Self-organization and morphological characteristics of selenium-containing nanostructures based on rigid-chain polymers

Macroinitiators containing β-diketonate fragments were prepared by copolymerization of styrene with cobalt(II) 5-Formation and morphological characteristics of selenium-containing nanostructures formed by reduction of selenious acid with ascorbic acid in the presence of ionic or nonionic polymeric stabilizer in aqueous solutions were studied by methods of nonlinear optics and flow birefringence at widely varied selenium to polymer weight ratio in solution ν. The molecular weights, root-mean-square and hydrodynamic sizes, and mean density of the nanostructures were calculated, and the trends in variation of these quantities were compared.     

Influence of the nature of the stabilizing polymeric matrix on the self-organization of selenium nanoclusters

The size characteristics and formation kinetics of selenium-containing nanosystems based on various polymeric matrices (nonionic polymers: polyvinylpyrrolidone, oxyethylated cellulose; cationic polyelectrolyte: poly-N,N,N,N-trimethylmethacryloyloxyethylammonium methyl sulfate; anionic polyelectrolytes: poly-2-acrylamido-2-methylpropanesulfonic acid, polymethacrylic acid) were studied by methods of molecular optics and spectrophotometry. The influence of the nature of the polymeric matrix and of the selenium: polymer weight ratio on the rate constant and hydrodynamic radius was determined.     

Morphology and thermodynamics of selenium-containing nanosystems: The effect of polymer stabilizers

Nanosystems based on zero-valent selenium and biocompatible polymer stabilizers (polyvinylpyrrolidone with molecular weight (MW) М _w = (10–55) × 10³, poly-N,N,N,N-trimethylacryloyloxyethylammonium methylsulfate with М _w = (30–250) × 10³ and polyethylene glycol with М _w = (1–40) × 10³) are studied by means of static and dynamic light scattering, and the resulting data are compared. Dense spherical multimolecular nanosystems are found to be formed. Morphological and thermodynamic characteristics of selenium-containing nanosystems, depending on the nature and MW of the polymer stabilizer, are determined. It is shown that the properties of nanosystems can be adjusted by varying the molecular weight of the polymer stabilizer.     

The influence of the ratio between the selenium: Polyvinylpyrrolidone complex components on the formation and morphological characteristics of nanostructures

Optical and spectral methods were used to study nanostructures formed in the reduction of ionic selenium in the selenite-ascorbate redox system in aqueous solutions of polyvinylpyrrolidone, a physiologically active polymer. The weight ratio between the selenium: polymer complex components (ν) was varied over a wide range (ν = 0.01?0.2). The adsorption of a substantial number of macromolecules (up to 1000 at ν = 0.1?0.2) on selenium nanoparticles was observed experimentally. This resulted in the formation of supramolecular spherical nanostructures with a high polymeric shell density. The Gibbs energies of macromolecule-Se⁰ nanoparticle interactions were calculated for polymeric nanostructures in the region of the formation of stable dispersions. The flow birefringence, dynamic light scattering, and spectrophotometry methods were used to determine the region of saturation of the adsorption capacity of selenium nanoparticles in selenium-containing nanocomposites (ν = 0.1?0.2).     

Silver nanocomposites based on a copolymer of 1-vinyl-1,2,4-triazole with crotonaldehyde

New polymer silver nanocomposites were synthesized using a copolymer of 1-vinyl-1,2,4-triazole with crotonaldehyde as the silver ion reducing agent and stabilizer of metal nanoparticles. The formation of the metallic phase in the nanoscale state was confirmed by UV spectroscopy and X-ray phase analysis. According to the transmission electron microscopy, nanoparticles have sizes of 2—14 nm and are uniformly distributed in the volume of the polymeric matrix.     

Antibacterial polyethylene - Ethylene vinyl acetate polymeric blend by incorporation of zinc oxide nanoparticles

In this work, a Low-Density Polyethylene (LDPE) - Ethylene Vinyl Acetate (EVA) polymeric blend with antimicrobial activity was obtained. The main objective was to develop an antibacterial LDPE-EVA polymeric blend from the incorporation of antibacterial nanoparticles to increase the antimicrobial and sanitary safety of this polymeric blend when applied in the manufacture of medical products. The antibacterial activity was obtained from the incorporation of zinc oxide nanoparticles (ZnO-NPs) in the LDPE-EVA polymeric blends and the thermal properties were evaluated by differential scanning calorimetry and the mechanical properties by tensile stress tests for different percentages of ZnO-NPs. Scanning electron microscopy was used to study the morphological characteristics of the ZnO-NPs and also the characteristics of the distribution of nanoparticles in the polymer blends. The dispersive energy of x-ray fluorescence spectroscopy was used to study the chemical composition of the nanoparticles. Microbiological tests were performed to evaluate the antibacterial activity of the LDPE-EVA polymeric blends without and with ZnO-NPs against the bacteria Staphylococcus aureus (gram-positive) and Escherichia coli (gram-negative). The results obtained were excellent for the future application of the antibacterial LDPE-EVA polymeric blends to the manufacture of medical products. The Young's modulus values decreased and the tensile strength values showed small reductions and the thermal properties of the LDPE-EVA were not modified. However, the antibacterial activity of LDPE-EVA with 4 wt% of ZnO-NPs was excellent, eliminating the gram-positive bacteria in just 2 h and the gram-negative bacteria in just 2.5 h on their surfaces.     

