ABSTRACTS
The following is a list of the abstracts for papers which will be presented in the INTERNATIONAL SYMPOSIUM ON POLYMER SURFACE CHARACTERIZATION The listing is alphabetical by presenting author. This list is updated continually to add abstracts as they become available and make appropriate corrections. This list may be conveniently searched by using the editor provided with most popular browsers (e.g. Microsoft Explorer, Netscape, ... etc.)
1) Saint-Gobain Recherche
2) Laboratoire CNRS/Saint-Gobain " Surface du Verre et Interfaces " 39, quai Lucien Lefranc. F-93303 Aubervilliers, FRANCE
Glass/polymer Adhesion. Surface Analysis of the Debonded Interface
Adhesion science is a cross-linked field of science that relates interfacial chemistry and fracture mechanics. This particular field of materials science throws a bridge between mechanical macroscopic properties and physical and chemical phenomena occurring at the molecular scale, namely chemical bonding, molecular friction, diffusion, aggregation, segregation and gradient of properties near the interface. While a battery of mechanical tests have been conceived to characterize the adhesion strength, there are few experimental methods that give relevant information about the local phenomena near the interface. This is mainly due to the fact that in situ analysis of the interface is very difficult to achieve. To overcome this problem, we have decided to focus our investigations on the surfaces that result from the interface debonding. We study these surfaces by infrared spectroscopy (IRS), Atomic Force Microscopy (AFM) and X-ray photo-emission spectroscopy (XPS).
In this paper, we report the results of a ten-years effort turned towards the understanding of the adhesion mechanisms between silicate glass and a specific polyurethane elastomer. The interest of this system lays in the fact that the adhesion strength and its evolution with aging show a strong dependence on the glass composition. IRS and AFM turn out to be very effective for the determination of the locus of failure. It is found that the failure is cohesive, interfacial or through an interphase of weak cohesion, depending on the nature of the substrate and on the aging conditions. From XPS experiments, it is possible to understand the role of the local organization of the polymer chains near the interface. From this set of results, we derive a model of the interface that accounts for the various features shown by the macroscopic adhesion mechanical tests.
1) lnstitut de Chimie de Surfaces et Interfaces - CNRS , Mulhouse (France) 2) Ecole Nationale Superieure d'Ingenieurs des Mines d'Albi - Carznaux, Albi (FRANCE)
Study of Surface Properties of Polymer Adsorbed on a Solid Surface Using IGC Techniques
The surface properties of polyethyleneoxide adsorbed or grafted on a solid - fumed silica and talc samples - was examined using Inverse: Gas Chromatographic Techniques. A special attention was paid to the influence of the impregnation or grafting ratios, the molecular weight. It was demonstrated that, on a silica surface; the potential of interaction is mainly dependent of the monomer unit density and not of the molecular weight. The same observation was confirmed for talc surfaces modified by controlled polyethylene oxide impregnation. The monomer unit mobility was examined calling on solid NMR Spectroscopies These experiments highlight a close correlation between the surface properties of the modified silica samples and the monomer unit mobility.
Comparison of the behavior of the adsorbed macromolecule between silica and talc samples will give access to the influence of surface heterogeneity on the modified surface properties. If fumed silica exhibits only a short-range heterogeneity, taking the monomer unit size as reference, it is obviously not the case of layered solid like talcs. The latter can be considered as macro-heterogeneous, in other words, basal and lateral surface dimensions exceed largely that of monomer units. It was observed that at low coverage ratio the polyethylene oxide adsorbed preferentially on the lateral surface. The complete shielding of the lateral surfaces lead to a strong decrease of the dispersive component of the surface energy (more than 100 mJ/m2) of the impregnated talcs. Origin of the talc has a major influence on the coverage ratio at which occurs this jump of surface properties. It will be certainly related to the lamellarity and/or micro-macro crystallinity of the studied solid.
1) Dept. of Materials and Laboratory for surface Studies, University of Wisconsin, Milwaukee, WI 53201
2) Advances Materials Processing and Analysis Center (AMPAC), Mechanical Materials and Aerospace Engineering, University of Central Florida, Orlando, FL 32816
Chemical Characterization of Polymer and Bio Surfaces, Following Growth, Modification and Interactions with Inorganic Clusters and Films
(Abstract not yet available)
Polymer Surface Characterization Using Secondary Ion Mass Spectrometry
(Abstract not yet available)
1) CEA-Saclay, DSM-DRECAM-SPCSI, bat. 466, F-91191 Gif-sur-Yvette Cedex, (France)
2) Dept of Chemistry, University of British Columbia, 2036 Main Mall,
Vancouver, BC, V6T 1Z1 (Canada).
