Controlled free radical photopolymerization of styrene initiated by trithiocarbonate

Abstract

Density functional theory calculations are reported for prediction of the trends in CS bond dissociation energies and atomic spin densities for radicals using S,S′‐bis(α,α′‐dimethyl‐α‐acetic acid) trithiocarbonate (TTCA) and bis(2‐oxo‐2‐phenylethyl) trithiocarbonate (TTCB) as reversible addition fragmentation chain transfer (RAFT) reagents. The calculations predict that the value of the CS bond length (1.865 Å) of TTCA is longer than that (1.826 Å) of TTCB, and TTCA is more effective for the polymerization of styrene (St) compared to TTCB as predicted by density functional theory. In photopolymerizations, pseudo‐first‐order kinetics were confirmed for TTCB‐mediated photopolymerization of St due to the linear increase of ln([M]0/[M]) up to about 28% conversion, suggesting the living characteristics behavior of the photopolymerization of St in the presence of TTCB. For both TTCA and TTCB the polydispersities change with increasing conversion in the range 1.10–1.45, typical for RAFT‐prepared (co)polymers and well below the theoretical lower limit of 1.50 for a normal free radical polymerization. In addition, the triblock copolymer polystyrene‐block‐poly(butyl acrylate)‐block‐polystyrene (PSPBAPS) was successfully prepared, with very good control over molecular weight and narrow polydispersity (Mw/Mn = 1.45), using PSSC(S)SPS as macro‐photoinitiator under UV irradiation at room temperature. This indicated that this reversible and valid strategy led to a better controlled block copolymer with defined structures. Copyright © 2007 Society of Chemical Industry

Living Radical Polymerization by the RAFT Process - A Second Update

“…108 [275] St [71,275] (St-b-BA) [275] S S S 109 [284] S S S 110* [283] BA [70] tBA [283] AM [285] St [70,286] St-b-NIPAM [286] tBA [284] St [284] tBA-b-St [284] St-b-BA [284] St/AA [287] St/AA-b-St [287] St/MAH/NVP [288,289] (Continued) [290] 111b RЈ ϭ C 2 H 5 [290] 111c RЈ ϭ i C 3 H 7 [290] 111d RЈ ϭ t C 4 H 9 [290] 111e RЈ ϭ CH 2 Ph [290] 112 [290] S…”

“…Recently, several groups have reported that the polymerization of monomers with primary amine functionality (273)(274)(275)(276) (Table 16) can be effectively controlled with the monomer as the ammonium salt and with no or minimal loss of the RAFT end-group. [90,152,153,166] Some of the more exotic monomer subjected to RAFT polymerization are included in the tables that follow.…”

“…In the case of bis-RAFT agents sequential polymerization of two monomers will yield a triblock. [269] BA [270] MA [270] NIPAM [269,[271][272][273] 420 [274] BA [281] DA [281] St [71,275] 2VP [276] NVP [103] NIPAM/274 [153] DEHEA [280] MA [281] TMAPMA/PEGMA/NIPAM [277] (PEGMA/320) [165] tBA [280] BA/AA [279] (PEGMA/344) [165] 331 [159] AEMA/325/328 [278] DEHEA-b-ODA [280] DMAM-b-331 [159] DMAM-b-331-b-NIPAM [159] DEHEA-b-tBA [280] NIPAM-b-DMAM [272] 2VP-b-EA [276] tBA-b-DEHEA [280] AEME/328/342 [278] 105 [282] [282] PEGA-b-St [282] 106 [188] [188] EHA-b-MA [188] S S S…”

“…[270,275,285,309,413,436] RAFT polymerization of St derivatives can be carried out at near ambient temperature (30 • C) with 115 as RAFT agent using 365 nm irradiation and (2,4,6-trimethylbenzoyl)-diphenylphosphine oxide as photoinitiator. [309] The same photoinitiator with 420 nm irradiation was used in ambient temperature RAFT polymerization of the UV sensitive cinnamate derivative 298 [436] and for polymerization of BA and MA under solar irradiation (>400 nm) at 20 • C. [270] The use of ionizing radiation to initiate RAFT polymerization has been reviewed.…”

Studies on Photoinduced ATRP in the Presence of Photoinitiator

“…[11][12][13][14][15] A thiocarbonylthio compound, known as a classical RAFT agent, is a photosensitive molecule that readily undergoes reversible b-cleavage at the carbon sulfur bond and thus yields some control over the radical polymerization process under UV irradiation. [16][17][18][19][20][21] Some studies have also focused on UV-induced ATRP and the effect of UV-Vis radiation on the controlled nature of the polymerization process. [22][23][24][25][26][27] Although some success was achieved by the above techniques, the conditions for true photoinduced controlled radical polymerization were not attained.…”