The Influence of Polymer—Selenium Complex Components and the Molecular Weight of the Ionogenic Polymeric Matrix on the Morphologic Characteristics of Selenium-Containing Nanostructures

Several optical methods were used to study nanostructures formed in the reduction of selenium ions in the selenite—ascorbate redox system in an aqueous solution of the poly-N,N,N,N-trimethylmethacryloyloxyethylammonium methyl sulfate polycation. The relation between the molecular weight of the polymeric matrix, which varied over a wide range, M _w = (0.03?13) × 10⁶, and the morphologic characteristics of nanostructures (molecular weight, density, shape, and statistical and hydrodynamic dimensions) was established. The weight ratio between the components of the polymer: selenium complex and the concentration of the polymer in the reaction mixture were shown to substantially influence certain morphologic characteristics of nanostructures. In the region of the formation of stable dispersions, the Gibbs energy of macromolecule—Se⁰ nanoparticle interactions was calculated. The thermodynamic state of solutions of nanostructures was characterized.     

Optical and Morphological Characteristics of Polymer Molecular Brushes with Varied Grafting Density and Binary Bioactive Radachlorine-Containing Nanosystems Based on Them

The optical and morphological characteristics of polymer molecular brushes with the polyimide backbone and polymethacrylic acid side chains, and also of binary nanosystems based on the molecular brushes and Radachlorine®, a photosensitizer of second generation, were studied. The brushes had the same backbone and approximately equal molecular mass of side chains, but strongly differed in the side chain grafting density. The side chain grafting density influences the molecular-conformation and morphological parameters of free molecular brushes and of the corresponding binary nanosystems.

     

The effect of polymer architecture on the nano self-assemblies based on novel comb-shaped amphiphilic poly(allylamine)

Twelve novel poly(allylamine) (PAA)-based, comb-shaped amphiphilic polymers have been developed. Hydrophobic groups of cetyl, palmitoyl and cholesteryl were randomly grafted to PAA and quaternisation was carried out on some modified polymers. Polymers were characterised using ¹H NMR, elemental analysis and differential scanning calorimetry. All polymers formed nano self-assemblies in the aqueous solution with a positive zeta potential and were able to encapsulate a hydrophobic agent, methyl orange, in the core. The critical aggregation concentration (CAC) and the microviscosity were found to be dependent on the polymer hydrophobicity. Being the most hydrophobic polymer, cholesteryl-grafted PAA had the lowest CAC (0.02 mg mL⁻¹) and the highest microviscosity. They appeared to form dense nanoparticles and were transformed into novel nanostructures in the presence of free cholesterol. Palmitoyl-grafted polymers formed nanoparticles while cetyl-grafted polymers formed polymeric micelles. The flexibility of cetyl chains possibly resulted in the formation of multicore polymeric micelles.     

Toward the innovative synthesis of columnar CeO2 nanostructures

We report on the preparation of supported columnar CeO(2) nanostructures by a simple catalyst-free chemical vapor deposition process at temperatures as low as 623 K. A suitable choice of experimental parameters enables us to control the structural and morphological features of the resulting ceria nanosystems.     

Facile Preparation of Polymeric Dimers from Amphiphilic Patchy Particles

A straightforward strategy for assembling polymeric dimers from amphiphilic nanoparticles is reported. Amphiphilic polymeric nanoparticles with a mixed‐shell of PEO/P2VN blocks and a flexible core of PAA blocks are fabricated by a non‐covalent crosslinking method. Uniform polymeric dimers are efficiently and simply obtained via hydrophobic interactions under optimized conditions in selective solvent. The steric hindrance generated by reorganization of hydrophilic polymer brushes during the interparticle association is critical for morphological selectivity in the assembly. General applicability offers the possibility to organize functional NPs into superstructures with well‐defined geometry and association numbers.     

