Combining Green Light-Activated Photoiniferter RAFT Polymerization and RAFT Dispersion Polymerization for Graft Copolymer Assemblies

Abstract

Although reversible addition−fragmentation chain transfer (RAFT) dispersion polymerization-induced self-assembly (PISA) has become one of the most attractive methods for the synthesis block copolymer assemblies, the synthesis of well-defined graft copolymer assemblies has rarely been reported. Herein, multifunctional macro-RAFT agents with well-defined structures were synthesized by green light-activated photoiniferter RAFT polymerization and subsequently used in RAFT dispersion polymerization for the synthesis of graft copolymers as well as graft copolymer assemblies. A direct comparison between RAFT-PISA behaviors of linear block copolymers and graft copolymers was conducted by using a monofunctional macro-RAFT agent and a multifunctional macro-RAFT agent, respectively. Transmission electron microscopy (TEM) analysis demonstrated that the structure of graft copolymers facilitated the creation of polymer nanoparticles with higher-order morphologies. Multifunctional macro-RAFT agents with different distributions of RAFT groups were also synthesized via a two-step photoiniferter RAFT polymerization. The influence of the distribution of solvophobic side chains on the RAFT-PISA process as well as graft copolymer assemblies was also investigated. We anticipate that this work should not only shed some light on the synthesis of well-defined graft copolymers and graft copolymer assemblies but also be useful to understand the mechanism RAFT-PISA of graft copolymers.

Efficient Synthesis and PISA Behavior of Molecular Bottlebrush Block Copolymers via a Grafting-From Strategy through RAFT Dispersion Polymerization

“…With the further increase of conversion from 67 to 75%, lamellar structures eventually evolved into vesicular structures as indicated in Figure c,d. Similar results were also found in the work of Tan and co-workers, by using a poly­(poly­(ethylene glycol) methyl ether methacrylate)- co -poly­(2-(2-(nbutyltrithiocarbonate)­propionate)­ethyl methacrylate) (PPEGMA m - co -BTPEMA n ) macro-CTA with a random sequence of backbone …”

“…Similar results were also found in the work of Tan and coworkers, by using a poly(poly(ethylene glycol) methyl ether methacrylate)-co-poly(2-(2-(nbutyltrithiocarbonate)propionate)ethyl methacrylate) (PPEGMA m -co-BTPEMA n ) macro-CTA with a random sequence of backbone. 55 In contrast, the PISA behaviors of P(NB-g-PEG 45 ) m -b-P(NB-CTA) n with a block sequence were investigated. For the morphology evolutions of P(NB-g-PEG 45 ) 20 -b-P(NB-CTA) 40 mediated RAFT dispersion polymerization , the spherical micelles with a growing size from the initial 35 nm of the seeded micelles to 59 nm were observed before 53% St monomer conversion, as shown in Figures 5a−c and S8).…”

“…In Zhao’ group, the RAFT PISA process on solid surfaces mediated by a mixture of molecularly dissolved macro-chain transfer agent (CTA) and surface-anchored RAFT agents were investigated, and different surface nanostructures based on the in situ co-assembly of surface-anchored polymers and “free” BCPs were fabricated . Very recently, Perrier and Tan groups have reported the PISA behaviors of graft copolymers using the multifunctional macro-CTA, and their exciting results indicated that the graft architecture made a great difference. − For example, Perrier and co-workers investigated the PISA behaviors of poly­(lauryl methacrylate)- graft -poly­(benzyl methacrylate) (PLMA- g -PBzMA) graft copolymers with low grafting density via RAFT dispersion polymerization, and a series of multi-core micelles with secondary microphase separation were observed in this process …”

In Situ Synthesis of Branched Block Copolymer Assemblies via RAFT Dispersion Polymerization Using Branched Macro‐RAFT Agents†

“…[ 55,63‐64 ] To further control the distribution of side chains, we combined photoiniferter RAFT polymerization and RAFT dispersion polymerization to synthesize a series of well‐defined graft copolymer assemblies. [ 65 ] Hong et al . [ 66 ] explored the first topological effect of cyclic and linear macro‐RAFT agents under RAFT‐PISA conditions, and it was found that the use of cyclic macro‐RAFT agent led to a delayed morphological transition as compared to its linear analog.…”

Exploiting the Monomer-Feeding Mechanism of RAFT Emulsion Polymerization for Polymerization-Induced Self-Assembly of Asymmetric Divinyl Monomers

“…Another significant advantage of PISA is that block copolymer nanoparticles with various morphologies could be directly produced at high solids. − A series of PPEGMA 14.9 -PAMA n nanoparticles were then prepared by RAFT emulsion polymerization of AMA (15% w/w) and characterized by transmission electron microscopy (TEM). Similar to other aqueous PISA formulations, , morphologies of these PPEGMA 14.9 -PAMA n nanoparticles were also sensitive to the volume ratio of two blocks.…”