Tailored Synthesis of Intelligent Polymer Nanocapsules: An Investigation of Controlled Permeability and pH-Dependent Degradability

In this study, we present a new route to synthesize an intelligent polymer nanocapsule with an ultrathin membrane based on surface-initiated reversible addition–fragmentation chain-transfer polymerization. The key concept of our report is to use pH-responsive polydiethylaminoethylmethacrylate as a main membrane-generating component and a degradable disulfide bond to cross-link the membrane. The permeability of membrane, tuned by adjusting pH and using different lengths of the cross-linkers, was proven by showing a dramatic swelling behavior of the nanocapsules with the longest cross-linker from 560 nm at pH 8.0 to 780 nm at pH 4.0. Also, due to the disulfide cross-linker, degradation of the capsules using GSH as reducing agent was achieved which is further significantly promoted at pH 4.0. Using a rather long-chain dithiol cross-linker, the synthesized nanocapsules demonstrated a good permeability allowing that an enzyme myoglobin can be postencapsulated, where the pH controlled enzyme activity by switching membrane permeability was also shown

Adsorption of Poly(vinyl formamide-<i>co</i>-vinyl amine) (PVFA-<i>co</i>-PVAm) Polymers on Zinc, Zinc Oxide, Iron, and Iron Oxide Surfaces

The adsorption of poly(vinyl formamide) (PVFA) and the statistic copolymers poly(vinyl formamide-<i>co</i>-vinyl amine) (PVFA-<i>co</i>-PVAm) onto zinc and iron metal particles as well as their oxides was investigated. The adsorbates were characterized by means of XPS, DRIFT spectroscopy, wet chemical analysis, and solvatochromic probes. Dicyano-<i>bis</i>-(1,10-phenanthroline)-iron(II) (<b>1</b>), 3-(4-amino-3-methylphenyl)-7-phenyl-benzo-[1,2-<i>b</i>:4,5-<i>b</i>′]difuran-2,6-dione (<b>2</b>), and 4-<i>tert</i>-butyl-2-(dicyano-methylene)-5-[4-(diethylamino)-benzylidene]-Δ³-thiazoline (<b>3</b>) as solvatochromic probes were coadsorbed onto zinc oxide to measure various effects of surface polarity. The experimental findings showed that the adsorption mechanism of PVFA and PVFA-<i>co</i>-PVAm strongly depends on the degree of hydrolysis of PVFA and pH values and also on the kind of metal or metal oxide surfaces that were employed as adsorbents. The adsorption mechanism of PVFA/PVFA-<i>co</i>-PVAm onto zinc oxide and iron oxide surfaces is mainly affected by electrostatic interactions. Particularly in the region of pH 5, the adsorption of PVFA/PVFA-<i>co</i>-PVAm onto zinc and iron metal particles is additionally influenced by redox processes, dissolution, and complexation reactions

Manganese-Cycling Microbial Communities Inside Deep-Sea Manganese Nodules

Polymetallic nodules (manganese nodules) have been formed on deep sea sediments over millions of years and are currently explored for their economic potential, particularly for cobalt, nickel, copper, and manganese. Here we explored microbial communities inside nodules from the northeastern equatorial Pacific. The nodules have a large connected pore space with a huge inner surface of 120 m²/g as analyzed by computer tomography and BET measurements. X-ray photoelectron spectroscopy (XPS) and electron microprobe analysis revealed a complex chemical fine structure. This consisted of layers with highly variable Mn/Fe ratios (<1 to >500) and mainly of turbostratic phyllomanganates such as 7 and 10 Å vernadites alternating with layers of Fe-bearing vernadite (δ-MnO₂) epitaxially intergrown with amorphous feroxyhyte (δ-FeOOH). Using molecular 16S rRNA gene techniques (clone libraries, pyrosequencing, and real-time PCR), we show that polymetallic nodules provide a suitable habitat for prokaryotes with an abundant and diverse prokaryotic community dominated by nodule-specific Mn­(IV)-reducing and Mn­(II)-oxidizing bacteria. These bacteria were not detected in the nodule-surrounding sediment. The high abundance and dominance of Mn-cycling bacteria in the manganese nodules argue for a biologically driven closed manganese cycle inside the nodules relevant for their formation and potential degradation

