Wettability Of Polymers Research Articles

Wettability, adhesion, adsorption and interface tension in the polymer/surfactant aqueous solution system: II. Work of adhesion and adsorption of surfactant at polymer–solution and solution–air interfaces

The values of the surface tension of aqueous solutions of Triton X-100, Triton X-114, Triton X-165, sodium dodecylsulfate, sodium hexadecylsulfonate, cetyltrimethylammonium bromide, cetylpyridinium bromide, sodium N-lauryl sarcosinate, dodecyldimethyethylammonium bromide, tetradecyltrimethylammonium bromide and benzyldimethyldodecylammonium bromide and those of contact angle measured in the polytetrafluoroethylene (polymethyl methacrylate, nylon 6)–solution–air system were applied for the studies of correlation between the adsorption of surfactants at the solution–air and polymer–solution interfaces, critical surface tension of polymer wetting and work of adhesion of aqueous solutions of these surfactants to the above mentioned polymer surfaces. On the basis of the surface tension of aqueous solutions of surfactants studied and polymer–solution interface tension the Gibbs surface excess concentration at the polymer–solution interface was calculated and compared to that at the solution–air one. Using the Gibbs surface excess concentration data the molar fraction of surfactants at the polymer–solution interface was determined and compared to that at the solution–air one. The values of the activity of surfactants at the polymer–solution interface obtained from the Sprow and Prausnitz equation were also compared to those at the solution–air one and next used for calculations of the work of adhesion of solution to the polymer surface. The obtained values were compared to those determined from the Young–Dupree equation.

Wettability, adhesion, adsorption and interface tension in the polymer/surfactant aqueous solution system. I. Critical surface tension of polymer wetting and its surface tension

The contact angle of aqueous solutions of Triton X-100, Triton X-114, Triton X-165, sodium dodecylsulfate, sodium hexadecylsulfonate, cetyltrimethylammonium bromide, cetylpyridinium bromide, sodium N-lauryl sarcosinate, dodecyldimethyethylammonium bromide, tetradecyltrimethylammonium bromide and benzyldimethyldodecylammonium bromide on polytetrafluoroethylene, polymethyl methacrylate and nylon 6 was studied. The contact angle values were used in the Young equation for the polymer–solution interface tension calculation and for the determination of the critical surface tension of polymer wetting. The critical surface tension of polymer wetting was obtained on the basis of the relationship between the cosine of contact angle and/or the adhesion tension as a function of the surface tension of aqueous solution of studied surfactants and then was discussed in relation to the Lifshitz–van der Waals components and electron-acceptor and electron-donor parameters of polytetrafluoroethylene, polymethyl methacrylate and nylon 6 surface tension. The role of the parameter of interfacial interactions in the relationship between the critical surface tension of polymer wetting and the surface tension was also considered. This parameter was calculated by using the polymer–solution interface tension as well as the polymer and aqueous solutions of surfactant surface tension.

Behavior of pH-Sensitive Core Shell Particles at the Air–water Interface

In this article, the adsorption of latex core-responsive polymer-shell nanoparticles at the air-water interface is investigated using a Langmuir trough. Phase transition isotherms are used to explore their responsive behavior at the interface as a function of changes in the pH of the subphase. By adjusting the pH of the water prior to particle deposition, we probe the effect of the stabilizing polymer wetting by the water subphase on the stability of these particles at the air-water interface. In addition, by initially compressing a stable film of adsorbed particles and then subsequently changing the pH of the subphase we study desorption of these particles into the water phase.

Tailoring the wetting properties of polymers from highly hydrophilic to superhydrophobic using UV laser pulses

This paper demonstrates the application of ultrashort-pulsed lasers as a unique tool for controllable modification of the surface wettability of polymers from high hydrophilicity to superhydrophobicity. This is achieved by exploiting the effect of laser pulse duration and photon energy on the surface chemistry and morphology and subsequent wetting properties of polymeric surfaces treated with UV laser pulses. In three different pulse duration regimes, ranging from femtosecond to nanosecond and two different photon wavelengths, we have systematically altered the wettability of polyethersulfone surfaces from highly hydrophilic to superhydrophobic. Our results indicate that, despite the remarkable changes in the surface morphology attained, the surface wettability variations are dominantly caused by laser-induced chemical modifications, which are highly dependent on the pulse energy and duration. The ability of tuning the wetting properties and thus the surface energy of laser-treated polymer surfaces within a broad range makes them excellent candidates for liquid flow control in microfluidics and biological adhesion applications.