Recent Advances in the Accurate and Practical Calculation of Core and Valence XPS Spectra Using DFT : New Crops of Information at Identical Experimental Resolution
(Abstract not yet available)
TOF-SIMS and XPS Characterization of Fatty Acid Esters in Polypropylene
Fatty acid esters are widely used in polypropylene processing since they can act as internal slip and antistatic agents. However, in order for these compounds to function they must migrate to the surface. In the best case the additive will be physically stable on the surface, i.e. will not be easily removed or transferred to a contacting surface. X-ray Photoelectron Spectroscopy (XPS), also known as Electron Spectroscopy for Chemical Analysis (ESCA), and Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) are ideally suited for studying these additives in polypropylene. In this paper the inherent quantitative precision and surface sensitivity of XPS is used to determine the concentration and orientation of fatty esters in injection molded polypropylene. In addition, the high spatial resolution and imaging capabilities of TOF-SIMS are used to identify additive domain formation in injection molded polypropylene.
1) Unité PCPM Université Catholique de Louvain, Place Croix du Sud 1, B1348 Louvain-La-Neuve, BELGIUM
2) Baxter R&D Europe, Rue du Progrès 7, B1400 Nivelles BELGIUM
Cyclic Oligomer Segregation at Metallized Polyethylene Terephtalate Surface
We have studied the segregation of cyclic oligomers onto the surface of metallized PET. The diffusion, nucleation and crystallisation aspects of the phenomenon have been investigated by means of several surface and imaging techniques. First approach by Rutherford Backscattering suggested a fast diffusion of the metal from the surface to the bulk of the polymer. AFM technique have shown the nucleation and growing of crystals described in the literature as being associated with cyclic trimers. SIMS technique revealed the absence of metal in those crystals.
A model in which Cyclic oligomer crystals is growing on an stable discontinuous metal layer is proposed. In order to verify the validity of this model, we have developed an RBS simulation tool to take into account the lateral inhomogeneity. This have shown very good agreement between the AFM and RBS quantitative data.
Finally, a model of the entire diffusion and crystallisation process will be proposed.
Modification of EPDM Rubber Surface for improved Adhesion to Polyurethane Coating
Ethylene Propylene Diene rubber (EPDM) is the most commonly used starting material for automotive window seal components as it has excellent ozone and weather resistance properties. One of the main disadvantages of EPDM rubber, is it's hydrocarbon nature which leads to inadequate surface chemical properties and hydrophobicity, resulting in poor adhesion to polyurethane (PU) coating used in automotive applications. To improve adhesion between EPDM and PU coatings, the rubber's surface needs to be polar. One common surface treatment method for elastomers is halogenation, typically chlorination. Chlorination is an efficient method to improve the wettability of unsaturated rubbers.