Facile Approach to Grafting of Poly(2-oxazoline) Brushes on Macroscopic Surfaces and Applications Thereof

This study reports on a facile and versatile approach for modification of macroscopic surface via grafting of multifunctional poly­(2-oxazoline) molecules in brush-like conformation. For this purpose, carboxyl-terminated poly­(2-isopropyl-2-oxazoline) molecules have been synthesized by ring-opening cationic polymerization and subsequently grafted on underlined substrates by exploiting the ”grafting to” approach. A systematic variation in thickness of the grafted poly (2-isopropyl-2-oxazoline) brushes has been demonstrated. Polymer-modified surfaces have been characterized by means of a number of analytical tools including ellipsometry, X-ray photoelectron spectroscopy, ultraviolate spectroscopy, attenuated total reflection infrared spectroscopy and atomic force microscopy. Interestingly, poly­(2-isopropyl-2-oxazoline) molecules have been found to retain their physical properties even after grafting on macroscopic surfaces. Finally, fabricated polymer brushes have been used as platform for stabilization of inorganic nanoparticles on macroscopic surfaces

Polymer-Inorganic Coatings Containing Nanosized Sorbents Selective to Radionuclides. 1. Latex/Cobalt Hexacyanoferrate(II) Composites for Cesium Fixation

Here we present a new approach to improve fixation of radionuclides on contaminated surfaces and eliminate their migration after nuclear accidents. The approach consists in fabrication of latex composite coatings, which combine properties of polymeric dust-suppressors preventing radionuclides migration with aerosols and selective inorganic sorbents blocking radionuclides leaching under contact with ground waters and atmospheric precipitates. Latex/cobalt hexacyanoferrate­(II) (CoHCF) composites selective to cesium radionuclides were synthesized via “in situ” growth of CoHCF crystal on the surface of carboxylic or amino latexes using surface functional groups as ion-exchange centers for binding precursor ions Co²⁺ and [Fe­(CN)₆]^4–. Casting such composite dispersions with variable content of CoHCF on ¹³⁷Cs-contaminated sand has yielded protective coatings, which reduced cesium leaching to 0.4% compared to 70% leaching through original latex coatings. ¹³⁷Cs migration from the sand surface was efficiently minimized when the volume fraction of CoHCF in the composite film was as low as 0.46–1.7%

Controlling the Growth of Palladium Aerogels with High-Performance toward Bioelectrocatalytic Oxidation of Glucose

We report the controllable synthesis of Pd aerogels with high surface area and porosity by destabilizing colloidal solutions of Pd nanoparticles with variable concentrations of calcium ions. Enzyme electrodes based on Pd aerogels co-immobilized with glucose oxidase show high activity toward glucose oxidation and are promising materials for applications in bioelectronics

Autotemplate Microcapsules of CaCO₃/Pectin and Nonstoichiometric Complexes as Sustained Tetracycline Hydrochloride Delivery Carriers

New types of composites were obtained by an autotemplate method for assembling hollow CaCO₃ capsules by using pH-sensitive polymers. Five pectin samples, which differ in the methylation degree and/or amide content, and some nonstoichiometric polyelectrolyte complex dispersions, prepared with the pectin samples and poly­(allylamine hydrochloride), were used to control the crystal growth. The morphology of the composites was investigated by scanning electron microscopy, and the polymorphs characteristics were investigated by FTIR spectroscopy. The presence of the polymer in the composite particles was evidenced by X-ray photoelectron spectroscopy, particle charge density, and zeta-potential. The new CaCO₃/pectin hollow capsules were tested as a possible matrix for a tetracycline hydrochloride carrier. The kinetics of the drug release mechanism was followed using Higuchi and Korsmeyer–Peppas mathematical models

Adsorption of Poly(vinylformamide-<i>co</i>-vinylamine) Polymers (PVFA-<i>co</i>-PVAm) on Copper

