Facile Synthesis of Fluorescent Silica-Doped Polyvinylpyrrolidone Composites: From Cross-Linked Composite Film to Core–Shell Nanoparticles

Fluorescent silica-doped polyvinylpyrrolidone (PVP) composites with high optical properties have been successfully prepared in a one-pot synthesis through the incorporation of silica nanoparticles and dye molecules into the cross-linked PVP. Scanning electron microscopy, transmission electron microscopy, and fluorescence spectrometry are used to investigate the morphologies and optical properties of the composites. By adjusting the PVP content and reaction time, fluorescent silica-doped PVP film and fluorescent PVP-covered silica core–shell nanoparticles are obtained without stirring and under magnetic stirring, respectively. Because both the silica nanoparticles and the dye molecules react with ring-opened PVP, the composites exhibit highly stable optical properties. The obtained fluorescent composites may have potential applications in sensing and photovoltaic systems. The facile approach can be extended to the preparation of multifunctional fluorescent PVP composites by introducing other types of oxides

Enhancement of Energy Density in the BOPP-Based Sandwich-Structured Film by the Synergistic Effect of BaTiO₃@Polyaniline Hybrid Dielectric Fillers

A series of polyaniline-coated BaTiO3 (BaTiO3@PANI) hybrid dielectric fillers were prepared through the in situ oxidative polymerization of aniline. The morphology of the hybrid fillers can be controlled by the ratio of aniline and BaTiO3 particles. Mulberry-like and core–shell BaTiO3@PANI composite particles are prepared successfully. The two kinds of dielectric fillers were introduced into the poly(vinylidene fluoride) (PVDF) matrix separately or simultaneously. The dielectric loss can be suppressed by the synergetic effect of these two hybrid fillers while enhancing the dielectric constant at the same time. The finite element simulation results showed that the surface morphology of adjacent hybrid fillers played an important role in the dielectric performance. The fillers were introduced in the biaxially oriented polypropylene (BOPP)-based sandwich-structured film; specifically, the outer layer was BOPP and the middle layer was the composites consisting of chlorinated polypropylene (CPP)/PVDF blends and the hybrid fillers. The energy storage density of the sandwich-structured film was improved significantly compared to that of the BOPP film. The highest discharge energy density was 7.31 J/cm3 at 450 MV/m, and the charge–discharge efficiency was 77.3% with 30 wt % hybrid fillers in the middle layer

Chiral Microspheres Consisting Purely of Optically Active Helical Substituted Polyacetylene: The First Preparation via Precipitation Polymerization and Application in Enantioselective Crystallization

This article reports on a novel type of microspheres (∼720 nm in diameter) prepared via precipitation polymerization and constructed by optically active helical substituted polyacetylene (PSA). The microspheres were obtained in high yield (>80%), with regular morphology and narrow size distribution. PSA forming the microspheres was found to adopt helices with predominant one-handed screw sense, according to circular dichroism and UV–vis absorption spectroscopies and specific optical rotation measurements. The helical conformations of PSA endowed the microspheres thereof with considerable optical activity. The chiral microspheres feature in combining in one entity the advantages of both chiral polymers and the micrometer-sized particles in scale and spherical morphology and thus are expected to find some significant applications. This is well exemplified by successful induction of enantioselective crystallization with the chiral microspheres. Such chiral microspheres efficiently induced enantioselective crystallization of alanine enantiomers: (<i>S</i>)-PSA preferably induced l-alanine to form octahedral crystals while (<i>R</i>)-PSA toward d-alanine forming needle-like crystals, with a remarkably high ee (85%). This is the first precipitation polymerization of substituted acetylenes for preparing chiral polymeric microspheres. The present chiral microspheres represent a new type of advanced functional chiral materials

Chiral Functionalization of Graphene Oxide by Optically Active Helical-Substituted Polyacetylene Chains and Its Application in Enantioselective Crystallization

This article reports an original, versatile strategy to chirally functionalize graphene oxide (GO) with optically active helical-substituted polyacetylene. GO was first converted into alkynyl-GO containing polymerizable −CC moieties, which took part in the polymerization of another chiral acetylenic monomer, yielding the expected GO hybrid covalently grafted with chiral helical polyacetylene chains. Transmission electron microscopy, atomic force microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analyses verified the successful attachment of substituted polyacetylene chains on GO by covalent chemical bonding. Moreover, circular dichroism effects and UV–vis absorption demonstrated that the GO hybrid possessed fascinating optical activity. It also largely improved the dispersibility of GO in tetrahydrofuran. The GO-derived hybrid was further used as a chiral inducer toward enantioselective crystallization of alanine enantiomers. l-Alanine was preferably induced to crystallize, forming rodlike crystals

“On–off–on” Switchable Sensor: A Fluorescent Spiropyran Responds to Extreme pH Conditions and Its Bioimaging Applications

A novel spiropyran that responds to both extreme acid and extreme alkali and has an “on–off–on” switch is reported. Benzoic acid at the indole N-position and carboxyl group at the indole 6-position contribute to the extreme acid response. The ionizations of carboxyl and phenolic hydroxyl groups cause the extreme alkali response. Moreover, the fluorescent imaging in bacterial cells under extreme pH conditions supports the mechanism of pH response

Thermostable Microspheres Consisting of Poly(<i>N</i>‑phenylmaleimide-<i>co</i>-α-methyl styrene) Prepared by Precipitation Polymerization

