Xanthate Mediated Living Polymerization of Vinyl Acetate: A Systematic Variation in MADIX/RAFT Agent Structure

Abstract

Eight xanthates were synthesized to induce living free radical polymerization of vinyl acetate. Four compounds, methyl (4‐methoxyphenoxy)carbonothioylsulfanyl acetate, methyl (methoxycarbonothioyl)sulfanyl acetate, methyl (ethoxycarbonothioyl)sulfanyl acetate and methyl (isopropoxycarbonothioyl)sulfanyl acetate were identified as suitable MADIX/RAFT agents, yielding low polydispersity (PDI < 1.2) poly(vinyl acetate) of molecular weights exceeding 5 × 104 g · mol−1. All suitable MADIX/RAFT agents exhibited extended periods of inhibition (0.3 h < tinh < 10 h) and moderate rate retardation. The ability of these compounds to control vinyl acetate polymerization can be correlated with the electron density on the central carbon atom of the xanthate. Electrospray ionization mass spectrometric analysis was performed to complete the investigation on the new MADIX/RAFT agents.

RAFT Polymerization of Vinyl Esters: Synthesis and Applications

“…In contrast to the trend observed with xanthates [86], the apparent chain transfer constant of the RAFT agent increased with the electron-withdrawing nature of the substituent, from 93 for N-(p-methoxyphenyl) N-pyridyl S-cyanomethyl xanthate to over 320 for N-(4-pyridyl) N-(p-cyanophenyl) S-cyanomethyl dithiocarbamate. All measured N,N-diaryl dithiocarbamates had higher apparent chain transfer constants and were more effective at controlling the polymerization of VAc than N-methyl N-(4-pyridyl) S-cyanomethyl dithiocarbamate, suggesting that the resonance-stabilizing ability of the substituent is of equal or greater importance than its electron-withdrawing ability in determining the activity of the RAFT agent.…”

“…In between these extremes, a wide range of R-groups may be employed to good effect, including esters of 1-acetyl [86][87][88][89][90]108,[110][111][112][113], 2-propionyl [3][4][5][6][7][8][9]30,31,34,66,69,70,[80][81][82]85,89,91,107,[114][115][116][117][118][119][120][121][122][123] and 2-methyl-2-propionyl [67,91], 2-acetic acid [124], 2-propionic acid [106,114,125], t-butyl [106], cyanomethyl [67,102], benzyl …”

“…Rhodixan A1 [7][8][9][80][81][82][83][84][85] MESA [53,61,[86][87][88][89][90] EESP [3][4][5][6]34,66,70,91,92] The sulfur atoms of the thiocarbonylthio group can be replaced by selenium, with N,N-dimethyl diselenocarbamates providing moderate control over the polymerization of VAc and VPiv [68]. Alternatively, the RAFT agent can be synthesized in situ, as exemplified by the use of isopropylxanthic disulfide [71,93].…”

“…Stenzel et al [86] In the case of dithiocarbamates, conjugation of the nitrogen lone pair with the thiocarbonyl group reduces the double bond character of the C=S bond, resulting in low rates of radical addition [101]. Substitution of the nitrogen with electron-withdrawing or resonance-stabilizing substituents such as carbonyl or phenyl groups hinders this delocalization [41,45].…”

Microwave-assisted synthesis of thermo- and pH-responsive antitumor drug carrier through reversible addition–fragmentation chain transfer polymerization

“…These reagents were used without further purification. 2-Ethoxycarbonothioylthio acetic acid (ECTA) was obtained through a reaction of 2-bromoacetic acid with potassium-o-ethyl dithiocarbonate, according to procedures outlined previously [37]. Mouse osteoblast-like cells (7F2), an osteoblastic cell line isolated from p53−/− mice was obtained from the Bioresource Collection and Research Center (Hsinchu, Taiwan).…”