared by RITP. The polymerization was followed by on-line 1H NMR spectroscopy, and the conversion of iodine was followed by titration with a thiol (thioglycolic acid). It was shown by SEC, titration of iodine, gas chromatography, and NMR analyses that RITP was split into two different periods: a first “inhibition” period during which iodine is consumed to form very short ω-iodotelomers, and a second period where the polymerization follows the kinetics of a conventional free radical polymerization governed by degenerative chain transfer. The degenerative chain transfer constant was estimated to be C ex ≈ 2.6 at T = 80 °C. Last, the iodine-end-capped structure of the polymers was demonstrated by different analytical techniques, and the iodine functionality of the PMMA chains was up to 95%.

Modification of RAFT‐polymers via thiol‐ene reactions: A general route to functional polymers and new architectures

“…, with f, k d, t representing the initiator efficiency (0.6 for AIBN), 77 decomposition constant, and polymerization time, respectively). The polymerizations were also stopped at low monomer conversions (60-75%).…”

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 Radical Ab Initio Emulsion Polymerization of n‐Butyl Acrylate by Reverse Iodine Transfer Polymerization (RITP): Effect of the Hydrolytic Disproportionation of Iodine

“…Since one molecule of iodine will control two polymer chains, the targeted mean number-average molecular weight (M n;targeted ) of the polymer is controlled by the ratio between the mass of monomer and twice the initial number of moles of iodine (n I2,initial ) [Equation (1) in which M AÀI is the molecular weight of the chain-ends]. RITP has been successfully applied to a wide range of monomers like acrylates, [18] a-fluoroacrylates, [17,20] styrene, [17,21] methyl methacrylate, [22] and copolymers of vinylidene chloride and methyl acrylate. [17,19] …”