Lifshitz-van Der Waals Component Research Articles

Comparison of surface tension, density, viscosity and contact angle of ethyl oleate to those of ethanol and oleic acid

Taking into account extensive practical application of ethyl oleate (EO) some of its physicochemical properties were determined and compared to those of ethanol (ET) and oleic acid (OA). For this purpose the surface tension, density, viscosity and contact angle of EO, ET and OA were measured. The contact angle was measured on the polytetrafluoroethylene (PTFE), poly(methyl methacrylate) (PMMA), steel and glass in the solid–liquid–air system. Based on the results of the surface tension and contact angle of ET, EO and OA on PTFE and PMMA the Lifshitz-van der Waals component as well as electron-acceptor and electron-donor parameters of the acid-base component of surface tension of these liquids were determined. For this determination the van Oss et al. method was applied. This method was carefully analyzed in terms of its usefulness for the systems studied by us. The components and parameters of the ET, EO and OA surface tension were analyzed with regard to their molecular structure. Based on the molecular structure and on the length of bonds and contact angle between them the size of the molecules and their contactable area were determined.

Modeling and prediction of surface free energy of pavement materials based on a single probe liquid using Artificial neural network

Surface free energy (SFE) is a vital material property employed for the assessment of various pavement performances such as asphalt-aggregate adhesion, moisture resistance, material compatibility, etc. However, the conventional models for estimating the SFE of materials require the contact angles (CA) of multiple probe liquids (PL) on the material's surface. In addition, the process requires further computational effort to arrive at the SFE components. In an attempt to offer an accurate and quicker alternative method of estimating the SFE of materials with lesser effort, this study has explored the use of artificial neural network (ANN) to predict the SFE of pavement materials. A simple but novel data structuring was employed to predict the SFE using inputs from just a single PL. Variables needed for the successful prediction of SFE components were identified and studied. Sensitivity analysis along with relative importance was used to rank the predicting variables. The Lifshitz-van der Waals (LW) component ANN-model showed the best accuracy (RMSE = 1.652 J/m2, R = 0.984). The base and acid components models showed relatively lower performances, (RMSE = 2.560 J/m2, R = 0.943) and (RMSE = 0.575 J/m2, R = 0.818) respectively. However, the SFE components estimated from the ANN-models yielded a total SFE with very good accuracy (RMSE = 2.049 J/m2, R = 0.982). Further insight into which variables such as substrate-type, CA test method, PL type, etc. facilitate model accuracy was provided.

Role of Membrane-Solute Affinity Interactions in Carbamazepine Rejection and Resistance to Organic Fouling by Nano-Engineered UF/PES Membranes.

In this study, polyethersulfone (PES) ultrafiltration (UF) membranes were modified with GO, Ag, ZnO, Ag-GO and ZnO-GO nanoparticles to improve carbamazepine removal and fouling prevention by making membrane surfaces more hydrophilic. The fabricated membranes were characterized for surface and cross-sectional morphology, surface roughness and zeta potential, as well as hydrophilicity, functional groups, surface tension parameters and water permeability Thereafter, the membranes were evaluated for their efficiency in removing MgSO4 and carbamazepine as well as antifouling properties. To understand the role of affinity interactions in rejection and fouling, membrane-solute adhesion energies (∆Gslm) were quantified based on the Lifshitz-van der Waals/acid-base method. Unlike previous studies, which have generalized fouling prevention to be due to improvements in hydrophilicity upon adding nanoparticles, this work further explored the role of surface tension components on rejection and fouling prevention. The addition of nanoparticles improved membrane hydrophilicity (77-62°), water permeability (11.9-17.7 Lm-2 h-1 bar-1), mechanical strength (3.46-4.11 N/mm2), carbamazepine rejection (30-85%) and fouling prevention (60-23% flux decline). Rejection and antifouling properties increased as ∆Gslm became more repulsive (i.e., less negative). Membrane modification reduced irreversible fouling, and the fouled membranes were cleaned by flushing with water. Fouling related more to membrane electron donor components (γ-), while the roles of electron acceptor (γ+) and Lifshitz-van der Waals components (γLW) were less important. This work provides more insights into the role of affinity interactions in rejection and fouling and how rejection and fouling mechanisms change with nanoparticle addition.

