Polymer Xerogel Research Articles

Photostabilisation of an omniphobic, drop-castable surface coating by transformation of a self-assembled supramolecular xerogel into a covalent polymer xerogel

Simple drop-casting of a new gelator, incorporating a diacetylene core and fluorous ponytails, yields porous, omniphobic surface coatings.

Morphological analysis of corn xerogel and its shape shifting in water

This research aims to develop cereal-based dried polymer gel (xerogel), investigate the use of these products as two-dimensional food paradigms that can be morphed into 3D forms, and quantify their hydrostimulated nature. Corn hydrogel (5 g/100 mL) was dried using a sessile drop drying process to obtain 2D flat corn xerogel. The upper and bottom portion of corn polymer xerogel was characterized as non-porous and porous nature. The FTIR spectroscopy discovered that the chemical nature of xerogel was not changed significantly from that of corn flour. Non-thermal plasma-treated corn polymer xerogel programmed into different 3D shapes like a spiral, and tubular through water stimuli (30 s). Corn xerogel self-bends due to its anisotropic nature. In this study, angle, height, the curve of bending are measured as indicators of shape change. Using hydro-stimulated shape changes, this paper discusses a new technology for designing attractive pasta made of 2D corn polymer xerogel. • Plasma induced corn xerogel resulted good adhesion properties. • Characterization of corn xerogel reveals dense top and porous bottom surfaces. • Corn xerogel with ethyl cellulose coating triggered 3D shape change in water.

Humidity-sensitive polymer xerogel actuators prepared by biaxial pre-stretching and drying.

This communication provides a facile approach to prepare a polyacrylamide polymer xerogel film which exhibits humidity-sensitive actuation and ionic conductivity.

Stochastic models of disordered mesoporous materials for small-angle scattering analysis and more

Small-angle scattering of either x-rays (SAXS) or neutrons (SANS) is one of the few experimental techniques that can be used to study the structure of porous materials on the entire range from 1 to 100 nm, which makes it particularly suited for mesoporous materials. Because the information in scattering patterns is a correlation function, models are generally needed to convert data into structurally meaningful information. In this paper, we discuss five stochastic models that capture qualitatively different disordered structures, notably concerning the connectivity and the tortuosity of the phases. The models are two variants of the Boolean model, a dead leaves model, as well as two clipped Gaussian field models. The paper is illustrated with the SAXS analysis of a polymer xerogel, of a fumed silica as well as of a mesoporous alumina, and the fitted models are compared with pore size distributions derived from nitrogen adsorption. In the case of the xerogel and silica it is possible to pinpoint a single model that describes the structure best. In the case of the alumina, however, the scattering cannot discriminate the models. Even so, the models are useful because they enable one to quantitate the structural ambiguity of the SAXS data.

Slow dynamics of nanocomposite polymer aerogels as revealed by X-ray photocorrelation spectroscopy (XPCS)

We report on a novel slow dynamics of polymer xerogels, aerogels, and nanocomposite aerogels with iron oxide nanoparticles, as revealed by X-ray photon correlation spectroscopy. The polymer aerogel and its nanocomposite aerogels, which are porous in nature, exhibit hyper-diffusive dynamics at room temperature. In contrast, non-porous polymer xerogels exhibit an absence of this peculiar dynamics. This slow dynamical process has been assigned to a relaxation of the characteristic porous structure of these materials and not to the presence of nanoparticles.

Novel synthesis route of metal doped resorcinol–formaldehyde polymer xerogels with tuned porosity

The complex preparation route of resorcinol–formaldehyde (RF) organogels offers several opportunities for developing metal-containing mesoporous carbon gels. Incorporation of the metal during the sol–gel stage, however, is not always trivial because it can inhibit the polycondensation reaction. A new route is proposed to circumvent this difficulty in the case of molybdenum. We show that a long enough pre-polymerization period (PP) (minimum 110min in our case) before adding the metal salt yields a mesoporous polymer monolith. Scanning electron microscopy (SEM), low temperature N2 adsorption and small angle X-ray scattering (SAXS) investigations reveal how changing the PP modifies the structure at various length scales. Adjusting the PP offers a new means of tuning the mesoporosity of the resulting molybdenum-containing RF gels.

