Renhua Deng

Encapsulation of Nanoparticles in Block Copolymer Micellar Aggregates by Directed Supramolecular Assembly

Incorporation of inorganic nanoparticles (NPs) into selfassembled block copolymers offers a powerful route for the formation of hybrid materials with desired optical, electronic, and magnetic properties through the choice of NPs and their distribution in polymer assemblies. Nanostructured block copolymer domains act as a scaffold that directs not only the position of the NPs but also their orientation. NPs/polymer hybrid materials have been prepared in solution by incorporating one or multiple hydrophobic NPs into a hydrophobic core of spherical amphiphilic block copolymer micelles. Careful control of micellization conditions will allow other hydrophobic ingredients to co-assemble with the amphiphilic polymers, resulting in micelles that encapsulate therapeutic molecules and NPs for imaging and targeting. Cylindrical or wormlike micelles show particular interest in drug delivery because of their large core volume (per carrier) and elongated structures, which offer additional opportunities to control biodistribution and release profiles of therapeutic agents. The “precipitation method”, which is a practical way to incorporate NPs into micelles, does not easily allow the growth of extended wormlike micelles with NPs encapsulated in the core. Several groups have reported the successful incorporation of NPs into hydrophilic portions of wormlike micelles through electrostatic interaction of corona-forming blocks with NPs. Recently, we reported the encapsulation of iron oxide NPs within wormlike micelle cores through interfacial instabilities of emulsion droplets containing amphiphilic polymers. However, it is hard to achieve high loading and uniform dispersion of NPs in wormlike micelle cores. So far, precise control over NPs position in wormlike micelle cores with homogeneous distribution remains a challenge. Herein we introduce a simple, yet versatile approach for the encapsulation of NPs within wormlike micelle cores through directed supramolecular assembly. The concept for preparation of the hybrid nano-objects is illustrated in Figure 1a. Typically, polystyrene–poly(4-vinylpyridine) (PS20k–P4VP17k, volume fraction of PS fPS= 56%) and pentadecylphenol (PDP) were dissolved in chloroform to form PS–P4VP(PDP)x (x represents the ratio of PDP to 4VP

Mesoporous Block Copolymer Nanoparticles with Tailored Structures by Hydrogen‐Bonding‐Assisted Self‐Assembly

A simple, yet robust route to prepare polymer nanoparticles with tunable internal structures through supramolecular assembly within emulsion droplets is presented. Nanoparticles with various internal morphologies, including dispersed spheres, dispersed spirals, stacked toroids, and concentric lamellae, are obtained due to the 3D confinement and variation of hydrogen-bonding agent. This method also allows us to form mesoporous particles through further disassembly of the supramoleclar assemblies by rupturing the hydrogen bonding.

Janus Nanodisc of Diblock Copolymers

Janus nanodiscs of diblock copolymers are prepared by stepwise disassembly of PS-b-P4VP disc-stacked particles. The Janus nanodiscs are uniform in thickness and regular in contour. By preferential growth of functional materials at the positively charged P4VP side, the composition, microstructure, and performance of the Janus nanodiscs are tunable.

Shaping Functional Nano‐objects by 3D Confined Supramolecular Assembly

Nano-objects are generated through 3D confined supramolecular assembly, followed by a sequential disintegration by rupturing the hydrogen bonding. The shape of the nano-objects is tunable, ranging from nano-disc, nano-cup, to nano-toroid. The nano-objects are pH-responsive. Functional materials for example inorganic or metal nanoparticles are easily complexed onto the external surface, to extend both composition and microstructure of the nano-objects.