Inhibition of multi-species biofilm formation using chitosan-based film supplemented with essential oils

The biofilm development following microbial attachment on food-grade surfaces represents a main problem in the food sector, leading to significant economic losses. To overcome that, the present investigation aimed to develop biodegradable films that protect against heterogeneous biofilms using chitosan and essential oils (EOs). First, the cross-streak method revealed the absence of antagonism between Staphylococcus aureus, Enterococcus hirae, Escherichia coli, and Pseudomonas aeruginosa strains. The contact angle findings revealed a drop in the electron acceptor (γ+) and qualitative hydrophobicity (θw) associated with an increase in the Lifshitz-van Der Waals component (γLW) and electron donor (γ−) regarding the treated chitosan-based films (CH-films). The environmental scanning electron microscopy (ESEM) images showed that among all the treatments, the CH-film treated with the Pelargonium asperum EO exhibited the weakest antiadhesion activity (73.89 ± 1.42% of the covered surface) while the CH-film treated with the Pelargonium asperum, Thymus satureioides, Cinnamomum zeylanicum, and Eugenia caryophyllus EOs mixture had the strongest activity (9.23 ± 1.66% of the covered surface). From these results, the CH-film containing the EOs mixture presents a high potential for utilization in the food industry as an active coating and packaging that prevent the microorganisms' attachment and the eventual biofilm development.

Effect of Resin Content on the Surface Wettability of Engineering Bamboo Scrimbers

Bamboo scrimber refers to a lignocellulosic structural material, which is usually attacked by water, ultraviolet radiation and fungus. Surface coating is an effective way to protect it, and its coating properties depend on surface wettability. In this study, the surface wettability of bamboo scrimbers with varying resin content was investigated via the comprehensive analysis of surface roughness, surface contact angle, surface free energy, surface chemical composition and coating properties. The resultant scrimbers had a similar profile with low roughness. Their surface was hydrophilic, but the hydrophilicity decreased with the increase in resin content. High resin content gave rise to low total free energy, in which the Lifshitz–van der Waals component was dominant and it decreased with the increasing resin content. Meanwhile, the ratio of the electron-accepting component to the electron-donating component becomes higher. This was due to the decreasing hydrophilic groups (e.g., -OH and -COOH groups) and the increasing oxygen-free groups (e.g., C-H and -CH2 groups) on the scrimber surface. The resin content affected the adhesion by decreasing the surface wettability, but the coating adhesion still reached the level of 2 for all bamboo scrimbers. The results will provide a theoretical reference for the surface coating of bamboo scrimbers in the structural application for good coating durability.

Antiadhesion effect of the chitosan-based film incorporated with essential oils against foodborne bacteria

In the food sector, bacterial adhesion on surfaces followed by biofilm development is responsible for food contamination and spoilage, and foodborne illness , leading to considerable economic losses. Therefore, this present study aimed to elaborate a biodegradable material that inhibits bacterial adhesion and thus biofilm formation. For this purpose, chitosan-based films (CH-films) containing four different essential oils (EOs) were elaborated. The impact of these EOs on the physicochemical properties as well as the antiadhesion activity of the CH-films was evaluated. The contact angle results showed that the addition of EOs has modified significantly the physicochemical properties of the CH-film. The electron donor (γ - ) and Lifshitz-Van der Waals component (γ LW ) values increased, whereas the qualitative hydrophobicity ( θ w) and electron acceptor (γ + ) values decreased. The analysis of bacterial adhesion using environmental scanning electron microscopy (ESEM) revealed that the CH-film containing C. zeylanicum EO exhibits the strongest antiadhesion activity against E. coli , E. hirae , and S. aureus compared to the other CH-films, with coverage rate values equal to 5.16 ± 1.13%, 2.8 ± 0.38%, and 1.52 ± 0.53%, respectively. Moreover, ESEM analysis showed that the antiadhesion effect of C. zeylanicum EO on P. aeruginosa strain was accompanied by a rupture of bacterial cells. From these findings, the CH-films incorporated with EOs could potentially be applied in the food industry to prevent microbial adhesion to surfaces and eventual biofilm formation. • The elaboration of a biodegradable film with antiadhesion activity using chitosan and essential oils. • The chemical constituents of pelargonium, thyme, cinnamon, and clove essential oils were identified. • The physicochemical properties of the chitosan-based film were affected by the incorporation of essential oils. • The chitosan-based film containing cinnamon essential oil showed strong antiadhesion activity against the tested strains. • The cell structure of P. aeruginosa was destabilized after contact with the film containing cinnamon essential oil.