In this study, surface modification has been performed on both extruded and milled unvulcanised EPDM rubbers, by surface treating the rubber compound with trichloroisocyanuric acid (TCICA). The modified rubber surfaces were characterised by analytical surface techniques such as contact angles and X-ray Photoelectron Spectroscopy (XPS). EPDM has little unsaturation to provide a reaction site for the addition of chlorine to its surface. Prolonged treatment of the milled unvulcanised rubber showed that the percentage chlorine concentration increased with an increase of treatment time. The surface energy of both extruded and milled unvulcanised EPDM rubber increased with increasing treatment time. Stability of the treated rubber remained unchanged after 6 months of treatment, as determined by XPS. Adhesion performance was evaluated using several complimentary techniques such as peel, abrasion, crack and wettability by primer. Failure surfaces were analysed with Scanning Electron Microscopy (SEM) coupled with Energy Dispersive X-ray Analysis (EDAX
Adhesion of Microcantilevers for MEMS Reliability Studies
Changes in tribological properties between contacting surfaces of compliant mechanisms in microelectromechanical systems (MEMS) due to usage or time is preventing many applications from entering the market place. Very low adhesion and friction are desired. Monolayer silane coupling agents are often applied to polycrystalline silicon surfaces to reduce surface energy and lessen sensitivity to environmental constituents such as moisture. Nonetheless, under humid conditions, adhesion has been observed to increase dramatically. It is important to elucidate the mechanisms by which this increase occurs. We employ micron scale cantilever beams fabricated side-by-side with MEMS devices to measure adhesion of the beams to the substrate in a controlled humidity ambient using a fracture mechanics formalism. Beam deflections are measured in-situ at the nm scale by taking advantage of Michelson interferometry. Uncoated hydrophilic surfaces display an exponential increase of adhesion with relative humidity (RH), with values ranging from 1 to 100 milliJ/m2. The results can be explained in terms of a simple Kelvin model. Silane coupling agents such as octadecyltrichlorosilane (OTS, C18H37SiCl3) and perfluorodecyltrichlorosilane (FDTS, C8F17C2H4SiCl3) have been succesfully applied to MEMS resulting in hydrophobic monolayer coatings. The treated surfaces exhibit contact angles of 110° and 115° with water respectively. Cantilever beams coated by OTS and FDTS indeed exhibit very low adhesion values of 8 and 2 microJ/m2 respectively at low RH. The values can be explained by very low real contact area between the surfaces. However, at high RH, the FDTS-coated cantilevers exhibit a strong increase in adhesion. Atomic force microscopy images of exposed surfaces reveal agglomerates which we interpet as a reconfiguration of the monolayer from a surface phase into a bulk phase, leaving behind locally hydrophilic areas. Microcapillary bridging between the surfaces then causes the adhesion increase. Adhesion hysteresis mechanics for the cantilever beams have been developed to support this notion. These studies on in-situ test structures have enabled us to evaluate the mechanisms by which moisture affects MEMS reliability.
T. Twardowski4, E. Gentile4, D. Brennan1 and A. Fernandez5
1) Department of Physics, Drexel University
2) Department of Chemical Engineering, University of Pennsylvania
3) Department of Chemistry, Drexel University
4) Department of Materials Engineering, Drexel University
5) Cognis Corporation
HREELS and SPM Applied to Polymer Surfaces and Interfaces
In recent years, High Resolution Electron Energy Loss Spectroscopy (HREELS) and Scanning Probe Microscopy (SPM) have greatly contributed to the study of the growth and evolution of polymer films deposited on various substrates. With the improved resolution of new instrumentation, HREELS can provide key information on bonding and electronic structure of polymer surfaces and interfaces by comprehensive analysis of sequentially-measured vibrational and electronic excitation spectra noting that both optically-active and optically-forbidden transitions can be excited. SPM provides the ability to analyze the nanometer scale structure of polymer films as well as localized force interactions that can depend on chemistry and process parameters. We present two studies: (1) HREELS applied to study growth, ultra thin film polymerization, and conductivity of vapor-deposited polyaniline films on metal surfaces and (2) SPM applied to study the formation and processing of surfactant stabilized latex particles on steel and mica surfaces.
Nanostructured Organic Thin Film Deposition from Low Energy Polyatomic Ions
Mass selected polyatomic ions beams are used to deposit cross-linked organic thin films on polymer surfaces. These films are chemically similar to plasma polymers. However, the film properties can be directly and unambiguously controlled by selecting the mass and energy of the incident ions. These organic films maintain at least a portion of the chemical structure of the incident ions when deposited at low energies. The organic films deposited from these polyatomic ions are several nanometers thick and can display a nanometer scale texture, demonstrating the high surface selectivity of polyatomic ions. Mass-selected beams of 15 - 100 eV CF3+, C3F5+, SO3+, SF5+, and (CH3)5Si2O+ ions are used to deposit fluorocarbon and organosiloxane films on polystyrene, silicon, and metal surfaces. Film chemistry is examined by monochromatic x-ray photoelectron spectroscopy and other methods. Film structure is examined by atomic force microscopy and x-ray reflectivity. Molecular dynamics simulations of the fluorocarbon ion deposition on polystyrene, performed by Susan Sinnott and coworkers of the University of Kentucky, show good agreement with experimental results. These experimental and computational results indicate that polyatomic ions in plasmas may contribute significantly to film deposition, even at incident energies above 100 eV.
