https://onlinelibrary.wiley.com/doi/pdf/10.1002/pol.20210430

Block copolymer solution self-assembly: Recent advances, emerging trends, and applications

Reversible addition–fragmentation chain transfer (RAFT) polymerization is an increasingly popular method of controlled radical polymerization and remarkable advances is made in recent years. This polymerization technique offers great chances for more sustainable routes to obtain tailor-made polymers with high precision. This article may be of interest not only for readers familiar with the technique, but also to newcomers to the field or colleagues, who are looking for more sustainable or safer polymerization techniques to obtain an extensive number of possible polymer structures. After an introduction to RAFT polymerization, different novel paths to carry out RAFT polymerization are discussed in terms of their potential and also advancements in the polymerization technology such as polymerization induced self-assembly or carrying out the polymerization in continuous flow reactors are highlighted. At the end some upcoming application areas of polymers prepared by RAFT are presented.

https://hal.archives-ouvertes.fr/hal-03377914/document

Polymerizations by RAFT: Developments of the Technique and Its Application in the Synthesis of Tailored (Co)polymers

Recent progress in the application of pH-responsive polymers in separation science

Solubility and functionality of polymeric materials are essential properties determining their role in any application. In that regard, double hydrophilic copolymers (DHC) are typically constructed from two chemically dissimilar but water-soluble building blocks. During the past decades, these materials have been intensely developed and utilised as, e.g., matrices for the design of multifunctional hybrid materials, in drug carriers and gene delivery, as nanoreactors, or as sensors. This is predominantly due to almost unlimited possibilities to precisely tune DHC composition and topology, their solution behavior, e.g., stimuli-response, and potential interactions with small molecules, ions and (nanoparticle) surfaces. In this contribution we want to highlight that this class of polymers has experienced tremendous progress regarding synthesis, architectural variety, and the possibility to combine response to different stimuli within one material. Especially the implementation of DHCs as versatile building blocks in hybrid materials expanded the range of water-based applications during the last two decades, which now includes also photocatalysis, sensing, and 3D inkjet printing of hydrogels, definitely going beyond already well-established utilisation in biomedicine or as templates.

Double hydrophilic copolymers - synthetic approaches, architectural variety, and current application fields.

Two series of poly(vinyl amine) (PVAm)-based block copolymers with zwitterionic and thermoresponsive segments were synthesized by the reversible addition-fragmentation chain transfer polymerization. A mixture of the two copolymers, poly(N-acryloyl-l-lysine) (PALysOH) and poly(N-isopropylacrylamide) (PNIPAM), which have the same cationic PVAm chain but different shell-forming segments, were used to prepare mixed polyplex micelles with DNA. Both PVAm-b-PALysOH and PVAm-b-PNIPAM showed low cytotoxicity, with characteristic assembled structures and stimuli-responsive properties. The cationic PVAm segment in both block copolymers showed site-specific interactions with DNA, which were evaluated by dynamic light scattering, zeta potential, circular dichroism, agarose gel electrophoresis, atomic force microscopy, and transmission electron microscopy measurements. The PVAm-b-PNIPAM/DNA polyplexes showed the characteristic temperature-induced formation of assembled structures in which the polyplex size, surface charge, chiroptical property of DNA, and polymer-DNA binding were governed by the nitrogen/phosphate (N/P) ratio. The DNA binding strength and colloidal stability of the PVAm-b-PALysOH/DNA polyplexes could be tuned by introducing an appropriate amount of zwitterionic PALysOH functionality, while maintaining the polyplex size, surface charge, and chiroptical property, regardless of the N/P ratio. The mixed polyplex micelles showed temperature-induced stability originating from the hydrophobic (dehydrated) PNIPAM chains upon heating, and remarkable stability under salty conditions owing to the presence of the zwitterionic PALysOH chain on the polyplex surface.

Mixed Polyplex Micelles with Thermoresponsive and Lysine-Based Zwitterionic Shells Derived from Two Poly(vinyl amine)-Based Block Copolymers.

