Degradable Block Copolymer Nanoparticles Synthesized by Polymerization-Induced Self-Assembly

Polymerization-induced self-assembly (PISA) combines polymerization and in situ self-assembly of block copolymers in one system and has become a widely used method to prepare block copolymer nanoparticles at high concentrations. The persistence of polymers in the environment poses a huge threat to the ecosystem and represents a significant waste of resources. There is an urgent need to develop novel chemical approaches to synthesize degradable polymers. To meet with this demand, it is crucial to install degradability into PISA nanoparticles. Most recently, degradable PISA nanoparticles have been synthesized by introducing degradation mechanisms into either shell-forming or core-forming blocks. This Minireview summarizes the development in degradable block copolymer nanoparticles synthesized by PISA, including shell-degradable, core-degradable, and all-degradable nanoparticles. Future development will benefit from expansion of polymerization techniques with new degradation mechanisms and adaptation of high-throughput approaches for both PISA syntheses and degradation studies.

Fluoropolymer Nanoparticles Synthesized via Reversible-Deactivation Radical Polymerizations and Their Applications

Fluorinated polymeric nanoparticles (FPNPs) combine unique properties of fluorocarbon and polymeric nanoparticles, which has stimulated massive interest for decades. However, fluoropolymers are not readily available from nature, resulting in synthetic developments to obtain FPNPs via free radical polymerizations. Recently, while increasing cutting-edge directions demand tailored FPNPs, such materials have been difficult to access via conventional approaches. Reversible-deactivation radical polymerizations (RDRPs) are powerful methods to afford well-defined polymers. Researchers have applied RDRPs to the fabrication of FPNPs, enabling the construction of particles with improved complexity in terms of structure, composition, morphology, and functionality. Related examples can be classified into three categories. First, well-defined fluoropolymers synthesized via RDRPs have been utilized as precursors to form FPNPs through self-folding and solution self-assembly. Second, thermally and photoinitiated RDRPs have been explored to realize in situ preparations of FPNPs with varied morphologies via polymerization-induced self-assembly and cross-linking copolymerization. Third, grafting from inorganic nanoparticles has been investigated based on RDRPs. Importantly, those advancements have promoted studies toward promising applications, including magnetic resonance imaging, biomedical delivery, energy storage, adsorption of perfluorinated alkyl substances, photosensitizers, and so on. This Review should present useful knowledge to researchers in polymer science and nanomaterials and inspire innovative ideas for the synthesis and applications of FPNPs.

Expanding the Scope of Polymerization-Induced Self-Assembly: Recent Advances and New Horizons

Over the past decade or so, polymerization-induced self-assembly (PISA) has become a versatile method for rational preparation of concentrated block copolymer nanoparticles with a diverse set of morphologies. Much of the PISA literature has focused on the preparation of well-defined linear block copolymers by using linear macromolecular chain transfer agents (macro-CTAs) with high chain transfer constants. In this review, a recent process is highlighted from an unusual angle that has expanded the scope of PISA including i) synthesis of block copolymers with nonlinear architectures (e.g., star block copolymer, branched block copolymer) by PISA, ii) in situ synthesis of blends of polymers by PISA, and iii) utilization of macro-CTAs with low chain transfer constants in PISA. By highlighting these important examples, new insights into the research of PISA and future impact these methods will have on polymer and colloid synthesis are provided.

Constructing Cylindrical Nanostructures Via Directional Morphology Evolution Induced by Seeded Polymerization

Herein, spindle-shaped block copolymer (BCP) nanoparticles are used in seeded polymerization of methyl methacrylate as a novel approach to generating cylindrical nanostructures. The chain-extension of BCP seeds by an amorphous coil-type polymer within the seed core composed of semifluorinated liquid-crystalline blocks triggers the deforming, stretching, and directional growth of the seeds along the long axis, eventually leads to nanorods.

Preparation of Block Copolymer Nano-Objects with Embedded β-Ketoester Functional Groups by Photoinitiated RAFT Dispersion Polymerization

Herein, a photoinitiated reversible addition-fragmentation chain transfer (RAFT) dispersion polymerization of 2-(acetoacetoxy)ethyl methacrylate (AEMA) in ethanol/water at room temperature for in situ preparation of β-ketoester-functionalized block copolymer nano-objects is reported. AEMA is also copolymerized with isobornyl methacrylate (IBOMA) to improve the colloidal stability of PIBOMA-based block copolymer nano-objects prepared by photoinitiated RAFT dispersion polymerization at low temperatures. A series of P(IBOMA-stat-AEMA)-based block copolymer nano-objects are prepared by changing reaction parameters. Finally, lanthanide-doped block copolymer nano-objects with luminescent and magnetic properties are also prepared based on the complexation of various lanthanide ions with the β-ketoester group. It is expected that the current study will provide a facile platform for the in situ preparation of β-ketoester-functionalized block copolymer nano-objects with different morphologies for specific applications.

Towards nanoparticles with site-specific degradability by ring-opening copolymerization induced self-assembly in organic medium

Radical ring-opening copolymerization-induced self-assembly (rROPISA) was successfully applied to the synthesis of core-, surface- or surface plus core-degradable nanoparticles in heptane, leading to site-specific degradability by rROPISA.

Solution self-assembly of fluorinated polymers, an overview

The incorporation of fluorinated moieties into a polymer can confer unique properties and often lead in solution to original morphologies endowed with rare properties.