Multiresponsive Hydrogel Photonic Crystal Microparticles with Inverse-Opal Structure

Hydrogel photonic crystal microparticles (HPCMs) with inverse-opal structure are generated through a combination of microfluidic and templating technique. Temperature and pH responsive HPCMs have firstly been prepared by copolymerizing functional monomers, for example, N-isopropylacrylamide (NIPAm) and methacrylic acid (MAA). HPCMs not only show tunable color variation almost covering the entire wavelength of visible light (above 150 nm of stop-band shift) by simply tailoring temperature or pH value of the solution, but also display rapid response (less than 1 min) due to the small volume and well-ordered porous structure. Importantly, the temperature sensing window of the HPCMs can be enlarged by controlling the transition temperature of the hydrogel matrix, and the HPCMs also exhibit good reversibility and reproducibility for pH response. Moreover, functional species or particles (such as azobenzene derivative or magnetic nanoparticles) can be further introduced into the hydrogel matrix by using post-treatment process. These functionalized HPCMs can respond to the UV/visible light without significantly influencing the temperature and pH response, and thus, multiresponsive capability within one single particle can be realized. The presence of magnetic nanoparticles may facilitate secondary assembly, which has potential applications in advanced optical devices.

Biodegradable Polymer Microcapsules Fabrication through a Template-Free Approach

A detailed study on the direct synthesis of biocompatible polyesters (e.g., PLA, PLGA or PCL) microcapsules and multifunctional microcapsules, which does not require any template and core removal, is presented. The technique is based on the modified self-emulsification process within the emulsion droplets by simply adding sodium dioctyl sulfosuccinate (Aerosol OT or AOT) as a cosurfactant to the initial polymer solution, followed by double emulsion formation due to the coalescence of the internal water droplets. Microcapsules with tunable sizes (ranging from hundreds of nanometers to tens of micrometers) and morphologies were then obtained through solidification of droplet shell of the double emulsion via solvent removal. In this report, we have systematically investigated the effect of experimental parameters, such as polymer and AOT concentration, polymer molecular weight on the double emulsion formation process, and the final morphologies of the microcapsules. We demonstrate that the capsules can encapsulate either hydrophobic or hydrophilic dyes during solvent evaporation. Dye-release studies show a correlation between shell thickness, capsules size, and diffusive release rate, providing insights into the shell formation and shell thickness processing. Moreover, hydrophobic nanoparticles, such as oleic-acid coated Fe(3)O(4) nanoparticles and quantum dots, can also be incorporated into the walls of the microcapsules. Such functional microcapsules might find applications in the fields of controlled release, bioimaging, diagnostics, and targeting.

Multifunctional biodegradable polymer nanoparticles with uniform sizes: generation and in vitro anti-melanoma activity.

We present a simple, yet versatile strategy for the fabrication of uniform biodegradable polymer nanoparticles (NPs) with controllable sizes by a hand-driven membrane-extrusion emulsification approach. The size and size distribution of the NPs can be easily tuned by varying the experimental parameters, including initial polymer concentration, surfactant concentration, number of extrusion passes, membrane pore size, and polymer molecular weight. Moreover, hydrophobic drugs (e.g., paclitaxel (PTX)) and inorganic NPs (e.g., quantum dots (QDs) and magnetic NPs (MNPs)) can be effectively and simultaneously encapsulated into the polymer NPs to form the multifunctional hybrid NPs through this facile route. These PTX-loaded NPs exhibit high encapsulation efficiency and drug loading density as well as excellent drug sustained release performance. As a proof of concept, the A875 cell (melanoma cell line) experiment in vitro, including cellular uptake analysis by fluorescence microscope, cytotoxicity analysis of NPs, and magnetic resonance imaging (MRI) studies, indicates that the PTX-loaded hybrid NPs produced by this technique could be potentially applied as a multifunctional delivery system for drug delivery, bio-imaging, and tumor therapy, including malignant melanoma therapy.

