External Oil Phase Research Articles

Novel Environmentally Friendly Nanomaterials for Drag Reduction of the Emulsified Acid System.

Matrix acidizing is a technique that is widely used in the petroleum industry to remove scales and create channels in the rock. Removal of scales and creation of channels (wormhole) enhance productivity. Conventional acidizing fluids, such as hydrochloric acid (HCl) for carbonate and a mixture of hydrofluoric acid (HF) and HCl acid, are used for the matrix acidizing process. However, these fluids have some drawbacks, including strong acid strength, corrosion at high temperatures, and quick reactions with scale and particles. Emulsified acid systems (EASs) are used to address these drawbacks. EASs can create deeper and narrower wormholes by reducing the reaction rate of the acid due to the external oil phase. However, EASs have a much higher viscosity compared to conventional acidizing fluids. The high viscosity of EASs leads to a high drag that restricts pumping rates and consumes energy. This study aims to utilize environmentally friendly and widely available nanomaterials as drag-reducing agents (DRAs) of the EAS. The nanomaterials used in this study are carbon nanodots (CNDs). CNDs have unique properties and are used in diverse applications in different industries. The size of these CNDs is usually smaller than 10 nm. CNDs are characterized by their biocompatibility and chemical stability. This study investigates the use of CNDs as DRAs for EAS. Several experiments have been conducted to investigate the CNDs as a DRA for the EAS. The developed EAS was initially tested for conductivity and drop-test analysis to ensure the formation of an inverted emulsion. Thereafter, the thermal stability for the range of temperatures and the rheological properties of the EAS were evaluated to meet the criteria of field operation. Then flow experiments with EASs were conducted before and after adding the CNDs to investigate the efficacy of drag reduction of EASs. The results revealed that CNDs can be used as viscosity reducers for the EAS, where adding the CNDs to the EAS reduces the viscosity at two different HCl concentrations (15 and 20%). It reduces the viscosity of the EAS in the presence of corrosion inhibitors as well as other additives to the EAS, showing its compatibility with the field formulation. The drag reduction was observed at the range of temperatures investigated in the study. The conductivity, stability, and rheology experiments for the sample taken after the flow experiment are consistent, ensuring CNDs work as a DRA. The developed EAS with CNDs is robust in terms of field mixing procedures and thermally stable. The CNDs can be used as a DRA with EAS, which will reduce drag in pipes, increasing pumping rates and saving energy.

Sucrose Esters and Beeswax Synergize to Improve the Stability and Viscoelasticity of Water-in-Oil Emulsions.

W/O emulsions are commonly used to prepare stable low-fat products, but their poor stability limits widespread applications. In this study, sucrose ester (SE) and beeswax were utilized to prepare an oil dispersion system in rapeseed oil, which was used as the external oil phase to further synergistically construct the W/O emulsion systems. The results show that spherical and fine crystals are formed under the synergistic effect of SE and BW (1.5 SE:0.5 BW). In this state, a dense interfacial crystal layer was easily formed, preventing droplet aggregation, leading to droplet size reduction (1-2 μm) and tight packing, improving viscoelasticity and resistance to deformation, and increasing the recovery rate (52.26%). The long-term stability of W/O emulsions containing up to 60 wt% water was found to be more than 30 days. The increase in the aqueous phase led to droplet aggregation, which increased the viscosity (from 400 Pa·s to 2500 Pa·s), improved the structural strength of the emulsion, and increased the width of the linear viscoelastic region (from 1% strain to 5% strain). These findings provide some technical support for the further development of stable low-fat products.

Development of emulsified acid system (EAS) using organoclays (OC): Rheology and implication to the acidizing

