Synthesis and Characterization of a Thermoresponsive Copolymer with an LCST-UCST-like Behavior and Exhibiting Crystallization.

In this work, the diblock copolymer methoxy-poly(ethylene glycol)--poly(ε-caprolactone) (MPEG--PCL) was synthesized with a block composition that allows this polymer in aqueous media to possess both an upper critical solution temperature (UCST) and a lower critical solution temperature (LCST) over a limited temperature interval. The value of the UCST, associated with crystallization of the PCL-block, depended on heating (H) or cooling (C) of the sample and was found to be CP = 32 °C and CP = 23 °C, respectively. The LCST was not affected by the heating or cooling scans; assumed a value of 52 °C (CP = CP).

Intercalation of CO Selected by Type of Interlayer Cation in Dried Synthetic Hectorite.

Clay minerals are abundant in caprock formations for anthropogenic storage sites for CO, and they are potential capture materials for CO postcombustion sequestration. We investigate the response to CO exposure of dried fluorohectorite clay intercalated with Li, Na, Cs, Ca, and Ba. By powder X-ray diffraction, we demonstrate that fluorohectorite with Na, Cs, Ca, or Ba does not swell in response to CO and that Li-fluorohectorite does swell.

Interactions in Aqueous Mixtures of Cationic Hydroxyethyl Cellulose and Different Anionic Bile Salts.

It is known that the reduction of blood cholesterol can be accomplished through foods containing a large number of dietary fibers; this process is partially related to the binding of bile salt to fibers. To gain new insights into the interactions between dietary fibers and bile salts, this study investigates the interactions between cationic hydroxyethyl cellulose (catHEC) and sodium deoxycholate (NaDC) or sodium cholate (NaC), which have a similar structure. Turbidity measurements reveal strong interactions between catHEC and NaDC, and under some conditions, macroscopic phase separation occurs.

Influence of Lysine and TRITC Conjugation on the Size and Structure of Dextran Nanoconjugates with Potential for Biomolecule Delivery to Neurons.

As a potent nonviral system for biomolecular delivery to neurons via their axons, we have studied molecular characteristics of lysinated fluorescent dextran nanoconjugates with degrees of conjugation of 0.54-15.2 mol lysine and 0.

CO Adsorption Enhanced by Tuning the Layer Charge in a Clay Mineral.

Due to the compact two-dimensional interlayer pore space and the high density of interlayer molecular adsorption sites, clay minerals are competitive adsorption materials for carbon dioxide capture. We demonstrate that with a decreasing interlayer surface charge in a clay mineral, the adsorption capacity for CO increases, while the pressure threshold for adsorption and swelling in response to CO decreases. Synthetic nickel-exchanged fluorohectorite was investigated with three different layer charges varying from 0.

Glyceraldehyde as an Efficient Chemical Crosslinker Agent for the Formation of Chitosan Hydrogels.

The rheological changes that occur during the chemical gelation of semidilute solutions of chitosan in the presence of the low-toxicity agent glyceraldehyde (GCA) are presented and discussed in detail. The entanglement concentration for chitosan solutions was found to be approximately 0.2 wt.

Small-Angle Neutron Scattering Characterization of SrCl-ENG Composites for Thermochemical Heat Storage.

This work presents an in situ nanoscale structural characterization of a SrCl-expanded natural graphite (ENG) composite during ammonia absorption and desorption using small-angle neutron scattering (SANS) together with X-ray powder diffraction and sorption measurements. For the processing of the composite material SANS patterns, we developed and implemented two methods, which showed comparable results. The study allowed following the evolution of the SrCl particles and the nanopores inside the particles during five sorption cycles.

Unmodified Clay Nanosheets at the Air-Water Interface.

Quasi-two-dimensional (2D) nanolayers, such as graphene oxide or clay layers, adhere to gas-liquid or liquid-liquid interfaces. Particularly, clays are of wide general interest in this context because of their extensive and crucial use as Pickering emulsion stabilizers, as well as for their ability to provide colloidosome capsules. So far, clays could only be localized at oil-water or air-saline-water interfaces in aggregated states, while our results now show that clay nanosheets without any modification can be located at air-deionized-water interfaces.

Spherical Micelles with Nonspherical Cores: Effect of Chain Packing on the Micellar Shape.

Self-assembly of amphiphilic polymers into micelles is an archetypical example of a "self-confined" system due to the formation of micellar cores with dimensions of a few nanometers. In this work, we investigate the chain packing and resulting shape of C -PEO micelles with semicrystalline cores using small/wide-angle X-ray scattering (SAXS/WAXS), contrast-variation small-angle neutron scattering (SANS), and nuclear magnetic resonance spectroscopy (NMR). Interestingly, the -alkyl chains adopt a rotator-like conformation and pack into prolate ellipses (axial ratio ϵ ≈ 0.

From Single-Core Nanoparticles in Ferrofluids to Multi-Core Magnetic Nanocomposites: Assembly Strategies, Structure, and Magnetic Behavior.