Effect of sodium and potassium on polysaccharide fouling on PVDF and graphene oxide modified PVDF membrane surfaces

This study presented the contribution of monovalent cations (Na+ and K+) to the adsorptive sodium alginate (SA) fouling in real-time using a quartz crystal microbalance and dissipation (QCM-D). Polyvinylidene fluoride (PVDF) and graphene oxide modified PVDF membrane (GO-PVDF) were selected as representative membrane materials. Atomic force microscopic (AFM) equipped with probes modified with foulant was used for exploring the adhesion force changes between SA and the membrane. The results showed that both Na+ and K+ can promote the adsorption capacity of SA on the membrane surface. SA fouling in Na+ condition was more severe than that in K+ circumstance due to higher attraction forces under identical ion strength. In addition, the GO-PVDF membrane is more readily/severely fouled than PVDF by SA when Na+ or K+ is present. The difference in the interaction forces was further interpreted using XDLVO theory. The results suggested that the Lewis acid-base adhesion free energy (ΔGflfAB) between SA decreased gradually with increasing Na+ concentration, while in the K+ environment, ΔGflfAB increased instead. Moreover, the increase of the Lifshitz-van der Waals components (γmLW) of the GO membrane, resulted in a higher attractive interaction in the initial phase of the SA fouling. The results of this study provide a microscopic analysis of the possible fouling mechanism of Na+ and K+ on membrane fouling and as well as provide insightful reflections for an appropriate approach (whether GO modified or not) to membrane fouling control.

Surface Energy Changes Involved in Apatite Formation in Copper-Containing Bioactive Glasses

The aim of this work was to use the Washburn capillary rise method to evaluate changes in surface energy promoted by the insertion of CuO in a 58S glass and its implication in bioactivity. The presence of CuO decreased the surface wettability by decreasing the Lewis acid-base component γSAB and increasing the Lifshitz-van der Waals component γSLW. The insertion of CuO also diminished the value of the electron donor parameter γS-; i.e., the number of negative groups. This was accompanied by a nonuniform apatite formation on the surface, likely because the presence of CuO-rich regions with lower electron donor values impaired the adsorption of Ca2+, preventing uniform apatite precipitation. Therefore, surface energy was extremely sensitive to small physical and chemical changes in the glass structure and the behavior of the electron donor parameter could be used as an adequate probe to predict glass bioactivity.

Virus adhesion to archetypal fomites: A study with human adenovirus and human respiratory syncytial virus

Adhesion of two viruses – one enveloped (human respiratory syncytial virus, HRSV) and one non-enveloped (human adenovirus 5, HAdV5) – to four fomites (silica, nylon, stainless steel, polypropylene) was quantified and interpreted based on physicochemical properties of viruses and fomites. The selected fomites are tentatively identified as “archetypes” representing groups of materials distinctly different in mechanisms of their interfacial interactions. The surfaces are typified on the basis of their surface energy components including the dispersive (Lifshitz-van der Waals) component and two polar (electron donor and electron acceptor) components. Virus-fomite interactions are predicted using the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory and are experimentally assessed in tests with quartz crystal microbalance with dissipation (QCM-D). Polar interactions (manifested as hydrophobic attraction for all virus-fomite pairs but HAdV5/silica) governed virus attachment to fomites from a solution of high ionic strength typical for a respiratory fluid, while dispersive interactions played a relatively minor role. For both HAdV5 and HRSV, the areal mass density of deposited viruses correlated with the free energy of virus-fomite interfacial interaction in water, ΔGvwf. The dependence of virus-fomite attachment probability on ΔGvwf collapsed into one trend for both HAdV5 and HRSV pointing to the possibility of using ΔGvwf as a predictor of virus adhesion. Fomite rinsing with DI water resulted in a partial virus removal attributable to longer range repulsive electrostatic interactions. The proposed methodology can guide screening and selection of materials that discourage virus adhesion. The information on the efficiency of virus attachment to materials as a function of their surface energy components can help design anti-adhesive surfaces, develop surface cleaning solutions and protocols, and inform transport and fate models for viruses in indoor environments.

Effect of contact surface, plasticized and crosslinked zein films are cast on, on the distribution of dispersive and polar surface energy using the Van Oss method of deconvolution

This study characterized, the surface properties of plasticized and crosslinked zein films. We showed that the distribution of the surface energy into dispersive and polar components of the amphiphilic zein protein was strongly affected by the surface zein is cast on when zein was cast on polystyrene, polydimethylsiloxane (PDMS) and polytetrafluoroethylene (PTFE, Teflon™). Plasticized zein films had higher fractions of dispersive Lifshitz-Van der Waals (γLW) components than the Lewis acid base (γAB) polar components overall when the surface energy was analyzed and deconvoluted using the Van Oss method. When cast on PDMS the polar component increased, water contact angles were the lowest and the total surface free energy increased as a result. Oleic acid and glutaraldehyde concentration, were also varied during fabrication of the films in addition to contact surfaces. Film composition did not have an equally significant effect on the surface energy of films but as expected affected mechanical properties.