Synthesis of star-shaped polyzwitterions with adjustable UCST and fast responsiveness by a facile RAFT polymerization

We describe crosslinking of polyzwitterions for the formation of novel star-shaped polymers with low polydispersities and dual-responsiveness using RAFT polymerization.

Uncontrolled polymerization that occurred during photoinitiated RAFT dispersion polymerization of acrylic monomers promotes the formation of uniform raspberry-like polymer particles

Uniform raspberry-like polymer particles are prepared by a different type of photoinitiated RAFT dispersion polymerization.

Photoinitiated Polymerization-Induced Self-Assembly via Visible Light-Induced RAFT-Mediated Emulsion Polymerization

Aqueous emulsion polymerization is one of the most commonly used techniques in industry for the production of polymer latexes. In this contribution, we present photoinitiated polymerization-induced self-assembly (photo-PISA) based on aqueous visible light-induced reversible addition-fragmentation chain transfer (RAFT)-mediated emulsion polymerization at room temperature. A wide range of morphologies including spheres, worms, and vesicles have been achieved at room temperature by modulating reaction parameters. Additionally, this method enables access to inorganic nanoparticles-loaded vesicles by adding inorganic nanoparticles at the beginning of the polymerization. Finally, an oxygen-tolerant RAFT-mediated emulsion polymerization has been developed, allowing the synthesis of polymer nano-objects at low volumes (e.g., in a 96-well plate). This study is expected to expand the scope of photo-PISA for the preparation of various block copolymer nano-objects in water at room temperature.

Synthesis of block copolymer nano-assemblies via ICAR ATRP and RAFT dispersion polymerization: how ATRP and RAFT lead to differences

Block copolymer nano-assemblies were synthesized via ICAR ATRP dispersion polymerization employing the CuBr₂/tris(2-pyridylmethyl)amine catalyst in an alcoholic solvent at a relatively low temperature of 45 °C.

Spindle-like and telophase-like self-assemblies mediated by complementary nucleobase molecular recognition

Supramolecular nanoparticles based on complementary nucleobase interactions have aroused wide interest.

Nonspherical Liquid Crystalline Assemblies with Programmable Shape Transformation

Liquid crystalline (LC) assemblies with tailored shape and programmable shape transformation were prepared via polymerization-induced self-assembly. The influence of polymerization temperature and solvent on the shape of the LC assemblies indicated that shape of the LC assemblies could be delicately regulated by the repulsive interaction among the solvophilic chains and LC ordering. Programmable shape transformation of ellipsoidal LC assemblies was achieved, taking advantage of the smectic-to-isotropic phase transition. The ellipsoidal assemblies could remain ellipsoids or transform to faceted spheres and spheres, depending on the temperature procedure used. Besides, the generated spheres could be reshaped to ellipsoids with high shape recovery ratio. Small angle X-ray scattering study indicated that the interplay of the reversible smectic-to-isotropic phase transition and kinetic trapping underpins the programmed shape transformation. As a general approach to LC assemblies with programmable shape transformation, our strategy would provide a reliable platform for nanoactuators, nanomotors, and adaptive colloidal devices.

Poly(Pentafluorophenyl Methacrylate)-Based Nano-Objects Developed by Photo-PISA as Scaffolds for Post-Polymerization Functionalization

The preparation of a functional fluorine-containing block copolymer using reversible addition-fragmentation chain-transfer dispersion polymerization in DMSO as a "platform/scaffold" is explored. The nanostructures, comprised of poly(ethyleneglycol)-b-poly(pentafluorophenyl methacrylate) or PEG-b-P(PFMA), are formulated via photo-initiated polymerization-induced self-assembly (PISA) followed by post-polymerization modification using different primary amines. A combination of light scattering and microscopy techniques are used to characterize the resulting morphologies. It is found that upon varying the degree of polymerization of the core-forming block of PFMA, only uniform spheres (with textured surfaces) are obtained. These nanostructures are subsequently modified by cross-linking using a non-responsive and a redox-responsive diamine, thus imparting stability to the particles in water. In response to intracellular glutathione (GSH) concentration, destabilization of the micelles occurs as evidenced by dynamic light scattering. The well-defined size, inherent reactivity of the nanoparticles toward nucleophiles, and GSH-responsiveness of the nanospheres make them ideal scaffolds for drug delivery to intracellular compartments with reductive environments.

New Insights into RAFT Dispersion Polymerization-Induced Self-Assembly: From Monomer Library, Morphological Control, and Stability to Driving Forces

Polymerization-induced self-assembly (PISA) has been established as an efficient, robust, and versatile approach to synthesize various block copolymer nano-objects with controlled morphologies, tunable dimensions, and diverse functions. The relatively high concentration and potential scalability makes it a promising technique for industrial production and practical applications of functional polymeric nanoparticles. This feature article outlines recent advances in PISA via reversible addition-fragmentation chain transfer dispersion polymerization. Considerable efforts to understand morphological control, broaden the monomer library, enhance morphological stability, and incorporate multiple driving forces in PISA syntheses are summarized herein. Finally, perspectives on the future of PISA research are discussed.

Polymerization-induced self-assembly of liquid crystalline ABC triblock copolymers with long solvophilic chains

Polymerization-induced self-assembly was exploited to investigate the self-assembly behavior of liquid crystalline triblock copolymers with long solvophilic chains.

Synthesis, self-assembly, and base-pairing of nucleobase end-functionalized block copolymers in aqueous solution

As a novel strategy, nucleobase-containing copolymers are created for molecular recognition and nucleobase releasing.