Iron oxide nanoparticles are the basic components of the most promising magnetoresponsive nanoparticle systems for medical (diagnosis and therapy) and bio-related applications. Multi-core iron oxide nanoparticles with a high magnetic moment and well-defined size, shape, and functional coating are designed to fulfill the specific requirements of various biomedical applications, such as contrast agents, heating mediators, drug targeting, or magnetic bioseparation. This review article summarizes recent results in manufacturing multi-core magnetic nanoparticle (MNP) systems emphasizing the synthesis procedures, starting from ferrofluids (with single-core MNPs) as primary materials in various assembly methods to obtain multi-core magnetic particles.

How Detergents Dissolve Polymeric Micelles: Kinetic Pathways of Hybrid Micelle Formation in SDS and Block Copolymer Mixtures.

Mixtures of amphiphilic polymers and surfactants are used in a wide range of applications, e.g., pharmaceuticals, detergents, cosmetics, and drug delivery systems.

Antitubercular nanocarrier monotherapy: Study of In Vivo efficacy and pharmacokinetics for rifampicin.

Tuberculosis represents a major global health problem for which improved approaches are needed to shorten the course of treatment and to combat the emergence of resistant strains. The development of effective and safe nanobead-based interventions can be particularly relevant for increasing the concentrations of antitubercular agents within the infected site and reducing the concentrations in the general circulation, thereby avoiding off-target toxic effects. In this work, rifampicin, a first-line antitubercular agent, was encapsulated into biocompatible and biodegradable polyester-based nanoparticles.

Poly(2-isopropyl-2-oxazoline)--poly(lactide) (PiPOx--PLA) Nanoparticles in Water: Interblock van der Waals Attraction Opposes Amphiphilic Phase Separation.

Poly(2-isopropyl-2-oxazoline)--poly(lactide) (PiPOx--PLA) diblock copolymers comprise two miscible blocks: the hydrophilic and thermosensitive PiPOx and the hydrophobic PLA, a biocompatible and biodegradable polyester. They self-assemble in water, forming stable dispersions of nanoparticles with hydrodynamic radii ( ) ranging from ∼18 to 60 nm, depending on their molar mass, the relative size of the two blocks, and the configuration of the lactide unit. Evidence from H nuclear magnetic resonance spectroscopy, light scattering, small-angle neutron scattering, and cryo-transmission electron microscopy indicates that the nanoparticles do not adopt the typical core-shell morphology.

Self-assembly and nanostructure of poly(vinyl alcohol)-graft-poly(methyl methacrylate) amphiphilic nanoparticles.

Hypothesis: Poly(vinyl alcohol)-g-poly(methyl methacrylate) (PVA-g-PMMA) amphiphilic copolymers self-assemble to form multi-micellar colloidal systems.

Experiments: A PVA-g-PMMA copolymer containing 16-17% w/w of PMMA was synthesized by the free radical graft polymerization of methyl methacrylate on a PVA backbone by utilizing cerium(IV) ammonium nitrate as initiator and tetramethylethylenediamine (TEMED) as initiation activator. The aggregation behavior of the copolymer in water was comprehensively characterized by dynamic light scattering (DLS) and static light scattering (SLS), small angle neutron scattering (SANS), asymmetrical flow field-flow fractionation (A4F) and transmission electron microscopy (TEM).

Chitosan-graft-poly(methyl methacrylate) amphiphilic nanoparticles: Self-association and physicochemical characterization.

In this work, we synthesized and characterized the self-assembly behavior of a chitosan-poly(methyl methacrylate) graft copolymer and the properties of the formed nanoparticles by static and dynamic light scattering, small-angle neutron scattering, and transmission electron microscopy. Overall, our results indicate that the hydrophobization of the chitosan side-chain with PMMA leads to a complex array of small unimolecular and/or small-aggregation number "building blocks" that further self-assemble into larger amphiphilic nanoparticles.

A nano-silicate material with exceptional capacity for CO capture and storage at room temperature.

In order to mitigate climate change driven by the observed high levels of carbon dioxide (CO) in the atmosphere, many micro and nano-porous materials are being investigated for CO selectivity, capture and storage (CCS) purposes, including zeolites, metal organic frameworks (MOFs), functionalized polymers, activated carbons and nano-silicate clay minerals. Key properties include availability, non-toxicity, low cost, stability, energy of adsorption/desorption, sorbent regeneration, sorption kinetics and CO storage capacity. Here, we address the crucial point of the volumetric capture and storage capacity for CO in a low cost material which is natural, non-toxic, and stable.

Sample cell for studying liquid interfaces with an in situ electric field using X-ray reflectivity and application to clay particles at oil-oil interfaces.

Commissioning results of a liquid sample cell for X-ray reflectivity studies with an in situ applied electrical field are presented. The cell consists of a Plexiglas container with lateral Kapton windows for air-liquid and liquid-liquid interface studies, and was constructed with grooves to accept plate electrodes on the walls parallel to the direction of the beam. Both copper and ITO plate electrodes have been used, the latter being useful for simultaneous optical studies.

