SET-LRP of methyl acrylate to complete conversion with zero termination

Screening Libraries to Discover Molecular Design Principles for the Targeted Delivery of mRNA with One-Component Ionizable Amphiphilic Janus Dendrimers Derived from Plant Phenolic Acids

Viral and synthetic vectors to deliver nucleic acids were key to the rapid development of extraordinarily efficient COVID-19 vaccines. The four-component lipid nanoparticles (LNPs), containing phospholipids, PEG-conjugated lipids, cholesterol, and ionizable lipids, co-assembled with mRNA via a microfluidic technology, are the leading nonviral delivery vector used by BioNTech/Pfizer and Moderna to access COVID-19 mRNA vaccines. LNPs exhibit a statistical distribution of their four components when delivering mRNA. Here, we report a methodology that involves screening libraries to discover the molecular design principles required to realize organ-targeted mRNA delivery and mediate activity with a one-component ionizable multifunctional amphiphilic Janus dendrimer (IAJD) derived from plant phenolic acids. IAJDs co-assemble with mRNA into monodisperse dendrimersome nanoparticles (DNPs) with predictable dimensions, via the simple injection of their ethanol solution in a buffer. The precise location of the functional groups in one-component IAJDs demonstrated that the targeted organs, including the liver, spleen, lymph nodes, and lung, are selected based on the hydrophilic region, while activity is associated with the hydrophobic domain of IAJDs. These principles, and a mechanistic hypothesis to explain activity, simplify the synthesis of IAJDs, the assembly of DNPs, handling, and storage of vaccines, and reduce price, despite employing renewable plant starting materials. Using simple molecular design principles will lead to increased accessibility to a large diversity of mRNA-based vaccines and nanotherapeutics.

Stimuli-Responsive Principles of Supramolecular Organizations Emerging from Self-Assembling and Self-Organizable Dendrons, Dendrimers, and Dendronized Polymers

All activities of our daily life, of the nature surrounding us and of the entire society and its complex economic and political systems are affected by stimuli. Therefore, understanding stimuli-responsive principles in nature, biology, society, and in complex synthetic systems is fundamental to natural and life sciences. This invited Perspective attempts to organize, to the best of our knowledge, for the first time the stimuli-responsive principles of supramolecular organizations emerging from self-assembling and self-organizable dendrons, dendrimers, and dendronized polymers. Definitions of stimulus and stimuli from different fields of science are first discussed. Subsequently, we decided that supramolecular organizations of self-assembling and self-organizable dendrons, dendrimers, and dendronized polymers may fit best in the definition of stimuli from biology. After a brief historical introduction to the discovery and development of conventional and self-assembling and self-organizable dendrons, dendrimers, and dendronized polymers, a classification of stimuli-responsible principles as internal- and external-stimuli was made. Due to the enormous amount of literature on conventional dendrons, dendrimers, and dendronized polymers as well as on their self-assembling and self-organizable systems we decided to discuss stimuli-responsive principles only with examples from our laboratory. We apologize to all contributors to dendrimers and to the readers of this Perspective for this space-limited decision. Even after this decision, restrictions to a limited number of examples were required. In spite of this, we expect that this Perspective will provide a new way of thinking about stimuli in all fields of self-organized complex soft matter.

Assembling Complex Macromolecules and Self-Organizations of Biological Relevance with Cu(I)-Catalyzed Azide-Alkyne, Thio-Bromo, and TERMINI Double "Click" Reactions

In 2022, the Nobel Prize in Chemistry was awarded to Bertozzi, Meldal, and Sharpless "for the development of click chemistry and biorthogonal chemistry". Since 2001, when the concept of click chemistry was advanced by Sharpless laboratory, synthetic chemists started to envision click reactions as the preferred choice of synthetic methodology employed to create new functions. This brief perspective will summarize research performed in our laboratories with the classic Cu(I)-catalyzed azide-alkyne click (CuAAC) reaction elaborated by Meldal and Sharpless, with the thio-bromo click (TBC) and with the less-used, irreversible TERminator Multifunctional INItiator (TERMINI) dual click (TBC) reactions, the last two elaborated in our laboratory. These click reactions will be used to assemble, by accelerated modular-orthogonal methodologies, complex macromolecules and self-organizations of biological relevance. Self-assembling amphiphilic Janus dendrimers and Janus glycodendrimers together with their biological membrane mimics known as dendrimersomes and glycodendrimersomes as well as simple methodologies to assemble macromolecules with perfect and complex architecture such as dendrimers from commercial monomers and building blocks will be discussed. This perspective is dedicated to the 75th anniversary of Professor Bogdan C. Simionescu, the son of my (VP) Ph.D. mentor, Professor Cristofor I. Simionescu, who as his father, took both science and science administration in his hands, and dedicated his life to handling them in a tandem way, to their best.

