“…We proved that chain branching occurs during the polymerization by cleavage of the products. As shown in Scheme , the branched structure can be broken by aminolyzing the dithioester moiety at the branch point. 3 Aminolysis and Subsequent Reduction of the Branched Product…”
Styrene radical polymerization was carried out in the presence of a polymerizable dithioester, benzyl 4-vinyldithiobenzoate, which possesses a dithioester group and a polymerizable double bond. Branched polystyrene was formed during the polymerization, as indicated by multimodal GPC curves of the products. The branched polystyrene contains a dithiobenzoate C(dS)S moiety at each branch point and thus can be analyzed by cleavage with amine. After cleavage, the GPC profiles became narrow. The molecular weight of the cleaved product increased linearly with monomer conversion, illustrating a living fashion of the polymerization. Solution property obtained by simultaneous online measurements of viscosity and light scattering indicates that the viscosity of the branched product decreased remarkably as compared to the linear polystyrene of equivalent molecular weight. The copolymerization behavior of styrene and benzyl 4-vinyldithiobenzoate was investigated by FT-IR monitoring during the polymerization. The results show that the latter was incorporated homogeneously into polystyrene chain. Therefore, branched polystyrene was synthesized with controlled architecture in the light of the length and narrow distribution of primary chains as well as the degree and the distribution of branching along the polymer chain.
“…We proved that chain branching occurs during the polymerization by cleavage of the products. As shown in Scheme , the branched structure can be broken by aminolyzing the dithioester moiety at the branch point. 3 Aminolysis and Subsequent Reduction of the Branched Product…”
Styrene radical polymerization was carried out in the presence of a polymerizable dithioester, benzyl 4-vinyldithiobenzoate, which possesses a dithioester group and a polymerizable double bond. Branched polystyrene was formed during the polymerization, as indicated by multimodal GPC curves of the products. The branched polystyrene contains a dithiobenzoate C(dS)S moiety at each branch point and thus can be analyzed by cleavage with amine. After cleavage, the GPC profiles became narrow. The molecular weight of the cleaved product increased linearly with monomer conversion, illustrating a living fashion of the polymerization. Solution property obtained by simultaneous online measurements of viscosity and light scattering indicates that the viscosity of the branched product decreased remarkably as compared to the linear polystyrene of equivalent molecular weight. The copolymerization behavior of styrene and benzyl 4-vinyldithiobenzoate was investigated by FT-IR monitoring during the polymerization. The results show that the latter was incorporated homogeneously into polystyrene chain. Therefore, branched polystyrene was synthesized with controlled architecture in the light of the length and narrow distribution of primary chains as well as the degree and the distribution of branching along the polymer chain.
“…[46][47][48][49][50][51][52][53][54] To the best of our knowledge, however, there is only one Scheme 2. Synthesis of the Di-and Trifunctional RAFT Agents reported example of multifunctional dithioesters being synthesized by this procedure.…”
Section: Resultsmentioning
confidence: 99%
“…The difunctional dithioesters thus obtained have not been used for RAFT polymerizations but in a step growth process for the preparation of polythioamides. For the synthesis of our dithioesters, we employed benzyl thiol, rather than methanol as did Levesque et al, 52 and reacted it with P 4 S 10 in the presence of either a di-or a tricarboxylic acid because benzyl dithiobenzoate derivatives thus formed are better RAFT agents than their methyl version. 2 In a RAFT process, indeed, such compounds expel benzyl radicals after fragmentation (Z ) -CH 2 Ph in Scheme 1): as compared to primary methyl radicals, benzyl radicals are not only substantially better leaving groups but they also initiate styrene and acrylate polymerization more efficiently, 55 which is crucial for a successful RAFT polymerization.…”
Section: Resultsmentioning
confidence: 99%
“…2,[36][37][38][39][40] Generally speaking, the procedures for synthesizing RAFT agents, including multifunctional ones, suffer from some disadvantages, such as the use of toxic reagents (e.g., iodine, carbone disulfide) or procedures that are not tolerant of functional groups. [46][47][48][49][50][51][52][53] Here, we demonstrate that the use of cheap and mild reactants such as cyclic tetrathiophosphates (P 4 S 10 and Davy reagents) for the synthesis of a di-and a trifunctional dithioester can substantially prevent some of the shortcomings associated with the synthesis of RAFT agents. P 4 S 10 and Davy reagents have been employed for the thionation of carbonyl groups and the preparation of thioamides, thiopeptides, thiolactames, and dithioesters.…”
Section: Introductionmentioning
confidence: 93%
“…P 4 S 10 and Davy reagents have been employed for the thionation of carbonyl groups and the preparation of thioamides, thiopeptides, thiolactames, and dithioesters. [46][47][48][49][50][51][52][53] We have recently shown that dithioesters can be obtained in just one step from the reaction of P 4 S 10 (or Davy reagents) with a carboxylic acid in the presence of an alkyl bromide -or radical source -and can be used in situ to control free-radical polymerizations by a RAFT-type mechanism. 54 This report describes (i) the synthesis of multifunctional dithioesters using P 4 S 10 , a thiol (RSH), and a multicarboxylic acid precursor, and (ii) the subsequent utilization of these dithioesters to prepare ABA-type triblock copolymers and three-arm polystyrene stars by RAFT.…”
The reaction of tetraphosphorus decasulfide (P4S10) with multicarboxylic acids and benzyl thiol afforded multifunctional dithioesters by a simple experimental procedure. The dithioesters were subsequently used as chain transfer agents to grow poly(tert-butylacrylate) and/or polystyrene chains in a controlled fashion by reversible addition-fragmentation chain transfer (RAFT). RAFT polymerizations of styrene were performed thermally at 110°C either in bulk or in toluene solution, while tert-butylacrylate was polymerized at 60°C in toluene in the presence of AIBN as the radical source. The multifunctional RAFT agents provided good control over the molar masses and polydispersities of the polymers formed, even though the presence of some linear dead chains generated by irreversible terminations could not be avoided. The contribution of the latter reactions was enhanced with the increase of viscosity at high conversion and with the "shielding effect" created by the polymeric arms around the RAFT centers of the core. Better control could be achieved when performing RAFT-mediated polymerizations in toluene solution as compared to bulk experiments. This methodology was applied to synthesize not only linear poly(tertbutylacrylate-b-styrene-b-tert-butylacrylate) triblock copolymers, but also three-arm polystyrene stars following an "arm-first" approach.
Radikalkettenpolymerisationen von Styrol mit (Meth)acrylsäuremethylester können durch eine Kombination aus Davy‐Reagentien oder P4S10 und Benzoesäure kontrolliert werden. In situ gebildete Dithioester (siehe Schema) steuern als Kettenüberträger die Reaktion. Im System P4S10/PhCOOH ist Dithiobenzoesäure ein Schlüsselintermediat.
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