Synthesis of Multifunctional Dithioesters Using Tetraphosphorus Decasulfide and Their Behavior as RAFT Agents

Abstract

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.

Living Radical Polymerization by the RAFT Process

“…With symmetrical trithiocarbonates (e.g. 54-57) [96,99] or bis-RAFT agents such as 89 [14] or 90, [211] the RAFT functionality remains in the centre of the block (Scheme 18). The merits and demerits of the two approaches will be discussed further in the section on star polymers.…”

“…The challenge in preparing such multifunctional molecules lies with developing reactions that proceed in quantitative yield and produce no by-products. Whereas incomplete reaction or side reactions in the synthesis of a 88 [195] S S S S 89 [14] S S S S 90 [211] Scheme 18. monofunctional compound will give residual starting materials or an easily removed by-product, in the case of multifunctional compounds such process lead to molecules with incomplete functionality. For example, in the case of an eight-armed core, a yield of 95% for an individual functionalization step means that <70% of the product would contain the requisite number of arms.…”

“…These peaks are also observed by GPC with UV detection. 92 [198] 93 n ϭ 3 (1,3,5-substitution) [211] 94 n ϭ 4 (1,2,4,5-substitution) [77] 95 n ϭ 6 [77,213] 96 [214] Scheme 25. associated with attack of the propagating radical at the core of the star would be an issue particularly at high conversions. There is, however, no direct evidence of problems attributable to this cause in the examples we have reported.…”

Temperature-responsive self-assembly of star block copolymers with poly(ionic liquid) segments

“…[36][37][38][39][40][41] Previously, we synthesized poly(Nvinylcarbazole) stars and star block copolymers using the R-group approach in which the leaving groups are linked to the core, and the core is transformed into a radical by fragmentation. 42 In the present study, two R-designed tetrafunctional CTAs, including a xanthatetype tetrafunctional CTA (CTA 1) and a dithiocarbamate-type tetrafunctional CTA (CTA 2), were used for the synthesis of thermoresponsive-ionic star block copolymers, as shown in Scheme 1.…”

RAFT Polymerization of Styrene Using Dithioester with Anthracene Z Group as Chain Transfer Agent

“…The BAC was synthesized by coupling 9-formyl anthracene and benzyl mercaptan under P S 4 10 according to similar route as in literature (Scheme 1) [23][24][25]. A typical reaction procedure is as follows: 9-formyl anthracene (1.11 g, 5 mmol), benzyl mercaptan (0.682 g, 5.5 mmol), P S 4 10 (2.22 g, 1.5mmol), and sodium bicarbonate (1.0g) 35~40 mL toluene were added to a 50 mL three neck round flask.…”