Phosphonic Acid-Functionalized Diblock Copolymer Nano-Objects via Polymerization-Induced Self-Assembly: Synthesis, Characterization, and Occlusion into Calcite Crystals

Dual-Polymer Functionalized Melanin-AgNPs Nanocomposite with Hydroxyapatite Binding Ability to Penetrate and Retain in Biofilm Sequentially Treating Periodontitis

Periodontitis is the leading cause of adult tooth missing. Thorny bacterial biofilm and high reactive oxygen species (ROS) levels in tissue are key elements for the periodontitis process. It is meaningful to develop an advanced therapeutic system with sequential antibacterial/ antioxidant ability to meet the overall goals of periodontitis therapy. Herein, a dual-polymer functionalized melanin-AgNPs (P/D-MNP-Ag) with biofilm penetration, hydroxyapatite binding, and sequentially treatment ability are fabricated. Polymer enriched with 2-(Dimethylamino)ethyl methacrylate (D), can be protonated in an acid environment with enhanced positive charge, promoting penetration in biofilm. The other polymer is rich in phosphate group (P) and can chelate Ca2+, promoting the polymer to adhere to the hydroxyapatite surface. Melanin has good ROS scavenging and photothermal abilities, after in situ reduction Ag, melanin-AgNPs composite has sequentially transitioned between antibacterial and antioxidative ability due to heat and acid accelerated Ag+ release. The released Ag+ and heat have synergistic antibacterial effects for bacterial killing. With Ag+ consumption, the antioxidant ability of MNP recovers to scavenge ROS in the inflammatory area. When applied in the periodontitis model, P/D-MNP-Ag has good therapeutical effects to ablate biofilm, relieve inflammation state, and reduce alveolar bone loss. P/D-MNP-Ag with sequential treatment ability provides a reference for developing advanced oral biofilm eradication systems.

Synergistic Effect of Hydroxyl and Carboxyl Groups on Promoting Nanoparticle Occlusion within Calcite

Direct occlusion of guest nanoparticles into host crystals enables the straightforward preparation for various of nanocomposite materials with emerging properties. Therefore, it is highly desirable to elucidate the 'design rules' that govern efficient nanoparticle occlusion. Herein, a series of sterically-stabilized nanoparticles are rationally prepared, where the surface stabilizer chains of such nanoparticles are composed of either poly(methacrylic acid), or poly(glycerol monomethacrylate), or poly((2-hydroxy-3-(methacryloyloxy)propyl)serine). Systematic investigation reveals that hydroxyl groups and carboxyl groups play a synergistic role in driving nanoparticle incorporation into calcite crystals, where the hydroxyl groups enhance colloidal stability of the nanoparticles and the carboxyl groups provide binding sites for efficient occlusion. The generality of these findings is further validated by extending it to polymer-stabilized gold nanoparticles. This study demonstrates that precision synthesis of polymer stabilizers comprising of synergistic functional groups can significantly promote nanoparticle occlusion, thus enabling the efficient construction of organic-inorganic hybrid materials via nanoparticle occlusion strategy.

Preparation of polymer nanoparticle-based complex coacervate hydrogels using polymerisation-induced self-assembly derived nanogels