Effect of Polysorbates on Solids Wettability and Their Adsorption Properties

The wettability of solids is important from both practical and theoretical viewpoints. In this study, we measured the contact angle of aqueous solutions of polysorbates (Tween 20, Tween 60, and Tween 80) on polytetrafluoroethylene (PTFE), polyethylene (PE), polymethyl methacrylate (PMMA), polyamide (nylon 6), and quartz. Based on the obtained results, the adsorption of Tween 20 (T20), Tween 60 (T60), and Tween 80 (T80) at the solid-water interface was determined based on the structure and size of their molecules. Next, the tendency of polysorbates to adsorb at the solid-water interface was considered based on the Gibbs standard free energy of adsorption (ΔGadso). This energy was evaluated using various methods, including a method we propose based on the critical micelle concentration (CMC) and the contact angle of water and solution at the CMC, as well as their surface tension. The ΔGadso values obtained by this method were comparable to those calculated from the Langmuir equation. Taking into account the Tweens tendency to adsorb at the solid-water interface, the measured contact angle, the components and parameters of surface tension of Tweens solutions and solids, and the surface tension of water and its Lifshitz-van der Waals component that we determined, the wetting process in the solid-solution drop-air system was analyzed. The results based on the mentioned parameters showed that it is possible to predict the wettability of apolar, monopolar, and bipolar solids using the aqueous Tweens solution and their solution adhesion.

Wetting and adhesion properties of rhamnolipid and surfactin

The measurements of the contact angle of the aqueous solution of rhamnolipid (RL) and surfactin (SF) on polytetrafluoroethylene (PTFE), polyethylene (PE), polymethyl methacrylate (PMMA), nylon 6 and quartz were performed. The obtained values of the contact angle were analyzed by applying the components and parameters of the surface tension of aqueous solution of surfactants, PTFE, PE, PMMA, nylon 6 and quartz. This analysis showed that the contact angle of the solution on the hydrophobic solids can be predicted theoretically knowing the Lifshitz-van der Waals component of the water surface tension, the surface tension of the solids and that of the solution. Based on the contact angle values the critical surface tension of studied solids wetting, the adsorption of surfactants at the solid-water interface, the standard Gibbs free energy of adsorption as well as the work of adhesion of solutions to PTFE, PE, PMMA, nylon 6 and quartz surfaces were determined. It proved that the critical surface tension of wetting of the studied solids is different from their surface tension and that the work of adhesion of the aqueous solutions of RL and SF to PTFE, PE, PMMA, nylon 6 and quartz surfaces can be predicted from the components and parameters as well as the total surface tension of solids and solutions.

Components and parameters of liquids and some polymers surface tension at different temperature

The measurements of the contact angle for several apolar and polar liquids on the polytetrafluoroethylene (PTFE), polyethylene (PE), polymethyl methacrylate (PMMA) and polyamide (nylon 6) surfaces were made at 293, 303 and 313K. From the obtained contact angle for n-alkanes on PTFE the values of its surface tension at different temperatures were established. As follows this surface tension does not depend on the temperature in the range from 293 to 313K. Next, the Lifshitz-van der Waals and dispersion components of several liquids were determined from the contact angle on the PTFE surface at different temperatures by applying the same values of PTFE surface tension. The obtained components were next applied for determination of electron-acceptor and electron-donor parameters of water, formamide, glycerol and ethylene glycol surface tension on the basis of the contact angle on the PMMA surface which was assumed to be a monopolar solid. The significance of the obtained components and parameters of the surface tension of studied liquids was tested in the calculations of PE, PMMA and nylon 6 surface tension components and parameters. The calculated values of surface tension of PTFE, PE, PMMA and nylon 6 components and parameters were compared to those reported in the literature. Our calculations indicate that the surface tension of studied polymers, their components and parameters as well as the Lifshitz-van der Waals component of polar liquids practically do not depend on the temperature in the studied range.

Interplay between Vacuum-Grown Monolayers of Alkylphosphonic Acids and the Performance of Organic Transistors Based on Dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene.