Polymer–xerogel composites for controlled release wound dressings

Many polymers and composites have been used to prepare active wound dressings. These materials have typically exhibited potentially toxic burst release of the drugs within the first few hours followed by a much slower, potentially ineffective drug release rate thereafter. Many of these materials also degraded to produce inflammatory and cytotoxic products. To overcome these limitations, composite active wound dressings were prepared here from two fully biodegradable and tissue compatible components, silicon oxide sol–gel (xerogel) microparticles that were embedded in tyrosine-poly(ethylene glycol)-derived poly(ether carbonate) copolymer matrices. Sustained, controlled release of drugs from these composites was demonstrated in vitro using bupivacaine and mepivacaine, two water-soluble local anesthetics commonly used in clinical applications. By systematically varying independent compositional parameters of the composites, including the hydrophilic:hydrophobic balance of the tyrosine-derived monomers and poly(ethylene glycol) in the copolymers and the porosity, weight ratio and drug content of the xerogels, drug release kinetics approaching zero-order were obtained. Composites with xerogel mass fractions up to 75% and drug payloads as high as 13% by weight in the final material were fabricated without compromising the physical integrity or the controlled release kinetics. The copolymer–xerogel composites thus provided a unique solution for the sustained delivery of therapeutic agents from tissue compatible wound dressings.

고다공성 카본 에어로젤(C-Aerogel) 표면 특성

The pyrolysized carbon xerogel and aerogels were prepared from the sol-gel polymerization of resorcinol-formaldehyde(RF) followed by the dry process under ambient pressure and supercritical carbon dioxide condition respectively. The thermal behaviour of RF polymer xerogel was investigated with TGA analyzer to correspond with the pyrolysis process. The surface properties such as particle size, morphology and the point of zero charge of the pyrolysized porous carbon aerogels were studied for the precious metal catalyst supported media. It was found that the volume of the polymer aerogel decreased because of the significant linear shrinkage and weight loss of polymer gel during the carbonization. The point of zero charge of the carbon aerogel pyrolysized at <TEX>$1050^{\circ}C$</TEX> under inert gas flow was about 10.

A Flexible Approach to the Preparation of Polymer Scaffolds for Tissue Engineering

Porous polyester thermoset xerogels have been produced via sol-gel chemistry as a first step in the development of sol-gel derived tissue engineering scaffolds templated by replica molding and/or salt leaching. The pore structure of these untemplated thermosets is tunable and can be altered independent of or in tandem with alterations in composition. Cytocompatibility studies on these xerogels imply the effects of both pore size and materials chemistry, with fully aliphatic polyesters with large pore structures allowing the growth of mammalian cells. To the best of our knowledge, this represents the first report examining the preparation and potential of sol-gel derived porous polymer xerogels as tissue engineering scaffolds.

Luminescence Quenching of Eu(III) Carboxylates by Cu(II) in a Composite Polymer Xerogel Film†

Three Eu(III) luminescent compounds were separately entrapped in a xerogel porous silica matrix and finely ground particles of it were deposited on a glass support with polyvinylacetate (PVAc) as a binder to build a thin film sensor. These 3 devices were immersed in aqueous solutions of Cu(II) and the content of this metal was evaluated by emission-quenching experiments. The sensor containing the highly luminescent antenna chelate of diethylenetriaminepentaacetic acid (dtpa) sensitized with Coumarin120 rendered the largest Stern-Volmer constant (K(SV) = 1.49 x 10(4) M(-1)), showing no leaching of the Eu(III) complex to the aqueous solution and a reproducible value of the luminescence ratio between water and Cu(II) solution. The in situ sensor we developed can measure the concentration of Cu(II) in aqueous media down to the ppm level by emission-quenching experiments. This methodology permits a simple calibration of the sensor and an easy to use reusable device.

Carbon xerogel supported Pt and Pt–Ni catalysts for electro-oxidation of methanol in basic medium

Highly mesoporous carbon was obtained by carbonization of a polymer xerogel previously synthesized via sol–gel condensation of resorcinol and formaldehyde. The investigation describes electro-oxidation of methanol in alkaline electrolyte using Pt and Pt–Ni catalysts supported on this high surface area mesoporous carbon. The electrocatalytic tests showed better performance of the catalysts when impregnated with this carbon support.