Morphological characteristics of selenium-containing nanostructures based on rigid-chain molecules

Selenium-containing nanostructures of rigid-chain polymers with close molecular masses were studied by flow birefringence (FB) and static and dynamic light scattering at a fixed selenium to polymer mass ratio ν = 0.1 in solution. The group of polymers under study included the cationic polyelectrolyte poly-N,N,N,N-trimethylmethacryloyloxyethylammonium methyl sulfate, anionic polyelectrolyte carboxymethylcellulose, and nonionogen polymer oxyethylcellulose. High-molecular selenium-containing polymer nanostructures were found in all cases. Nanostructures with a maximum molecular mass and the largest number of constituent macromolecules were obtained using oxyethylcellulose. At ν = 0.1 the mean square radii of inertia of the nanostructures were almost independent of the nature of the polymer matrix. The thermodynamic state of the solutions of nanostructures was close to the ideal one in all cases. For the region where stable dispersions formed, the Gibbs energies of macromolecule-selenium nanoparticle interactions were calculated and shown to be almost independent of the nature of the polymer matrix at ν = 0.1. The close mean square radii of inertia R _g^* of the nanostructures, the Gibbs energies of interaction, and the equivalence of the thermodynamic state of the solutions of nanostructures obtained for all polymer matrices at ν = 0.1 suggest that ν = 0.1 corresponds to the ultimate adsorption capacity of selenium nanoparticles; the considerable differences between the molecular masses (for close R _g ^* values), mean densities, and structural conformation parameters ρ* point to different packings of macromolecules in the nanostructures under study.     

Spiky gold nanoshells

We report a high-yield synthetic method for a new type of metal nanostructure, spiky gold nanoshells, which combine the morphological characteristics of hollow metal nanoshells and nanorods. Our method utilizes block copolymer assemblies and polymer beads as templates for the growth of spiky nanoshells. Various shapes of spiky metal nanoshells were prepared in addition to spherical nanoshells by using block copolymer assemblies such as rod-like micelles, vesicles, and bilayers as templates. Furthermore, spiky gold shells encapsulating magnetic nanoparticles or quantum dots were prepared based on the ability of block copolymers to self-assemble with various types of nanoparticles and molecules. The capability to encapsulate other materials in the core, the shape tunability, and the highly structured surface of spiky nanoshells should benefit a range of imaging, sensing, and medical applications of metal nanostructures.     

Interfacially formed organized planar inorganic, polymeric and composite nanostructures

This paper discusses synthetic strategies for fabrication of new organized planar inorganic, polymeric, composite and bio-inorganic nanostructures by methods based on chemical reactions and physical interactions at the gas-liquid interface, Langmuir monolayer technique, interfacial ligand exchange and substitution reactions, self-assembling and self-organization processes, DNA templating and scaffolding. Stable reproducible planar assemblies of ligand-stabilized molecular nanoclusters containing definite number of atoms have been formed on solid substrate surfaces via preparation and deposition of mixed Langmuir monolayers composed by nanocluster and surfactant molecules. A novel approach to synthesis of inorganic nanoparticles and to formation of self-organized planar inorganic nanostructures has been introduced. In that approach, nanoparticles and nanostructures are fabricated via decomposition of insoluble metal-organic precursor compounds in a layer at the gas-liquid interface. The ultimately thin and anisotropic dynamic monomolecular reaction system was realized in that approach with quasi-two-dimensional growth and organization of nanoparticles and nanostructures in the plain of Langmuir monolayer. Photochemical and redox reactions were used to initiate processes of interfacial nucleation and growth of inorganic phase. It has been demonstrated that morphology of resulting inorganic nanostructures can be controlled efficiently by variations of growth conditions via changes in state and composition of interfacial planar reaction media, and by variations of composition of adjacent bulk phases. Planar arrays and chains of iron oxide and ultrasmall noble metal (Au and Pd) nanoparticles, nanowires and new organized planar disk, ring, net-like, labyrinth and very high-surface area nanostructures were obtained by methods based on that approach. Highly organized monomolecular polymeric films on solid substrates were obtained via deposition of Langmuir monolayer formed by water-insoluble amphiphilic polycation molecules. Corresponding nanoscale-ordered planar polymeric nanocomposite films with incorporated ligand-stabilized molecular metallic nanoclusters and interfacially grown nanoparticles were fabricated successfully. Novel planar DNA complexes with amphiphilic polycation monolayer were formed at the gas-aqueous phase interface and then deposited on solid substrates. Toroidal and new net-like conformations were discovered in those complexes. Nanoscale supramolecular organization of the complexes was dependent on cationic amphiphile monolayer state during the DNA binding. These monolayer and multilayer DNA/amphiphilic polycation complex Langmuir-Blodgett films were used as templates and nanoreactors for generation of inorganic nanostructures via metal cation binding with DNA and following inorganic phase growth reactions. As a result, ultrathin polymeric nanocomposite films with integrated DNA building blocks and organized inorganic semiconductor (CdS) and iron oxide quasi-linear nanostructures were formed. It has been demonstrated that interaction of deposited planar DNA/amphiphilic polycation complexes with bulk phase colloid inorganic cationic ligands (CdSe nano-rods) can result in formation of new highly organized hybrid bio-inorganic nanostructures via interfacial ligand exchange and self-organization processes. The methods developed can be useful for investigation of fundamental mechanisms of nanoscale structural organization and transformation processes in various inorganic and molecular systems including bio-molecular and bio-inorganic nanostructures. Also, those methods are relatively simple, environmentally safe and thus could prove to be efficient practical instruments of molecular nanotechnology with potential of design and cost-effective fabrication of new controlled-morphology organized planar inorganic and composite nanostructured materials. Possible applications of obtained nanostructures and future developments are also discussed.     

