Controlled Bimodal Molecular‐Weight‐Distribution Polymers: Facile Synthesis by RAFT Polymerization

Abstract

The RAFT agents RAFT-1 and RAFT-2 were used for RAFT polymerization to synthesize well-defined bimodal molecular-weight-distribution (MWD) polymers. The system showed excellent controllability and "living" characteristics toward both the higher- and lower-molecular-weight fractions. It is important that bimodal higher-molecular-weight (HMW) polymers and block copolymers with both well-controlled molecular weight (MW) and MWD could be prepared easily due to the "living" features of RAFT polymerization. The strategy realized a mixture of higher/lower-molecular-weight polymers at the molecular level but also preserved the features of living radical polymerization (LRP) of the RAFT polymerization.

Producing bimodal molecular weight distribution polymers through facile one‐pot/one‐step RAFT polymerization

“…As simulated by Barner‐Kowollik30 and reported by our previous work,31 the propagating radicals with different chain length could grow simultaneously in a same RAFT process. In this work, two RAFT agents, one monofunctional dibenzyl trithiocarbonate 1 and another difunctional trithiocarbonate 2 were simultaneously added into the RAFT polymerization system.…”

“…According to the RAFT mechanism using trithiocarbonates as the RAFT agents,34 monofunctional dibenzyl trithiocarbonate 1 should give rise to polymer with structure 3 ; Similarly, difunctional trithiocarbonate 2 should grow in four directions, yielding polymers with structure 4 , as shown in Scheme . However, in this work, the molecular weights of HMW chains was almost three times (not twice) those of LMW chains in most cases, which indicated that the mechanism is more complicated than the hypothesis as reported by our previous work, where a pair of mono‐ and difunctional dithiocarbamate RAFT agents was used 31. To further investigate the possible mechanism, the polymerization of St was conducted using difunctional trithiocarbonate 2 as the RAFT agent solely at 75°C.…”

“…Barner‐Kowollik and coworkers simulated a RAFT process where poly‐RAFT species and a small molecule RAFT agent could grow simultaneously in the same polymerization system 30. Very recently, we have reported a novel strategy for the facile synthesis of well‐defined bimodal MWD (co)polymers via one‐pot RAFT polymerization using a pair of mono‐ and difunctional dithiocarbamate RAFT agents 31. Inspired by these results, in this work, we extend this strategy to another type of RAFT agents, a pair of mono‐ and difunctional trithiocarbonates to synthesize bimodal MWD (co)polymers.…”

Living Radical Polymerization by the RAFT Process – A Third Update

“…A [522] St [522] 257 [539] St [539] St-b-MA [539] St-b-AN [539] St-b-NIPAm [539] 258 N S S CN A* VAc [366] VC [529] …”

One‐pot synthesized poly(vinyl pyrrolidone‐co‐methyl methacrylate‐co‐acrylic acid) blended with poly(ether sulfone) to prepare blood‐compatible membranes

“…RAFT polymerization is a living/controlled method that is used to achieve well‐defined polymers with both controlled molecular weights and MWDs . Herein, a series of poly(VP‐ co ‐MMA‐ co ‐AA) copolymers were synthesized via RAFT polymerization and blended with PES to prepare anticoagulant membranes.…”