High Temperature Initiator-Free RAFT Polymerization of Methyl Methacrylate in a Microwave Reactor

Abstract

The reversible addition–fragmentation chain transfer (RAFT) polymerization of methyl methacrylate (MMA) was investigated under microwave irradiation. At first, a comparison was made between microwave and thermal heating for the RAFT polymerization of MMA with azobis(isobutyronitrile) (AIBN) as initiator and 2-cyano-2-butyldithiobenzoate (CBDB) as RAFT agent, revealing comparable polymerization kinetics indicating the absence of non-thermal microwave effects. Second, the CBDB-mediated RAFT polymerization of MMA was investigated at high temperatures (120°C, 150°C, and 180°C, respectively) in the absence of a radical initiator, showing a linear increase of the molar masses with conversion. The polydispersity indices remained below 1.5 up to 25% MMA conversion at 120°C and 150°C, indicating a controlled polymerization. This control over the polymerization was confirmed by the ability to control the molar masses by the concentration of RAFT agent.

Living Radical Polymerization by the RAFT Process - A Second Update

“…The microwave effect, particularly with MMA and MA, was suggested to be greater than expected for an effect of temperature alone, [432] although an alternate explanation has not yet been provided. A more recent study on MMA polymerization [109] indicates that the polymerization kinetics are independent of whether microwave or conventional heating processes are used. The advantage of a microwave reactor is that it allows RAFT polymerization to be readily conducted at high temperatures in superheated monomer.…”

“…For an efficient RAFT polymerization (Scheme 1, Fig. 3 22* [86] S S MA [54] AAEMA [87] MAEP [87] MMA [88,89] AEMA [90] DMAEMA [91] (TPMMA) [92] TFPMA [93] St [48,94,95] 277 [96] 278 [96] 392 [97,98] 345 [99] 348 [100] 347 [101] St [51] 364 [102] 365 [102] NVP [103] 385 [104] 386 [98] 387 [104] 388 [104] 389 [104] 390 [104] BA/ 407 [105] St/MAH [53] AAEMA-b-AEP [87] AAEMA-b-MAEP [87] MAEP-b-AAEMA [87] BMA/TMSEMA [106] TFPMA-b-tBA [93] St-b-NIPAM [95] St-b-HEMA/DMAEMA [86] 364-b-384 [102] 365-b-384 [102] 386-b-392 [97] 23* [107] S CN S DEGMA [108] EGMA [108] MAA [108] MMA [109] PEGMA …”

Living Radical Polymerization by the RAFT Process – A Third Update

“…Recent examples include RAFT polymerization of MMA, [564] acrylamides (NIPAm, DMAm) and their block copolymers, [392] vinylsilazane (452), [535] and vinyl esters (VAc, VBz, VPv) and their block copolymers. [523] Each of these studies indicate substantial acceleration of polymerization with respect to similar conventionally heated polymerizations.…”

One Decade of Microwave‐Assisted Polymerizations: Quo vadis?

“…Schubert and coworkers investigated the RAFT polymerization of MMA under microwave irradiation. [49] The comparison between microwave-assisted and thermal heating for the RAFT polymerization of MMA with AIBN as initiator and 2-cyano-2-butyldithiobenzoate (CBDB) as RAFT agent exhibited quasi-identical polymerization kinetics, indicative of the absence of non-thermal microwave effects. The CBDB-mediated RAFT polymerization of MMA at high temperatures ranging from 120 to 180 8C in the absence of the radical initiator AIBN showed a linear increase of the molar masses with conversion, while the polydispersity indices remained below 1.5 for MMA conversions lower than 25%.…”