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We report a one-step solvothermal method to prepare magnetic hybrid copolymer–Co hierarchical hollow spheres by localized Ostwald ripening. The initial stage is the aggregation of primary inorganic nanoparticles whose surfaces are partially adsorbed by copolymer PEG–PPG–PEG to form solid spheres followed by hollowing of the core and the progressive matter redistribution from the interior to the exterior. Meanwhile, amorphous inorganic particles grow to cubic crystallites. Finally, a hollow spherical architecture with an extensively roughened surface is obtained by this self-transformation. The effect of NaOH concentration (served as a catalyst and reagent) on the sphere morphology is also checked by time-dependent experiments. When decreasing the mass of NaOH from 7.5 to 2.5 mmol, a morphology transformation from porous hollow spheres to double-wall spheres and then to single-wall spheres with platelet-like building units aligned disorderly on the outer surfaces is observed, and this morphology transformation is related to Ostwald ripening. Our results suggest that these nanoparticle-based hollow hierarchical spheres collected by the self-transformation of precursor objects could be of potential applicability in the fields of material science and biomedical technology. [ABSTRACT FROM AUTHOR]

A highly regioselective tetra-ortho-iodination reaction of perylene diimides (PDIs) has been developed, which could be conducted on a multigram scale (>10 g), featuring a column chromatography-free workup and purification. The ortho-iodinated-PDIs serve as key intermediates for the preparation of a variety of ortho-functionalized PDIs and PDI-based conjugated polymers. [ABSTRACT FROM AUTHOR]

Diffusion of drug molecules in polymer materials is of great importance in controlled drug release, and the investigation of the mechanism of drug release from the polymer matrix would help us to understand the release behavior of the controlled release system. In this work, molecular dynamics simulations were employed to investigate the diffusion mechanisms of penetrant molecules with different sizes in poly(lactic acid-co-ethylene glycol) (PLA-PEG). The size effect on the diffusion mechanism of penetrant molecules in polymer matrixes was discussed in detail. A competition mechanism in a two-step diffusion process(1) motion within the cavities (free volumes), and (2) jumps between cavities or movement of the cavity itself originated from the wriggling of the polymer chainswas observed, and the contributions of these two factors to the diffusion coefficient were successfully separated. With the medium volume of penetrant molecules (e.g., benzene), a competition between these two steps was observed. Step (2) controlled the diffusion when penetrant molecules became bigger. [ABSTRACT FROM AUTHOR]

Thin polymer films with well-assembled fluorinated groups on their surfaces are not easily achieved via spin-coating film-fabrication methods because the solution solidifies very rapidly during spin-coating, which hinders the fluorinated moieties from segregating and organizing on the film surface. In this contribution, we have proposed a comprehensive strategy toward achieving well-ordered fluorinated thin films surfaces by optimizing the molecular organization at air/liquid interface of the film-formation solutions. To validate such a route, poly(methyl methacrylate) (PMMA) end-capped with several 2-perfluorooctylethyl methacrylate (FMA) units was employed as the model polymer for investigations. The air/solution interfacial structures were optimized by systematically changing the polymer chain structures and properties of the casting solvents. It was found that the polymers that form loosely associated aggregates (e.g., FMA1-ec-PMMA65-ec-FMA1) and a solvent with better solubility to FMA while having not too low surface tension (i.e., toluene) can combine to produce solutions with well-assembled FMA at the interfaces. By spin-coating the solutions with well-organized interfaces, an ultrathin film with perfluorinated groups that were highly oriented toward the film surface was readily achieved, exhibiting surface energies as low as 7.2 mJ/m2, which is among the lowest reported so far for the spin-coated thin films, and a very high F/C ratio (i.e., 0.98). [ABSTRACT FROM AUTHOR]

High-throughput synthesis of well-defined polymer nano-objects has long been an attractive yet challenging topic in the area of polymer chemistry and material science. Herein, we report an enzyme-assisted photoinitiated polymerization-induced self-assembly (photo-PISA) approach to prepare well-defined AB diblock or ABC triblock copolymer nano-objects at room temperature in open vessels and multiwell plates. Kinetic studies indicated that the presence of glucose oxidase (GOx) endowed the polymerizations with excellent oxygen tolerance. Good control was maintained during the enzyme-assisted photo-PISA process. This method facilitates high-throughput PISA, allowing for the construction of a detailed phase diagram in a rather short time. We also demonstrate the potential bio-related application of this method by the successful encapsulation of horseradish peroxidase (HRP) and bovine serum albumin (BSA) into self-assembled polymer vesicles without compromising protein activities. This robust oxygen-tolerant PISA approach leads to unprecedented access to well-defined polymer nano-objects for nonexperts. [ABSTRACT FROM AUTHOR]

A facile method was developed to measure the utmost distance of polymer dynamics suppressed by a solid substrate by investigating the diffusion of a fluorinated tracer-labeled polymer in the bottom layer of bilayer samples. Here, a labeled layer of fluorinated tracer-labeled at the polymer chain end of variable thickness was supported on a substrate, and the corresponding homopolymer layer of fixed thickness was deposited on top of the bottom layer. From the critical time (t*) required for the fluorinated component to diffuse from the bottom layer to the bilayer film surface as a function of the thickness of the bottom layer, a critical thickness of the bottom layer (hc*), corresponding to the thickness at which t* started to increase, was obtained. This thickness was related to the distance over which polymer dynamics were altered by the substrate. The results showed that hc* was very sensitive to the surface chemistry of the substrate and exhibited both molecular weight and temperature dependencies. [ABSTRACT FROM AUTHOR]

Nanomaterials have been actively pursued for biological and medical applications in recent years. Here, we report the synthesis of several new poly(ethylene glycol) grafted branched polymers for functionalization of various nanomaterials including carbon nanotubes, gold nanoparticles (NPs), and gold nanorods (NRs), affording high aqueous solubility and stability for these materials. We synthesize different surfactant polymers based upon poly(γ-glutamic acid) (γPGA) and poly(maleic anhydride-alt-1-octadecene) (PMHC18). We use the abundant free carboxylic acid groups of γPGA for attaching lipophilic species such as pyrene or phospholipid, which bind to nanomaterials via robust physisorption. Additionally, the remaining carboxylic acids on γPGA or the amine-reactive anhydrides of PMHC18 are then PEGylated, providing extended hydrophilic groups, affording polymeric amphiphiles. We show that single-walled carbon nanotubes (SWNTs), Au NPs, and NRs functionalized by the polymers exhibit high stability in aqueous solutions at different pH values, at elevated temperatures, and in serum. Morever, the polymer-coated SWNTs exhibit remarkably long blood circulation (t1/2 = 22.1 h) upon intravenous injection into mice, far exceeding the previous record of 5.4 h. The ultralong blood circulation time suggests greatly delayed clearance of nanomaterials by the reticuloendothelial system (RES) of mice, a highly desired property for in vivo applications of nanomaterials, including imaging and drug delivery. [ABSTRACT FROM AUTHOR]