This paper reports a generic method to prepare polymer nanoparticle-based complex coacervate (PNCC) hydrogels by employing rationally designed nanogels synthesised by reversible addition-fragmentation chain-transfer (RAFT)-mediated polymerisation-induced self-assembly (PISA). Specifically, a poly(potassium 3-sulfopropyl methacrylate) (PKSPMA) macromolecular chain-transfer agent (macro-CTA) was synthesised via RAFT solution polymerisation followed by chain-extension with a statistical copolymer of benzyl methacrylate (BzMA) and methacrylic acid (MAA) at pH 2. Thus, pH-responsive nanoparticles (NPs) comprising a hydrophobic polyacid core-forming block and a sulfonate-functional stabiliser block were formed. With the introduction of methacrylic acid into the core of the NPs, they become swollen with increasing pH, as judged by dynamic light scattering (DLS), indicating nanogel-type behaviour. PNCC hydrogels were prepared by simply mixing the PISA-derived nanogels and cationic branched polyethyleneimine (bPEI) at 20% w/w. In the absence of MAA in the core of the NPs, gel formation was not observed. The mass ratio between the nanogels and bPEI affected resulting hydrogel strength and a mixture of bPEI and PKSPMA₆₈-P(BzMA_0.6-stat-MAA_0.4)₃₀₀ NPs with a mass ratio of 0.14 at pH ∼7 resulted in a hydrogel with a storage modulus of approximately 2000 Pa, as determined by oscillatory rheology. This PNCC hydrogel was shear-thinning and injectable, with recovery of gel strength occurring rapidly after the removal of shear.

Micron-sized biogenic and synthetic hollow mineral spheres occlude additives within single crystals

Incorporating additives within host single crystals is an effective strategy for producing composite materials with tunable mechanical, magnetic and optical properties. The type of guest materials that can be occluded can be limited, however, as incorporation is a complex process depending on many factors including binding of the additive to the crystal surface, the rate of crystal growth and the stability of the additives in the crystallisation solution. In particular, the size of occluded guests has been restricted to a few angstroms - as for single molecules - to a few hundred nanometers - as for polymer vesicles and particles. Here, we present a synthetic approach for occluding micrometer-scale objects, including high-complexity unicellular organisms and synthetic hollow calcite spheres within calcite single crystals. Both of these objects can transport functional additives, including organic molecules and nanoparticles that would not otherwise occlude within calcite. Therefore, this method constitutes a generic approach using calcite as a delivery system for active compounds, while providing them with effective protection against environmental factors that could cause degradation.

Stimuli-responsive and core cross-linked micelles developed by NiCCo-PISA of helical poly(aryl isocyanide)s

We report the synthesis of redox- and pH-sensitive block copolymer micelles that contain chiral cores composed of helical poly(aryl isocyanide)s. Pentafluorophenyl (PFP) ester-containing micelles synthesised via nickel-catalysed coordination polymerisation-induced self-assembly (NiCCo-PISA) of helical poly(aryl isocyanide) amphiphilic diblock copolymers are modified post-polymerisation with various diamines to introduce cross-links and/or achieve stimulus-sensitive nanostructures. The successful introduction of the diamines is confirmed by Fourier-transform infrared spectroscopy (FT-IR), while the stabilisation effect of the cross-linking is explored by dynamic light scattering (DLS). The retention of the helicity of the core-forming polymer block is verified by circular dichroism (CD) spectroscopy and the stimuli-responsiveness of the nanoparticles towards a reducing agent (l-glutathione, GSH) and pH is evaluated by following the change in the size of the nanoparticles by DLS. These stimuli-responsive nanoparticles could find use in applications such as drug delivery, nanosensors or biological imaging.

Positively Charged Additives Facilitate Incorporation in Inorganic Single Crystals

Incorporation of guest additives within inorganic single crystals offers a unique strategy for creating nanocomposites with tailored properties. While anionic additives have been widely used to control the properties of crystals, their effective incorporation remains a key challenge. Here, we show that cationic additives are an excellent alternative for the synthesis of nanocomposites, where they are shown to deliver exceptional levels of incorporation of up to 70 wt % of positively charged amino acids, polymer particles, gold nanoparticles, and silver nanoclusters within inorganic single crystals. This high additive loading endows the nanocomposites with new functional properties, including plasmon coupling, bright fluorescence, and surface-enhanced Raman scattering (SERS). Cationic additives are also shown to outperform their acidic counterparts, where they are highly active in a wider range of crystal systems, owing to their outstanding colloidal stability in the crystallization media and strong affinity for the crystal surfaces. This work demonstrates that although often overlooked, cationic additives can make valuable crystallization additives to create composite materials with tailored composition-structure-property relationships. This versatile and straightforward approach advances the field of single-crystal composites and provides exciting prospects for the design and fabrication of new hybrid materials with tunable functional properties.

