Linear Block Copolymer Synthesis

Block copolymers form the basis of the most ubiquitous materials such as thermoplastic elastomers, bridge interphases in polymer blends, and are fundamental for the development of high-performance materials. The driving force to further advance these materials is the accessibility of block copolymers, which have a wide variety in composition, functional group content, and precision of their structure. To advance and broaden the application of block copolymers will depend on the nature of combined segmented blocks, guided through the combination of polymerization techniques to reach a high versatility in block copolymer architecture and function. This review provides the most comprehensive overview of techniques to prepare linear block copolymers and is intended to serve as a guideline on how polymerization techniques can work together to result in desired block combinations. As the review will give an account of the relevant procedures and access areas, the sections will include orthogonal approaches or sequentially combined polymerization techniques, which increases the synthetic options for these materials.

The Kinetics of 1,3-Dipolar Cycloaddition of Vinyl Monomers to 2,2,5,5-Tetramethyl-3-imidazoline-3-oxides

In our previous work [Edeleva et al. Chem. Commun. 2019, 55, 190-193], we proposed a versatile approach to the activation of the homolysis of an aldonitrone group-containing alkoxyamine by 1,3-dipolar cycloaddition to a vinyl monomer. Both nitroxide- and alkoxyamine-containing aldonitrones were found to be capable of reacting with the activated alkenes. In the present study, the kinetics of these reactions with 11 different vinyl monomers were investigated using EPR and NMR spectroscopy, and apparent activation energies as well as pre-exponential factors were determined. The influence of monomer structure on the rate of the 1,3-dipolar cycloaddition is discussed. For the vinyl monomers typically used in nitroxide mediated polymerization (styrene, methyl methacrylate) the rate coefficient of cycloaddition to the nitroxide is around k(353 K) ∼4 ⋅ 10-4  L mol-1  s-1 , whereas for n-butyl acrylate and methyl vinyl ketone we observed the fastest cycloaddition reaction with k(353 K)=8 ⋅ 10-3 and 4 ⋅ 10-2  L mol-1  s-1 respectively.

Modern trends in controlled synthesis of functional polymers: fundamental aspects and practical applications

Major trends in controlled radical polymerization (CRP) or reversible-deactivation radical polymerization (RDRP), the most efficient method of synthesis of well-defined homo- and copolymers with specified parameters and properties, are critically analyzed. Recent advances associated with the three classical versions of CRP: nitroxide mediated polymerization, reversible addition-fragmentation chain transfer polymerization and atom transfer radical polymerization, are considered. Particular attention is paid to the prospects for the application of photoinitiation and photocatalysis in CRP. This approach, which has been intensively explored recently, brings synthetic methods of polymer chemistry closer to the light-induced processes of macromolecular synthesis occurring in living organisms. Examples are given of practical application of CRP techniques to obtain industrially valuable, high-tech polymeric products.

The bibliography includes 429 references.

NMR and EPR Study of Homolysis of Diastereomeric Alkoxyamines

Three alkoxyamines based on imidazoline radicals with a pyridine functional group-potential initiators of nitroxide-mediated, controlled radical polymerization-were synthesized. Electron Paramagnetic Resonance (EPR) measurements reveal biexponential kinetics for the thermolysis for diastereomeric alkoxyamines and monoexponential kinetics for an achiral alkoxyamine. For comparison, the thermolysis of all three alkoxyamines was studied by NMR in the presence of three different scavengers, namely tetramethylpiperidine-N-oxyl (TEMPO), thiophenol (PhSH), and β-mercaptoethanol (BME), and detailed analysis of products was performed. NMR differentiates between N-inversion, epimerization, and homolysis reactions. The choice of scavenger is crucial for making a reliable and accurate estimate of the true homolysis rate constant.

On the nitroxide mediated polymerization of methacrylates derived from bio-sourced terpenes in miniemulsion, a step towards sustainable products

The typical use of toxic solvents, expensive control agents and the need of intermediate purification steps hinders the introduction of bio-sourced monomers into industrially viable block copolymers. This study aims at overcoming these limitations.