XPS Investigation of Metal/Conjugated Polymer Interfaces of Relevance to the Polymer-based Light Emitting Diodes
Angle-resolved X-ray photoelectron spectroscopy (XPS) was employed for the in situ studies of the physicochemical interactions at the electrode/polymer interfaces involving evaporated metals of high and low work functions and thin film of polyaniline (PANI), poly(p-phenylene vinylene) (PPV) and poly(2-methoxy-5-(2'-ethyl-hexyloxy)-1,4,-phenylene vinylene) (MEH-PPV). Four interfacial phenomena of relevance to the performance of light emitting diodes (LED's), viz., the metal diffusion at the interface, oxygen migration at the interface, interaction of the metals with the surface states of the conjugated polymers, and the changes in oxidation states of the metal at the interface, were investigated. The interfacial characteristics involving the polymers coated on high work function metal oxides, such as indium-tin oxide (ITO) and sputtered ITO on the polymers were also studied.
R. Ivkov and S. Satija; National Institute of Standards and Technology, Gaithersburg, MD.
J. Majewski; LANCSE, Los Alamos National Laboratories, Los Alamos, NM.
Crosslink Density Gradients Within Thin Epoxy Films Revealed By Solvent Swelling: A Neutron Reflectivity Study
Structure within thin epoxy films is investigated by neutron reflectivity (NR) as a function of resin/crosslinker composition and cure temperature. Variation in the crosslink density normal to the substrate surface is examined by swelling the films with the good solvent d-nitrobenzene (d-NB). The principle observation is a large excess of d-NB near the air surface. This is not a wetting layer, but rather indicates a lower crosslink density in the near-surface region. This effect is due to preferential segregation of the crosslinker to the air surface, driven by the lower surface tension of the crosslinker relative to the epoxide oligomers. The magnitude of the effect is a function of composition and cure temperature. Exclusion of d-NB from the region immediately adjacent to the substrate surface is also observed, possibly indicating a tightly bound layer of epoxy. Regarding swelling in the bulk of the films, the behavior is non-symmetric with departure from the stoichiometric ratio. The films deficient in curing agent show greater equilibrium swelling and faster swelling kinetics than the films with an excess of curing agent.
Acknowledgment This work was supported by the U.S. Department of Energy under contract CE-AC04-94AL85000. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the UnitedStates Department of Energy.
1)Joint Institute for Nuclear Research, Flerov Laboratory of Nuclear Reactions, 141980 Dubna, Russia; E-mail: kravets@nrsun.jinr.dubna.su
2) Tsiolkovsky Moscow State Aviation Technological University, 121552 Moscow, Russia E-mail: sasha@kurts.msk.ru
Modification of Track Membrane Structure and Surface in Non-polymerizing Gases Plasma
An investigation of the structure and the surface of poly(ethylene) terephthalate (PET), polycarbonate (PC) and polypropylene (PP) track memb--ranes (TM) subjected to the plasma RF-discharge treatment in non-polymerizing gases has been performed TM with the thickness of 10 m produced by physico-chemical treatment of a polymeric film exposed to krypton ions at the U-400 cyclotron (FLNR, JINR) were used in the experiments. The plasma treatment was carried out at the plasma chemical setup (MSTAU) for the RF-discharge at a frequency shift of 13.56 MHz. The plasma affected the membrane on one side. The air and mixture of nitrogen and oxygen in various ratios were used as a plasma-forming gas. The discharge parameters (gas pressure, discharge pressure) and the treatment ti-me were varied. It was found that the effect of the plasma of the used gases upon the PET TM leads to etching both the external membrane surface and the surface pore layer accompanied by lessening the membrane's thickness and increasing their effective pore dia-meter. The memb-rane's pore size and the shape change in this case. The etch rate depends on the discharge para-meters and on the contents of the plasma forming gas. Increase in the dis-charge para-meters and introduction of oxygen into the gas lead to increase of the etch rate. The use of pure oxygen as a plasma-forming gas allows one to increase essentially the etch rate. This permits to make the process of gas discharge etching more intensive.