Polymer-Inorganic Crystalline Nanocomposite Materials via Nanoparticle Occlusion

Efficient occlusion of guest nanoparticles into host single crystals opens up a straightforward and versatile way to construct functional crystalline nanocomposites. This new technique has attracted increasing research interest because it enables the composition, structure and property of the resulting nanocomposites to be well-controlled. In this review article, we aim to provide a comprehensive summary of nanoparticle occlusion within inorganic crystals. First, we summarize recently-developed strategies for the occlusion of various colloidal particles (e.g., diblock copolymer nanoparticles, polymer-modified inorganic nanoparticles, oil droplets, etc.) within host crystals (e.g., CaCO₃ , ZnO or ZIF-8). Second, new results pertaining to spatially-controlled occlusion and the physical mechanism of nanoparticle occlusion are briefly discussed. Finally, we highlight the physicochemical properties and potential applications of various functional nanocomposite crystals constructed via nanoparticle occlusion and we also offer our perspective on the likely future for this research topic. This article is protected by copyright. All rights reserved.

Exerting Spatial Control During Nanoparticle Occlusion within Calcite Crystals

In principle, nanoparticle occlusion within crystals provides a straightforward and efficient route to make new nanocomposite materials. However, developing a deeper understanding of the design rules underpinning this strategy is highly desirable. In particular, controlling the spatial distribution of the guest nanoparticles within the host crystalline matrix remains a formidable challenge. Herein, we show that the surface chemistry of the guest nanoparticles and the [Ca²⁺ ] concentration play critical roles in determining the precise spatial location of the nanoparticles within calcite crystals. Moreover, in situ studies provide important mechanistic insights regarding surface-confined nanoparticle occlusion. Overall, this study not only provides useful guidelines for efficient nanoparticle occlusion, but also enables the rational design of patterned calcite crystals using model anionic block copolymer vesicles.

Efficient Occlusion of Nanoparticles within Inorganic Single Crystals

In principle, the incorporation of guest nanoparticles within host crystals should provide a straightforward and versatile route to a wide range of nanocomposite materials. However, crystallization normally involves expelling impurities, so nanoparticle occlusion is both counter-intuitive and technically challenging. Clearly, the nanoparticles should have a strong interaction with the growing crystalline lattice, but quantifying such an affinity has been challenging; the basic principles that govern efficient nanoparticle occlusion within inorganic single crystals are rather poorly understood. In the past few years, we have focused on the elucidation of robust design rules for such systems; our progress is summarized in this article.Polymerization-induced self-assembly (PISA) is widely recognized as a powerful platform technology for the preparation of a broad range of model organic nanoparticles. Herein, PISA was exploited to prepare sterically stabilized diblock copolymer nano-objects (e.g., spheres, worms, or vesicles) of varying size using steric stabilizers of well-defined chain length, variable anionic charge density, tunable surface density, and adjustable chemical functionality (e.g., carboxylic acid, phosphate, sulfate or sulfonate groups). Thus, we were able to systematically investigate how such structural parameters influence nanoparticle occlusion. Given its commercial importance for many industrial sectors, calcium carbonate was selected as the model host crystal for nanoparticle occlusion studies. Perhaps surprisingly, the extent of nanoparticle occlusion is not particularly sensitive to nanoparticle size or morphology. However, the steric stabilizer chain length can play a key role: relatively short chains lead to surface-confined occlusion, while sufficiently long chains enable uniform nanoparticle occlusion to be achieved throughout the crystal lattice (albeit sometimes inducing a significant change in crystal morphology). Optimizing the anionic charge density and surface density of the stabilizer chains is required to maximize the extent of nanoparticle occlusion, while steric stabilizer chains comprising anionic carboxylate groups led to greater occlusion compared to those composed of phosphate, sulfate, or sulfonate groups when examining a model vesicle system.Subsequently, our occlusion studies were extended to include functional hybrid nanocomposite crystals. For example, the spatially controlled occlusion of poly(glycerol monomethacrylate)-stabilized gold nanoparticles was achieved within semiconductive ZnO crystals by either controlling the nanoparticle concentration or by delaying their addition to the reaction mixture. Moreover, oil droplets of up to 500 nm have been incorporated into calcite crystals at up to 11% by mass, despite the large mismatch in surface energy between the hydrophobic oil droplets and the ionic crystal lattice. We have also explored a "Trojan horse" strategy, whereby cargos comprising nanoparticles or soluble dye molecules are first encapsulated within anionic block copolymer vesicles prior to their incorporation within calcite crystals. This approach offers a generic and efficient strategy for the occlusion of many types of guest species into single crystals. In summary, we have established important guidelines for efficient nanoparticle occlusion within crystals, which opens up new avenues for the synthesis of next-generation hybrid materials.

