Characterization of polysulfone and polysulfone/vanillin microcapsules by 1H NMR spectroscopy, solid-state 13C CP/MAS-NMR spectroscopy, and N2 adsorption-desorption analyses

Core-shell droplets and microcapsules formed through liquid-liquid phase separation of a colloid-polymer mixture

Microcapsules allow for the controlled containment, transport, and release of cargoes ranging from pharmaceuticals to fragrances. Given the interest from a variety of industries in microcapsules and other core-shell structures, a multitude of fabrication strategies exist. Here, we report on a method relying on a mixture of temperature-responsive microgel particles, poly(N-isopropylacrylamide) (pNIPAM), and a polymer which undergo fluid-fluid phase separation. At room temperature this mixture separates into colloid-rich (liquid) and colloid-poor (gas) fluids. By heating the sample above a critical temperature where the microgel particles shrink dramatically and develop a more deeply attractive interparticle potential, the droplets of the colloid-rich phase become gel-like. As the temperature is lowered back to room temperature, these droplets of gelled colloidal particles reliquefy and phase separation within the droplet occurs. This phase separation leads to colloid-poor droplets within the colloid-rich droplets surrounded by a continuous colloid-poor phase. The gas/liquid/gas all-aqueous double emulsion lasts only a few minutes before a majority of the inner droplets escape. However, the colloid-rich shell of the core-shell droplets can solidify with the addition of salt. That this method creates core-shell structures with a shell composed of stimuli-sensitive microgel colloidal particles using only aqueous components makes it attractive for encapsulating biological materials and making capsules that respond to changes in, for example, temperature, salt concentration, or pH.

Enhanced hydrophilicity and antifouling performance of PES-C/emodin ultrafiltration membrane

In this article, an ultrafiltration membrane was fabricated from phenolphthalein polyethersulfone (PES-C) modified with emodin using a phase-inversion method. ATR-FTIR and UV-vis analysis showed that emodin had good compatibility with the PES-C ultrafiltration membrane. SEM showed that the prepared ultrafiltration membranes consisted of a porous skin layer and a macroporous support sublayer. The contact angle value of the pure PES-C ultrafiltration membrane was 77.71° and that of the PES-C ultrafiltration membrane blended with 0.105 wt.% emodin decreased to 65.71°, which explained the fact why its pure water flux significantly increased from 190 L/m2·h to 387 L/m2·h. The antifouling properties of the obtained ultrafiltration membranes were assessed by static protein adsorption, bacterial adhesion, antibacterial tests, and filtration experiments with BSA. The PES-C (13.895 wt.%)/emodin (0.105 wt.%) ultrafiltration membrane presented the lowest protein adsorption rate (1.44%), the highest flux recovery ratio (57%), and the largest inhibition zone diameter (3.0 ± 0.06 mm). Compared with that of the pure PES-C ultrafiltration membrane, the bacterial adhesion effect of the PES-C/emodin (0.105 wt.%) ultrafiltration membrane was significantly reduced. In addition, PES-C incorporated into the emodin ultrafiltration membrane had excellent stability in a deionized water system.

Tuning the Encapsulation of Simple Fragrances with an Amphiphilic Graft Copolymer

The encapsulation of poorly water-soluble compounds such as perfumes, flavors, and bioactive molecules is a key step in the formulation of a large variety of consumer products in the fields of household care and personal care. We study the encapsulation ability of an amphiphilic poly(ethylene glycol)-graft-poly(vinyl acetate) (PEG-g-PVAc) graft copolymer, extending the focus to the entire phase diagram of polymer/perfume/water systems with three common natural fragrances. The three perfume molecules (2-phenyl ethanol, L-carvone, and α-pinene) possess different water affinities, as expressed by their octanol/water partition coefficients. The investigation of the polymorphism of PEG-g-PVAc in these systems is carried out by means of dynamic light scattering, small-angle X-ray scattering, NMR spectroscopy, and confocal laser scanning microscopy. The results presented here demonstrate that the choice of fragrance can dramatically affect the supramolecular structures formed by the polymer in aqueous solution, with important consequences on formulations of industrial interest such as the demixing of complex perfume blends when one or more of the components have no chemical affinity for any of the polymer blocks.

High-capacity extraction chromatographic materials based on polysulfone microcapsules for the separation and preconcentration of lanthanides from aqueous solution

Extractant-loaded polysulfone (PS) capsules suitable for the separation and preconcentration of rare earth ions from acidic media have been prepared and characterized. Specifically, PS macro- and microcapsules have been impregnated with bis(2-ethylhexyl)phosphoric acid (HDEHP), and their performance in the extraction of europium (Eu³⁺) from nitric acid solution evaluated. The HDEHP-loaded microcapsules were found to exhibit sorption efficiency superior to those of analogous macrocapsules. Comparison to a conventional (i.e., commercial) extraction chromatographic (EXC) material (Ln•Resin), comprising HDEHP-loaded beads of poly(methyl methacrylate) (PMMA) of comparable size (50-100 µm), showed that the capacity of the HDEHP-loaded microcapsules for europium is ca. 2.5-fold greater than that of the conventional material. This larger capacity is the apparent result of both the higher extractant loading achievable with the microcapsules and an unexpected change in the complexation stoichiometry of europium by HDEHP upon extractant encapsulation. The microcapsule-based sorbent equaled or exceeded the performance of the commercial EXC material in other respects as well, most notably uptake kinetics and column efficiency, making it a promising alternative to established EXC resins.

