An official website of the United States government
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
This content will become publicly available on March 20, 2026
Electrolyte Effect on Electrochemically Controlled Polymerizations
Abstract Electrochemically controlled redox-switchable polymerization uses an electric potential to bias the monomer selectivity of a catalyst. Many ferrocene-appended catalysts can exist in two oxidation states, a neutral reduced state and an oxidized cationic state. Electrochemical generation of the oxidized cationic state produces a charged species whose counteranion is determined by the identity of the supporting electrolyte anion. Herein, the role the counteranion has on monomer selectivity and polymerization kinetics is investigated. Minimal differences in monomer selectivity in the reduced state was found, however, in the oxidized state, the coordinating ability of the counteranion greatly influenced the rate of polymerization. How activity differences governed by the choice of electrolyte can be utilized to access desired diblock copolymers is also described.
more »
« less
- Award ID(s):
- 2400314
- PAR ID:
- 10632992
- Publisher / Repository:
- Thieme
- Date Published:
- Journal Name:
- Synthesis
- Volume:
- 57
- Issue:
- 08
- ISSN:
- 0039-7881
- Page Range / eLocation ID:
- 1469 to 1474
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract The unique properties of cationic nanogels, such as their hydrophilicity and high loading capacity, make them a promising platform as drug delivery agents, particularly for the delivery of hydrophilic biomolecules. Although several synthetic methods exist for cationic nanogels, polymerization in dispersed media is advantageous due to its ability to provide control over composition and high monomer conversion. However, polymer droplets typically suffer from a significant increase in size during polymerization due to the Ostwald ripening process. Herein, the preparation of cationic nanogels by atom transfer radical polymerization under inverse microemulsion conditions of a hydrophilic inimer that prevents monomer diffusion and hence limits droplets’ growth during polymerization is reported. Additionally, the surface functionality of the nanogels can be modulated by the application of hydrophobic reactive surfactants or by grafting hydrophilic shells to form core‐shell cationic nanogels. The synthesized cationic nanogels are biocompatible, internalized to HEK 293 cells, and have a high complexation ability for plasmid DNA.more » « less
-
A zirconium compound, (salfen)Zr(O i Pr) 2 (salfen = N , N ′-bis(2,4-di- tert -butylphenoxy)-1,1′-ferrocenediimine), was tested as a redox switchable catalyst for the ring opening polymerization of cyclic esters and epoxides. Different activities were observed in the reduced and oxidized state, and an orthogonal switch on monomer activities could be achieved. Diblock and triblock copolymers were synthesized using an in situ redox switch of the catalyst oxidation state.more » « less
-
Abstract The synthesis of high‐molecular‐weight poly(vinyl ethers) under mild conditions is a significant challenge, since cationic polymerization reactions are highly sensitive to chain‐transfer and termination events. We identified a novel and highly effective hydrogen bond donor (HBD)–organic acid pair that can facilitate controlled cationic polymerization of vinyl ethers under ambient conditions with excellent monomer compatibility. Poly(vinyl ethers) of molar masses exceeding 50 kg mol−1can be produced within 1 h without elaborate reagent purification. Modification of the HBD structure allowed tuning of the polymerization rate, while DFT calculations helped elucidate crucial intermolecular interactions between the HBD, organic acid, and polymer chain end.more » « less
-
Photoacid generators (PAGs) have facilitated a number of technology breakthroughs in the electronic, coating, and additive manufacturing industries. Traditionally, PAGs that contain weakly coordinating anions, such as PF6-, generate Brønsted superacids under UV irradiation for rapid cationic polymerizations. However, PAGs with strongly coordinating anions remain under-utilized as they form weak acids that are inefficient or even incapable of initiating polymerization. To expand the scope of potential counteranions in PAGs, we leveraged a thiophosphoramide hydrogen bond donor (HBD) to catalyze photoinitiated cationic polymerizations from diphenyliodonium PAGs. Through the formation of hydrogen bonds between the HBD and PAG counteranion, acceleration of the polymerization rate was observed for a range of non-coordinating and coordinating anions. The effect of the HBD on the polymerization kinetics was investigated by 1H-NMR titrations and geometry optimizations. Extending HBD catalysis beyond photopolymerizations, addition of HBD also enabled hydrochloric acid to initiate controlled reversible addition-fragmentation chain transfer (RAFT) polymerization under ambient conditions. With the versatility of HBD, there is potential to access initiation systems that were previously believed to be impractical for cationic polymerization.more » « less