Flame Retardant Submicron Particles via Surfactant-Free RAFT Emulsion Polymerization of Styrene Derivatives Containing Phosphorous

The reversible addition–fragmentation chain transfer (RAFT) emulsion polymerization of diethyl-(4-vinylbenzyl) phosphate (DEVBP) was performed using PEG-TTC as a macro RAFT agent. PEG-TTC (M_W 2000, 4000) was synthesized by the esterification of poly (ethylene glycol) methyl ether with a carboxylic-terminated RAFT agent, composed a hydrophilic poly (ethylene glycol) (PEG) block and a hydrophobic dodecyl chain. The RAFT emulsion polymerization of DEVBP was well–controlled with a narrow molecular size distribution. Dynamic light scattering and confocal laser scanning microscopy were used to examine the PEG-b-PDVBP submicron particles, and the length of the PEG chain (hydrophilic block) was found to affect the particle size distribution and molecular weight distribution. The submicron particle size increased with increasing degree of polymerization (35, 65, and 130), and precipitation was observed at a high degree of polymerization (DP) using low molecular weight PEG-TTC (DP 130, A3). The flame retardant properties of the PEG-b-PDVBP were evaluated by thermogravimetric analysis (TGA) and micro cone calorimeter (MCC). In the combustion process, the residue of PEG-b-PDEVBP were above 500 °C was observed (A1 ~ B3, 27 ~ 38%), and flame retardant effect of PEG-b-PDEVBP submicron particles/PVA composite were confirmed by increasing range of temperature and decreasing total heat release with increasing contents of PEG-b-PDEVBP. The PEG-b-PDEVBP submicron particles can provide flame retardant properties to aqueous, dispersion and emulsion formed organic/polymer products.

Spatially Controlled Occlusion of Polymer-Stabilized Gold Nanoparticles within ZnO

In principle, incorporating nanoparticles into growing crystals offers an attractive and highly convenient route for the production of a wide range of novel nanocomposites. Herein we describe an efficient aqueous route that enables the spatially controlled occlusion of gold nanoparticles (AuNPs) within ZnO crystals at up to 20 % by mass. Depending on the precise synthesis protocol, these AuNPs can be (i) solely located within a central region, (ii) uniformly distributed throughout the ZnO host crystal or (iii) confined to a surface layer. Remarkably, such efficient occlusion is mediated by a non-ionic water-soluble polymer, poly(glycerol monomethacrylate)₇₀ (G₇₀ ), which is chemically grafted to the AuNPs; pendent cis-diol side groups on this steric stabilizer bind Zn²⁺ cations, which promotes nanoparticle interaction with the growing ZnO crystals. Finally, uniform occlusion of G₇₀ -AuNPs within this inorganic host leads to faster UV-induced photodegradation of a model dye.

Rationally designed anionic diblock copolymer worm gels are useful model systems for calcite occlusion studies

Binary mixtures of RAFT macromolecular chain transfer agents are utilized to rationally design anionic diblock copolymer nanoparticles via PISA. The role of carboxylate groups in directing calcite growth within copolymer worm gels is investigated.

