Polymerization-induced Self-assembly Research Articles

Sequence structure controllable polymerization-induced self-assembly

Sequence structure controllable polymerization-induced self-assembly

Renewable and Functional Latexes Synthesized by Polymerization-Induced Self-Assembly for UV-Curable Films.

After the development of polymer coatings and films based on renewable resources, there remains a challenge of combining the advantages of water-borne acrylic latexes with the excellent physical properties of cross-linked solvent-borne coatings. After polymerization, the renewable 4-oxocyclopentenyl acrylate (4CPA) is capable of undergoing photocyclodimerization under UV light, yielding a cross-linked polyacrylate. In this work, we investigate the polymerization-induced self-assembly (PISA) of 4CPA with several renewable acrylic monomers in the presence of a macro-RAFT agent. The produced latexes have a small particle size, good colloidal stability, and are free of volatile organic compounds. After film formation and UV curing, flexible to rigid films can be obtained depending on the monomer composition and UV irradiation time. The cross-linked films show promise as oil and water barriers in paper coating applications. This work outlines the development and application of renewable and functional cross-linkable latexes synthesized by PISA.

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.

Ultrafast Xanthate-Mediated Photoiniferter Polymerization-Induced Self-Assembly (PISA).

Polymerization-induced self-assembly (PISA) is a powerful technique for preparing block copolymer nanostructures. Recently, efforts have been focused on applying photochemistry to promote PISA due to the mild reaction conditions, low cost, and spatiotemporal control that light confers. Despite these advantages, chain-end degradation and long reaction times can mar the efficacy of this process. Herein, we demonstrate the use of ultrafast photoiniferter PISA to produce polymeric nanostructures. By exploiting the rapid photolysis of xanthates, near-quantitative monomer conversion can be achieved within five minutes to prepare micelles, worms, and vesicles at various core-chain lengths, concentrations, or molar compositions.

Surface Hybridization Chain Reaction of Binary Mixture DNA-PEG Corona Nanostructures Produced by Low-Volume RAFT-Mediated Photopolymerization-Induced Self-Assembly.

DNA-polymer hybrids have been attracting interest as adaptable functional materials by combining the stability of polymers with DNA nanotechnology. Both research fields have in common the capacity to be precise, versatile, and tunable, a prerequisite for creating powerful tools which can be easily tailored and adapted for bio-related applications. However, the conjugation of hydrophilic DNA with hydrophobic polymers remains challenging. In recent years, polymerization-induced self-assembly (PISA) has attracted significant attention for constructing nano-objects of various morphologies owing to the one-step nature of the process, creating a beneficial method for the creation of amphiphilic DNA-polymer nanostructures. This process not only allows pure DNA-polymer-based systems to be produced but also enables the mixture of other polymeric species with DNA conjugates. Here, we present the first report of a DNA-PEG corona nano-object's synthesis without the addition of an external photoinitiator or photocatalyst via photo-PISA. Furthermore, this work shows the use of DNA-macroCTA, which was first synthesized using a solid-support method resulting in high yields, easy upscaling, and no need for HPLC purification. In addition, to the formation of DNA-polymer structures, increasing the nucleic acid loading of assemblies is of great importance. One of the most intriguing phenomena of DNA is the hybridization of single-stranded DNA with a second strand, increasing the nucleic acid content. However, hybridization of DNA in a particle corona may destabilize the nanomaterial due to the electrostatic repulsive force on the DNA corona. Here, we have investigated how changing the DNA volume fraction in hybrid DNA-polymer self-assembled material affects the morphology. Moreover, the effect of the corona composition on the stability of the system during the hybridization was studied. Additionally, the hybridization chain reaction was successfully applied as a new method to increase the amount of DNA on a DNA-based nano-object without disturbing the morphology achieving a fluorescence signal amplification.

Exploiting the Monomer-Feeding Mechanism of RAFT Emulsion Polymerization for Polymerization-Induced Self-Assembly of Asymmetric Divinyl Monomers.

