The following is a list of the abstracts for papers which will be presented in the THIRD INTERNATIONAL SYMPOSIUM ON POLYMER SURFACE MODIFICATION 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.)
Surface of Silicon Chemical composition Cleaning Using Clean Solutions With Surfactants and Chelates
This paper reports a new type of semiconductor cleaning detergents and cleaning technique using clean solution with surfactants and chelates. The results of cleaning using the new type of cleaning technique and the RCA standard cleaning technique are compared. The results are the silicon surface chemical composition obtained by X-ray photoelectron spectra and infrared absorption spectra. The measurement results show that a thin layer of oxide in the act of their cleaning is grown.. Two types of cleaning technique produces organic carbon contaminants, but the new technique is significantly less than the RCA standard system. .
Plasma Treatment Of Cellulosic Fibres and Its Effects on Interfacial Bonding: A Taguchi Analysis
Natural fibres, such as sisal and wood fibres, are abundantly available renewable materials. Recently, environmental awareness of renewable materials and social interest in recycling have provided the impetus for reinforcing thermoplastic polymers with natural cellulosic fibres. The full potential of such composite materials has not been realised due to the often-found poor interfacial bonding between the fibres and the thermoplastic polymers. While chemical treatment of fibre surfaces has been somewhat successful in improving interfacial bonding, there are environmental concerns related to the disposal of chemicals after treatment. Physical treatment of fibre surfaces, such as plasma treatment, is clean and dry and without environmental problems.
This paper describes the radio-frequency generated plasma treatment of these fibres and its effects on the interfacial bonding with polypropylene. Argon gas is used to either etch the fibre surface or plant reactive groups on the surface. SEM analyses of the fibre surfaces have shown differences in surface structure between the untreated and treated fibres. The Taguchi method of experimental design with three factors and multiple levels has been used to optimise the treatment parameters in relation to fibre strength and reduce the number of actual experiments. Results show that the principal parameters affecting the results are the treatment time, the input power level and the working chamber pressure. The variation in uncontrolled factors has little effect on the treatment. The effects of such treatment on the interfacial bonding are also discussed.
Taylor Made Concepts for Monolayer and Multllayer Coating of Membranes With Natural Occurring and Regioseletively Modified Polysaccharides for Athrombogenic Artificial Kidney
The athrombogenicity or platelet inertness represents the highest standard hemocompatibility in nature, which will be realized by natural undamaged endothelium, the interface between blood and the undamaged glycocalix. This high standard of hemocompatibility is needed also for biomaterials eg. membranes for artificial kidney. In the present overview different naturaly occurring polysaccharides from the vessel wall and different regioselectively modified polysaccharides such as heparin, cellulose and chitosan will be immobilized as a monolayer and multilayer and tested by platelet adhesion. Several carriers will be used such as cellulose- and polysulfone membranes, The surfaces are additionally analyzed with chemical methods tar estimating directly the repeating units of the polysaccharide and with physical methods such as ESCA and AFM. The stability of the coatings will be tested,too,°phe development give rise trends for taylor made athrombogenic artificial membranes and other biomaterials.
l) H. Baumann, A. Kokott, J. Biomater. Sci. Polymer Edn, Vol. 11, 3, 245-2 72 (2000)
2,)H. Banrnann, A.Richter,D. Klemm and V. Faust, Macromol. Chem, Phy., 201,1950-1962 (2000)
Robert Miller, Cynthia Nickerson and Li-Ping Yu; Genzyme Corporation, 1 Kendall Square, Cambridge, MA 02139
Hydrogel Modification of Medical Device and Tissue Surfaces to Improve Therapeutic Outcomes
Implanted hydrogels often elicit very mild inflammatory responses and present surfaces to internal tissues which can resist fouling by humoral or cellular components. Moreover, they are lubricious in aqueous media and loadable with bioactive agents to address a range of therapeutic indications. Medical device and even living tissue surfaces can be modified with hydrogels in a variety of ways including coupling via covalent, ionic or electrostatic bonds, encapsulation and chain entanglement as dictated by the durability and persistence of the coating required.
Hydrogel device coatings intended for long-term implant have been used on devices such as central venous catheters and pacemaker leads. In such cases, the intent of the coatings is for lubricity upon insertion. Hydrogel coatings on implantable vascular stents serve as drug delivery vehicles. Devices intended for acute applications such as angioplasty and urinary catheters also use hydrogel coatings beneficially for lubricity and drug delivery. The hydrogel coatings can be based on natural or synthetic polymers with the intention of remaining in place for the lifetime of the device or degrading in situ.
