Controlled accommodation of metal nanostructures within the matrices of polymer architectures through solution-based synthetic strategies

Rapid gram-scale synthesis of Au/chitosan nanoparticles catalysts using solid mortar grinding

Owing to the abundant functional groups present in the chitosan polymer, high density catalytic tiny gold particles with greater dispersion can be anchored on the chitosan powder using simple mortar and pestle.

Guided Assembly of Well-Defined Hierarchical Nanoporous Polymers by Lewis Acid-Base Interactions

Three-dimensional hierarchical nanoporous polymers and carbon nanomaterials with well-defined superstructures are of great interest for various intelligent applications, whereas a facile and versatile approach to access those materials with a high surface area, stable well-defined morphology, and ordered pores still remains a significant challenge. Herein, we report a self-regulated Lewis acid-base interaction-mediated assembly strategy for the in situ synthesis of morphology-engineered hyper-cross-linked porous polymers and carbon materials. A series of functionalized aromatic compounds (FAC) is subjected to self-cross-linking via classic Friedel-Crafts chemistry to achieve stable porous polymers with a high surface area. Varying the monomer/catalyst combination had a dramatic effect on the acid-base interaction, facilitating the tailoring of the self-assembled morphologies from nanotubes to hollow nanospheres, and even nanosheets. A mechanistic study showed that the byproducts generated during cross-linking orchestrate the interactions between the catalyst (acid) and FAC (base) and simultaneously drive the self-assembly to yield specific morphologies. Based on the rigid hollow polymer framework and intrinsic hydroxyl functionality, the hyper-cross-linked hollow nanospheres were easily transformed to an acid-functionalized catalyst for efficient biodiesel production. Moreover, high-quality porous carbonaceous nanocounterparts such as carbon nanotubes, hollow carbon nanospheres, and carbon nanosheets could also be produced by direct pyrolysis of the corresponding polymer precursors. These findings may provide guidance for the facile design of morphology-controlled functionalized polymers and carbon nanomaterials for various applications.

Electrospun amorphous solid dispersions of poorly water-soluble drugs: A review

The development of oral dosage forms for poorly water-soluble active pharmaceutical ingredients (APIs) is a persistent challenge. A range of methods has been explored to address this issue, and amorphous solid dispersions (ASDs) have received increasing attention. ASDs are typically prepared by starting with a liquid precursor (a solution or melt) and applying energy for solidification. Many techniques can be used, with the emergence of electrospinning as a potent option in recent years. This method uses electrical energy to induce changes from liquid to solid. Through the direct applications of electrical energy, electrospinning can generate nanofiber-based ASDs from drug-loaded solutions, melts and melt-solutions. The technique can also be combined with other approaches using the application of mechanical, thermal or other energy sources. Electrospinning has numerous advantages over other approaches to produce ASDs. These advantages include extremely rapid drying speeds, ease of implentation, compatibility with a wide range of active ingredients (including those which are thermally labile), and the generation of products with large surface areas and high porosity. Furthermore, this technique exhibits the potential to create so-called 'fifth-generation' ASDs with nanostructured architectures, such as core/shell or Janus systems and their combinations. These advanced systems can improve dissolution behaviour and provide programmable drug release profiles. Additionally, the fiber components and their spatial distributions can be precisely controlled. Electrospun fiber-based ASDs can maintain an incorporated active ingredient in the amorphous physical form for prolonged periods of time because of their homogeneous drug distribution within the polymer matrix (typically they comprise solid solutions), and ability to inhibit molecular motion. These ASDs can be utilised to generate oral dosage forms for poorly water-soluble drugs, resulting in linear or multiple-phase release of one or more APIs. Electrospun ASDs can also be exploited as templates for manipulating molecular self-assembly, offering a bridge between ASDs and other types of dosage forms. This review addresses the development, advantages and pharmaceutical applications of electrospinning for producing polymeric ASDs. Material preparation and analysis procedures are considered. The mechanisms through which performance has been improved are also discussed.

Uniform Distance Scaling Behavior of Planet-Satellite Nanostructures Made by Star Polymers

Planet-satellite nanostructures from RAFT star polymers and larger (planet) as well as smaller (satellite) gold nanoparticles are analyzed in experiments and computer simulations regarding the influence of arm number of star polymers. A uniform scaling behavior of planet-satellite distances as a function of arm length was found both in the dried state (via transmission electron microscopy) after casting the nanostructures on surfaces and in the colloidally dispersed state (via simulations and small-angle X-ray scattering) when 2-, 3-, and 6-arm star polymers were employed. This indicates that the planet-satellite distances are mainly determined by the arm length of star polymers. The observed discrepancy between TEM and simulated distances can be attributed to the difference of polymer configurations in dried and dispersed state. Our results also show that these distances are controlled by the density of star polymers end groups, and the number of grabbed satellite particles is determined by the magnitude of the corresponding density. These findings demonstrate the feasibility to precisely control the planet-satellite structures at the nanoscale.

A simple approach to obtain hybrid Au-loaded polymeric nanoparticles with a tunable metal load

A new strategy to nanoengineer multi-functional polymer-metal hybrid nanostructures is reported. By using this protocol the hurdles of most of the current developments concerning covalent and non-covalent attachment of polymers to preformed inorganic nanoparticles (NPs) are overcome. The strategy is based on the in situ reduction of metal precursors using the polymeric nanoparticle as a nanoreactor. Gold nanoparticles and poly(DL-lactic-co-glycolic acid), PLGA, are located in the core and shell, respectively. This novel technique enables the production of PLGA NPs smaller than 200 nm that bear either a single encapsulated Au NP or several smaller NPs with tunable sizes and a 100% loading efficiency. In situ reduction of Au ions inside the polymeric NPs was achieved on demand by using heat to activate the reductive effect of citrate ions. In addition, we show that the loading of the resulting Au NPs inside the PLGA NPs is highly dependent on the surfactant used. Electron microscopy, laser irradiation, UV-Vis and fluorescence spectroscopy characterization techniques confirm the location of Au nanoparticles. These promising results indicate that these hybrid nanomaterials could be used in theranostic applications or as contrast agents in dark-field imaging and computed tomography.

The Structure of Gold-Nanoparticle Networks Cross-Linked by Di- and Multifunctional RAFT Oligomers

Gold nanoparticle (AuNP) network structures featuring particles from the two-phase Brust-Schiffrin synthesis and linear RAFT oligomers of styrene with two and multiple trithiocarbonate (TTC) groups along their backbone have been investigated in detail. Insights into the internal structures of these particle networks could be obtained from small-angle X-ray scattering experiments, showing that primary AuNPs are cross-linked by the employed molecular linker. The extent of AuNP network formation was investigated by means of dynamic light scattering and UV/visible extinction spectroscopy, showing an abrupt attenuation of network formation after a critical degree of polymerization of the cross-linker is exceeded. Analysis of transmission electron micrographs indicated a three-dimensional shape of the particle superstructures, which is evenly filled with the primary AuNPs. From the results obtained in this study, guidelines for the fabrication of nanoparticle networks from the self-assembly with macromolecular cross-linkers are suggested.