Synthesis of Magnetite-Based Polymers as Mercury and Anion Sensors Using Single Electron Transfer-Living Radical Polymerization

In this work, hydrophilic polymers modified with iron oxide nanoparticles, such as iron oxide-poly(2-dimethylaminoethyl methacrylate) [P(DMAEMA)] magnetite-based and iron oxide-poly(acrylamide) [P(AAm)] magnetite-based polymers, were prepared via a single electron transfer-living radical polymerization approach. Bile acid and 2-bromo-2-methylpropionic acid were covalently attached onto the surface of Fe3O4 nanoparticles, and these immobilized magnetite nanoparticles were used as an initiator for the polymerization. The binding capabilities of different ions, such as Hg2+, CN-, Cl-, F-, and NO3 -, were tested using these polymeric sensors monitored by UV-vis spectroscopy. Magnetite-based P(DMAEMA) showed enhanced binding capability due to the presence of tertiary amine groups. In addition, it was possible to easily separate the bound ions from aqueous media using an external magnetic field.

Can We Push Rapid Reversible Deactivation Radical Polymerizations toward Immortality?

All reversible deactivation radical polymerization (RDRP) processes require a compromise between the rate of polymerization, which requires a high radical concentration, and retention of chain end functionality, which requires a low radical concentration. Here, we demonstrate that this compromise may be partially averted where fast deactivation of the propagating radical occurs. It is shown that, contrary to the predictions of classical reaction kinetics, when the probability density functions of the termination reactions are adjusted to take into account the time needed for radical diffusion, a reduction in the extent of termination can be expected if chain deactivation is rapid. We subsequently use this framework to explain experimental results in the copper(0)-mediated polymerization of acrylamide. The main concept put forward in the paper questions the commonly held assumptions of the limitations of RDRP processes and suggests the ability for a seemingly impossible level of control of radical reactions.

Recoverable and recyclable nickel–cobalt magnetic alloy nanoparticle catalyzed reversible deactivation radical polymerization of methyl methacrylate at 25 °C

Recyclable Ni–Co alloy catalyzed synthesis of well-defined poly(methyl methacrylate) (PMMA, up to 129 500 g mol⁻¹) with narrow-dispersity (Đ = 1.30) via a reversible deactivation radical polymerization technique is reported.

pH-Responsive Micellar Nanoassemblies from Water-Soluble Telechelic Homopolymers Endcoding Acid-Labile Middle-Chain Groups in Their Hydrophobic Sequence-Defined Initiator Residue

A middle-chain cleavable telechelic poly(oligoethylene glycol) methyl ether acrylate) (MCCT-POEGA-Br) was synthesized by single-electron transfer living radical polymerization (SET-LRP) initiated from an acetal-containing hydrophobic sequence-defined difunctional initiator. In aqueous medium, above a certain concentration, this hydrophilic homopolymer self-assembled into nanogel-like large micelles that exhibit an encapsulating capacity for both hydrophobic and hydrophilic cargo. The sequence-defined cleavage pattern encoded in the initiator residue allowed precise middle-chain cleavage, leading to quantitative disassembly of the corresponding nanoobjects. Dye release studies performed in an acidic environment demonstrated the potential of this new design concept in the preparation of pH-responsive nanocarriers. In addition, fluorescently tagged nanoassemblies could also be obtained via the thio-bromo "click" modification of MCCT-POEGA-Br prior to self-assembly. This strategy may provide facile access to a diversity of multistimuli-responsive nanocarriers based on commercially available hydrophilic monomers and sequence-defined difunctional initiators synthesized by this simple design strategy.

SET-LRP of Bio- and Petroleum-Sourced Methacrylates in Aqueous Alcoholic Mixtures

Single-electron transfer-living radical polymerization (SET-LRP) in "programmed" aqueous organic biphasic systems eliminates the judicious choice of solvent and also provides accelerated reaction rates. Herein, we report efforts to expand the monomer scope for these systems by targeting methacrylic monomers and polymers. Various environmentally friendly aqueous alcoholic mixtures were used in combination with Cu(0) wire catalyst, tris(2-dimethylaminoethyl)amine (Me₆-TREN) ligand, and p-toluenesulfonyl chloride (Ts-Cl) initiator to deliver well-defined polymethacrylates from methyl methacrylate, butyl methacrylate, and other monomers derived from biomass feedstock (e.g., lactic acid, isosorbide, furfural, and lauric acid). The effect of water on the nature of the reaction mixture during the SET-LRP process, reaction rate, and control of the polymerization is discussed. The control retained under the reported conditions is demonstrated by synthesizing polymers of different targeted molar mass as well as quasi-block AB copolymers by "in situ" chain extension at high conversion. These results highlight the capabilities of SET-LRP to provide sustainable solutions based on renewable resources.