In this work, novel chiral-achiral ampholytic block copolymers comprising poly(N-acryloyl amino acid) and poly(vinyl amine), poly(VAm), were synthesized by the reversible addition-fragmentation chain transfer (RAFT) polymerization of N-acryloyl-L-glutamic acid (A-Glu-OH), which has two carboxylic acid moieties. The precursor of the cationic poly(VAm) segment, poly(NVPI), was prepared by the RAFT polymerization of N-vinylphthalimide (NVPI), which was employed as the macro-chain transfer agent (CTA). RAFT polymerization of A-Glu-OH in the presence of the dithiocarbamate-terminated poly(NVPI) macro-CTA and subsequent deprotection afforded ampholytic block copolymers with positive poly(VAm) and negative poly(A-Glu-OH) segments. For comparison, an ampholytic block copolymer with an amino acid-based polyelectrolyte having one carboxylic acid moiety in the monomer unit was prepared by the RAFT polymerization of N-acryloyl-L-alanine (A-Ala-OH). The resulting ampholytic block copolymers formed self-assembled micelles with electrostatically complexed cores and anionic shells, which were affected by pH values and salt and urea concentrations. In these micelles, interpolyelectrolyte complexes between the cationic poly(VAm) and anionic amino acid-based segment, corresponding to the core and chiral segment [poly(A-Glu-OH) or poly(A-Ala-OH)], respectively, contribute towards the manipulation of the multi-stimuli-responsive properties and functions of the shell. Selective interactions of DNA with the cationic poly(VAm) segment in the block copolymer were further investigated.

Multi-stimuli-responsive chiral-achiral ampholytic block copolymers composed of poly(N-acryloyl amino acid) and poly(vinyl amine)

Dipeptide diphenylalanine has attracted significant research interests because of its ability to self‐assemble into various nanostructures such as nanotubes, nanowires, and nanoribbons. In this article, we present the synthesis and self‐assembly of a novel diphenylalanine‐based homopolymer and block/random copolymers by the reversible addition–fragmentation chain transfer (RAFT) polymerization of an acrylamide having a dipeptide moiety. The RAFT polymerization of N‐acryloyl‐l,l‐diphenylalanine (A‐Phe‐Phe‐OH) afforded novel amino acid‐based polymers with predetermined molecular weights and relatively narrow‐molecular weight distributions. The hierarchical self‐assembled structures of poly(A‐Phe‐Phe‐OH), which involve nanorods, larger nanofiber‐like microcrystals, and fiber bundles, were characterized by atomic force microscopy (AFM), transmission electron microscopy, scanning electron microscopy, and dynamic light scattering measurements. The circular dichroic measurements of poly(A‐Phe‐Phe‐OH) revealed its characteristic chiroptical property, which is affected by the nature of the solvents and the addition of urea and salts via hydrophobic, hydrogen bonding, and electrostatic interactions. Thermo‐ and pH‐responsive block and random copolymers composed of A‐Phe‐Phe‐OH and N‐isopropylacrylamide were synthesized by RAFT polymerization, and the thermoresponsive properties and assembled structures of the resulting copolymers were investigated by AFM and turbidity measurements. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2562–2574

Synthesis and Hierarchical Self‐Assembly of Diphenylalanine‐Based Homopolymer and Copolymers By RAFT Polymerization

Nonconventional stimuli-responsive luminescent polymers without aromatic units have garnered considerable attention. In this study, luminescent ampholytic block copolymer (BCP) and random copolymer (RCP) consisting of nonconjugated vinyl amine (VAm) and N-acryloyl-L-threonine (AThrOH) were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization and subsequent deprotection. The ampholytic BCP and RCP display concentration-enhanced emissions, which are apparently higher than those of the VAm homopolymer and polyion complex, and wavelength-dependent emissions, thus validating clusterization-triggered emission (CTE). The intrinsic photoluminescence properties of the primary amine-containing ampholytic copolymers and corresponding polyion complexes were investigated in aqueous solution in response to the change in pH. Two noncovalent interactions, which involve electrostatic interactions between cationic VAm and anionic AThrOH units and hydrogen bonds (e.g., the amino group in VAm/hydroxyl and amide groups in AThrOH), contribute to the achievement of unique self-assembled structures and stimuli-responsive and fluorescent properties of VAm-containing BCP and RCP, which were verified by dynamic light scattering, circular dichroism, and fluorescence measurements. The ability of the copolymers to form clusterized states of the VAm unit can be governed by the comonomer sequence and external stimuli (e.g., pH change, the addition of salt and urea), leading to the manipulation of the assembled structures with CTE features. 

Ryo Yonenuma

Papers

Multi-stimuli-responsive chiral-achiral ampholytic block copolymers composed of poly(N-acryloyl amino acid) and poly(vinyl amine)

Mixed Polyplex Micelles with Thermoresponsive and Lysine-Based Zwitterionic Shells Derived from Two Poly(vinyl amine)-Based Block Copolymers.

Synthesis and Hierarchical Self‐Assembly of Diphenylalanine‐Based Homopolymer and Copolymers By RAFT Polymerization

Clusterization-triggered emission of poly(vinyl amine)-based ampholytic block and random copolymers

Synthesis and self-assembly of a diphenylalanine–tetraphenylethylene hybrid monomer and RAFT polymers with aggregation-induced emission