Matrix acidizing is a well-stimulation technique extensively used in the petroleum industry to increase well productivity by removing scales and creating channels in the rocks. However, conventional acidizing fluids used in this process have some limitations such as rapid reactions with scale and fines, high acid strength, and corrosion of equipment at high temperatures. To address these issues, emulsified acid system (EAS) is used in fracturing and acidizing operations for carbonate reservoirs to improve well productivity by removing formation damage. EAS can help to improve well productivity by creating deeper and narrower wormholes through reduced reaction rates of acid due to the external oil phase. However, EAS has limitations such as low stability at high temperatures, high viscosity that restricts pumping rates, potential formation damage, and difficulty in achieving homogenous mixing. Pickering emulsions, which use solid microparticles as a stabilizer instead of surfactants, show promise in overcoming these challenges due to their easy preparation, good thermal stability, and low viscosity at high shear rates.This study investigates the use of different types of organoclays (OC) for the development of an emulsified HCl acid systems for carbonate reservoirs. Several experiments were conducted to demonstrate and evaluate the use of OC for EAS and to improve field operations. To advance the development of EAS, a meticulous process was undertaken to select and optimize OCs as the key component. It include mineral characterization by XRD and XRF techniques, optimization of OC concentration (250–1000 ppm), and mixing speed (4000–8000 RPM). The thermal stability of the EAS was evaluated for a temperature range of 25–160 °C and a comprehensive analysis of EAS rheology (0.1–1000 sec−1) was performed. The conductivity, drop-test analysis, as well as micrographic analysis, were carried out to ensure the formation of invert emulsion. It was found that the required mixing speed was 6000 RPM and the optimum OC concentration was 500 ppm for developing a stable invert emulsion. The viscosity of the EAS shows increasing trends with an increase in temperature at the low shear rates (below 10 sec−1); however, at high shear rates (higher than 10 sec−1), the EAS viscosity decreases with temperature. The study found that OCs are promising emulsifiers for creating EAS with good thermal stability and low viscosity at high shear rates. The EAS formulated using OC were robust and thermally stable, making them suitable for field mixing procedures. Additionally, the OC used in the study are cost-effective, readily available, environmentally friendly, and have a high surface area, making them advantageous as an emulsifier.

Water-in-oil oleogel with biphasic stabilization for fabrication of low-fat salad dressing

Salad dressing has become a popular condiment for consumers in many countries, especially for vegetarians. However, the rapid increase in the prevalence of obesity worldwide has been partially attributed to the overconsumption of fats. In this study, we constructed a water-in-oil oleogel with biphasic stabilization for fabrication of low-fat salad dressing. The oleogel was stabilized by adding beeswax to the external oil phase and curdlan to the internal aqueous phase. The oleogel exhibited shear thinning behavior and had a higher storage modulus than the loss modulus, which indicated good elastic behavior. The oleogel displayed high stability as the volume fraction of the internal aqueous phase was increased to 70% because of biphasic stabilization. Beeswax had a positive effect on the structure of the oil phase in the oleogel. When the concentration of beeswax reached 3%, the oleogel exhibited a uniform distribution, a small droplet size, and considerable freeze-thaw stability. In comparison with the oleogel where curdlan alone was used in the internal aqueous phase, the viscoelastic properties and stability could be improved by using a mixture of curdlan and pullulan or curdlan and β-cyclodextrin. Our study provides a green and sustainable method for fabrication of low-fat salad dressing.

Construction of stable O/W/O multiple emulsions using beeswax to control the melting point of the continuous oil phase

Oil-in-water-in-oil (O/W/O) multiple emulsions could be used as simulated fat substitutes to reduce the intake of trans- or saturated-fatty acids. In this study, O/W/O multiple emulsions had been fabricated by using carboxymethyl chitosan to stabilize O/W emulsion firstly, and the obtained O/W emulsion was used as the inner dispersed phase, and the beeswax was used as external oil phase for the construction of the O/W/O multiple emulsions. The impact of beeswax content (2–8 wt%) and the volume fraction of the inner O/W emulsion (10–50 v%) on the morphology, stability and rheological properties of the O/W/O multiple emulsions had been investigated. When the O/W multiple emulsion as inner phase ratio was increased, the droplet size of the O/W/O multiple emulsions was increased. With the increasing of the content of beeswax in the continuous oil phase, the O/W/O multiple emulsions droplet size was decreased while the stability of the O/W/O multiple emulsions was improved. The increase of beeswax content could improve the viscosity and viscoelastic modulus of the O/W/O multiple emulsions system, endowing the O/W/O multiple emulsion with improved stability. It made it possible to change the texture of the O/W/O multiple emulsions co-containing water-soluble and oil-soluble components.