Fast track access to multi-block copolymers via thiol-bromo click reaction of telechelic dibromo polymers

Multi-block copolymers offer a plethora of exciting properties, easily tuned by modulating parameters such as monomer composition, block length, block number and dispersity.

Highly reactive α-bromoacrylate monomers and Michael acceptors obtained by Cu(ii)Br2-dibromination of acrylates and instantaneous E2 by a ligand

The importance of the order of addition of reagents in SET-LRP.

Macromonomers, telechelics and more complex architectures of PMA by a combination of biphasic SET-LRP and biphasic esterification

Macromonomers and telechelics of PMA via biphasic SET-LRP and biphasic esterification with potassium acrylate.

Acrylate-macromonomers and telechelics of PBA by merging biphasic SET-LRP of BA, chain extension with MA and biphasic esterification

Chain extension of PBA with MA allows the preparation of acrylate-functional PBA.

SET-LRP in biphasic mixtures of fluorinated alcohols with water

Efficient and inexpensive SET-LRP in biphasic-mixtures of fluorinated alcohols with water.

Recent Developments in the Synthesis of Biomacromolecules and their Conjugates by Single Electron Transfer-Living Radical Polymerization

Single electron transfer-living radical polymerization (SET-LRP) represents a robust and versatile tool for the synthesis of vinyl polymers with well-defined topology and chain end functionality. The crucial step in SET-LRP is the disproportionation of the Cu(I)X generated by activation with Cu(0) wire, powder, or nascent Cu(0) generated in situ into nascent, extremely reactive Cu(0) atoms and nanoparticles and Cu(II)X₂. Nascent Cu(0) activates the initiator and dormant chains via a homogeneous or heterogeneous outer-sphere single-electron transfer mechanism (SET-LRP). SET-LRP provides an ultrafast polymerization of a plethora of monomers (e.g., (meth)-acrylates, (meth)-acrylamides, styrene, and vinyl chloride) including hydrophobic and water insoluble to hydrophilic and water soluble. Some advantageous features of SET-LRP are (i) the use of Cu(0) wire or powder as readily available catalysts under mild reaction conditions, (ii) their excellent control over molecular weight evolution and distribution as well as polymer chain ends, (iii) their high functional group tolerance allowing the polymerization of commercial-grade monomers, and (iv) the limited purification required for the resulting polymers. In this Perspective, we highlight the recent advancements of SET-LRP in the synthesis of biomacromolecules and of their conjugates.

Exploring structural effects in single-chain “folding” mediated by intramolecular thermal Diels–Alder chemistry

We describe a method to fold single polymer chains into nanoparticles using simple thermal Diels–Alder (DA) chemistry.

Acetone–water biphasic mixtures as solvents for ultrafast SET-LRP of hydrophobic acrylates

Transformation of SET-LRP catalyzed with Cu(0) wire from single phase (acetone/water = 9/1, v/v) into biphase (acetone/water = 8/2, v/v).

Searching for efficient SET-LRP systems via biphasic mixtures of water with carbonates, ethers and dipolar aprotic solvents

Screening biphasic mixtures of water with carbonates, ethers and dipolar aprotic solvents to discover new SET-LRP solvent systems.

SET-LRP mediated by TREN in biphasic water–organic solvent mixtures provides the most economical and efficient process

Screening ligands and solvents for economical and efficient biphasic SET-LRP.

Glass surface modification via Cu(0)-mediated living radical polymerization of fluorinated and non-fluorinated acrylates

The glass surface was modified via Cu(0)-mediated living radical polymerization of butyl acrylate and trifluoroethyl methacrylate by using the grafting from and grafting to methodologies.

The stirring rate provides a dramatic acceleration of the ultrafast interfacial SET-LRP in biphasic acetonitrile–water mixtures

The rate of interfacial SET-LRP in biphasic acetonitrile–water mixtures is stirring rate dependent.

