Norbornenyl-Based RAFT Agents for the Preparation of Functional Polymers via Thiol–Ene Chemistry

Abstract

A synthetic platform for the preparation of various norbornenyl (Nb) containing reversible additionÀfragmentation chain transfer (RAFT) agents has been developed. The design of the chain transfer agents (CTAs) is based on the desymmetrization of R,R 0 -dibromo-p-xylene by monosubstitution with an alkoxide anion and subsequent replacement of the residual bromine atom in the benzylic bromide to create several series of RAFT CTA including trithiocarbonate, xanthate and dithiobenzoate CTAs, allowing for the possibility to introduce other functional groups besides Nb, such as an allyl group. While a norbornene functionality was chosen as most reactive functional group toward thiols in radical-mediated thiolÀene chemistry, an allyl group was introduced for the sake of direct comparison of the double bond reactivity in the thiolÀene reaction. Control of the radical polymerization of acrylates, styrene and vinyl acetate has been achieved by using this novel family of CTAs. The results indicate that the Nb group remained intact at low monomer conversions (e.g., below 50% for styrene and vinyl acetate, below 30% for acrylates) and at optimal reaction temperatures (e.g., 70 °C for styrene and vinyl acetate, 62 and 65 °C for 1-ethoxyethyl acrylate and methyl acrylate, respectively), while the monomer-to-CTA ratio was kept high. Polymers with high end-group fidelity were modified with a series of thiol-containing compounds, leading to R-semitelechelics with different chain-end structures. While allyl-containing polymers exhibited a significantly lower reactivity, modification of the Nb-containing semitelechelics was rapid and fully accomplished under the same reaction conditions. However, for the given conditions, dodecanethiol and benzyl mercaptan showed a lower reactivity toward Nb-containing polymers, as evidenced by the obtained modification efficiency of 70% and 45%, respectively.

Living Radical Polymerization by the RAFT Process – A Third Update

“…A [285] BA [285] St [285] 54 S S * St [132,286] PFPVS [169] PVS [169] 381 [287] (382) [287] 414 [288] BA [286] 364 [289] (VAc) [274] (NVP) [248] (NES) [290] (BES) [290] MAA/EGDMA [291] (PFPVS-b-PS) [169] (399-b-EA) [288] 364-b-387 [289] 55 S S * tBA [292] 368 [292] tBA-b-368 [292] (Continued ) [293] St [293] 57 S S N * iBoA [268,[294][295][296] 351 [297] St [298] 58…”

“…A [285] VAc [285] 235 [520,521] 236 O S S A* (NES) [290] (BES) [290] (Continued ) [293] VAc [293] 238…”

One‐pot, facile synthesis of well‐defined molecular brush copolymers by a tandem RAFT and ROMP, “Grafting‐through” strategy

“…Cheng and coworkers46 reported a one‐pot grafting‐from synthesis of brush copolymers by combining ROMP and polymerization of amino acid N ‐carboxyanhydrides; however, when a grafting‐through method was attempted, the polymerizations were uncontrolled and led to broad MWDs. Inspired by recent studies of the direct synthesis of NB macromonomer by selective controlled radical polymerizations (RAFT and ATRP)36, 38, 47–49 and the high efficacy of ROMP of NB‐functionalized (macro)monomers by Grubbs' catalysts in the presence of methacrylate functional groups,50, 51 in this communication, we report advancement of synthetic methodologies to accomplish the facile, one‐pot tandem RAFT and ROMP, grafting‐through preparation of well‐defined brush copolymers with controllable dimensions.…”

Efficient DNA–Polymer Coupling in Organic Solvents: A Survey of Amide Coupling, Thiol-Ene and Tetrazine–Norbornene Chemistries Applied to Conjugation of Poly(N-Isopropylacrylamide)

“…Next, DNA–polymer conjugation was attempted using poly(NIPAM) end-capped with a Nb group ( P8 )52. After reacting with 10  μ M s0 - Tz DNA overnight at room temperature in DMF, DMAc or NMP (see Table 2), 15% native PAGE analysis revealed that the conjugate had been formed in up to 50% yield (by densitometry) – see Fig.…”