We exploited the monomer-feeding mechanism of reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization to achieve the successful polymerization-induced self-assembly (PISA) of asymmetric divinyl monomers. Colloidally stable cross-linked block copolymer nanoparticles with various morphologies, such as vesicles, were directly prepared at high solids. Morphologies of the cross-linked block copolymer nanoparticles could be controlled by varying the monomer concentration, degree of polymerization (DP) of the core-forming block, and length of the macro-RAFT agent. X-ray photoelectron spectroscopy (XPS) characterization confirmed the presence of unreacted vinyl groups within the obtained block copolymer nanoparticles, providing a landscape for further functionalization via thiol-ene chemistry. Finally, the obtained block copolymer nanoparticles were employed as additives to tune the mechanical properties of hydrogels. We expect that this study not only offers considerable opportunities for the preparation of well-defined cross-linked block copolymer nanoparticles, but also provides important insights into the controlled polymerization of multivinyl monomers.

Interfacial Supra-Assembly of Copolymer Nanoparticles Enables the Formation of Nanocomposite Crystals with a Tunable Internal Structure.

It is highly desirable but technically challenging to precisely control the spatial composition and internal structure of crystalline nanocomposite materials, especially in a one-pot synthetic route. Herein, we demonstrate a versatile pathway to tune the spatial distribution of guest species within a host inorganic crystal via an incorporation strategy. Specifically, well-defined block copolymer nanoparticles, poly(methacrylic acid)x-block-poly(styrene-alt-N-phenylmaleimide)y [PMAAx-P(St-alt-NMI)y], are synthesized by polymerization-induced self-assembly. Such anionic nanoparticles can supra-assemble onto the surface of larger cationic nanoparticles via an electrostatic interaction, forming colloidal nanocomposite particles (CNPs). Remarkably, such CNPs can be incorporated into calcite single crystals in a spatially controlled manner: the depth of CNPs incorporation into calcite is tunable. Systematic investigation indicates that this interesting phenomenon is governed by the colloidal stability of CNPs, which in turn is dictated by the PMAAx-P(St-alt-NMI)y adsorption density and calcium ion concentration. This study opens up a general and efficient route for the preparation of a wide range of crystalline nanocomposite materials with a controlled internal composition and structure.

Poly(ionic liquid) nanogel with tunable morphologies achieved via cross-linking polymerization induced self-assembly

Polymerization-induced self-assembly (PISA) has been the focus of extensive research as an effective approach to create polymer nanoobjects. However, it still confronts hurdles in terms of nano-object stability and the availability of hydrophilic macromolecular agents. In this study, an innovative and productive approach for developing poly(ionic liquid) (PIL) nano-objects was successfully established through cross-linking polymerization induced self-assembly (CPISA). The suggested approaches employ reversible addition fragmental transfer (RAFT) polymerization of ethylene glycol dimethacrylate (EGDMA) mediated by PIL macromolecular chain transfer agents (macro-CTAs) in selected solvents. Core-cross-linked PIL nanogels with various morphologies such as sphere, fiber, and ring were achieved by varying the molecular weight of PIL macro-CTAs and the solvent. Furthermore, PIL nanogels were demonstrated to be effective catalysts for the cycloaddition reaction between CO2 and epoxides. This versatile method allows for a controllable manner to produce cross-linked polymer nano-objects. Therefore, the findings have significant potential in the fields of polymer synthesis, nanomedicine and catalysis.

