Functional spaces in star and single-chain polymers via living radical polymerization

Cationic Alternating Copolymerization of Vinyl Esters and 3-Alkoxyphthalides: Side Chain-Crosslinkable Polymers for Acid-Degradable Single-Chain Nanoparticles

Cationic copolymerization of vinyl acetate and 3-alkoxyphthalides (ROPTs) was demonstrated to proceed using GaCl3 as a Lewis acid catalyst. Both monomers did not undergo homopolymerization, while copolymerization smoothly occurred via the crossover reactions, resulting in alternating copolymers with molecular weights of over 104. The obtained copolymers could be degraded by acid due to the cleavage of the diacyloxymethine moieties, which were derived from the crossover reactions from vinyl acetate to ROPT, in the main chain. An advantage of not radical but cationic copolymerization of vinyl esters was exerted by copolymerizations of radically reactive group-containing vinyl esters with ROPTs. For example, vinyl cinnamate was successfully copolymerized with an ROPT by the cationic mechanism, while keeping the cinnamoyl groups intact. The obtained alternating copolymer was subjected to a photodimerization reaction of the cinnamoyl groups in the side chains, resulting in an acid-degradable single-chain nanoparticle via the intramolecular crosslinking reactions.

Biocompatible Polymer-Grafted TiO2 Nanoparticle Sonosensitizers Prepared Using Phosphonic Acid-Functionalized RAFT Agent

Sonodynamic therapy is widely used in clinical studies including cancer therapy. The development of sonosensitizers is important for enhancing the generation of reactive oxygen species (ROS) under sonication. Herein, we have developed poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC)-modified TiO₂ nanoparticles as new biocompatible sonosensitizers with high colloidal stability under physiological conditions. To fabricate biocompatible sonosensitizers, a grafting-to approach was adopted with phosphonic-acid-functionalized PMPC, which was prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) using a newly designed water-soluble RAFT agent possessing a phosphonic acid group. The phosphonic acid group can conjugate with the OH groups on the TiO₂ nanoparticles. We have clarified that the phosphonic acid end group is more crucial for creating colloidally stable PMPC-modified TiO₂ nanoparticles under physiological conditions than carboxylic-acid-functionalized PMPC-modified ones. Furthermore, the enhanced generation of singlet oxygen (¹O₂), an ROS, in the presence of PMPC-modified TiO₂ nanoparticles was confirmed using a ¹O₂-reactive fluorescent probe. We believe that the PMPC-modified TiO₂ nanoparticles prepared herein have potential utility as novel biocompatible sonosensitizers for cancer therapy.

Fluorous-Core Nanoparticle-Embedded Hydrogel Synthesized via Tandem Photo-Controlled Radical Polymerization: Facilitating the Separation of Perfluorinated Alkyl Substances from Water

Per- and polyfluorinated alkyl substances (PFASs) are broadly used as surfactants and water/oil repellents for many decades. However, they are toxic, environmental persistence, and widely detected in water sources. In this work, we developed a fluorous-core nanoparticle-embedded hydrogel (FCH) synthesized by the metal-free tandem photocontrolled radical polymerization under visible-light irradiation. With the FCH material, the scope of absorbable PFASs has been expanded to neutral, anionic, cationic and zwitterionic PFASs with the same adsorbent for the first time. The fluorous nanoparticles exhibited strong and selective affinity toward PFASs without being dramatically influenced by pH levels and background ions, enabling efficient removing of PFASs at high to environmentally relevant concentrations (10 mg/L to 1 μg/L). Furthermore, the FCH network has shown good mechanical performance, facilitating the separation, regeneration, and recycling of adsorbent for multiple runs. These results demonstrate the promise of the FCH material for PFASs separation and adsorbent recycling toward sustainable environment.

Single-chain crosslinked polymers via the transesterification of folded polymers: from efficient synthesis to crystallinity control

Herein we report efficient synthetic systems of single-chain crosslinked polymers via the intramolecular transesterification of folded random copolymers in organic media and the unique crystallization behavior of their crosslinked polymers.

Folded amphiphilic homopolymer micelles in water: uniform self-assembly beyond amphiphilic random copolymers

Herein, we developed precision self-assembly systems of amphiphilic homopolymers into folded micelles in water.