Monolayers of six alkylphosphonic acids ranging from C8 to C18 were prepared by vacuum evaporation and incorporated into low-voltage organic field-effect transistors based on dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT). Similar to solution-assembled monolayers, the molecular order for vacuum-deposited monolayers improved with increasing length of the aliphatic tail. At the same time, Fourier transform infrared (FTIR) measurements suggested lower molecular coverage for longer phosphonic acids. The comparison of FTIR and vibration frequencies calculated by density functional theory indicated that monodentate bonding does not occur for any phosphonic acid. All monolayers exhibited low surface energy of ∼17.5 mJ/m(2) with a dominating Lifshitz-van der Waals component. Their surface roughness was comparable, while the nanomechanical properties were varied but not correlated to the length of the molecule. However, large improvement in transistor performance was observed with increasing length of the aliphatic tail. Upon going from C8 to C18, the mean threshold voltage decreased from -1.37 to -1.24 V, the field-effect mobility increased from 0.03 to 0.33 cm(2)/(V·s), the off-current decreased from ∼8 × 10(-13) to ∼3 × 10(-13) A, and for transistors with L = 30 μm the on-current increased from ∼3 × 10(-8) to ∼2 × 10(-6) A, and the on/off-current ratio increased from ∼3 × 10(4) to ∼4 × 10(6). Similarly, transistors with longer phosphonic acids exhibited much better air and bias-stress stability. The achieved transistor performance opens up a completely "dry" fabrication route for ultrathin dielectrics and low-voltage organic transistors.

Surface tension of polytetrafluoroethylene and its wetting by aqueous solution of some surfactants and their mixtures

Measurements of the contact angle of aqueous solution of rhamnolipid (RL) mixture with n-octyl-β-d-glucopyranoside (OGP), Triton X-100 (TX-100) or/and sodium dodecylsulfate (SDDS) on polytetrafluoroethylene (PTFE) were made. To this aim there was used a plate whose surface topography was analyzed by means of optical profilometry method. Additionally, plate surface chemistry was studied employing the Fourier transform infrared spectroscopy. The obtained values of contact angle were discussed based on the PTFE surface tension (γSV) as well as the Lifshitz-van der Waals component of the water surface tension (γWLW). The contact angle of aqueous solution of several surfactants and their mixtures on PTFE was also considered on the basis of γSV and γWLW. It occured that by using the values of γSV, γWLW and surface tension of the aqueous solution of surfactants and their mixtures, the contact angle on PTFE can be predicted. It also occured that changes of adhesion tension of aqueous solutions of surfactants as a function of their concentration can be determined by the exponential function of the first or second order. Using such functions Gibbs surface excess concentration of surfactants at the PTFE-water interface, mole fraction of surfactant in the mixed monolayer and fraction of the area occupied by given surfactants in the monolayer were determined. Gibbs surface free energy of adsorption of a given surfactant in the presence of another one and adhesion work of the aqueous solution of surfactants to the PTFE surface were also evaluated.

Wettability prediction of such polymers as polyethylene and polytetrafluoroethylene by aqueous solutions of classical surfactants and biosurfactants

The measurements of the contact angle (θ) of aqueous solutions of rhamnolipid (RL), n-octyl-β-d-glucopyranoside (OGP), Triton X-100 (TX-100) and sodium dodecylsulfate (SDDS) on the polyethylene (PE) surface were carried out. The θ values on PE and polytetrafluoroethylene (PTFE) were also determined theoretically by using the values of surface tension of polymers and the Lifshitz-van der Waals component of water surface tension. On the basis of θ values of surfactant solutions on PE the critical micelle concentration of RL, OGP, TX-100 and SDDS, critical surface tension of PE wetting (γC), Gibbs surface excess concentration of these surfactants at the PE-water interface, work of adhesion of surfactant solutions to PE, fraction of PE occupied by surfactant molecules and Gibbs standard free energy of surfactants adsorption at the PE-water interface were established. The γC of PE wetting from the relationship between the adhesion and surface tension of surfactant solutions and standard Gibbs free energy of adsorption from the Langmuir equation were determined. The standard Gibbs free energy of adsorption at the PE-water interface was compared to that at the water-air one. The good agreement between the measured and calculated θ values of RL, OGP, TX-100 and SDDS solutions on PTFE and PE was obtained.