Preparation of functional nanoparticles of mPEG‐b‐P(DMA‐co‐HA) copolymers via polymerization‐induced thermal self‐assembly

AbstractSelf‐assembled polymeric nanoparticles have been of great interest for various biological applications such as drug delivery, catalysis, and biosensing. In this regard, polymerization‐induced self‐assembly (PISA) has been widely explored as a more efficient technique than conventional self‐assembly methods as it can be conducted in one pot and does not require harsh conditions. Recently, a method known as polymerization‐induced thermal self‐assembly (PITSA) has emerged, exploiting the inherent phase transition behavior of thermoresponsive polymers at a critical temperature point to generate thermoresponsive nanoparticles in situ. However, the narrow range of monomers suitable for PITSA limits the design of diverse thermoresponsive nanoparticles, and therefore this process has not yet been explored to its fullest capacity. In this study, we demonstrate the preparation of thermoresponsive nanoparticles based on hydrophilic N,N‐dimethyl acrylamide (DMA) and hydrophobic hexyl acrylate (HA) monomers. This is particularly interesting as these monomers produce non‐responsive homopolymers but display thermoresponsive behavior when copolymerized. The nanoparticles obtained were crosslinked to enable their characterization at room temperature, and further functionalized with a short synthetic antibacterial peptide (WR)3 to demonstrate proof‐of‐concept potential as antimicrobial agents. Overall, this work expands the library of monomers amenable to PITSA for the production of thermoresponsive nanoparticles, contributing to the design of new functional nanoparticles for therapeutic purposes.

Seeded Raft Polymerization-Induced Self-assembly: Recent Advances and Future Opportunities.

Over the past decade, polymerization-induced self-assembly (PISA) has fully proved its versatility for scale-up production of block copolymer nanoparticles with tunable sizes and morphologies; yet, there are still some limitations. Recently, seeded PISA approaches combing PISA with heterogeneous seeded polymerizations have been greatly explored and are expected to overcome the limitations of traditional PISA. In this review, recent advances in seeded PISA that have expanded new horizons for PISA are highlighted including i) general considerations for seeded PISA (e.g., kinetics, the preparation of seeds, the selection of monomers), ii) morphological evolution induced by seeded PISA (e.g., from corona-shell-core nanoparticles to vesicles, vesicles-to-toroid, disassembly of vesicles into nanospheres), and iii) various well-defined nanoparticles with hierarchical and sophisticated morphologies (e.g., multicompartment micelles, porous vesicles, framboidal vesicles, AXn -type colloidal molecules). Finally, new insights into seeded PISA and future perspectives are proposed. This article is protected by copyright. All rights reserved.

Fabrication of multi-compartmental vesicles via RAFT method in polymerization-induced self-assembly

Synthetic polymer nanomaterials have sparked considerable attention because to their use in a wide range of fields, including medication delivery, sensors, nano reactors, and catalytic supports. A popular approach for creating polymer nanoparticles is self-assembly of block copolymers in a diluted solution. Generally, the preparation of fine structural nanoparticles involves several steps, including the synthesis of block copolymers, exhausting purification to obtain perfect block copolymers, diluting the obtained block copolymers in a suitable solvent, and then cautiously replacing the decent solutes with a selective solvent. Furthermore, typical polymer nano-object manufacturing is frequently done in high dilution (concentration is usually below 1%). The procedure for producing block copolymers and allowing them to self-assemble is combined into one stage by polymerization-induced self-assembly, which significantly streamlines the creation of polymeric nanostructures and enables the fabrication of such materials at high concentrations (solid concentrations of 10–50%). This work used styrene as the monomer, E/W at a weight ratio of 7:3 as the solvent, and polyethylene glycol (PEG45-PETTC) as the macro-RAFT reagent to successfully create multi-chambered vesicles.