Fatty Acid-Based Radically Polymerizable Monomers: From Novel Poly(meth)acrylates to Cutting-Edge Properties

The increasing price of barrels of oil, global warming, and other environmental problems favor the use of renewable resources to replace the petroleum-based polymers used in various applications. Recently, fatty acids (FAs) and their derivatives have appeared among the most promising candidates to afford novel and innovative bio-based (co)polymers because of their ready availability, their low toxicity, and their high versatility. However, the current literature mostly focused on FA-based polymers prepared by condensation polymerization or oxypolymerization, while only a few works have been devoted to radical polymerization due to the low reactivity of FAs through radical process. Thus, the aim of this Review is to give an overview of (i) the most common synthetic pathways reported in the literature to provide suitable monomers from FAs and their derivatives for radical polymerization, (ii) the available radical processes to afford FA-based (co)polymers, and (iii) the different applications in which FA-based (co)polymers have been used since the past few years.

Photo-Controlled Polymerization-Induced Self-Assembly (Photo-PISA): A Novel Strategy Using In Situ Bromine-Iodine Transformation Living Radical Polymerization

A series of hydrophilic poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMA) macroinitiators and stabilizers are synthesized in methanol through in situ photo-controlled bromine-iodine transformation living radical polymerization, where ethyl α-bromophenylacetate (EBPA) is the initial initiator and is converted to an iodo-type initiator in the presence of NaI. The subsequent photo-controlled polymerization-induced self-assembly (photo-PISA) process is achieved by adding a second monomer, hydrophobic benzyl methacrylate (BnMA), under irradiation with blue light emitting diode (LED) light at room temperature. The effect of the target degree of polymerization (DP) of PPEGMA, PBnMA, as well as the solids content on the self-assembly behavior of block copolymer PPEGMA-b-PBnMA is evaluated by gel permeation chromatography (GPC), nuclear magnetic resonance (NMR) spectroscopy, transmission electron microscopy (TEM), and dynamic light scattering (DLS) characterization. Resulting uniform spherical micelles and vesicle aggregates are observed.

Photoinitiated Polymerization-Induced Self-Assembly (Photo-PISA): New Insights and Opportunities

The polymerization-induced self-assembly (PISA) process is a useful synthetic tool for the efficient synthesis of polymeric nanoparticles of different morphologies. Recently, studies on visible light initiated PISA processes have offered a number of key research opportunities that are not readily accessible using traditional thermally initiated systems. For example, visible light mediated PISA (Photo-PISA) enables a high degree of control over the dispersion polymerization process by manipulation of the wavelength and intensity of incident light. In some cases, the final nanoparticle morphology of a single formulation can be modulated by simple manipulation of these externally controlled parameters. In addition, temporal (and in principle spatial) control over the Photo-PISA process can be achieved in most cases. Exploitation of the mild room temperature polymerizations conditions can enable the encapsulation of thermally sensitive therapeutics to occur without compromising the polymerization rate and their activities. Finally, the Photo-PISA process can enable further mechanistic insights into the morphological evolution of nanoparticle formation such as the effects of temperature on the self-assembly process. The purpose of this mini-review is therefore to examine some of these recent advances that have been made in Photo-PISA processes, particularly in light of the specific advantages that may exist in comparison with conventional thermally initiated systems.

Comparison of photo- and thermally initiated polymerization-induced self-assembly: a lack of end group fidelity drives the formation of higher order morphologies