吴氏作图法的实验证明

"吴氏作图法"为高分子微球的大小和单体与稳定剂之比之间的关系提供了有效的定量数据分析方法.其基本点是,对于表面活性剂、离子基团或聚合物链所稳定的高分子微球,每个稳定剂所占有的高分子微球表面积(S)为一常数.过去的大量实验已证明,"吴氏作图法"适合应用于高分子纳米粒子.本文根据最近的实验结果,发现"吴氏作图法"同样适用于微米级高分子微球.这为分散聚合中设计和控制高分子微球的尺寸提供了理论依据.     

Nanoparticles on the basis of highly functionalized dextrans

New nanoparticles based on well-defined dextran esters were prepared by a dialysis process. Dextran was converted into a propionate with a degree of substitution of 1.70 and, subsequently, acylated under homogeneous reaction conditions with a pyroglutamic acid imidazolide, which is prepared in situ by conversion of pyroglutamic acid with N,N-carbonyldiimidazole. The synthesis path allows perfect control of the amphiphilicity and solubility. The highly functionalized polysaccharide derivative avoids the collapse of the nanostructure due to the prevention of hydrogen bond formation. The major fraction of the dextran propionate pyroglutamate nanoparticles investigated by SEM and AFM exhibits narrow size distribution with 370 nm as mean diameter and uniform spherical shape. The SEM image verifies that polymeric nanoparticles in the suspensions did not undergo any morphological changes within 3 weeks.     

SERS Investigation on the Polymerization of Carbazolyl-diacetylene Monolayers on Gold Surfaces

Surface Enhanced Raman Scattering experiments were performed on self-assembled carbazolyl-diacetylene monolayers chemisorbed on smooth gold substrates and UV irradiated. The Raman enhancement was ensured by depositing silver colloidal nanoparticles, which strongly increase the surface roughness. The co-existence of two polymer phases, characterized by different degree of order in the polymeric backbone, was detected by SERS results, which suggest a polymerization scheme with conjugated triple bonds nearly parallel to the plane of the metal surface.     

Biogenic nanosized systems based on selenium nanoparticles: Self-organization, structure, and morphology

Selenium-containing biogenic nanosized systems based on polymer stabilizers (PSts) of different natures are obtained. A comparative investigation of the kinetic parameters of self-organization and the dimensional characteristics of forming nanostructures and their shapes is performed by means of light scattering, UV spectrophotometry, atomic force microscopy, and small angle X-ray scattering. The effect of the nature of PSts on the structural and morphological parameters (hydrodynamic radius, mean-squared radius of gyration, selenium core radius, and density) of selenium-containing nanostructures is established.     

Tuning of Thermoresponsivity of a Poly(2‐alkyl‐2‐oxazoline) Block Copolymer by Interaction with Surface‐Active and Chaotropic Metallacarborane Anion

Thermoresponsive nanoparticles based on the interaction of metallacarboranes, bulky chaotropic and surface‐active anions, and poly(2‐alkyl‐2‐oxazoline) block copolymers were prepared. Recently, the great potential of metallacarboranes have been recognized in biomedicine and many delivery nanosystems have been proposed. However, none of them are thermoresponsive. Therefore, a thermoresponsive block copolymer, poly(2‐methyl‐2‐oxazoline)‐block‐poly(2‐n‐propyl‐2‐oxazoline) (PMeOx–PPrOx), was synthesized to encapsulate metallacarboranes. Light scattering, NMR spectroscopy, isothermal titration calorimetry, and cryogenic TEM were used to characterize all solutions of the formed nanoparticles. The cloud‐point temperature (T_CP) of the block copolymer was observed at 30 °C and polymeric micelles formed above this temperature. Cobalt bis(dicarbollide) anion (COSAN) interacts with both polymeric segments. Depending on the COSAN concentration, this affinity influenced the phase transition of the thermoresponsive PPrOx block. The T_CP shifted to lower values at a lower COSAN content. At higher COSAN concentrations, the hybrid nanoparticles are fragmented into relatively small pieces. This system is also thermoresponsive, whereby an increase in temperature leads to higher polymer mobility and COSAN release.