General polymeric microspheres are not satisfactorily thermostable. This article reports on an unprecedented type of poly­(<i>N</i>-phenylmaleimide-<i>co</i>-α-methyl styrene) [denoted as poly­(<i>N</i>-PMI-<i>co</i>-AMS)] microspheres showing remarkable thermal stability. The microspheres were prepared by free-radical precipitation polymerization in a solvent mixture consisting of methyl ethyl ketone (favorable solvent) and heptane (unfavorable solvent). Microspheres of good morphology and narrow size distribution were obtained in high yield (>85%) under appropriate conditions. Growth of poly­(<i>N</i>-PMI-<i>co</i>-AMS) microspheres was characterized by scanning electron microscopy. The microspheres, although without cross-linking, exhibited excellent thermal stability, and their decomposition temperature was up to about 370 °C. This feature cannot be achieved in typical polymeric microspheres. Also, notably, this is the first precipitation polymerization of maleimide and AMS and their derivatives for preparing microspheres. The present novel microspheres are expected to find practical applications as novel heat-resistant additives, solid carriers for catalysts, and so on

Separated Immobilization of Incompatible Enzymes on Polymer Substrate via Visible Light Induced Living Photografting Polymerization

The use of the mixed catalytic system with several enzymes can provide multiple benefits in terms of the cost, simplification of a multistep reaction, and effectiveness of complex chemical reactions. Although study of different enzyme coimmobilization systems has attracted increasing attention in recent years, separately immobilizing enzymes which can not coexist on one support is still one of the great challenges. In this paper, a simple and effective strategy was introduced to separately encapsulate incompatible trypsin and transglutaminase (TGase) into different poly­(ethylene glycol) (PEG) network layer grafted on low-density polyethylene (LDPE) film via visible light induced living photografting polymerization. As a proof of concept, this dual-enzyme separately loaded film was used to catalyze the synthesis of a new target antitumor drug LTV-azacytidine. The final results demonstrated that this strategy could maintain higher activities of both enzymes than the mixed coimmobilization method. And the mass spectra analysis results demonstrated that LTV-azacytidine was successfully synthesized. We believe that this facile and mild separately immobilizing incompatible enzyme strategy has great application potential in the field of biocatalysis

Direct One-Pot Synthesis of Chemically Anisotropic Particles with Tunable Morphology, Dimensions, and Surface Roughness

Previously, synthesis of anisotropic particles by seeded polymerizations has involved multiple process steps. In conventional one-pot dispersion polymerization (Dis.P) with a cross-linker added, only spherical particles are produced due to rapid and high cross-linking. In this Article, a straightforward one-pot preparation of monodisperse anisotropic particles with tunable morphology, dimensions, surface roughness, and asymmetrically distributed functional groups is described. With a cross-linker of divinylbenzene (DVB, 8%), ethylene glycol dimethacrylate (EGDMA, 6%), or dimethacryloyloxybenzophenone (DMABP, 5%) added at 40 min, shortly after the end of nucleation stage in Dis.P of styrene (St) in methanol and water (6/4, vol), the swollen growing particles are inhomogeneously cross-linked at first. Then, at low gel contents of 59%, 49%, and 69%, corresponding to the cases using DVB, EGDMA, and DMABP, respectively, the growing particle phase separates and snowman- or dumbbell-like particles are generated. Thermodynamic and kinetic analyses reveal that moderate cross-linking and sufficient swelling of growing particles determine the formation and growth of anisotropic particles during polymerization. Morphology, surface roughness, sizes, and cross-linking degrees of each domain of final particles are tuned continuously by varying start addition time and contents of cross-linkers. The snowman-like particles fabricated with DVB have a gradient cross-linking and asymmetrical distribution of pendant vinyl groups from their body to head. The dumbbell-like particles prepared using DMABP have only one domain cross-linked; i.e., only one domain contains photosensitive benzophenone (BP) groups. With addition of glycidyl methacrylate (GMA) or propargyl methacrylate (PMA) together with DVB or EGDMA, epoxy or alkynyl groups are asymmetrically incorporated. With the aid of these functional groups, carboxyl, amino, or thiol groups and PEG (200) are attached by thiol–ene (yne) click and photocoupling reactions

An Extremely Simple and Effective Strategy to Tailor the Surface Performance of Inorganic Substrates by Two New Photochemical Reactions

This article reports on a new sequential strategy to fabricate monolayer functional organosilane films on inorganic substrate surfaces, and subsequently, to pattern them by two new photochemical reactions. (1) By using UV light (254 nm) plus dimethylformamide (DMF), a functional silane monolayer film could be fabricated quickly (within minutes) under ambient temperature. (2) The organic groups of the formed films became decomposed in a few minutes with UV irradiation coupled with a water solution of ammonium persulfate (APS). (3) When two photochemical reactions were sequentially combined, a high-quality patterned functional surface could be obtained thanks to the photomask

Synthesis of hypergrafted poly[4-(N,N-diphenylamino)methylstyrene] through tandem anionic-radical polymerization of radical-inimer

<p>In this paper, we present a tandem anionic-radical approach for synthesizing hypergrafted polymers. We prepared 4-(N,N-diphenylamino)methylstyrene (DPAMS) as a new radical-based inimer. Linear PDPAMS was prepared through anionic polymerization. Hypergrafted PDPAMS was synthesized through the self-condensing vinyl polymerization of DPAMS with linear PDPAMS. The linear backbone of PDPAMS, which incorporated latent radical initiating sites, served as a ‘hyperlinker’ to link hyperbranched side chains. The molecular weights of hypergrafted polymers increased as the length of the linear backbone chain increased. The hypergrafted structure of the resulting polymer was confirmed using a conventional gel permeation chromatograph apparatus equipped with a multiangle light scattering detector, nuclear magnetic resonance, differential scanning calorimetry, and thermogravimetric analysis. This strategy can be applied to synthesize other complex architectures based on hyperbranched polymers by changing the structure of a polymer backbone through anionic polymerization.</p