Effects of gelation on the stability, tribological properties and time-delayed release profile of double emulsions

Due to the unique multi-chamber structure of the double emulsion (DE), gelation different compartments of double emulsions with different gelling strength offers flexible control over their encapsulation and delivery properties. Herein, the aqueous or oil phase of DE was gelled with alginate or beeswax at different gelling strength, and the effects of gelation on the processing stability, rheological and tribological properties as well as the digestion profile of double emulsions were investigated. Gelation in each phase improved the stability of DE (0,0,0), with the oil or external aqueous phase gelation being more efficient in lifting the encapsulation stability after 14 days’ storage (increased from 67.50 ± 2.47% to 86–90% and 84–90%, respectively). Under processing conditions, the oil phase gelled DE was easily destabilized when subjected to heating treatment, but maintained better stability under freeze-thaw or osmotic pressure treatment compared to the internal and external water phase gelled ones. Gelation also actively regulated the rheological and tribological properties of DE, wherein gelation in internal water phase showed the least impact on the rheological properties, gelation in the external aqueous phase and oil phase exerted more significant influence on the viscosity and the tribological properties of DE, respectively. The external water phase gelled DE manifested the time-delayed digestion profile with only 8.09 ± 0.12% of internal marker release at the end of gastric digestion and the FFA release extent was decreased by 41.66% as compared to the DE (0,0,0). The present study offers a valuable guide for rational design of double emulsions with tailor-made processing stability, oral sensation and digestive characteristics.

Effects of the Distribution Site of Crystallizable Emulsifiers on the Gastrointestinal Digestion Behavior of Double Emulsions.

Double emulsions (DEs) are promising delivery vehicles for the protective and programmed release of bioactive compounds. Herein, DEs with monoglycerides crystallized at the internal- or external interface or oil phase were fabricated. The results suggested that the crystallization site of monoglycerides exerts a significant role in retarding the structural degradation and lipid digestion of DEs by affecting the available contact area of lipase. At the initial stage of intestinal digestion, compared with noncrystalline DEs (82.1%, 3.7 min), the burst release of internal markers in the internal interface crystallized emulsions was decreased by 42.4% and the lag time of free fatty acid (FFA) release was delayed by 5.8 min in the external interface crystallized emulsions. The structural integrity and digestion kinetics of the external interface crystallized DEs were synchronized with the retention time of the interfacial crystals. Therefore, crystallizable emulsifiers exhibit unique and fine regulatory effects on the digestive properties of emulsions.

Design and Comparative Evaluation of Vancomycin HCl-Loaded Rosin-Based In Situ Forming Gel and Microparticles.

Vancomycin hydrochloride (HCl) is a glycopeptide antibiotic used to treat serious or life-threatening infections, and it reduces plaque scores and gingivitis in periodontal patients. In this study, vancomycin HCl was incorporated into rosin in situ forming gel (ISG) and rosin in situ forming microparticles (ISM) to generate a local drug delivery system to treat periodontal disease. The physical properties of the ISG and ISM were measured, including pH, viscosity, injectability, adhesion properties, in-vitro transformation, and drug release. Moreover, the effectiveness of antimicrobial activity was tested using the agar-cup diffusion method against Staphylococcus aureus, Streptococcus mutans, Porphyromonas gingivalis, and Escherichia coli. Vancomycin HCl-loaded rosin-based ISG and ISM had a pH value in the range of 5.02–6.48 and exhibited the ease of injection with an injection force of less than 20 N. Additionally, the lubricity effect of the external oil phase of ISM promoted less work of injection than ISG and 40–60% rosin-based ISM showed good emulsion stability. The droplet size of emulsions containing 40%, 50%, and 60% rosin was 98.48 ± 16.11, 125.55 ± 4.75, and 137.80 ± 16.8 µm, respectively. Their obtained microparticles were significantly smaller in diameter, 78.63 ± 12.97, 93.81 ± 10.53, and 118.32 ± 15.61 µm, respectively, because the particles shrank due to the solvent loss from solvent exchange. Moreover, increasing the concentration of rosin increased the size of microparticles. After phase transformation, all formulations had better plasticity properties than elasticity; therefore, they could easily adapt to the specific shape of a patient’s gum cavity. Both developed ISG and ISM presented inhibition zones against S. mutans and P. gingivalis, with ISG presenting significantly more effectively against these two microbes (p < 0.05). The vancomycin HCl-loaded rosin ISG and ISM delayed drug release for 7 days with efficient antimicrobial activities; thus, they exhibit potential as the drug delivery systems for periodontitis treatment.