Polymerization-induced self-assembly (PISA) is an emerging industrially relevant technology, which allows the preparation of defined and predictable polymer self-assemblies with a wide range of morphologies. In recent years, interest has turned to photoinitiated PISA processes, which show markedly accelerated reaction kinetics and milder conditions, thereby making it an attractive alternative to thermally initiated PISA. Herein, we attempt to elucidate the differences between these two initiation methods using isothermally derived phase diagrams of a well-documented poly(ethylene glycol)-b-(2-hydroxypropyl methacrylate) (PEG-b-HPMA) PISA system. By studying the influence of the intensity of the light source used, as well as an investigation into the thermodynamically favorable morphologies, the factors dictating differences in the obtained morphologies when comparing photo- and thermally initiated PISA were explored. Our findings indicate that differences in a combination of both reaction kinetics and end group fidelity led to the observed discrepencies between the two techniques. We find that the loss of the end group in photoinitiated PISA drives the formation of higher order structures and that a morphological transition from worms to unilamellar vesicles could be induced by extended periods of light and heat irradiation. Our findings demonstrate that PISA of identical block copolymers by the two different initiation methods can lead to structures that are both chemically and morphologically distinct.

Polymerization-Induced Self-Assembly of Homopolymer and Diblock Copolymer: A Facile Approach for Preparing Polymer Nano-Objects with Higher-Order Morphologies

Polymerization-induced self-assembly of homopolymer and diblock copolymer using a binary mixture of small chain transfer agent (CTA) and macromolecular chain transfer agent (macro-CTA) is reported. With this system, homopolymer and diblock copolymer were formed and chain extended at the same time to form polymer nano-objects. The molar ratio of homopolymer and diblock copolymer had a significant effect on the morphology of the polymer nano-objects. Porous vesicles, porous nanospheres, and micron-sized particles with highly porous inner structure were prepared by this method. We expect that this method will greatly expand the promise of polymerization-induced self-assembly for the synthesis of a range of polymer nano-objects with unique morphologies.

Morphological Evolution of Self-Assembled Structures Induced by the Molecular Architecture of Supra-Amphiphiles

A series of telechelic supramolecular amphiphiles [POSS-Azo₈@(β-CD-PDMAEMA)_1→8] was accomplished by orthogonally coupling the multiarm host polymer β-cyclodextrin-poly(dimethylaminoethyl methacrylate) (β-CD-PDMAEMA) with an octatelechelic guest molecule azobenzene modified-polyhedral oligomeric silsesquioxanes (POSS-Azo₈) under different host-guest ratios. These telechelic supramolecular amphiphiles possess a rigid core and flexible corona. Increasing the multiarm host polymer coupled onto the rigid POSS core made the molecular architecture tend to be symmetrical and spherical. POSS-Azo₈@[β-CD-PDMAEMA]_1→8 could self-assemble into diverse morphologies evolving from spherical micelles, wormlike micelles, and branched aggregates to bowl-shaped vesicles. Distinct from the traditional linear amphiphilic polymers, we discovered that the self-assembly of POSS-Azo₈@[β-CD-PDMAEMA]_1→8 was dominantly regulated by their molecular architectures instead of hydrophilicity, which has also been verified using computer simulation results.

RAFT Dispersion Alternating Copolymerization of Styrene with N-Phenylmaleimide: Morphology Control and Application as an Aqueous Foam Stabilizer

We report a new nonaqueous polymerization-induced self-assembly (PISA) formulation based on the reversible addition-fragmentation chain transfer (RAFT) dispersion alternating copolymerization of styrene with N-phenylmaleimide using a nonionic poly(N,N-dimethylacrylamide) stabilizer in a 50/50 w/w ethanol/methyl ethyl ketone (MEK) mixture. The MEK cosolvent is significantly less toxic than the 1,4-dioxane cosolvent reported previously [Yang P.; Macromolecules2013, 46, 8545-8556]. The core-forming alternating copolymer block has a relatively high glass transition temperature (Tg), which leads to vesicular morphologies being observed during PISA, as well as the more typical sphere and worm phases. Each of these copolymer morphologies has been characterized by transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) studies. TEM studies reveal micrometer-sized elliptical particles with internal structure, with SAXS analysis suggesting an oligolamellar vesicle morphology. This structure differs from that previously reported for a closely related PISA formulation utilizing a poly(methacrylic acid) stabilizer block for which unilamellar platelet-like particles are observed by TEM and SAXS. This suggests that interlamellar interactions are governed by the nature of the steric stabilizer layer. Moreover, using the MEK cosolvent also enables access to a unilamellar vesicular morphology, despite the high Tg of the alternating copolymer core-forming block. This was achieved by simply conducting the PISA synthesis at a higher temperature for a longer reaction time (80 °C for 24 h). Presumably, MEK solvates the core-forming block more than the previously utilized 1,4-dioxane cosolvent, which leads to greater chain mobility. Finally, preliminary experiments indicate that the worms are much more efficient stabilizers for aqueous foams than either the spheres or the oligolamellar elliptical vesicles.