Living tissue surfaces can be modified with polymeric coatings to influence biological processes such as healing or biofouling. In such cases, the surfaces are modified by deposition of conformal materials as solids, liquids or gels. Adherence has been achieved by secondary bonding forces or by covalent reaction with functional groups on extracellular matrix proteins. Examples of hydrogel-modified tissues include surgical sites coated to reduce adhesions, luminal surfaces of blood vessels coated to reduce thrombosis or stenosis after angioplasty and organs coated to prevent air or liquid leaks. With such devices, drugs can often be delivered and the intent is usually for the hydrogels to resorb after they have done their job. The use of hydrogels in medical devices is growing rapidly as therapies requiring ever more sophisticated approaches are being targeted.
In Situ Process Control for Plasma Treatments of Polymers: Barrier Films, Hydrophobic Coatings, Antibacterial and non Fouling Surfaces
(Abstract not yet available)
Microwave Plasma Sources for Large Scale Applications
(Abstract not yet available)
1) Department of Biomaterials, University of Nijmegen, PO Box 9101, 6500 HB Nijmegen
2) Debye Institute, Utrecht University, PO Box 80000, 3508 TA Utrecht
Initial deposition of calcium phosphate coatings on bare and plasma pre-treated polystyrene and polytetrafluoroethylene
Calcium phosphate (CaP) coatings (e.g. Ca(PO4)3OH) may be applied to improve the biological performance of polymeric medical implants. A strong adhesion between the ceramic and the polymer is required for clinical applications. This study focuses on the development of the interface during RF magnetron sputter deposition of CaP (1-20 nm) on oxygen plasma pre-treated and untreated polystyrene and polytetrafluoroethylene.
During pre-treatment, C-O bonds are incorporated in the polystyrene surface. XPS shows that after deposition of 1.5 nm CaP the number of C-O bonds in untreated and pre-treated materials is equal. Then, 25% of the probed C atoms are present in a C-O bond. AFM shows that the nucleation site density increases from 1*1010 to 13*1010 sites/cm2 as a result of the pre-treatment.
The oxygen plasma pre-treatment does not incorporate oxygen in polytetrafluoroethylene. However, during CaP deposition C-F bonds are broken and F escapes. Ca-F bonds form at the interface. Initially, almost no P is deposited. Presumably, P reacts with F and escapes as a PF3 gas molecule.
Apparently, the two substrates possess strongly different reactivity towards CaP. The final structure of the interface seems to be influenced by energetic argon escaping from the plasma, and not by the plasma pre-treatment.
Pontstr. 49, D-52062 Aachen, GERMANY
Investigations on the Substrate Influence on the Layer Growth of Plasma-polymerized Coatings
In this presentation three aspects of the growing process of plasma polymerized silicon organic coatings on polycarbonate (PC) are described. These are the morphology, the growing process on micro-structured substrates and the optical properties.
Plasma-polymerized HMDSO (hexamethyldisiloxane) coatings have a cauliflower-like structure with embedded agglomerates. Oxygen as an additional reactive gas leads to more glass-like coatings with a smoother surface. Also the structure of the substrate affects the structure of the plasma-polymerized coating. Thus defects on the substrate cause volume polymerization as well as an increased agglomerate growth. These agglomerates have an oxygen-enriched and silicon-reduced chemical composition compared to the surrounding matrix. The growing process of plasma-polymerized layers was investigated on PC samples, which were either scratched with triangular notches or samples with elevated rectangular structures. After a certain coating time, a complete closure/coverage of the investigated structures or of the layers deposited on them is observed, which makes the sample surface look smoother. The coating time or especially the layer thickness that is necessary for this effect depends on the lateral extension of the defect. A characteristic quantity to describe this effect is the ratio r between the layer thickness d and the width of the triangular notch or distance between the rectangular structures w (r = d/w), which is significantly dependent on the process gas composition and the geometry of the structure.
Understanding these layer growth aspects is necessary to improve the layer behavior on thin films under strain. For investigating the optical properties both the surface roughness and the diffuse light reflection were measured. The roughness measurements showed that the surface roughness of the substrate has only an influence on the coating roughness up to a certain point. In case the substrate roughness is very high the coating has the same roughness.The reflection measurements demonstrated that in spite of the different measured roughness of the samples no change in the reflection was measurable.
The investigations presented in this report received financial support from the Deutsche Forschungsgemeinschaft (DFG), to whom we submit our thanks.
