A Potential New RAFT - Click Reaction or a Cautionary Note on the Use of Diazomethane to Methylate RAFT-synthesized Polymers

Abstract

It has been found that diazomethane undergoes a facile 1,3-dipolar cycloaddition with both dithiobenzoate RAFT agents and the dithiobenzoate end-groups of polymers formed by RAFT polymerization. Thus, 2-cyanoprop-2-yl dithiobenzoate on treatment with diazomethane at room temperature provided a mixture of stereoisomeric 1,3-dithiolanes in near quantitative (495%) yield. A low-molecular-weight RAFT-synthesized poly(methyl methacrylate) with dithiobenzoate end-groups underwent similar reaction as indicated by immediate decolourization and a quantitative doubling of molecular weight. Higher-molecular-weight poly(methyl methacrylate)s were also rapidly decolourized by diazomethane and provided a product with a bimodal molecular weight distribution. Under similar conditions, the trithiocarbonate group does not react with diazomethane.

Mechanism and Kinetics of Dithiobenzoate‐Mediated RAFT Polymerization – Status of the Dilemma

“…Consistent with their high activity as RAFT agents, the dithiobenzoates are also more reactive in other contexts. In particular, the dithiobenzoate end groups are more readily removed or transformed, which can be essential or advantageous in many biomedical and optoelectronic applications . However, the use of dithiobenzoates in controlling polymerization of styrenes and acrylates has significantly diminished in recent years, mainly in favor of trithiocarbonate RAFT agents, which generally are more readily synthesized, are less sensitive to hydrolytic and most other forms of degradation, and polymerizations with these reagents generally display much less and (sometimes) no discernable retardation.…”

Living Radical Polymerization by the RAFT Process – A Third Update

“…[309] The Thiocarbonyl 1,3-Dipolar Cycloaddition Reaction It has been found that diazomethane undergoes a facile 1,3-dipolar cycloaddition with dithiobenzoate RAFT agents and with dithiobenzoate end-groups of polymers formed by reversible addition-fragmentation chain transfer (RAFT) polymerization. [181] Thus, 2-cyanoprop-2-yl dithiobenzoate (12), on treatment with diazomethane at room temperature, provided stereoisomeric 1,3-dithiolanes in near quantitative (.95 %) yield. A low molar mass RAFT-synthesized poly(MMA) with dithiobenzoate end-groups underwent similar reaction as indicated by immediate decolourization and a quantitative doubling of molar mass.…”

“…S S * BzMA [161] MMA [162] PEGMA [163] 302 [164] 301 [165] 312 [166] 396 [167] MA [168] PFPVB [169] PVS [169] St [132,162] 359 [170] St [171] BA [122] MMA/BDSMA [172] (MAA/TPMMA) [173] (MAA/293) [173] DEGMA/PEGMA [174] tBMA/DMAEMA/290 [175] MMA/LMA [163] 396-b-PEGMA [167] St/AcS [176] 4VP/EGDMA [177] (St-b-DMAEMA) [171] BzMA-b-HPMAm [161] DEGMA/PEGMA-b-DMAPMAm [174] PEGMA-b-MMA [163] LMA/MMA-b-PEGMA [163] 12 S S CN D* [178] MMA [178][179][180][181][182][183][184] PEGMA [111,185] GMA [186] 289 [186,187] 297 [188] 324 [189] 453 [190] iPOx [191] St [132,…”

Synthesis and Characterization of PDMS Based Triblock and Pentablock Copolymers

“…Silicones have been used as co-monomers incorporating other monomers and polymers to yield new properties. Condensation polymerization has been widely utilized to prepare the copolymers of silicone with urethane and amides [1,2]. The excellent properties of silicones with their marvelous thermal properties and stability, and relatively low glass transition temperatures have made this polymer ideal for manufacturing membranes [3][4][5].…”