Reversible addition fragmentation chain transfer (RAFT) polymerization of styrene in fluid CO2

Abstract

Reversible addition fragmentation chain transfer (RAFT) polymerizations of styrene in fluid CO 2 have been carried out at 80°C and 300 bar using cumyl dithiobenzoate as the controlling agent in the concentration range of 3.5·10 -3 to 2.1·10 -2 mol/L. This is the first report on RAFT polymerization in fluid CO 2 . The polymerization rates were retarded depending on the employed RAFT agent concentration with no significant difference between the RAFT polymerization performed in fluid CO 2 and in toluene. Full chain length distributions were analyzed with respect to peak molecular weights, indicating the successful control of radical polymerization in fluid CO 2 . A characterization of the peak widths may suggest a minor influence of fluid CO 2 on the addition reaction of macroradicals on the dithiobenzoate group.

Comparative study of the catalytic activity of the complexes Cp*RuCl(PAr3)2 [Ar = -C6H5 and 4-CF3-C6H4] in the ATRP of styrene

“…The percent of functionalization indicated that termination occurred to the extent of about 17%, a value which is little higher than that found by SEC but is in accord with reported data about enhanced termination reactions in scCO 2 . 29 The analysis of PS by IR spectroscopy obtained after 48 h of reaction also gives evidence of the endfunctionalization of the chains by the initiator fragment; signals with medium intensity at 1731 and 1179 cm -1 were assigned to ν(C=O) and ν as (O=C−OEt) of the ester group of the initiator. For comparison, the stretching signals of the pure ethyl 2-bromopropionate were observed at 1740 and 1168 cm -1 .…”

“…Other studies of polymerization in scCO 2 have been reported using RAFT and SFRP methodologies. 26,29 In Table 1, we summarize the results obtained in three preliminary polymerizations in scCO 2 .…”

“…Other studies of polymerization in scCO 2 have been reported using RAFT and SFRP methodologies. 26,29 In Table 1, we summarize the results obtained in three preliminary polymerizations in scCO 2 .As can be seen, only polymerizations carried out with catalyst 2 generate polystyrene, showing the important role of the fluorine atoms present in the P(4-CF 3 −C 6 H 4 ) 3 ligand of complex 2. The PS was obtained in low yield and was …”

“…Moreover, an increase in termination in radical polymerizations when CO 2 is used as solvent has also been reported. 29 The 1 H NMR spectroscopic analysis of PS obtained after 48 h of reaction showed signals characteristic of end groups: a broad signal centered at 4.4 ppm assigned to a proton alpha to Br in the −CH(Br) Ph end group, and another broad signal at 3.95 ppm, assigned to the methylene protons of the ethoxy group of the -CH(Me) CO 2 Et end group. The degree of polymerization (DP n ) was calculated from the ratio of the integrals of the aromatic protons divided by five and the integrals of α-proton in the halogenated fragment.…”

Controlled/living heterogeneous radical polymerization in supercritical carbon dioxide

“…94 However, fairly extensive data have indicated that for peroxide initiators, the rate of initiator decomposition is only marginally affected, if at all, by scCO 2 (relative to n-heptane). 83 Homogeneous RAFT polymerization of S 95 and methyl acrylate 96 have been carried out in scCO 2 , resulting in a somewhat narrower main peak of the MWD than in toluene in the case of S. 95 This was proposed to be the result of an increase in the rate of addition of propagating radicals to RAFT end groups due to the lower viscosity (i.e., assuming this reaction step to be diffusion-controlled), which would in turn give a higher number of activation-deactivation cycles. Homogeneous iodide-mediated polymerization of vinylidene fluoride has also been carried out successfully in scCO 2 .…”