Controlled radical polymerization (CRP) has both revolutionized the synthesis of linear polymers and enabled unprecedented topological complexity. While the synthesis of many polymeric architectures requires careful planning and specialized precursors, branched macromolecules such as segmented hyperbranched polymers (SHPs), knotted polymers, core‐crosslinked stars (CCSs), and more can be synthesized through the copolymerization of vinyl monomers and divinyl crosslinkers in only a few steps. In the nearly two decades since its discovery, this strategy has helped elucidate the fundamental polymerization behavior of crosslinkers and also yielded a variety of functional and stimuli‐responsive materials. The purpose of this mini‐review is to therefore overview critical fundamental aspects of CRP of crosslinkers and materials derived therefrom. The process by which both SHPs and CCS polymers are synthesized, the effect of key reaction parameters and intriguing recent advances are described with the intent of both educating new researchers and inspiring new directions in this area. © 2020 Society of Industrial Chemistry
This content will become publicly available on March 25, 2025
Controlled radical polymerization (CRP) techniques enable the preparation of diverse, chemically tailored polymers with a variety of chain architectures. Separately, light‐mediated polymerization reactions offer a number of advantages over thermal polymerizations in terms of energy efficiency, sustainability, and versatility. Recent work has combined photopolymerization and CRP techniques to advance the synthesis of polymers with nonlinear architectures, including bottlebrush polymers, star polymers, hyperbranched polymers, and cyclic polymers. These photoCRP methods offer novel routes to nonlinear polymers using mild reaction conditions. In this review, we provide an overview of photoCRP techniques for the synthesis of nonlinear polymers. We start with a discussion of photoCRP applied to the synthesis of linear polymers and discuss the underlying reaction mechanisms. Then, we discuss photoCRP applied to the synthesis of bottlebrush, star, hyperbranched, cyclic, and surface‐initiated polymer brushes. For each case, we discuss the synthetic strategy and the unique properties and characteristics of the resulting polymers, and we provide a perspective on potential future directions for research.
more » « less- NSF-PAR ID:
- 10496862
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Journal of Polymer Science
- ISSN:
- 2642-4150
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract -
more » « less
ABSTRACT This article reports a chain‐growth coupling polymerization of AB difunctional monomer via copper‐catalyzed azide–alkyne cycloaddition (CuAAC) reaction for synthesis of star polymers. Unlike our previously reported CuAAC polymerization of AB
n (n ≥ 2) monomers that spontaneously demonstrated a chain‐growth mechanism in synthesis of hyperbranched polymer, the homopolymerization of AB monomer showed a common but less desired step‐growth mechanism as the triazole groups aligned in a linear chain could not effectively confine the Cu catalyst in the polymer species. In contrast, the use of polytriazole‐based core molecules that contained multiple azido groups successfully switched the polymerization of AB monomers into chain‐growth mechanism and produced 3‐arm star polymers and multi‐arm hyperstar polymers with linear increase of polymer molecular weight with conversion and narrow molecular weight distribution, for example,M w/M n ~ 1.05. When acid‐degradable hyperbranched polymeric core was used, the obtained hyperstar polymers could be easily degraded under acidic environment, producing linear degraded arms with defined polydispersity. © 2019 Wiley Periodicals, Inc. J. Polym. Sci.2020 ,58 , 84–90 -
more » « less
Abstract Atom transfer radical polymerization (ATRP), as one of the most successful controlled radical polymerization techniques, has been broadly used by polymer chemists and nonspecialists for synthesis of various functional materials, although the use of copper as traditional catalyst often results in undesired color or properties. The first homopolymerization of an initiable monomer, that is, inimer, is reported via metal‐free ATRP using 10‐phenylphenothiazine (Ph‐PTH) as photocatalyst in both solution and microemulsion media. Although polymerizations of inimers in both media can be carried out, only the microemulsion polymerization of methacrylate‐based inimer 1 effectively confines the random bimolecular reaction within each segregated latex and produces hyperbranched polymers with high molecular weight and low polydispersity. Several experimental parameters in the microemulsion polymerization of inimer 1 are subsequently studied, including the Ph‐PTH amount, the solids content of microemulsion, and the light source of irradiation. The results not only provide an effective method to tune the structure and molecular weights of hyperbranched polymers in confined‐space polymerization, but also expand the toolbox of using metal‐free ATRP method for synthesizing highly branched polymers in controlled manner.
-
more » « less
Abstract An orthogonal combination of cationic and radical RAFT polymerizations is used to synthesize bottlebrush polymers using two distinct RAFT agents. Selective consumption of the first RAFT agent is used to control the cationic RAFT polymerization of a vinyl ether monomer bearing a secondary dormant RAFT agent, which subsequently allows side‐chain polymers to be grafted from the pendant RAFT agent by a radical‐mediated RAFT polymerization of a different monomer, thus completing the synthesis of bottlebrush polymers. The high efficiency and selectivity of the cationic and radical RAFT polymerizations allow both polymerizations to be conducted in one‐pot tandem without intermediate purification.
-
more » « less
Abstract An orthogonal combination of cationic and radical RAFT polymerizations is used to synthesize bottlebrush polymers using two distinct RAFT agents. Selective consumption of the first RAFT agent is used to control the cationic RAFT polymerization of a vinyl ether monomer bearing a secondary dormant RAFT agent, which subsequently allows side‐chain polymers to be grafted from the pendant RAFT agent by a radical‐mediated RAFT polymerization of a different monomer, thus completing the synthesis of bottlebrush polymers. The high efficiency and selectivity of the cationic and radical RAFT polymerizations allow both polymerizations to be conducted in one‐pot tandem without intermediate purification.