It is shown that in the gas-discharge etch in plasma of non-polymerizing gases the relief of the TM surface changes1). Numerous craters (oxidation-destruction region) appear on the ini-tially smooth surface. This phe-nomenon is probably caused by different etch rates for crys-ta-lline and amorphous regions. The membrane surface becomes rough. Besides, the plasma effect the formation of a thin modifying layer with higher con-tents of functional groups on the memb-rane surface2). This makes the membranes sur-fa-ce hydrophilic. The de-ve-lop-ment of the memb-rane sur-face's erosion and their hydro-phi-lization result in increasing the TM wettability the value of the water contact angle dras-tically diminishes2). This leads to improving the memb-rane characteristics. It is shown that it is possible to change the structure of the track memb-ranes directly by the gas discharge etching method. Depending on the choice of discharge pa-rameters it is possible to make etching either in a part of the channel or over the whole length of the pore channels. In both cases asymmetric membranes are formed which possess higher poro-sity and flow rate. The membranes in which only a part of pore channels were etched in plas-ma are of particular interest. The gas discharge etching in the layer of such membranes leads to for-ma-tion of cone-type recesses increasing their volume porosity. The initial pore size re-mains the same in the layer not affected by plasma etching, its structure remains the same and does not cause a decrease of the separation selectivity. The use of such membranes allows one to raise effectiveness of the filtration processes.
References
1) Dmitriev S.N., Kravets L.I., Sleptsov V.V. Nucl. Instrum. and Meth. 142 B, 43 (1998).
2 )Dmitriev S.N., Kravets L.I., Simakina N.V., Sleptsov V.V. Nucl. Tracks Radiat. Meas. 25, 723 (1995).
1) Joint Institute for Nuclear Research, Flerov Laboratory of Nuclear Reactions,
141980 Dubna, Russia; Tel., Fax: (7-09621) 65955, E-mail: kravets@nrsun.jinr.dubna.su
2) Tsiolkovsky Moscow State Aviation Technological University, 121552 Moscow, Russia, Tel., Fax: (7-095) 7111957, E-mail: sasha@kurts.msk.ru
A High-frequency Plasma Discharge Effect on Track Membranes
Effect of a plasma discharge on track membranes (TM) from poly(ethylene) terephthalate, poly-carbonate and polypropylene have been investigated. One side of the membranes treated to a plasma. Studied was an influence of the composition of the plasma-forming gas, the parameters and the duration of the discharge on the structure and the properties of the TM resulting at high-frequency plasma discharge (13.56 MHz) treatment. It has been figured out that the gas-discharge etch of a polymeric matrix, its hyrdophilization and generation of radicals in the surface layer of the membranes are the main processes when treating the track membranes by a non-polymerizing (inorganic) gas plasma. We show that the gas-discharge etching of TM in the plasma causes dec-reasing a mass part of the low-molecular products in the membrane as well as changing a relief of the surface layer and the shape of the TM pores. The latter is the basis for creation of asymmetric TM1). The observed process of hydro-phi-lization of the TM surface on exposure to a gas-discharge is related to a formation of func-tional carboxylic groups2). Their appearance is caused by oxidation of the end-groups due to effect of the active plasma particles here the chemical bonds break down. The formation of radicals in the TM surface layer allows one to make the grafting of monomers to their surface.
The treatment of the membranes with the plasma of organic compounds results in a depo-sition on their surface of a thin polymeric film. Depending on the duration of the plasma treatment, one can obtain TM for microfiltration, ultrafiltration and reverse osmosis. In the last case, a thin semipermeable layer that fully covering the pores, is deposited on the TM surface. The possibility of adjusting the width of the polymerized layer and the wide range of organic compounds for producing the membranes of this type make this method very promising. New properties of the surface of the composite materials produced this way, mainly depend on a type of the chemical compound used. For example, when using carbo-hydrates as a plasma-forming gas, a thin polymeric chemically stable diamond-like film is formed on the surface exposed to plasma of does not possess functional groups. This provides a way for producing hydrophobic composite membranes posses-sing a mechanical and che-mical strength2). While depositing the polymeric film from the discharge to hexamethyl-di-sizane, the membranes having bactericide properties are generated. The a positive or negative charge appearing due to the introduction of the functional groups is one more thing allowing one to regulate the membranes' characteristics. For instance, the use of n-vinylpyrrolidone as a plasma-forming gas serves as a basis for creation of hydrophilic composite membranes. The use of allyl alcohol as a plasma-forming gas allows one to improve hydrodynamic charac-teristics of the track membranes3). When a polymeric film is deposited on the TM surface from the discharge in butylamine, bipolar membranes are formed which have two layers with different electric conductivity.
References
1)Dmitriev S.N., Kravets L.I., Sleptsov V.V. Nucl. Instrum. and Meth. 142 B, 43 (1998).
