Precision synthesis of acrylate multiblock copolymers from consecutive microreactor RAFT polymerizations

Abstract

Well‐defined acrylate RAFT polymers and multiblock‐copolymers have been synthesized via the use of a continuous‐flow microreactor, in which polymerizations could be executed in 5−20 min reaction time. First, Poly(n‐butyl acrylate) (PnBuA) was synthesized in the micro‐flowreactor by using two different trithiocarbonate RAFT agents. Reaction time and reaction temperature were optimized and collected samples were directly studied with NMR, SEC and ESI‐MS to determine conversion, molar mass and end group fidelity. Using the continuous flow technique, highly reproducible and fast polymerizations yielded quantitatively functionalized PnBuA in a very facile and efficient manner. One batch of RAFT acrylate polymer with a molar mass of 1100 g mol−1 and excellent end group fidelity was employed as a macro‐RAFT agent for the subsequent copolymerization with different acrylate monomers (2‐ethylhexyl acrylate, t‐butyl acrylate, n‐butyl acrylate). Using this procedure, a sequential multiblock‐copolymer (Mn = 31,200 g mol−1, PDI = 1.46) consisting of five consecutive acrylate blocks was synthesized. This study clearly demonstrates the potential of using a continuous‐flow microreactor for subsequent RAFT polymerizations towards well‐defined multiblock‐copolymers. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013, 51, 2366–2374

Efficiency assessment of single unit monomer insertion reactions for monomer sequence control: kinetic simulations and experimental observations

“…1b). Note that the addition of the monomer to the radical fragment R-M • was considered to proceed with k p (2) k p (1) 770 000 L mol −1 s −1 k p (2) 420 000 L mol −1 s −1 k p (3) 245 000 L mol −1 s −1 k p (4) 157 500 L mol −1 s −1 k p (5) 113 750 L mol −1 s −1 k p (6) 91 875 L mol −1 s −1 k p (∞) 70 000 L mol −1 s −1 theoretical yield of 56% (at exactly x = 0.33, note that the absolute maximum is reached slightly above this monomer conversion) is obtained for the desired SUMI-2AB. 1b nicely demonstrate that chainlength effects must clearly play a role in the SUMI reactions when comparing these results with the experimentally derived theoretical yields (see below).…”

“…[6][7][8][9][10][11][12][13][14] Through controlled radical polymerization techniques, numerous multiblock copolymers have to date been achieved, mostly using acrylates or acrylamides to encode information in the main chain. Often, synthesis routes are available, but overall yields are low due to extensive reaction steps or tedious product isolation procedures.…”

RAFT Polymerization – Then and Now

“…In this context we (190)(191)(192)(193)(194)(195) and others (196,197) have examined RAFT polymerization in continuous flow reactors. Recent research at CSIRO in this area has involved developing processes for monomer degassing prior to polymerization (192), block copolymer synthesis (193), RAFT end-group removal (191,194,195), and sequential RAFT polymerization and end-group removal by, for example, thermolysis (194) or aminolysis (Scheme 23) (195).…”

Continuous Flow Synthesis of RAFT Block Copolymers

“…Recently, Vandenberg and coworkers [18] reported the RAFT polymerization of acrylate monomers and synthesis of multi-block copolymers using a continuous flow microreactor and different CTAs.…”