Supramolecular Single-Chain Polymeric Nanoparticles

Nature has unparalleled control over the conformation and dynamics of its folded macromolecular structures. Nature’s ability to arrange amino acids into a precise spatial organization by way of folding allows proteins to fulfill specific functions in an extremely efficient manner. Chemists and materials scientists have used the delicate structure–function relationships observed in proteins to elucidate nature’s design principles. These insights have led to the development of various revolutionary macromolecular architectures, mimicking the structural features of proteins. In this review, we focus on the folding of single polymer chains into well-defined nanoparticles using supramolecular interactions and their possible use as enzyme mimics.

Orthogonal Folding of Amphiphilic/Fluorous Random Block Copolymers for Double and Multicompartment Micelles in Water

Here, we report orthogonal folding and self-assembly systems of amphiphilic/fluorous random block copolymers for double core and multicompartment micelles in water. For this, we developed the precision folding techniques of polymer chains via the selective self-assembly of the pendant groups. Typically, A/C-B/C random block copolymers were designed: Hydrophobic dodecyl groups (A) and fluorous fluorinated octyl groups (B) were introduced into the respective blocks, while hydrophilic poly(ethylene glycol) chains (C) were randomly incorporated into all the segments. By controlling the chain length and composition of the respective blocks, the copolymers induce orthogonal single-chain folding in water to form double-compartment micelles comprising hydrophobic and fluorous cores. The copolymers were site-selectively folded in a fluoroalcohol to result in tadpole unimer micelles comprising a hydrophobic A/C unimer micelle and an unfolded fluorous B/C chain. Additionally, asymmetric A/C-B/C random block copolymers with short and highly hydrophobic or fluorous segments were effective for multicompartment micelles in water.

Compartmentalization Technologies via Self-Assembly and Cross-Linking of Amphiphilic Random Block Copolymers in Water

Orthogonal self-assembly and intramolecular cross-linking of amphiphilic random block copolymers in water afforded an approach to tailor-make well-defined compartments and domains in single polymer chains and nanoaggregates. For a double compartment single-chain polymer, an amphiphilic random block copolymer bearing hydrophilic poly(ethylene glycol) (PEG) and hydrophobic dodecyl, benzyl, and olefin pendants was synthesized by living radical polymerization (LRP) and postfunctionalization; the dodecyl and benzyl units were incorporated into the different block segments, whereas PEG pendants were statistically attached along a chain. The copolymer self-folded via the orthogonal self-assembly of hydrophobic dodecyl and benzyl pendants in water, followed by intramolecular cross-linking, to form a single-chain polymer carrying double yet distinct hydrophobic nanocompartments. A single-chain cross-linked polymer with a chlorine terminal served as a globular macroinitiator for LRP to provide an amphiphilic tadpole macromolecule comprising a hydrophilic nanoparticle and a hydrophobic polymer tail; the tadpole thus self-assembled into multicompartment aggregates in water.

Self-assembly of PEG/dodecyl-graft amphiphilic copolymers in water: consequences of the monomer sequence and chain flexibility on uniform micelles

Self-assembly of hydrophilic poly(ethylene glycol) and hydrophobic dodecyl-graft amphiphilic copolymers in water was investigated in detail, by focusing on the effects of the monomer sequence and chain flexibility on micelles.

Star Polymer Gels with Fluorinated Microgels via Star-Star Coupling and Cross-Linking for Water Purification

Two types of star polymer gels containing perfluorinated microgels were created as purification materials to separate polyfluorinated surfactants (e.g., perfluorooctanoic acid) from water. One macrogel is prepared by the radical coupling of fluorine and/or amine-functionalized microgel star polymers alone, while another is done by the radical cross-linking of the star polymers with poly(ethylene glycol) methyl ether methacrylate. Importantly, the reactive olefin remaining within the microgel cores was directly employed for both coupling and cross-linking reactions. Swelling properties of star polymer gels were effectively controlled by the latter cross-linking technique. Analyzed by small-angle X-ray scattering, a star-star coupling gel typically consists of a three-dimensional network where star polymers are sequentially connected with the microgels at the constant interval of about 20 nm. Owing to the fluorous and acid/base cooperative interaction, star polymer gels carrying fluorine/amine-functionalized microgels efficiently captured polyfluorinated surfactants in water and successfully afforded the removal from water via simple mixing and filtration.

Fluorinated microgel star polymers as fluorous nanocapsules for the encapsulation and release of perfluorinated compounds

Fluorinated microgel star polymers work as fluorous nanocapsules to efficiently capture and thermo-responsively release perfluorinated guest compounds.