L-Histidine Salt-Bridged Monomer Preassembly and Polymerization-Induced Electrostatic Self-Assembly

<scp>l</scp>-Histidine Salt-Bridged Monomer Preassembly and Polymerization-Induced Electrostatic Self-Assembly

Kinetic Studies and Temperature‐Induced Morphological Changes of Peptide Decorated Nano‐Objects via Polymerization‐Induced Self‐Assembly

AbstractIn the present work, combining polymerization‐induced self‐assembly (PISA) with self‐assembling peptides (SAPs) peptide−polymer hybrid nanostructures are prepared, harnessing the advantages of PISA and the self‐assembling driving force of SAPs. A tripeptide methacrylamide denoted as MAm‐GFF, where MAm, G, and F stand for methacrylamide, glycine, and phenylalanine, is copolymerized with glycerol monomethacrylate (GMA) by reversible addition−fragmentation chain transfer polymerization (RAFT) in dimethylformamide to produce a P(GMA62‐stat‐(MAm‐GFF)7) macromolecular chain transfer agent (macro‐CTA). This peptide‐containing macro‐CTA is then successfully chain‐extended with poly(2‐hydroxypropyl methacrylate) (PHPMA) by aqueous dispersion PISA, forming P(GMA62‐stat‐(MAm‐GFF)7)‐b‐PHPMA27 self‐assembled objects. The impacts of temperature and monomer conversion on the morphologies formed during the PISA process are investigated by analyzing samples withdrawn at different time during the polymerization of HPMA using transmission electron microscopy (TEM) and dynamic light scattering (DLS) at different temperatures (5–70 °C).

Azobenzene-Containing Liquid Crystalline Twisted Ribbons via Polymerization-Induced Hierarchical Self-Assembly.

Polymerization-induced self-assembly incorporating liquid crystallization, as a polymerization-induced hierarchical self-assembly (PIHSA) method to produce polymeric particles with anisotropic morphologies facilely and efficiently, has drawn wide attention recently. However, the means of regulating the morphologies of liquid crystalline (LC) polymer assemblies still need to be explored. Herein, a route is presented to fabricate the twisted ribbons via PIHSA containing azobenzene based on poor reversible addition-fragmentation chain transfer (RAFT) control, called poorly controlled PIHSA. Cyano-4-(dodecylsulfanylthiocarbonyl)sulfanyl pentanoic acid-2-(2-pyridyldithio) ethyl ester is used as the RAFT agent with poor controllability, and the morphological evolution from ribbons to twisted ribbons can be observed in the corresponding PIHSA system. The formation mechanism of the twisted ribbons is studied systematically and the broad molecular weight distribution is considered to be the decisive factor. Moreover, the supramolecular chirality induced by symmetry breaking is also related to the twist of the ribbons. This study enriches the methods of controlling the morphologies of LC polymer particles and is helpful for further clarifying the mechanism of PIHSA.

Efficient Synthesis of Hydrolytically Degradable Block Copolymer Nanoparticles via Reverse Sequence Polymerization‐Induced Self‐Assembly in Aqueous Media

AbstractHydrolytically degradable block copolymer nanoparticles are prepared via reverse sequence polymerization‐induced self‐assembly (PISA) in aqueous media. This efficient protocol involves the reversible addition‐fragmentation chain transfer (RAFT) polymerization of N,N′‐dimethylacrylamide (DMAC) using a monofunctional or bifunctional trithiocarbonate‐capped poly(ϵ‐caprolactone) (PCL) precursor. DMAC monomer is employed as a co‐solvent to solubilize the hydrophobic PCL chains. At an intermediate DMAC conversion of 20–60 %, the reaction mixture is diluted with water to 10–25 % w/w solids. The growing amphiphilic block copolymer chains undergo nucleation to form sterically‐stabilized PCL‐core nanoparticles with PDMAC coronas. 1H NMR studies confirm more than 99 % DMAC conversion while gel permeation chromatography (GPC) studies indicate well‐controlled RAFT polymerizations (Mw/Mn≤1.30). Transmission electron microscopy (TEM) and dynamic light scattering (DLS) indicate spheres of 20–120 nm diameter. As expected, hydrolytic degradation occurs within days at 37 °C in either acidic or alkaline solution. Degradation is also observed in phosphate‐buffered saline (PBS) (pH 7.4) at 37 °C. However, no degradation is detected over a three‐month period when these nanoparticles are stored at 20 °C in deionized water (pH 6.7). Finally, PDMAC30‐PCL16‐PDMAC30 nanoparticles are briefly evaluated as a dispersant for an agrochemical formulation based on a broad‐spectrum fungicide (azoxystrobin).