Fabrication of porous polymer microparticles with tunable pore size and density through the combination of phase separation and emulsion-solvent evaporation approach

A facile and versatile route to prepare porous polymer microparticles with tunable pore size and density through the combination of phase separation and emulsion-solvent evaporation method is demonstrated. When volatile organic solvent (e.g., chloroform) diffuses through the aqueous phase containing poly(vinyl alcohol) (PVA) and evaporates, n-hexadecane (HD) and polystyrene (PS) in oil-in-water emulsion droplets occur to phase separate due to the incompatibility between PS and HD, ultimately yielding microparticles with porous structures. Interestingly, density of the pores (pore number) on the shell of microparticles can be tailored from one to hundreds by simply varying the HD concentration and/ or the rate of solvent evaporation. Moreover, this versatile approach for preparing porous microparticles with tunable pore size and density can be applied to other types of hydrophobic polymers, organic solvents, and alkanes, which will find potential applications in the fields of pharmaceutical, catalyst carrier, separation, and diagnostics.

Polymer–inorganic hybrid microparticles with hierarchical structures formed by interfacial instabilities of emulsion droplets

We introduce a facile, yet robust route for fabricating polymer–inorganic hybrid microparticles with hierarchically-structured morphologies by taking advantage of the interfacial instabilities of emulsion droplets and the sol–gel chemistry of silica precursors. In general, chloroform-in-water emulsion droplets containing an amphiphilic diblock copolymer [polystyrene-b-poly (ethylene oxide) (PS–PEO)] and metal oxide precursors [tetraethyl orthosilicate (TEOS) or mixtures of TEOS and tetra-tert-butyl orthotitanate (TBOT)] were prepared by shaking. Upon solvent evaporation, interfacial instabilities occurred while the inorganic precursors started to hydrolyze and condense when brought in contact with the aqueous solution, ultimately leading to the formation of a mineralized shell at the oil–water interface and hybrid microparticles. By varying the rate of solvent evaporation, qualitatively different mechanisms of the instabilities (e.g., the budding of vesicles or a spines-to-vesicles transition) were observed. The effect of the synthesis conditions, such as the amount of TEOS, the solvent evaporation rate, and the pH value on the self-assembly of the copolymer, the interfacial behavior of the solvent/water, and the morphology of the microparticles were investigated. Hierarchical microparticles with different morphologies, ranging from cage-like, honeycomb-like, dendritic, to budded microparticles, were prepared by combining the sol–gel process with the self-assembly of the polymers in the emulsion droplets. Moreover, the intermediate structures of the instabilities were kinetically trapped by the mineralization process. Our study indicated that the hybrid microparticles formed by interfacial instabilities of emulsion droplets can significantly expand the range of accessible morphologies, which provides the potential for advanced applications in drug storage, coatings, controlled release, and catalysis.

Recent advances in the synthesis of Janus nanomaterials of block copolymers

We present a review of the very recent advances in the synthesis of block copolymer (BCP) Janus nanomaterials. Although Janus micelles can form by the self-assembly of BCPs in solution, patchy or core–shell structures are usually dominant. Structural transformation of the core–shell structure or disassembly of the patchy structure is further employed to achieve Janus nanomaterials. Disassembly of ABC tri-block terpolymer supramolecular structures is advantageous in tuning much more easily the shapes of the Janus nanomaterials from spherical to cylindrical and sheet/disc-like. Narrow molecular weight distributions and strict processing conditions are required. Emulsion droplet confined self-assembly of BCPs can directly achieve Janus nanomaterials in a sufficiently small droplet and/or at low polymer concentration. A neutral emulsion interface is required using proper surfactants. Alternatively, a general method has been proposed to prepare Janus nanomaterials by guided self-assembly of BCPs within a confined environment by the strong interaction and the selective crosslinking of one block. The aforementioned Janus nanomaterials are in the form of a polymer cluster. Single chain Janus nanomaterials of BCPs can be prepared by intramolecular crosslinking of one block in a very dilute solution. It remains challenging to synthesize single chain Janus nanomaterials at high solid content for example tens of percent. At the end of this review, a perspective on BCP Janus nanomaterials is provided.