Highly stiff yet elastic microcapsules incorporating cellulose nanofibrils

Microcapsules with high mechanical stability and elasticity are desirable in a variety of contexts. We report a single-step method to fabricate such microcapsules by microfluidic interfacial complexation between high stiffness cellulose nanofibrils (CNF) and an oil-soluble cationic random copolymer. Single-capsule compression measurements reveal an elastic modulus of 53 MPa for the CNF-based capsule shell with complete recovery of deformation from strains as large as 19%. We demonstrate the ability to manipulate the shell modulus by the use of polyacrylic acid (PAA) as a binder material, and observe a direct relationship between the shell modulus and the PAA concentration, with moduli as large as 0.5 GPa attained. These results demonstrate that CNF incorporation provides a facile route for producing strong yet flexible microcapsule shells.

Preparation of high encapsulation efficiency fragrance microcapsules and their application in textiles

Poly(1,4-butanediol dimethacrylate) (PBDDMA) microcapsules with PBDDMA as the shell and dementholized peppermint oil (DPO) fragrance as the core material have been synthesized through a novel interfacial free-radical polymerization.

Plasmonic-polymer hybrid hollow microbeads for surface-enhanced Raman scattering (SERS) ultradetection

Hybrid composites are known to add functionality to plasmonic nanomaterials. Although these substrates can be produced by common synthetic methods, the percentage of metal loaded into the functional material is usually small. Herein, we exploit a phase inversion precipitation method to incorporate large amounts of silver nanoparticles inside the polymeric matrix of polysulfone microbeads. The composite material combines the high SERS activity resulting from the plasmonic coupling of highly interacting nanoparticles and the ability to accumulate analytes of the polysulfone porous support. This allows for the quantitative SERS detection down to the nanomolar level, with a liner response that extends over an impressive concentration range of five orders of magnitude.

Probing the nanostructure, interfacial interaction, and dynamics of chitosan-based nanoparticles by multiscale solid-state NMR

Chitosan-based nanoparticles (NPs) are widely used in drug and gene delivery, therapy, and medical imaging, but a molecular-level understanding of the internal morphology and nanostructure size, interface, and dynamics, which is critical for building fundamental knowledge for the precise design and efficient biological application of the NPs, remains a great challenge. Therefore, the availability of a multiscale (0.1-100 nm) and nondestructive analytical technique for examining such NPs is of great importance for nanotechnology. Herein, we present a new multiscale solid-state NMR approach to achieve this goal for the investigation of chitosan-poly(N-3-acrylamidophenylboronic acid) NPs. First, a recently developed (13)C multiple cross-polarization magic-angle spinning (MAS) method enabled fast quantitative determination of the NPs' composition and detection of conformational changes in chitosan. Then, using an improved (1)H spin-diffusion method with (13)C detection and theoretical simulations, the internal morphology and nanostructure size were quantitatively determined. The interfacial coordinated interaction between chitosan and phenylboronic acid was revealed by one-dimensional MAS and two-dimensional (2D) triple-quantum MAS (11)B NMR. Finally, dynamic-editing (13)C MAS and 2D (13)C-(1)H wide-line separation experiments provided details regarding the componential dynamics of the NPs in the solid and swollen states. On the basis of these NMR results, a model of the unique nanostructure, interfacial interaction, and componential dynamics of the NPs was proposed.

Preparation and characterization of light-sensitive microcapsules based on a liquid crystalline polyester

Photosensitive microcapsules and membranes based on poly(α-methylstilbenesebacoate-co-α-methylstilbeneisophthalate), containing the photosensitive α-methylstilbene moiety, were prepared by a phase-inversion precipitation process. In order to simulate the morphology and behavior of the microcapsule shell under UV irradiation, an exhaustive characterization of a membrane was first performed by ESEM, POM, AFM, and contact angle measurements. The prepared microcapsules contained either chloroform or a concentrated solution of vanillin in chloroform as the core; in all cases, before UV irradiation, their outer surface appeared smooth and dense. The influence of vanillin on microcapsule cross-section morphology was observed by ESEM microscopy. Release of vanillin in water, at room temperature, was markedly influenced by UV irradiation: in the absence of irradiation, it was practically negligible, while when microcapsules were submitted to continuous irradiation with UV light, the surface morphology of the capsules changed drastically and vanillin started to be released after ca. 20 min of irradiation.