Occlusion of Sulfate-Based Diblock Copolymer Nanoparticles within Calcite: Effect of Varying the Surface Density of Anionic Stabilizer Chains

Polymerization-induced self-assembly (PISA) offers a highly versatile and efficient route to a wide range of organic nanoparticles. In this article, we demonstrate for the first time that poly(ammonium 2-sulfatoethyl methacrylate)-poly(benzyl methacrylate) [PSEM–PBzMA] diblock copolymer nanoparticles can be prepared with either a high or low PSEM stabilizer surface density using either RAFT dispersion polymerization in a 2:1 v/v ethanol/water mixture or RAFT aqueous emulsion polymerization, respectively. We then use these model nanoparticles to gain new insight into a key topic in materials chemistry: the occlusion of organic additives into inorganic crystals. Substantial differences are observed for the extent of occlusion of these two types of anionic nanoparticles into calcite (CaCO₃), which serves as a suitable model host crystal. A low PSEM stabilizer surface density leads to uniform nanoparticle occlusion within calcite at up to 7.5% w/w (16% v/v), while minimal occlusion occurs when using nanoparticles with a high PSEM stabilizer surface density. This counter-intuitive observation suggests that an optimum anionic surface density is required for efficient occlusion, which provides a hitherto unexpected design rule for the incorporation of nanoparticles within crystals.

A Critical Appraisal of RAFT-Mediated Polymerization-Induced Self-Assembly

Recently, polymerization-induced self-assembly (PISA) has become widely recognized as a robust and efficient route to produce block copolymer nanoparticles of controlled size, morphology, and surface chemistry. Several reviews of this field have been published since 2012, but a substantial number of new papers have been published in the last three years. In this Perspective, we provide a critical appraisal of the various advantages offered by this approach, while also pointing out some of its current drawbacks. Promising future research directions as well as remaining technical challenges and unresolved problems are briefly highlighted.

Incorporating Diblock Copolymer Nanoparticles into Calcite Crystals: Do Anionic Carboxylate Groups Alone Ensure Efficient Occlusion?

New spherical diblock copolymer nanoparticles were synthesized via RAFT aqueous dispersion polymerization of 2-hydroxypropyl methacrylate (HPMA) at 70 °C and 20% w/w solids using either poly(carboxybetaine methacrylate) or poly(proline methacrylate) as the steric stabilizer block. Both of these stabilizers contain carboxylic acid groups, but poly(proline methacrylate) is anionic above pH 9.2, whereas poly(carboxybetaine methacrylate) has zwitterionic character at this pH. When calcite crystals are grown at an initial pH of 9.5 in the presence of these two types of nanoparticles, it is found that the anionic poly(proline methacrylate)-stabilized particles are occluded uniformly throughout the crystals (up to 6.8% by mass, 14.0% by volume). In contrast, the zwitterionic poly(carboxybetaine methacrylate)-stabilized particles show no signs of occlusion into calcite crystals grown under identical conditions. The presence of carboxylic acid groups alone therefore does not guarantee efficient occlusion: overall anionic character is an additional prerequisite.

An aggregation-induced emission star polymer with pH and metal ion responsive fluorescence

A one-pot strategy from ring-opening metathesis polymerization was employed to prepare AIE-active star polymers, which were designed to have multi-responsive fluorescence to varied stimuli including pH, CO₂, and metal ions.