Effect of Glow-Discharge Air Plasma Treatment on Wettability of Synthetic Polymers

Main aim of this study was focused on characterization of the effect of microwave air plasma treatment on wettability of synthetic polymer surfaces. Wettability of solid polymer surfaces polyethylene, polypropylene, polystyrene (PE, PP, PS) was followed as a function of plasma treatment time. For evaluation the equilibrium contact angles of wetting as well as dynamic contact angles of wetting were determined by means of sessile drop and Wilhelmy plate methods. Free surface energy (SFE) of studied samples were calculated from the experimentally determined contact angles using Fowkes and van Oss, Chaudhury and Good (vOCG) approaches. It was found that with prolonged treatment time the total surface free energy of PE was two times increased from 23 mJ/m2 to 45 mJ/m2 after 360 s plasma treatment time (calculated for W and EG as wetting liquids). Similar effect was found for all studied polymers. With respect to the dispersive and polar components of the total surface free energy the vigorous effect was found for polar component, for which it was increased from 7 mJ/m2 to 20 mJ/m2.

Vitamin E modifies poly(D,L)lactic acid wettability and reduces bacterial adhesion

Highly biocompatible polylactic acid (PLA)-derived polymers are used for different biomedical applications such as orthopaedic screws and drug delivery devices. Nevertheless their clinical use is limited by their proinflammatory characteristics. Vitamin E (α-tocopherol, Vit. E), a natural antioxidant and anti-inflammatory agent has been used to improve different biomaterials biostability [1], and among them also P(D,L)LA [2]. In this work, addition of Vit.E (10-40% w/v) to P(D,L)LA films obtained by solvent casting technique increased polymer surface wettability and human plasma protein adsorption, while addition of Vit.E acetate (Vit.E Ac, 10-40% w/v), the acetic ester of α-tocopherol, often used as an alternative to Vit.E itself, failed in modifying polymer wettability. On the other hand, bacterial adhesion experiments onto control, Vit.E and Vit.E Ac enriched P(D,L)LA films showed that both presence of Vit.E and Vit.E Ac was able to reduce the adhesion of the RP62A Staphylococcus epidermidis strain [3]. In particular, in PLA + Vit. E samples the decrease in bacterial adhesion was of 56%, while, in the case of PLA + Vit. E Ac samples the decrease was of 40%. These preliminary data suggest that Vit. E addition to PLA containing medical devices could improve their resistance to bacterial infections.

Control of Wettability of Plasma Polymers by Application of Ti Nano‐Clusters

AbstractTwo‐step process that allows controlling independently roughness and chemical composition of plasma polymers, i.e., two parameters determining the wettability of such materials, is presented. In the first step a film composed of Ti nano‐clusters is deposited on a smooth substrate. Nano‐cluster films of different roughness can be obtained depending on deposition time. In the second step the nano‐cluster films are overlaid by a thin layer of plasma polymer having the desired chemical structure. This approach allows the tuning of wettability of the deposited films to as much as 50% of the wettability of the films having the same chemical structure but deposited on a smooth substrate.magnified image

Surface energy and wettability of polymers light-cured by two different systems

ObjectivesThis study evaluated the surface energy and wettability of composite resins polymerized by different light-curing units to ascertain the good wetting of tooth surfaces to achieve adhesion. Material and MethodFiltek Z350 (3M ESPE), Admira (VOCO) and Grandio (VOCO) resins were selected for the testing procedures. The resins were light cured using LED and Halogen devices. Contact angles were measured goniometrically (Ramé-Hart F100) using water and glycerol as test liquids. Surface energy values were calculated with a software program (DROPimage Standard) that uses the harmonic mean method applied to the acid-base theory. The data were analyzed statistically by ANOVA and Tukey's test with a significance of 0.05. Results and ConclusionsNo statistically significant differences were found between the values of surface energy. The measured wettability differed statistically in most combinations as a function of the type of composite resin, type of light-curing unit, and the test liquid.

Polymer Filling of Silicon Trenches for 3-D Through Silicon vias Applications

Ring-shaped silicon trenches with a depth of 50 were filled with different spin-on dielectric (SOD) polymers. Ultimately, the polymer should serve as deep trench isolation layers, also called liners, for 3-D wafer-level packaging through silicon vias (TSVs). TSVs allow the vertical stacking and interconnection of multiple devices. 3-D packaging is an emerging technology that can be an alternative solution to scaling issues in complementary metal oxide semiconductors. SODs with different electrical, chemical, and mechanical properties were tested. The filling was conducted using spin coating, which is a readily available technology. In order to improve the filling performances, a prewetting solvent was applied prior to coating. Contact angle measurements were carried out to assess the polymer wetting properties. Without prewetting, it was observed that too high an affinity for the wafer surface was probably detrimental. With prewetting, the wetting was improved but this did not significantly modify the filling itself. The filling was rather improved due to the mechanical action of the solvent. Overall, most of the SOD could successfully fill the trenches, however, stress-related delamination could almost always be detected at the polymer/silicon interface. A stress study was carried out by finite element modeling in order to address the delamination issue. It was concluded that the level of stress is mainly governed by the cure temperature and other mechanical properties. This paper concludes with some recommendations on the choice of an SOD for filling applications.

