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

Abstract

Summary: Controlled radical polymerization of n‐butyl acrylate by reverse iodine transfer polymerization (RITP) was achieved in ab initio emulsion polymerization to yield a stable and uncolored latex (particle diameter dp = 106 nm). Hydrolysis of iodine, I2, was responsible for an upward deviation from the targeted molecular weight $\overline M _{{\rm n},{\rm targeted}}$ = 10 400 g · mol−1. The iodide concentration [I−] was followed by an iodide selective electrode and the amount of efficient iodine (33%) was successfully correlated with the experimental molecular weight $\overline M _{{\rm n},{\rm exp}}$ = 31 000 g · mol−1. Finally, a simplified mechanism of RITP in ab initio emulsion polymerization taking into account the iodine hydrolysis was proposed.Evolution of molecular weight and polydispersity index in RITP of BuA in ab initio emulsion.magnified imageEvolution of molecular weight and polydispersity index in RITP of BuA in ab initio emulsion.

Use of Sodium Iodide as the Precursor to the Control Agent in Ab Initio Emulsion Polymerization

“…The low pH values associated with this process should enhance the initiation rate 23. Importantly, a low pH value is also beneficial in limiting the hydrolytic disproportionation of iodine 18 …”

Molecular iodine in monomer and polymer designing

“…Also, homopolymer of p-vinylbenzylchloride (VBC) was produced with AIBN-based RITP technique, and its molecular weight was found to increase with the conversion of VBC and the PDI was almost unchanged, indicating the living character of the polymerization. Lacroix-Desmazes and his co-workers [95] tackled the ab initio emulsion polymerization, a process largely used in the industry, of n-butyl acrylate (nBuA) by RITP method using 4,4-azobis(4-cyanopentanoic acid) (ACPA) as a radical initiator and sodium dodecylsulfate (SDS) as an emulsifier, at a temperature of 85°C and for a time of 7 h. An inhibition period of a nearly 100 min was observed for monomer conversion up to 20% beyond, which conversion increased almost linearly with time. Molecular weight rose with monomer conversion and PDI remained in the range of 1.…”

Aqueous reverse iodine transfer polymerization of acrylic acid

“…It should be noted that the experimentally estimated M n values generally exceeded the theoretical number‐average molar mass. Irrespective of the relative measure of molar mass, these high molar masses could be, in part, due to the hydrolysis of iodine in water, resulting in inefficient generation of the R n ‐I chain‐transfer agent as well as loss of the iodo group from the chain‐end . Notwithstanding this limitation, a particular benefit of this method is the preparation of a colorless product [Fig.…”

“…Irrespective of the relative measure of molar mass, these high molar masses could be, in part, due to the hydrolysis of iodine in water, resulting in inefficient generation of the R n -I chain-transfer agent as well as loss of the iodo group from the chain-end. 30 Notwithstanding this limitation, a particular benefit of this method is the preparation of a colorless product [ Fig. 2(c)], which stands in contrast to colored PAA materials prepared using RAFT due to the functional (i.e., trithiocarbonate) chain-end.…”