Thickness dependent wetting properties and surface free energy of HfO2 thin films

We show here that intrinsic hydrophobicity of HfO2 thin films can be easily tuned by the variation of film thickness. We used the reactive high-power impulse magnetron sputtering for preparation of high-quality HfO2 films with smooth topography and well-controlled thickness. Results show a strong dependence of wetting properties on the thickness of the film in the range of 50–250 nm due to the dominance of the electrostatic Lifshitz-van der Waals component of the surface free energy. We have found the water droplet contact angle ranging from ≈120° for the thickness of 50 nm to ≈100° for the thickness of 2300 nm. At the same time the surface free energy grows from ≈25 mJ/m2 for the thickness of 50 nm to ≈33 mJ/m2 for the thickness of 2300 nm. We propose two explanations for the observed thickness dependence of the wetting properties: influence of the non-dominant texture and/or non-monotonic size dependence of the particle surface energy.

Adhesion of canola and diesel oils to some parts of diesel engine in the light of surface tension components and parameters of these substrates

Measurements of the surface tension of canola oil from different manufacturers, diesel oil and water–oil interface tension as well as the contact angle on different parts of the diesel engine were made. The contact angle for canola and diesel oils on polytetrafluoroethylene (PTFE) and polymethyl methacrylate (PMMA) surfaces as well as for water, diiodomethane and formamide on different parts of the diesel engine was also measured. On the basis of the obtained results as well as the van Oss et al. approach to the interfacial tension and the Young equation the Lifshitz–van der Waals component of the surface tension and electron-donor and electron-acceptor parameters of the acid–base components of this tension of canola and diesel oils and parts of diesel engine were determined. Taking into account the determined values of the parameters and components of the surface tension of diesel and canola oils, their adhesion to the particular parts of a diesel engine was determined by using the van Oss et al. equation and compared to the adhesion work determined from the Young–Dupre equation. It appeared that the adhesion work determined from the van Oss et al. equation which decreased the precursor film pressure is comparable to that determined from the Young–Dupre equation. Adhesion work of the diesel oil to different parts of the diesel engine is somewhat lower than that of canola oils. In addition the water–diesel oil interface tension is lower than that for water–canola oil.

Work of adhesion and activity of aqueous solutions of ternary mixtures of hydrocarbon and fluorocarbon nonionic surfactants at the water–air and polymer–water interfaces

The values of the surface tension and contact angle on the polytetrafluoroethylene surface (PTFE) of aqueous solutions of the ternary mixtures of hydrocarbon surfactants, TX100 and TX165, and fluorocarbon FSN100 at different mole fractions of surfactants in the bulk phase were applied for the studies of the correlation between the adsorption of surfactants at the solution–air and polymer–solution interfaces, the work of adhesion determined from the Young–Dupree equation, the parameter of the intermolecular interactions and the spreading coefficient of aqueous solutions of the studied mixtures on the PTFE surface. For this purpose the values of the total mole fraction and activity of surfactants at the polymer–solution interface obtained from the Sprow and Prausnitz equation were compared to those at the solution–air one. Also on the basis of the mole fraction of the particular surfactants at the PTFE–solution and water–air interface and on the assumption of the additivity of the adhesion work, the work of adhesion of the fluorocarbon tail to the PTFE surface as well as the Lifshitz–van der Waals component of the PTFE surface tension were calculated.

Passivation of High-Surface-Energy Sites of Milled Ibuprofen Crystals via Dry Coating for Reduced Cohesion and Improved Flowability

Ibuprofen micronization with dry coating is investigated to examine its influence on passivation/stabilization of high-surface-energy sites and reduced cohesion. A fluid energy mill was used to micronize ibuprofen particles down to 5-28 μm with or without simultaneous nanosilica coating. Powder flow property and dispersibility were characterized using FT4 powder tester and Rodos/Helos laser diffraction particle sizer. Surface energy was characterized using a next generation inverse gas chromatography instrument. Uncoated micronized ibuprofen showed an increased Lifshitz-van der Waals (LW) dispersion component of surface energy with increasing milling intensity. In contrast, dry-coated milled powders showed a significant reduction in the LW component, whereas physical mixture of uncoated micronized ibuprofen and silica exhibited no reduction in surface energy, indicating that dry coating is necessary for the passivation of high-energy sites of ibuprofen created during micronization. Surface energy of pure micronized ibuprofen was highly heterogeneous, whereas dry-coated ibuprofen had greatly reduced heterogeneity. Micronization with dry coating also improved flowability and bulk density as compared with pure active pharmaceutical ingredient micronization without coating, or just blending with silica. Overall, dry coating leads to decreased cohesion and improved flowability because of reduced LW dispersive component of surface energy and creating nanoscale surface roughness.