Surface modification of poly(ethylene terephthalate) (PET) by magnet enhanced dielectric barrier discharge air plasma

In order to study the effect of magnet enhanced plasma on polymer surface, a dielectric barrier discharge (DBD) setup with and without magnet is presented and used to modify poly(ethylene terephthalate) (PET) films at atmospheric pressure in ambient air. Surface analysis and characterization of the air plasma-treated PET films are performed using contact angle measurements, surface free energy, Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS). The results show that air plasma leads to an obvious decrease in contact angle and increase in surface free energy. And surface wettability of the PET films treated by DBD with magnet is better than that without magnet. AFM images show an increase in surface roughness due to plasma etching. It is shown that O and N elements are introduced onto PET film surfaces as oxygen- and nitrogen-containing functional groups. The oxygen-containing groups can be identified as C O, C O and O C O. Their concentrations of the PET films treated with magnet are more than those treated without magnet. The difference is attributed to more active particles generated in DBD with magnet. Therefore, magnet field plays an important role in improving surface wettability of polymers.

Processing dependency of percolation threshold of MWCNTs in a thermoplastic elastomeric block copolymer

We prepared carbon nanotube thermoplastic elastomeric block copolymer nanocomposites using a commercial styrene–ethylenebutylene–styrene (SEBS) block copolymer and multiwall carbon nanotubes (MWCNTs) at different filler concentrations. Hereto we applied two different processing strategies, namely direct melt mixing and solution-precipitation. We observe that the mechanical and electrical properties such as storage module and electrical percolation threshold are clearly affected by the processing approach. We studied these effects in detail by means of dielectric spectroscopy, which provided important information about the dispersion state of the MWCNT filler network. It revealed a fractal filler behaviour of the samples independent of the processing method. However, in samples prepared by melt mixing an additional dielectric response related to nanoscopic gap junctions of 1.5nm was identified. This response was not present in solution-mixed samples, which are characterized by improved polymer wetting. We discuss how the interactions between CNTs and the two phases of the block copolymer matrix are affected by the processing conditions resulting in the important differences in the filler network structure, which directly influence the final electrical and mechanical properties of the composite.

Comparison of glow argon plasma-induced surface changes of thermoplastic polymers

Modification of high-density polyethylene (PE), polytetrafluoroethylene (PTFE), polystyrene (PS), polyethyleneterephthalate (PET) and polypropylene (PP) by Ar plasma was studied. The amount of the ablated material was determined by gravimetry. Wettability of polymers after the plasma treatment was determined from the contact angle measurement. The changes in the surface morphology of polymers were observed using atomic force microscopy (AFM). Chemical structure of modified polymers was characterized by X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). Surface changes were also studied by the determination of electrokinetic potential ( ζ-potential). It was found that under the plasma treatment the polymers are ablated and their surface morphology and roughness are changed dramatically. XPS measurements indicate an oxidation of the polymer surface. The plasma treatment results in a dramatic increase of the ζ-potential. EPR data show different radical amount present on the treated surface of all polymers. Most significant changes due to the degradation of polymer chains are observed on PTFE.

Effects of the degree of dispersion and the morphology of zinc powder on the thermodynamics of its interaction with polystyrene in solution and in composite films

The adsorption of block PS on the surface of spherical, round, and flaky particles of highly dispersed Zn powders with dimensions of 3.5–23 μm and the interaction of the polymer with the surface of Zn powders in the composite films are studied by refractometry and isothermal calorimetry. During establishment of adsorption equilibrium, the concentration of PS in the bulk of solution increases, while, near the surface of Zn particles, the concentration of PS decreases, thus indicating the predominance of absorption from solution of the solvent o-xylene. With the use of the thermodynamic cycle, including processes of solution of the polymer and Zn-PS film composite and wetting of the Zn powder, the enthalpies of formation of PS-Zn composites are estimated. The enthalpies of mixing of filled compositions comprise two contributions of opposite signs: In the low-filling region, the negative contribution of adhesion interactions prevails, while in the region of high-filled compositions, a positive structural contribution, which is associated with additional loosening of the glassy packing of PS near the filler surface, plays the decisive role. The contribution of adhesion interaction is largely determined by the dimensions of filler particles, while the structural contribution is controlled by their shape. The experimental evidence suggests that spherical particles possess the highest thermodynamic compatibility with the polymer matrix of the composite material.