Preparation of hierarchically porous carbons with enhanced porosity and energy storage capacity through an internal phase-external phase coefficient HIPE templating

High internal phase emulsion (HIPE) templating is a versatile strategy to prepare porous polymers and carbons. However, the prepared porous carbon materials usually show low specific surface area (SSA) due to the feature of macropores, which hampered their wider applications. This work developed a novel strategy, namely internal phase-external phase coefficient HIPE (IP-EP coHIPE) templating, to prepare polymer-derived hierarchically porous carbons (HPCs) with high SSA. In the strategy, sodium alginate (SA) aqueous solution was selected as the internal phase and emulsified in external oil phase containing divinylbenzene (DVB). HPCs were obtained by sequentially polymerizing the external phase, crosslinking the internal phase and carbonization. The testing results indicated that this strategy provided HPCs with notably enhanced porosity and increased SSA when compared with conventional HIPE method via the further utilization of the void space of polyHIPE-based HPCs via a facile way. The porous architectures of HPCs can be adjusted by changing the volume fraction and/or the concentration of the internal phase, respectively. The potential applications of the obtained HPCs were evaluated as the electrode material of supercapacitor. The specific capacitance of optimized HPC-based supercapacitor is 306 F/g, much higher than that based on general polyHIPE-derived HPC (145 F/g) at 1 A/g, which can be attributed to its enhanced porosity, hierarchically porous architecture and high SSA (2289 m 2 /g). • Hierarchically porous carbons (HPCs) were prepared through an internal phase-external phase coefficient HIPE templating. • This strategy provided HPCs with notably enhanced porosity and increased specific surface area. • The HPC-based supercapacitors present satisfied energy storage performance and excellent application prospects.

Tailored highly porous, templated polyurethane for sand consolidation

AbstractA novel polymeric resin formulation is developed to mitigate sand production from subterranean formations composed of unconsolidated or weakly consolidated sands via a chemical sand consolidation approach. The developed formulation aims to minimize the formation permeability loss commonly observed in a chemical sand consolidation treatment. The new formulation is a water‐in‐oil high internal phase emulsion with poly(ε‐caprolactone) polyol and isophorone diisocyanate monomer incorporated in the external oil phase. Highly porous, emulsion templated polyurethane forms through the reaction between polyol and isocyanate under elevated temperature. Additionally, CO2 generated through the reaction between excess isocyanate monomer and water leads to the formation of more pores in the cross‐linked polymeric network. When the developed formulation is applied for sand consolidation treatment, the interconnected pores formed after resin curing act as “channels” in the consolidated products and allow the produced fluid such as oil, water, or gas to easily flow through, thereby limiting permeability reduction. The effectiveness of using porous polyurethane material for sand consolidation is evaluated through a compressive strength and permeability study of the consolidated sandpacks prepared with this chemistry.

Bleached shellac in situ forming micro-particle fabricated with different oils as antibacterial delivery system for periodontitis treatment

In-situ forming micro-particle (ISM) is an emulsion system that could change into micro-particulate matrices by phase separation of matrix former. In this research work, bleach shellac (BS) was used as the matrix forming agent to develop the doxycycline hyclate (DH)-loaded ISM and the different oils were used as the external phase of non-aqueous in oil emulsion. ISMs were prepared by using BS dissolved in dimethyl sulfoxide (DMSO), N-methyl pyrrolidone (NMP), or 2-pyrrolidone (PYR) as the internal phase and the external phase containing glycerol monosterate (GMS) in various oils including camellia oil, canola oil, olive oil, safflower oil, and sesame oil. The physical properties of ISMs using PYR as the solvent of the internal phase were tested including viscosity, in vitro micro-particle formation, injectability, drug release, surface topography, and antibacterial activity against Porphyrommonas gingivalis. All DH-loaded ISMs were easy to be injected through a needle and formed into micro-particles after exposure to phosphate buffer. The external oil phase reduced the friction between barrel and plunger of syringe and thus promoting easier injectability. The particular drug-loaded ISM prepared from safflower oil was largest, while that prepared from sesame oil was smallest and that of the others had no significant difference (p < 0.05). After 60 sec, the particle size of drug-loaded formula had no presence of coalescence. DH released from BS ISM was sustainable longer than 50 days. Sponge topography of micro-particle after DH release test in SEM micrographs confirmed the solvent exchange initiated further phase separation of BS into a micro-particular sponge. They efficient inhibited against P. gingivalis with a sustainable drug release character from the retardation of drug diffusion. Thus, DH-loaded ISMs using PYR as the solvent of the internal phase could be fabricated with various oils and exhibited the potential use for periodontitis treatment.