Efficient Synthesis of Hydrolytically Degradable Block Copolymer Nanoparticles via Reverse Sequence Polymerization-Induced Self-Assembly in Aqueous Media.

Hydrolytically degradable block copolymer nanoparticles are prepared via reverse sequence polymerization-induced self-assembly (PISA) in aqueous media. This efficient protocol involves the reversible addition-fragmentation chain transfer (RAFT) polymerization of N,N'-dimethylacrylamide (DMAC) using a monofunctional or bifunctional trithiocarbonate-capped poly(ϵ-caprolactone) (PCL) precursor. DMAC monomer is employed as a co-solvent to solubilize the hydrophobic PCL chains. At an intermediate DMAC conversion of 20-60 %, the reaction mixture is diluted with water to 10-25 % w/w solids. The growing amphiphilic block copolymer chains undergo nucleation to form sterically-stabilized PCL-core nanoparticles with PDMAC coronas. 1 H NMR studies confirm more than 99 % DMAC conversion while gel permeation chromatography (GPC) studies indicate well-controlled RAFT polymerizations (Mw /Mn ≤1.30). Transmission electron microscopy (TEM) and dynamic light scattering (DLS) indicate spheres of 20-120 nm diameter. As expected, hydrolytic degradation occurs within days at 37 °C in either acidic or alkaline solution. Degradation is also observed in phosphate-buffered saline (PBS) (pH 7.4) at 37 °C. However, no degradation is detected over a three-month period when these nanoparticles are stored at 20 °C in deionized water (pH 6.7). Finally, PDMAC30 -PCL16 -PDMAC30 nanoparticles are briefly evaluated as a dispersant for an agrochemical formulation based on a broad-spectrum fungicide (azoxystrobin).

Continuous-Flow Laboratory SAXS for In Situ Determination of the Impact of Hydrophilic Block Length on Spherical Nano-Object Formation during Polymerization-Induced Self-Assembly.

In situ small-angle X-ray scattering (SAXS) is a powerful technique for characterizing block-copolymer nano-object formation during polymerization-induced self-assembly. To work effectively in situ, it requires high intensity X-rays which enable the short acquisition times required for real-time measurements. However, routine access to synchrotron X-ray sources is expensive and highly competitive. Flow reactors provide an opportunity to obtain temporal resolution by operating at a consistent flow rate. Here, we equip a flow-reactor with an X-ray transparent flow-cell at the outlet which facilitates the use of a low-flux laboratory SAXS instrument for in situ monitoring. The formation and morphological evolution of spherical block copolymer nano-objects was characterized during reversible addition fragmentation chain transfer polymerization of diacetone acrylamide in the presence of a series of poly(dimethylacrylamide) (PDMAm) macromolecular chain transfer agents with varying degrees of polymerization. SAXS analysis indicated that during the polymerization, highly solvated, loosely defined aggregates form after approximately 100 s, followed by expulsion of solvent to form well-defined spherical particles with PDAAm cores and PDMAm stabilizer chains, which then grow as the polymerization proceeds. Analysis also indicates that the aggregation number (Nagg) increases during the reaction, likely due to collisions between swollen, growing nanoparticles. In situ SAXS conducted on PISA syntheses using different PDMAm DPs indicated a varying conformation of the chains in the particle cores, from collapsed chains for PDMAm47 to extended chains for PDMAm143. At high conversion, the final Nagg decreased as a function of increasing PDMAm DP, indicating increased steric stabilization afforded by the longer chains which is reflected by a decrease in both core diameter (from SAXS) and hydrodynamic diameter (from DLS) for a constant core DP of 400.