The wettability of polytetrafluoroethylene and polymethylmethacrylate with regard to interface behaviour of Triton X-165 and short chain alcohol mixtures: I. Critical surface tension of wetting and adhesion work

Wetting of polymers (PTFE, PMMA) by aqueous solutions of Triton X-165 mixtures with methanol, ethanol and propanol was studied in a wide range of alcohol and Triton X-165 concentration. The Triton X-165 concentration range corresponded to its unsaturated and saturated monolayer in the absence of alcohol. The wetting properties of Triton X-165 and alcohol mixtures were determined on the basis of advancing contact angles measurements by the sessile drop method. From the obtained contact angle values the relationships between cos θ, the adhesion tension and surface tension of the solutions, cos θ and the reciprocal of the surface tension were determined. On the basis of these relationships the correlation between the critical surface tension of PTFE and PMMA wetting and the surface tension of these polymers and work of adhesion of aqueous solution of TX-165 and alcohols mixtures to PTFE and PMMA surface was discussed. The critical surface tension of PTFE wetting was found to be close to its surface tension determined from the contact angles for polar liquids, but the critical surface tension of PMMA wetting considerably lower than its surface tension and even the Lifshitz–van der Waals components of this surface tension.

Behavior of cationic surfactants and short-chain alcohols in mixed surface layers at water–air and polymer–water interfaces with regard to polymer wettability: II. Wettability of polymers

The wettability of polytetrafluoroethylene (PTFE) and polymethylmethacrylate (PMMA) by aqueous solutions of cetyltrimethylammonium bromide (CTAB) mixtures with short-chain alcohols such as methanol, ethanol, and propanol, as well as for 1-hexadecylpyridinium bromide (CPyB) with the same alcohols, was studied on the basis of advancing contact-angle measurements by the sessile drop method over a wide range of alcohol and cationic surfactant concentrations where they can be present in solution in monomeric or aggregated form. It should be noted that the contact angles for aqueous solution mixtures of cationic surfactants with propanol on PTFE surfaces were measured earlier and presented in our previous paper. From the obtained contact-angle values the relationships between cos θ and surface tension of the solutions ( γ LV ) and that between adhesion tension and γ LV were considered. The relationship between the cos θ and the reciprocal of γ LV was also discussed. From these relationships the critical surface tension of PTFE and PMMA wetting and the correlation between the adsorption of cationic surfactant and alcohol mixtures at water–air and polymer–water interfaces were deduced. On the basis of the contact angles and components and parameters of the surface tension of surfactants, alcohols, and polymers also the Gibbs and Guggenheim–Adam isotherm of adsorption and the effective concentration of alcohols and surfactants at polymer–water interfaces were calculated. Next, the work of adhesion of solution to polymer surface with regard to the surface monolayer composition was discussed. The analysis of the contact angles with regard to adsorption of surfactants and alcohols at polymer–water and water–air interfaces allowed us to conclude that the PTFE wetting depends only on the contribution of the acid–base interactions to the surface tension of aqueous solutions of cationic surfactant and alcohol mixtures, and the adhesion work of solution to its surface only slightly depends on the concentration and composition of solution, in contrast to PMMA. The critical surface tension of PTFE wetting is close to its surface tension determined for liquids in which the surface tension is two times or more higher than that of PTFE, but for PMMA it is considerably lower than its surface tension and even the Lifshitz–van der Waals component of this tension.

Wetting Technologies for High-Accuracy Sink-Float Separations in Water- Based Media

The accuracy of sink-float separations in water-based media such as Magnetic Density Separation is compromised by tiny air-bubbles attached to the surface of hydrophobic materials in the feed. Separations of plastics mixtures with accuracy better than 10 kg/m 3 require a total elimination of air-bubbles by pre-wetting the surface of the feed particles with a thin film of water. Theoretical and experimental results are compared for pre-wetting processes based on condensation from the gas phase and direct liquid-solid contact for both shredded waste and virgin polymers. The tests show that the wettability of most polymers improve slightly by steaming for about 1 minute, but the best wetting results are obtained with immersion in boiling tap water. The success of wetting in boiling water can be explained by the deposition of a thin layer of calcium carbonate. Shredded plastics are easier to be wetted than virgin polymers, probably because a relatively rougher surface is caused by the shredder process. A new wetting process to eliminate air bubbles was developed on the basis of these results, which carries a minimal amount of heat and water with the feed to the MDS process liquid.