Formulation of concentrated oil-in-water-in-oil double emulsions for fragrance encapsulation

We report the formulation of a concentrated double oil-in-water-in-oil (O/W/O) emulsion for fragrance encapsulation. As their water-in-oil-in-water homologous, these O/W/O emulsions, seldom described in literature, also require the use of two antagonist surfactants: a hydrophilic one (HS) to stabilize the fragrance-in-water droplets and a lipophilic one (LS) to stabilize the aqueous globules dispersed in oil, containing themselves the direct emulsion. An important issue in cosmetics is the necessity to adapt the formulation to each fragrance, so that a major progress would be the successful elaboration of an O/W/O emulsion insensitive to fragrance changes. In order to approach such a composition, two model fragrances composed of 10 and 13 molecules representative of the most used molecules in this domain were specially assembled for the study. The aim was to identify possible hydrophilic and lipophilic stabilizers leading to a double O/W/O emulsions and determine compositions able to encapsulate both fragrances. The double emulsion was prepared by a two-step process, allowing varying the double emulsion composition i.e the amount of both surfactants as well as the quantity of droplets inside the globules. By plotting “feasibility diagrams” we can propose a best composition shared by the two fragrances. Such a double emulsion is composed of 20 wt% of fragrance droplets with respect to the globule volume, 75 wt% of globules with respect to the total emulsion, 7.5 wt% of HS with respect to the intermediate aqueous phase and 10 wt% of LS with respect to external oil phase. The robustness of this optimized composition against molecule changes was tested using a third fragrance. Then the encapsulated efficiency was measured showing the high encapsulation rate (close to 99 %) of the selected system and a gas chromatography analysis of each molecule composing the complex fragrance showed no alteration of the encapsulated fragrance.

Magnetotactic bacteria in a droplet self-assemble into a rotary motor

From intracellular protein trafficking to large-scale motion of animal groups, the physical concepts driving the self-organization of living systems are still largely unraveled. Self-organization of active entities, leading to novel phases and emergent macroscopic properties, recently shed new light on these complex dynamical processes. Here we show that under the application of a constant magnetic field, motile magnetotactic bacteria confined in water-in-oil droplets self-assemble into a rotary motor exerting a torque on the external oil phase. A collective motion in the form of a large-scale vortex, reversable by inverting the field direction, builds up in the droplet with a vorticity perpendicular to the magnetic field. We study this collective organization at different concentrations, magnetic fields and droplet radii and reveal the formation of two torque-generating areas close to the droplet interface. We characterize quantitatively the mechanical energy extractable from this new biological and self-assembled motor.

Investigation of mathematical models based on diffusion control release for Paclitaxel from in-situ forming PLGA microspheres containing HSA microparticles

ABSTRACTPaclitaxel-loaded poly(lactic acid-co-glycolic acid) (PLGA) microspheres containing different portions of human serum albumin microparticles (mHSA) were prepared via an in situ forming method. The low solubility of Paclitaxel and presence of an external oil phase around the in situ-formed microspheres were investigated with the mathematical models based on the diffusion-control release. The release data were fitted with diffusion-based semi-empirical models including Ritger-Peppas, Weibull and Peppas-Sahlin models, and a theoretical model obtained from Fick’s second law. The release rate constants, release exponent and average drug diffusion coefficients microspheres were calculated and their variations with PLGA molecular weight and microparticles were established. Results showed good accordance between experimental and theoretical values. Besides, incorporation of mHSA within microspheres decreased the Paclitaxel diffusion. Result of docking studies showed that the binding site of mHSA sequences including HIS242 and ARG114 have more significant interaction with paclitaxel, but no significant interaction between PLGA and paclitaxel.

Preparation of Ethyl Cellulose Microspheres for Sustained Release of Sodium Bicarbonate.

Sustained release of thermal-instable and water-soluble drugs with low molecule weight is a challenge. In this study, sodium bicarbonate was encapsulated in ethyl cellulose microspheres by a novel solid-in-oil-in-oil (S/O/O) emulsification method using acetonitrile/soybean oil as new solvent pairs. Properties of the microspheres such as size, recovery rate, morphology, drug content, and drug release behavior were evaluated to investigate the suitable preparation techniques. In the case of that the ratio of the internal and external oil phase was 1: 9, Tween 80 as a stabilizer resulted in the highest drug content (2.68%) and a good spherical shape of microspheres. After the ratio increased to 1: 4, the microspheres using Tween 80 as the stabilizer also had high drug content (1.96%) and exhibited a sustained release behavior, with 70% of drug released within 12 h and a sustained release of more than 40 h. Otherwise, different emulsification temperatures at which acetonitrile was evaporated could influence the drug release behaviour of microspheres obtained. This novel method is a potential and effective method to achieve the encapsulation and the sustained release of thermal-instable and water-soluble drugs with low molecule weight.