2)Dmitriev S.N., Kravets L.I., Simakina N.V., Sleptsov V.V. Nucl. Tracks Radiat. Meas. 25, 723 (1995).
3)Dmitriev S.N., Kravets L.I., Levkovich N.V., Sleptsov V.V., Elinson V.M., Pot-----rya-sai V.V. Khimiya Vysokikh Energij 32, 310 (1998).
Novel Use of Neutron Scattering to Probe the Structure and Thermodynamics of Thin Polymer Films
(Abstract not yet available)
Surface Characterization of Polymers Modified by keV and MeV Ion Beams
The present work deals with two different surface modification techniques for altering the surface properties of polymers: plasma treatment and ion implantation. Polymer foils were exposed in an inductively coupled r.f. (13.56 MHz) plasma system with and without applying the negative high voltage pulse to the sample stage. The influence of low pressure plasmas of oxygen, nitrogen, or argon on the chemical composition, topography, and wettability of polymer surface was studied in detail. Etch rates of poly(ethylene terephthalate) for different plasma parameters were monitored. Polymer surface was also modified by using a high energy ion beam process. Polyimide films were implanted with different ion species such as Ar+, N+, C+, He+, and O+ with dose from 1 x 1015 to 1 x 1017 ions/cm2. Ion energy was varied from 10 keV to 60 keV for PSII experiment. Polyimide samples were also implanted with 1 MeV hydrogen, oxygen, nitrogen ions with a dose of 1x1015 ions/cm2. Depending on ion energy, doses, and ion type, the surface resistivity of the film is reduced by several orders of magnitude. A study on the ion beam-treated and plasma-treated polystyrene surfaces and their hydrophobic recovery was performed using TOF-SIMS, XPS, etch rate measurement, and water contact angle measurement.
Orientation Order in the Surface Layers of the Polymer Films
(Abstract not yet available)
Surface Analysis of Some Polymer-based Materials by Means of A Soft X-ray Emission Technique.
Within the last three decades many spectroscopic techniques have been developed to characterize the surface of a large variety of materials. Several of these methods have been applied to the study of surfaces and interfaces in polymeric materials. In this paper, performances and limits of low-energy electron-induced x-ray spectrometry (LEEIXS) [1, 2] in surface and very thin film analysis of polymer-based materials will be described and discussed.
In a first step, it will be shown that LEEIXS is basically an x-ray emission technique:
(i) using a windowless gas discharge tube operating under the primary vacuum of the x-ray spectrometer as an electronic excitation source (1-5 keV) and,
(ii) requiring the dispersion and detection of soft and ultra-soft x-rays (wavelengths in the range from some tenth to some nm).
Considering the nature of the excitation source used, and the relatively low current density (e.g., 0.1 mA cm-2) of the electron beam at the sample surface, the degradation of many materials may be prevented. Under these conditions, some organic materials can be investigated.
In a second step, it will be reported some applications which illustrate the LEEIXS capabilities particularly in light element analysis. Selected examples will be dealing with surface characterization of:
(i) thin polymer films obtained by plasma polymerization, electropolymerization or chemical deposition (dipping, spin-coating) and,
(ii) polymer substrates subjected to various surface treatments in liquid or gas phase.
REFERENCES
M. Romand, F. Gaillard, M. Charbonnier, Adv. X-ray Anal., 35 B (1992) 767.
M. Romand, M. Charbonnier, J. Baborowski, Adv. X-ray Anal., 40 (1997), CD-ROM Publication (March 1998).
N. Brack and P.J. Pigram; Centre for materials and Surface Science, La Trobe University, Bundoora, Vic. 3083, Australia
The Spreading of Alkyl Ketene Dimers (AKD) in Paper and on Smooth Hydrophilic Substrates
Alkyl ketene dimer (AKD) is a commonly used chemical in neutral and alkaline paper making for sizing i.e. imparting to cellulose fibres an appropriate degree of hydrophobicity. The application of AKD at the wet end of a paper machine involves mixing the AKD emulsion with the fibre suspension and strong sizing effect is achieved only after paper is heat treated at an elevated temperature (100 to 120°C). Questions that have not been completely answered, despite a substantial amount of research carried out in the past, are the mechanism of migration of AKD during heat treatment and the final distribution of AKD in sized paper.