Control of Wettability of Polymers by Surface Roughness Modification

Most polymeric materials, particularly polyolefins and their derivatives, present a low surface energy which is the cause of their poor wettability and limits processes such as adhesive bonding, painting, or metalizing. Many methods have been developed and used to modify polymer surfaces for improved wetting, including mechanical treatments, wet-chemical treatments with strong acids or bases, and exposure to flames or corona discharge. In this paper the improvement of wetting properties of several polymeric materials widely used in the automotive industry, such as high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP) and silicone, is studied by means of surface mechanical abrasion using sandpapers of different grain sizes (1000, 180 and 80). Measurements of the surface roughness are performed using a Hommel Tester T8000 device equipped with a diamond stylus, which provides data on the arithmetic average roughness R a parameter and Abbott–Firestone curve. Variations in the polymers surface energy (SE) are estimated through contact angle measurements using five test liquids of different polarities. Both components of the SE, dispersion (σ D) and polar (σ P), as well as total (σ T) at different conditions of treatment are analyzed using the Owens–Wendt–Rabel–Kaelble (OWRK) method. Morphological changes induced in the surface are analyzed by Scanning Electron Microscopy (SEM). Additionally, measurements of the static friction coefficient (μ s) are carried out by the standard method ASTM D 1894-08. A slight enhancement in surface wettability is found with the mechanical abrasion pre-treatment from the SE increase. Finally, a higher value of μ s is achieved for the abraded specimens as the normal force acting onto the system is increased.

Atomic Layer Deposition and Abrupt Wetting Transitions on Nonwoven Polypropylene and Woven Cotton Fabrics

Atomic layer deposition (ALD) of aluminum oxide on nonwoven polypropylene and woven cotton fabric materials can be used to transform and control fiber surface wetting properties. Infrared analysis shows that ALD can produce a uniform coating throughout the nonwoven polypropylene fiber matrix, and the amount of coating can be controlled by the number of ALD cycles. Upon coating by ALD aluminum oxide, nonwetting hydrophobic polypropylene fibers transition to either a metastable hydrophobic or a fully wetting hydrophilic state, consistent with well-known Cassie-Baxter and Wenzel models of surface wetting of roughened surfaces. The observed nonwetting/wetting transition depends on ALD process variables such as the number of ALD coating cycles and deposition temperature. Cotton fabrics coated with ALD aluminum oxide at moderate temperatures were also observed to transition from a natural wetting state to a metastable hydrophobic state and back to wetting depending on the number of ALD cycles. The transitions on cotton appear to be less sensitive to deposition temperature. The results provide insight into the effect of ALD film growth mechanisms on hydrophobic and hydrophilic polymers and fibrous structures. The ability to adjust and control surface energy, surface reactivity, and wettability of polymer and natural fiber systems using atomic layer deposition may enable a wide range of new applications for functional fiber-based systems.

Dewetting of PMMA on PS−Brush Substrates

We present experimental results quantifying the dewetting behavior of poly(methyl methacrylate) (PMMA) melt on polymer brushes of polystyrene (PS) molecules. Our studies indicate contact angles which display a brush molecular weight dependence similar to that expected for autophobic dewetting situation. We use strong segregation theory calculations to model the interfacial tension behavior in our observations and delineate the interplay between enthalpic and entropic effects in polymer wetting upon polymer brushes.

Effect of N-trimethyl chitosan enhancing the dissolution properties of the lipophilic drug cyclosporin A

The aim was to evaluate the influence of N-trimethyl chitosan chloride (TMC) as a carrier for solid dispersion on the dissolution of poorly water-soluble drugs. In this study, we used cyclosporin A(CyA) as a model drug and TMC as a carrier. The effect of various formulation and process variables including TMC-to-CyA mixing weight ratio, weigh molecular( M w) of TMC and methods used to disperse CyA along with the TMC on the drug dissolution was investigated. The nature of CyA dispersed in the matrix was studied by powder X-ray diffractometry (PXRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and dissolution rate analyses. It was proved that all solid mixtures of CyA with TMCs showed a significantly rapid dissolution rate compared to pure drug and physical mixture. The greater the TMC content the higher the drug dissolution was, up to a maximum corresponding to a polymer: drug ratio of 3:1. The lower the M w of TMC, the more important the polymer effect was. The dissolution of CyA was remarkably improved by the solid dispersion. The drug dissolution enhancement was attributed to the decreased drug crystallinity and size and polymer wetting effect. There was no significant difference in the efficiency of improving the drug dissolution between the solid dispersions prepared by solvent dispersing and by co-grinding. It was suggested that the TMC with a lower molecular weight is a useful carrier for solid dispersion.