Bleached Shellac as an Alternative Polymeric Matrix for &lt;i&gt;In Situ&lt;/i&gt; Microparticle

Bleached shellac (BS), a biodegradable natural resin purified from insect lac, has been used in a varity of controlled drug delivery systems. Nevertheless, there were negligible researches explored the potential of it as in injectable in situ microparticles (ISM) applications. The goal of this study was to utilize BS to form ISM (shellac-solution dispersed into an external olive oil phase, as o/o emulsion) prepared by two-syringe technique. Addition of glyceryl monostearate (GMS) as stabilizer obviously decreased the emulsion droplet size. ISM emulsion comprising 5% w/w GMS in external phase could form into droplets and precipitate in form of microparticles after exposure to phosphate buffer. 2-Pyrrolidone was the most appropriate solvent to form massive microparticles with regular shape especially at ratio of 7:3 external:internal phases. ISM transformation was occurred after exposure to phosphate buffer and tended to reduce the droplet size when ratio of external phase was higher than 50%. Incorporation of doxycycline hyclate did not influence the amount and size of ISM. Therefore shellac exhibited as an alternative polymer matrix for ISM which higher amount of GMS could reduce the size of emulsion droplet and volume phase ratio seriously influenced on emulsion size and ISM formation.

Biodegradable Injectable In Situ Implants and Microparticles for Sustained Release of Montelukast: In Vitro Release, Pharmacokinetics, and Stability

The objective of this study was to investigate the sustained release of a hydrophilic drug, montelukast (MK), from two biodegradable polymeric drug delivery systems, in situ implant (ISI) and in situ microparticles (ISM). N-Methyl pyrrolidone (NMP), dimethyl sulfoxide (DMSO), triacetin, and ethyl acetate were selected as solvents. The release of 10% (w/v) MK from both systems containing poly-lactic-co-glycolic acid (PLGA) as the biodegradable polymer was compared. Upon contact with the aqueous medium, the PLGA in ISI and ISM systems solidified resulting in implants and microparticles, respectively. The in vitro drug release from the ISI system showed marked difference from miscible solvents (NMP and DMSO) than the partially miscible ones (triacetin and ethyl acetate), and the drug release decreased with increased PLGA concentration. In the ISM system, the initial in vitro drug release decreased with decreased ratio of polymer phase to external oil phase. In vivo studies in rats showed that ISM had slower drug release than the drug release from ISI. Also, the ISM system when compared to ISI system had significantly reduced initial burst effect. In vitro as well as the in vivo studies for both ISI and ISM systems showed sustained release of MK. The ISM system is suitable for sustained release of MK over 4-week period with a lower initial burst compared to the ISI system. Stability studies of the ISI and ISM formulations showed that MK is stable in the formulations stored at 4°C for more than 2 years.

Acrylic‐Acid‐Functionalized PolyHIPE Scaffolds for Use in 3D Cell Culture

This study describes the development of a functional porous polymer for use as a scaffold to support 3D hepatocyte culture. A high internal phase emulsion (HIPE) is prepared containing the monomers styrene (STY), divinylbenzene (DVB), and 2-ethylhexyl acrylate (EHA) in the external oil phase and the monomer acrylic acid (Aa) in the internal aqueous phase. Upon thermal polymerization with azobisisobutyronitrile (AIBN), the resulting porous polymer (polyHIPE) is found to have an open-cell morphology and a porosity of 89%, both suitable characteristics for 3D cell scaffold applications. X-ray photo-electron spectroscopy reveals that the polyHIPE surface contained 7.5% carboxylic acid functionality, providing a useful substrate for subsequent surface modifications and bio-conjugations. Initial bio-compatibility assessments with human hepatocytes show that the acid functionality does not have any detrimental effect on cell adhesion. It is therefore believed that this material can be a useful precursor scaffold towards 3D substrates that offer tailored surface functionality for enhanced cell adhesion.