Recent Advances in Polymerization‐Induced Self‐Assembly (PISA) Syntheses in Non‐Polar Media

AbstractIt is well‐known that polymerization‐induced self‐assembly (PISA) is a powerful and highly versatile technique for the rational synthesis of colloidal dispersions of diblock copolymer nanoparticles, including spheres, worms or vesicles. PISA can be conducted in water, polar solvents or non‐polar media. In principle, the latter formulations offer a wide range of potential commercial applications. However, there has been just one review focused on PISA syntheses in non‐polar media and this prior article was published in 2016. The purpose of the current review article is to summarize the various advances that have been reported since then. In particular, PISA syntheses conducted using reversible addition‐fragmentation chain‐transfer (RAFT) polymerization in various n‐alkanes, poly(α‐olefins), mineral oil, low‐viscosity silicone oils or supercritical CO2 are discussed in detail. Selected formulations exhibit thermally induced worm‐to‐sphere or vesicle‐to‐worm morphological transitions and the rheological properties of various examples of worm gels in non‐polar media are summarized. Finally, visible absorption spectroscopy and small‐angle X‐ray scattering (SAXS) enable in situ monitoring of nanoparticle formation, while small‐angle neutron scattering (SANS) can be used to examine micelle fusion/fission and chain exchange mechanisms.

Recent Advances in Polymerization-Induced Self-Assembly (PISA) Syntheses in Non-Polar Media.

It is well-known that polymerization-induced self-assembly (PISA) is a powerful and highly versatile technique for the rational synthesis of colloidal dispersions of diblock copolymer nanoparticles, including spheres, worms or vesicles. PISA can be conducted in water, polar solvents or non-polar media. In principle, the latter formulations offer a wide range of potential commercial applications. However, there has been just one review focused on PISA syntheses in non-polar media and this prior article was published in 2016. The purpose of the current review article is to summarize the various advances that have been reported since then. In particular, PISA syntheses conducted using reversible addition-fragmentation chain-transfer (RAFT) polymerization in various n-alkanes, poly(α-olefins), mineral oil, low-viscosity silicone oils or supercritical CO2 are discussed in detail. Selected formulations exhibit thermally induced worm-to-sphere or vesicle-to-worm morphological transitions and the rheological properties of various examples of worm gels in non-polar media are summarized. Finally, visible absorption spectroscopy and small-angle X-ray scattering (SAXS) enable in situ monitoring of nanoparticle formation, while small-angle neutron scattering (SANS) can be used to examine micelle fusion/fission and chain exchange mechanisms.

Group-Transfer Polymerization-Induced Self-Assembly (GTPISA) in Non-polar Media: An Organocatalyzed Route to Block Copolymer Nanoparticles at Room Temperature.

Polymerization-induced self-assembly (PISA) enables the synthesis at large scale of a wide variety of functional nanoparticles. However, a large number of works are related to controlled radical polymerization (CRP) methods and are generally undertaken at elevated temperatures (>50 °C). Here is the first report on methacrylate-based nanoparticles fabricated by group transfer polymerization-induced self-assembly (GTPISA) in non-polar media (n-heptane). This GTPISA process is achieved at room temperature (RT) using 1-methoxy-1-(trimethylsiloxy)-2-methylprop-1-ene (MTS) and tetrabutylammonium bis-benzoate (TBABB) as initiator and organic catalyst, respectively. Under these conditions, well-defined metal-free and colorless diblock copolymers are produced with efficient crossover from the non-polar stabilizing poly(lauryl methacrylate) (PLMA) block to the non-soluble poly(benzyl methacrylate) (PBzMA) segment. The resulting PLMA-b-PBzMA block copolymers simultaneously self-assemble into nanostructures of various sizes and morphologies. GTPISA in non-polar solvent proceeds rapidly at RT and avoids the use of sulfur or halogenated compounds or metallic catalysts associated with the implementation of CRP methods, thus expanding the potential of PISA formulations for applications in non-polar environments.