Making the best of it: nitroxide-mediated polymerization of methacrylates via the copolymerization approach with functional styrenics

The addition of 5 mol% of functional styrenics imparts control to the SG1-mediated polymerization of methacrylates and provides access to nanostructured functional methacrylic materials.

β-Myrcene/isobornyl methacrylate SG1 nitroxide-mediated controlled radical polymerization: synthesis and characterization of gradient, diblock and triblock copolymers

β-Myrcene (My), a natural 1,3-diene, and isobornyl methacrylate (IBOMA), from partially bio-based raw materials sources, were copolymerized by nitroxide-mediated polymerization (NMP) in bulk.

Why can Dispolreg 007 control the nitroxide mediated polymerization of methacrylates?

The alkoxyamine 3-(((2-cyanopropan-2-yl)oxy)(cyclohexyl)amino)-2,2-dimethyl-3-phenylpropanenitrile (Dispolreg 007) has recently emerged as a robust regulator for the controlled (co)polymerization of methacrylates and styrene by nitroxide mediated polymerization.

Metal Free Reversible-Deactivation Radical Polymerizations: Advances, Challenges, and Opportunities

A considerable amount of the worldwide industrial production of synthetic polymers is currently based on radical polymerization methods. The steadily increasing demand on high performance plastics and tailored polymers which serve specialized applications is driven by the development of new techniques to enable control of polymerization reactions on a molecular level. Contrary to conventional radical polymerization, reversible-deactivation radical polymerization (RDRP) techniques provide the possibility to prepare polymers with well-defined structures and functionalities. The review provides a comprehensive summary over the development of the three most important RDRP methods, which are nitroxide mediated radical polymerization, atom transfer radical polymerization and reversible addition fragmentation chain transfer polymerization. The focus thereby is set on the newest developments in transition metal free systems, which allow using these techniques for biological or biomedical applications. After each section selected examples from materials synthesis and application to biomedical materials are summarized.

Novel alkoxyamines for the successful controlled polymerization of styrene and methacrylates

The design of alkoxyamine/nitroxide species capable of mediating the polymerization of both styrene and methacrylic monomers has been notoriously difficult.

High solids content nitroxide mediated miniemulsion polymerization of n-butyl methacrylate

The synthesis of poly(n-butyl methacrylate) by nitroxide mediated miniemulsion polymerization is described using the alkoxyamine 3-(((2-cyanopropan-2-yl)oxy)(cyclohexyl)amino)-2,2-dimethyl-3-phenylpropanenitrile.

New Class of Alkoxyamines for Efficient Controlled Homopolymerization of Methacrylates

Despite significant efforts, the design of alkoxyamines for polymerization of methacrylic monomers in a well-controlled fashion with good retention of the active chain ends remains a challenge. Herein, the facile synthesis of several alkoxyamines, which are capable of achieving this long sought-after goal, is reported. Controlled homopolymerization of methyl methacrylate is achieved as determined by a linear increase in molecular weight with conversion and first-order rate plots for various alkoxyamine concentrations. The versatility of the alkoxyamines is further exemplified by the ability to control the homopolymerization of styrene and by synthesis of a block copolymer of a second methacrylate in an efficient chain extension process.

Nitroxide-Mediated Polymerization of Methacrylic Esters: Insights and Solutions to a Long-Standing Problem

Nitroxide-mediated polymerization (NMP) is one of the most powerful reversible deactivation radical polymerization techniques and has incredibly gained in maturity and robustness over the last decades. However, control of methacrylic esters is one of the different aspects of NMP that still requires improvement. This family of monomers always represented an important challenge for NMP, despite the many different nitroxide structures that have been designed over the course of time. This Review aims to present the most successful strategies directed toward the control of the NMP technique of methacrylic esters and especially methyl methacrylate. NMP-derived materials comprising uncontrolled methacrylate segments will also be discussed.

The reactivity of manganese dioxide towards different substrates in organic solvents

The diverse reactivity of MnO₂ in organic solvents was evidenced, its reduction potential being estimated as 0.90 V vs. NHE.