This work focuses on understanding the driving forces involved in AKD migration during heat treatment. Filter paper and some smooth hydrophilic surfaces such as mica, glass and regenerated cellulose film were used for studying the spreading behaviour of AKD. A simple experimental device was made to examine this behaviour. ESCA, AFM and the Wilhelmy methods were used for studying the spreading and the distribution of AKD on these surfaces.
Our results show that AKD does not have a strong tendency to spread on smooth surfaces, even these surfaces are hydrophilic and have high energy. The capillary structures in the substrate strongly promote the spreading AKD by allowing liquid wicking. Surface energy alone is not responsible for extensive spreading of molten AKD during heating. Instead, capillary pressure is the major driving force for the migration of AKD in paper.
University, Manhattan, Kansas 66506-3701
Valence Band X-ray Photoemission as a Probe of Polymers and
Polymer Interfaces
Valence Band X-ray Photoelectron Spectroscopy is a valuable tool for the investigation of polymer surface chemistry and polymer interfaces. X-ray photoelectron spectroscopy (XPS) has the advantage of causing little if any sample damage (unlike some other surface analytical probes) especially when monochromatic X-ray light is used. The valence band region is especially valuable because polymer systems that give little chemical information in the core region can give substantial changes in the valence band region. This invited talk will present an overview of the application of valence band XPS to polymers, indicating how the valence band spectra obtained can be understood by comparison with cluster and band structure calculations. Specific examples will be discussed with a view to understanding particular structural features. The use of a thin film approach will be described which can probe polymer interfaces. Examples of this approach for polymer films on oxidized carbon fibers will be illustrated. The approach will be shown to have the capability to identify chemical bonding between polymers and oxidized carbon fiber surfaces.
Characterization of Surface Modified Aramid Fibers and Tire Cords by Plasma Polymerized Coatings
Films of organofunctional and non-organofunctional bis-silanes were deposited on various metals including cold-rolled steel, galvanized steel and aluminum alloys. It will be demonstrated that such films provide outstanding corrosion protection properties and therefore, silane-based processes can replace chromate treatments in many metal-finishing industries. The properties of the films were studied by EIS using a non-intrusive electrolyte. It will be shown that certain silanes have 'healing' properties, similar to chromates. In certain cases, the silane films can obviate the need for a chromate pigment in the primer. The mechanism of their performance is based on a passivation of the metal-organic interface. In some cases a new film is formed between the silane film and the metal oxide. In those systems a silane film can be classified as a true conversion coating.
Detailed Investigation of the Outer Surface Chemistry of Polymers Using ISS and SIMS: Practical Applications in Adhesion, Surface Treatment and Coatings
(Abstract not yet available)
Harmonically Modulated Friction Force Microscopy: an AFM Tool for
Analysis and Modification of Polymer Surfaces
canning Probe Microscopy, here Scanning Force Microscopy in the contact mode, is widely used not only to examine the 3-dimensional surface topography, but also to evaluate nano-mechanical surface properties. This contribution focuses on the tip-surface interaction due to a shear deformation, i. e., friction. During forward and backward scan with a given scanning (shear) velocity, the cantilever lateral bending (torsion) is a measure for the lateral force. Unfortunately, both scan directions must be acquired and subtracted to separate the topography cross-talk from the friction image. Superimposing a lateral displacement between tip and surface via a dither piezo, the shear deformation is sinusoidally modulated. Images of amplitude and phase shift of the dynamic cantilever torsion within a frequency range from 30 kHz up to 60 MHz are presented. Due to the fact that friction is always a dynamic process, we prefer to call this technique "Harmonically Modulated Friction Force Microscopy" (HM-FFM) instead of just "Dynamic Friction Microscopy". Several advantages, e. g., the fact that signal-to-noise ratios increase by using a lock-in technique, are discussed. The investigated systems include reference samples like Silicon or Titanium grids as well as heterogeneous polymer surfaces. AFM based lithography can be performed in a HM-FFM experiment by increasing the modulation amplitude. Due to the lateral tip movement, one direction is blurred, hence this technique is not suitable for writing fine lines, e. g., 30 nm wide and some nm deep. However, polymer material can be removed up to a depth of 500 nm within some seconds.