Carbide‐Derived Carbon Monoliths with Hierarchical Pore Architectures

Porous carbon materials are crucial components in catalysis, gas storage, electronics, and biochemistry. A hierarchical pore architecture in these materials is essential to achieve high surface areas combined with advanced mass transport kinetics. Widely used approaches for the generation of microor mesopores are activation and nanocasting. In contrast, macroporous carbon materials are primarily obtained by carbonization of polymeric precursor gels or replication of larger templates. A relatively new class of microand mesoporous carbon material with tunable porosity are carbide-derived carbon materials (CDCs). High-temperature chlorination of carbides leads to selective removal of metalor semi-metal atoms and allows control over the pore size of the resulting CDCs in a subngstrcm range by changing synthesis conditions or the carbide precursor. These materials have been studied for applications in gas storage and as electrode materials in supercapacitors because of their high specific surface areas. Recently, metal etching from pyrolyzed pre-ceramic components (polysilsesquioxanes or polysilazanes) was found to be a useful route towards carbide-derived carbon materials with enhanced porosity and gas-storage properties. A significant step towards ultrahigh specific surface area combined with a hierarchical mesoporous–microporous system was achieved using nanocasting of silica templates (SBA-15 or KIT-6) with polycarbosilane precursors and subsequent chlorine treatment of the resulting ordered mesoporous silicon carbides. These ordered mesoporous CDCs offer specific surface areas as high as 2800 mg 1 and total pore volumes of up to 2 cmg . Their mesostructure can be easily controlled by changing the silica hard template, resulting in excellent performance in protein adsorption, gas storage, and as electrodes for supercapacitors. However, such carbon materials are available only as nonstructured micrometer-sized powders and cannot be shaped into films without the addition of binders or the use of high mechanical stress, leading to structural deformation. Chlorine treatment of mechanically mixed Si/SiC precursors was found to be a useful route towards monolithic CDC with a hierarchical pore system. The presence of a free metal phase in the precursor system provides the opportunity to introduce a secondary macroporosity of 3 mm sized channels with a volume of 0.23 cmg 1 along with the microporous carbide-derived carbon material system. The introduction of large transport pores in polymerbased CDCs might be an alternative way to form materials that combine high surface areas with efficient fluid transport. The current literature describes a variety of routes for the production of highly macroporous ceramics from precursor polymers with controllable cell and window sizes. In particular, direct blowing of polycarbosilanes was found to be a useful approach for the generation of silicon carbide foams that might be suitable materials for the production of hierarchical CDCs. In the following, we describe a novel synthesis route for monolithic carbide-derived carbon materials, including micro-, meso-, and macroporous structures with extremely high specific surface area. They can be obtained by hightemperature chlorination of macroporous polymer-derived silicon carbide (SiC-PolyHIPE). A soft-templating approach starting from a high internal phase emulsion (HIPE) was used with an external oil phase consisting of liquid polycarbosilane SMP-10 and the cross-linker paradivinylbenzene. Using Span-80 as surfactant to stabilize the internal water phase, the application of oxidic or carbon hard templates and the corresponding template removal under harsh conditions is no longer necessary. After cross-linking the polymer chains, the resulting PolyHIPEs were pyrolyzed to silicon carbides at maximum temperatures of 700, 800, and 1000 8C and subsequently converted into CDCs by chlorine treatment at the maximum pyrolysis temperature (Supporting [*] M. Oschatz, L. Borchardt, Dr. I. Senkovska, N. Klein, Dr. R. Frind, Prof. Dr. S. Kaskel Department of Inorganic Chemistry Dresden University of Technology Bergstrasse 66, 01062 Dresden (Germany) E-mail: stefan.kaskel@chemie.tu-dresden.de

Sustained release microspheres of ropinirole hydrochloride: Effect of process parameters

An emulsion solvent evaporation method was employed to prepare microspheres of ropinirole hydrochloride, a highly water soluble drug, by using ethylcellulose and PEG with the help of 32 full factorial design. The microspheres were made by incorporating the drug in a polar organic solvent, which was emulsified using liquid paraffin as an external oil phase. Effects of various process parameters such as viscosity of the external phase, selection of the internal phase, surfactant selection and selection of stirring speed were studied. Microspheres were evaluated for product yield, encapsulation efficiency and particle size. Various drug/ethylcellulose ratios and PEG concentrations were assayed. In vitro dissolution profiles showed that ethylcellulose microspheres were able to control release of the drug for a period of 12 h.