Effect of PEGylation on the stability of thermoresponsive nanogels.

In biomedical applications, PEGylation is frequently utilized to enhance the nanoparticles (NPs) capability for long systemic circulation times in the blood and it is also crucial to stabilize the NPs and thereby minimize their ability to agglomerate. In this study, we have synthesized poly(N-isopropylacrylamide) (PNIPAAM) nanogels with covalently attached PEG chains of different length and PEG coating densities. It is observed that in the absence of PEG coating the nanogels aggregate at elevated temperatures.

Effect of PCL end-groups on the self-assembly process of Pluronic in aqueous media.

Understanding self-assembly of amphiphilic copolymers in aqueous solution is an important issue in many areas, e.g., in order to tailor-make carriers for drugs and genes.

Structural and Rheological Properties of Temperature-Responsive Amphiphilic Triblock Copolymers in Aqueous Media.

Thermoresponsive amphiphilic biodegradable block copolymers of the type poly(ε-caprolactone-co-lactide)-poly(ethylene glycol)-poly(ε-caprolactone-co-lactide) (PCLA-PEG-PCLA) have great potential for various biomedical applications. In the present study, we have surveyed the effects of PEG spacer length (m = 1000 and 1500), temperature, and polymer concentration on the self-assembling process to form supramolecular structures in aqueous solutions of the PCLA-PEG-PCLA copolymer. This copolymer has a lower critical solution temperature, and the cloud point depends on both concentration and PEG length.

Novel Structural Changes during Temperature-Induced Self-Assembling and Gelation of PLGA-PEG-PLGA Triblock Copolymer in Aqueous Solutions.

The thermoresponsive amphiphilic block copolymer poly(d,l-lactic acid-co-glycolic acid)-block-poly(ethylene glycol)-block-poly(d,l-lactic acid-co-glycolic acid) (PLGA-PEG -PLGA), which exhibits a reversible temperature-induced sol-gel transition at higher polymer concentrations in aqueous solution has attached a great deal of interest because of its potential in biomedical applications. In the present work, the length of the hydrophobic PLGA blocks is kept constant, whereas the length of the hydrophilic PEG block is altered and this variation has a pronounced impact on the phase behavior of the aqueous samples and the structure of the polymer. A short PEG block promotes gelation at a low temperature, whereas a longer PEG block shifts the gelation point to higher temperature.

Effects of Bile Salt Sodium Glycodeoxycholate on the Self-Assembly of PEO-PPO-PEO Triblock Copolymer P123 in Aqueous Solution.

A comprehensive experimental study on the interaction between the PEO-PPO-PEO block copolymer P123 (EO20PO68EO20) and the anionic bile salt sodium glycodeoxycholate (NaGDC) in water has been performed. The work was aimed at investigating the suitability of using P123 as bile salt sequestrant beside the fundamental aspects of PEO-PPO-PEO block copolymer-bile salt interactions. Various experimental techniques including dynamic and static light scattering, small-angle X-ray scattering, and differential scanning calorimetry (DSC) were employed in combination with electrophoretic mobility measurements.

Tailoring the amphiphilicity and self-assembly of thermosensitive polymers: end-capped PEG-PNIPAAM block copolymers.

In this work we report on the synthesis and self-assembly of a thermo-sensitive block copolymer system of n-octadecyl-poly(ethylene glycol)-block-poly(N-isopropylacrylamide), abbreviated as C18-PEGn-b-PNIPAAMm. We present a facile synthetic strategy for obtaining highly tunable thermo-responsive block copolymers starting from commercial PEG-based surfactants (Brij®) or a C18 precursor and conjugating with PNIPAAM via an Atom Transfer Radical Polymerization (ATRP) protocol. The self-assembly and detailed nanostructure were thoroughly investigated in aqueous solutions using both small-angle X-ray and neutron scattering (SAXS/SANS) combined with turbidity measurements.

Aggregation of tetrameric acids in aqueous media studied by small-angle neutron scattering.

This article presents the characterization of two self-associated structures, a C(80)-tetraacid (also known as ARN), which is an aliphatic molecule present in crude oil and responsible for the formation of deposits, and BP-10, a molecule designed to model the properties of the C(80)-tetraacid. These molecules have four carboxylic functions at the end of four interconnected hydrocarbon chains and can be dissolved in aqueous solution and in basic media. In this paper we have used small-angle neutron scattering (SANS) as the main method to study the tetrameric acids in solution.

Oxygen-controlled phase segregation in poly(N-isopropylacrylamide)/laponite nanocomposite hydrogels.

The combination of nanoparticles and polymers into nanocomposite gels has been shown to be a promising route to creating soft materials with new or improved properties. In the present work, we have made use of Laponite nanoparticles in combination with a poly(N-isopropylacrylamide) (PNIPAAM) polymer and describe a phenomenon taking place during the polymerization and gelling of this system. The presence of small amounts of oxygen in the process induces two distinctly separated phases, one polymer-rich and one polymer-deficient water-clay phase.