The adsorption of poly­(vinylformamide) (PVFA) and its derivative statistical copolymer poly­(vinyl-formamide-<i>co</i>-vinylamine) (PVFA-<i>co</i>-PVAm) on metallic copper and copper oxide particles as well as planar copper surfaces was studied as a function of the degree of hydrolysis of PVFA, the pH, and the polymer concentration in solution. The chemical composition and molecular structure of the PVFA-<i>co</i>-PVAm layers were investigated by surface-sensitive spectroscopic methods such as XPS, DRIFT spectroscopy, and ellipsometry. The findings allowed us to explain the adsorption mechanisms and the forces driving the PVFA-<i>co</i>-PVAm adsorption. It was shown that PVFA-<i>co</i>-PVAm layers thicker than 30 nm are able to protect the planar copper surface against corrosive attack

Polymer–Inorganic Coatings Containing Nanosized Sorbents Selective to Radionuclides. 2. Latex/Tin Oxide Composites for Cobalt Fixation

Colloidal tin oxide with an average particle size of 3.5 nm, which was ex-situ synthesized by the sol–gel method, has been attached to the surface of amino-functionalized poly­(acrylate-<i>co</i>-silane) latex particles with a diameter of 100 nm to yield a composite with selective sorption properties toward Co²⁺ ions. Electrokinetic properties and the colloidal stability of the synthesized latex/SnO₂ composites have been evaluated in dependence on SnO₂ content and pH; the sorption capacity and distribution coefficients of composites for Co²⁺ ions were in accordance with the SnO₂ content and its sorption performance as an individual compound. Composite coatings obtained by casting latex/SnO₂ dispersions on quartz sand spiked with ⁵⁷Co radionuclide have efficiently eliminated radionuclides migration from the surface when the SnO₂ volume fraction in the film was 3.5–4.7%. Furthermore, at these SnO₂ loadings, the composite coatings retained the coherent structure of the original latex coating with SnO₂ particles homogeneously distributed over the film thickness. The presence of competing Ca²⁺ ions in the leaching media at a concentration of above 0.01 mol/L results in a decrease of the distribution coefficients of the latex/SnO₂ composite and significantly higher ⁵⁷Co leaching. The value of the distribution coefficient of the sorption material to be used in latex composite coatings to prevent migration of radionuclides shall be close to 10⁶ mL/g

Effect of Surface Properties on the Microstructure, Thermal, and Colloidal Stability of VB₂ Nanoparticles

Recent years have seen an increasing research effort focused on nanoscaling of metal borides, a class of compounds characterized by a variety of crystal structures and bonding interactions. Despite being subject to an increasing number of studies in the application field, comprehensive studies of the size-dependent structural changes of metal borides are limited. In this work, size-dependent microstructural analysis of the VB₂ nanocrystals prepared by means of a size-controlled colloidal solution synthesis is carried out using X-ray powder diffraction. The contributions of crystallite size and strain to X-ray line broadening is separated by introducing a modified Williamson–Hall method taking into account different reflection profile shapes. For average crystallite sizes smaller than ca. 20 nm, a remarkable increase of lattice strain is observed together with a significant contraction of the hexagonal lattice decreasing primarily the cell parameter <i>c</i>. Exemplary density-functional theory calculations support this trend. The size-dependent lattice contraction of VB₂ nanoparticles is associated with the decrease of the interatomic boron distances along the <i>c</i>-axis. The larger fraction of constituent atoms at the surface is formed by boron atoms. Accordingly, lattice contraction is considered to be a surface effect. The anisotropy of the size-dependent lattice contraction in VB₂ nanocrystals is in line with the higher compressibility of its macroscopic bulk structure along the <i>c</i>-axis revealed by theoretical calculations of the respective elastic properties. Transmission electron microscopy indicates that the VB₂ nanocrystals are embedded in an amorphous matrix. X-ray photoelectron spectroscopy analysis reveals that this matrix is mainly composed of boric acid, boron oxides, and vanadium oxides. VB₂ nanocrystals coated with these oxygen containing amorphous species are stable up to 789 °C as evidenced by thermal analysis and temperature dependent X-ray diffraction measurements carried out under Ar atmosphere. Electrokinetic measurement indicates that the aqueous suspension of VB₂ nanoparticles with hydroxyl groups on the surface region has a good stability at neutral and basic pH arising from electrostatic stabilizatio