Polymersomes with Asymmetric Membranes Based on Readily Accessible Di- and Triblock Copolymers Synthesized via SET-LRP

One of the hallmarks of nature is compartmentalization, and natural cell membranes are often asymmetric in terms of the inner and outer side. This communication describes work toward synthesizing such an asymmetric membrane from the bottom-up. A family of amphiphilic di- and triblock copolymers were synthesized via Cu(0)-mediated single electron transfer-living radical polymerization with the aim to generate polymer vesicles, or polymersomes, with an asymmetric membrane. Self-assembly of these polymeric amphiphiles in aqueous media was investigated using asymmetric field-flow fractionation and cryo-electron microscopy. Utilizing mixtures of diblock copolymers with differing hydrophilic moieties resulted in the formation of vesicles with an asymmetric segregation of charge between the inner and outer leaflet, confirmed by zeta potential measurements. These polymers, synthesized in good yields and using a biologically compatible method to induce self-assembly, have a promising range of applications from nanomedicine to synthetic cell research.

Surface-initiated SET-LRP mediated by mussel-inspired polydopamine chemistry for controlled building of novel core–shell magnetic nanoparticles for highly-efficient uranium enrichment

Surface-initiated SET-LRP integrated with polydopamine chemistry to prepare core–shell magnetic nanoparticles for uranium enrichment.

Ultrafast SET-LRP of hydrophobic acrylates in multiphase alcohol–water mixtures

A multiphase SET-LRP system using thein situgenerated Cu(0) by reduction of Cu(ii)Br₂with NaBH₄in various alcohols containing water was developed and used for SET-LRP of hydrophobic acrylates. From left to right: a solution of methanol/water containing Cu(ii)Br₂, the same solution after addition of BA and its SET-LRP.

SET-LRP of NIPAM in water via in situ reduction of Cu(ii) to Cu(0) with NaBH4

The direct and quantitative reduction of the air-stable Cu(ii)Br₂/Me₆TREN to Cu(0) by NaBH₄ represents a new method for the aqueous single electron transfer-living radical polymerization (SET-LRP) of water soluble polymers.

Ultrafast SET-LRP in biphasic mixtures of the non-disproportionating solvent acetonitrile with water

The two kinetic regime, low conversion and low chain end functionality seen in copper catalyzed polymerization of acrylates in acetonitrile was transformed into a SET-LRP kinetic, to complete conversion and quantitative chain end functionality in a biphasic mixture containing 10% water.

Surface-initiated SET living radical polymerisation for the synthesis of silica–polymer core–shell nanoparticles

We report the use of surface-initiated single-electron transfer living radical polymerisation (SI SET-LRP) to prepare inorganic–organic core–shell nanoparticles with functional grafted chains of high molecular weight.

A multiple-stage activation of the catalytically inhomogeneous Cu(0) wire used in SET-LRP

The surface of a Cu(0) wire used as a catalyst in SET-LRP is inhomogeneous since it contains a combination of Cu(111) and Cu(100) faces of the FCC unit cell whose ratio is dependent on the fabrication method. A method to activate this inhomogeneous Cu(0) wire for SET-LRP is reported.

The synergistic effect during biphasic SET-LRP in ethanol–nonpolar solvent–water mixtures

Adding a nonpolar solvent to ethanol–water reaction mixtures transforms SET-LRP of BA from triphasic to biphasic exhibiting a synergistic effect.

Aqueous SET-LRP catalyzed with “in situ” generated Cu(0) demonstrates surface mediated activation and bimolecular termination

Ultrafast, inversely temperature dependent aqueous SET-LRP with “in situ” generated Cu(0) yields quantitative chain-ends demonstrating surface mediated activation and termination.

A rational approach to activated polyacrylates and polymethacrylates by using a combination of model reactions and SET-LRP of hexafluoroisopropyl acrylate and methacrylate

A new class of activated polyacrylates was elaborated by a combination of model reactions and SET-LRP of hexafluoroisopropyl acrylate and methacrylate.

Synthesis of non-fouling poly[N-(2-hydroxypropyl)methacrylamide] brushes by photoinduced SET-LRP

Surface-initiated photoinduced SET-LRP of N-(2-hydroxypropyl)methacrylamide from an initiator-containing monolayer yields micropatterned brushes resistant to blood plasma fouling.

A coumarin dimer probe of mechanochemical scission efficiency in the sonochemical activation of chain-centered mechanophore polymers

A coumarin dimer mechanophore is used to probe the effect of polymer size and polydispersity on mechanochemical activation.