1) Materials Science and Engineering, University of Florida, Gainesville, FL 32611
Nanoscale surface mechanical properties of polymer thin films
Mechanical properties measurements at the nanoscale are important for understanding the behavior of ultrathin films developed for adhesives, electronics packaging, microelectromechanical (MEMS) devices, and lubrication. Traditional methods to determine surface mechanical properties (e.g. surface force apparatus (SFA), nanoindentation, and atomic force microscopy (AFM)) lack either high spatial resolution or surface sensitivity, or provide only qualitative results. Recently, we have implemented an approach combining hybrid nanoindentation (depth-sensing nanoindentation with AFM imaging capabilities) and AC force modulation techniques. This combination enables surface sensitive, quantitative mechanical properties and dynamics measurements of films as thin as a few nanometers. The sensitivity of the instrument is sufficient to detect long range surface forces, damping losses of nanoscale contacts, and rheological properties of surface films. Quantitative measurements are made both at a single point as well as in a scanned image format. We present results of localized mechanical property measurements on polymer thin films (e.g. loss and storage modulus, hardness) as well as examine dynamic processes that occur during the formation and breaking of nanometer scale adhesive contacts.
Interaction of Metal Atoms with Polymer Surfaces: Model Studies Using Organic Surfaces of Self-assembled Monolayers
A detailed spectroscopical analysis on the interaction between (neutral) metal atoms and polymer surfaces is often hampered by the presence of the various functions in the polymer subunits. In the case of polyimide the decision on whether Cr atoms are first attached to the carbonyl units or to a ?-system cannot be answered in a straightforward fashion, even if high-quality data from IR-spectroscopy or x-ray photoelectron spectroscopy (XPS) are available. A significantly more straightforward analysis of experimental data becomes possible if organic surfaces consisting of functionalities of one kind only are prepared by grafting suitable monomers to a metal surface. Here we will focus on the interaction of several types of metal atoms with phenyl-terminated organic surfaces and relate the findings, in particular those obtained by x-ray absorption spectroscopy (NEXAFS), to corresponding results for polymer surfaces.
Mass Spectrometry Applications to Combinatorial Chemistry
We have employed imaging time-of-flight secondary ion mass spectrometry to characterize the spatial distribution of molecules across a surface. Using this technology, arrays of polystyrene spheres which are chemically modified as part of a combinatorial library syntheses are chemically assayed at a rate of about 1-10 beads per second. Examples of the characterization of polystyrene spheres functionalized with different linkers including acid-sensitive, photosensitive, and thermal linkers will be given with a special emphasis on sample treatment. XPS data on the changes of polystyrene surface will also be presented.
Embedding of Noble Metal Nanoclusters into Polymers as a Probe of the Surface Glass Transition
It is well known nowadays that thin surface layers of polymers as well as polymers in a thin film configuration may have physical properties different from those of the bulk material due to interfacial interaction and effects of surface molecular motion. Therefore, knowledge of the surface glass transition temperature is of both fundamental as well as practical interest. X-ray photoelectron spectroscopy (XPS) has been applied to study the embedding of Au and Cu nanoclusters into Bispenol-A-Polycarbonate (BPA-PC) and bisphenol trimethylcyclohexane polycarbonate (TMC-PC) as well as polystyrene with different molecular weight. Our recent TEM and AFM measurement show that the evaporated metals initially form discontinuous layers on all polymer substrates consisting of spherical clusters, whose density and size depends on the deposition parameters as well as on the particular metal-polymer combination [1]. The clusters are embedded into the polymer bulk upon heating the polymer above its glass transition temperature, where the polymer chains attain long-range mobility. There is a driving force for embedding the metal clusters since the surface tension gM of the metal particles exceeds the sum of the interfacial tension gMP and the polymer surface tension gP: It was shown that the temperature dependence of the embedding depth can be used to determine the glass-transition temperature at the polymer surface, Tg(s). A depression of the surface Tg compared with that of the bulk sample was observed for all polymers under investigation. The effect of molecular architecture on the surface molecular motion was investigated using BPA-and TMC-polycarbonate. It was found that in case of TMC-PC the depression of Tg was significantly higher compared to the other polymer. It was found that a treatment of the polymers with Ar+ ions at low fluence leads to a significant increase in the surface Tg.
1) V. Zaporojtchenko, T. Strunskus, K. Behnke, C. v Bechtolsheim, M. Kiene and
F. Faupel, J.Adhesion Sci. Technol. 14, 467 (2000)
2) G. J. Kovacs, and P. S. Vincett, J. Colloid Interface Sci. 90, 335 (1982).