1) Institute for Plasma Research, University Stuttgart, Pfaffenwaldring 31, D-70569 Stuttgart
2) Muegge Electronic GmbH Hochstr. 4-6 D-64385 Reichelsheim
Microwave Plasma Sources for Large Scale Applications
Plasma technology is used in a wide field of application, especially for PECVD-deposition, activation and etching. The microwave plasma has the capability to activate surfaces very careful and effective. In this presentation a new kind of linearly extended microwave plasma source is introduced. Starting from the so called Duo-Plasmaline® the expansion in one and two dimensions will be discussed. The Duo-Plasmaline® can be used in a wide field of pressure and microwave frequency. The reason is the relationship to a coaxial wave guide. The working principle with a linear inner conductor centred in a dielectric tube is similar. If the tube, in the simplest form a glass tube, leads through a vacuum vessel, the microwave can penetrate into the low pressure regime. With sufficient field strength, the plasma ignition starts, consuming microwave power. The plasma density increases until the cut-off density of the plasma (as a conductive medium) prevents a further penetration of the microwave. Then the microwave propagates along the tube until the plasma density allows again the penetration and generation of further plasma. The cut off density for microwaves is very high that a good quality of plasma application is possible. The linear extension of the plasma along the tube is mainly limited by the microwave power. The in first order linear decay of the plasma density apart from the microwave source can be compensated through the superposition of the microwave input from both sides of the tube. With standard magnetrons of 1 kW power a 1m plasma in the pressure regime of 10 Pa to about 1000 Pa can be maintained.
The Duo-Plasmaline® itself and the combination and variation of lines up to homogeneous plasma arrays, opens a complete new field of large scale applications. Plasma lines up to 3.5m length and plasma arrays of 0.5 m² are realised. The separation of microwave input line and plasma with a bifocal arrangement opens the processing window up to atmospheric pressure.
1) 4th State Inc., 1260 Elmer Street, Belmont, CA 94002-2806
2) Integument Technologies, Inc., 70 Pearce Avenue, Tonawanda, NY 14150-6711
Plasma Modification of Fluoropolymers: An Overview
(Abstract not yet available)
Preparation and Characterization of Thin Polymer- and Biofilms for Functional Biointerfaces
Thin polymer films, including biopolymers, have a broad variety of applications e.g. in microelectronics, materials science, biomedicine and biotechnology. The focus in the present context is thin films (one to a few hundred nanometers) built up on some supporting surface, e.g. a medical implant or a biosensor, to provide a functional surface for biointerfacial processes. Functionality can be obtained through the surfaces' topographic microarchitecture, chemical composition, or viscoelastic properties, or combinations of them. In the first part of the talk the scientific and technical challenges in this area are briefly summarized. Examples are then given of the preparation of functional surfaces using modern micro- and nanofabrication methods, and/or chemical functionalization by e.g. supported (bio) biomembranes or plasma modified polymers. Surface analytical tools are used for characterization. In this context the unique information about thin viscoelastic films obtained by a new QCM-D method (Quartz Crystal
Microbalance -Dissipation) is described. It can be used as a fingerprint method or as a quantifiable method to characterize the elastic and viscoelastic properties of thin "soft" polymer and biofilms and kinetic processes in or on them.
1)- Institute of Technical Chemistry, Ural Division of RAS, Perm` , Russian Federation , 13a,Lenin str.,614600, Perm`, RUSSIA.
2)- SRC RF GNIICHTEOS, sh. Entuziastov, 38, 111123, Moscow, RUSSIA.
Organosilicon Compounds in the Field of Plasma Technologies.
New plasma coatings based on oxide carbide systems have been actively developed recently. Investigations carried out in St-Petersburg University by I.A.Soshin and L.A.Topolyanskii showed a possibility to prepare the thin silicon-carbon containing films on metal surface by arc plasmatron.
We have investigated the properties and structure of coatings, obtained using organosilicon compounds, introduced into argon arc plasma zone.
Hexamethyldisilazane, hexamethylcyclotrisilazane, and hexaphenyltrisilazane have been studied as organosilicon compounds used in this process. Relationship between coating properties and structure of organosilicon compounds nature was found.
This process practically performed with arc plasmatron allows realizing the reinforcement of technological rigging, cutting tools and parts that must meet requirement of high wear resistance.
Service test of tools showed that application of such coatings improves resistance of drills of 2-mm diameter by 1,89 times, cutting picks of salt-mining combines by 2-2,5 times.
C.S.Lee2, D.H. Yoo2
1) Thin Film Technology Research Center, Korea Institute of Science and
Technology, Cheongryang P. O. Box 131, Seoul, 130-150, Korea,
2) P&I Corp. KIST Venture Town, 9232, Cheongryang P.O. Box 131, 130-650, Korea
Changing Surface Chemical Structure by Ion Assisted Reaction
Addition of functional group on polymer surface without surface damage has been carried out by a keV ion beam irradiation in reactive gas environment. The functional group formation has been much depended on the type of the reactive gases which were blown near the surface with assisting the keV ion beam irradiation. Permanent hydrophilic surfaces of polymers (advanced wetting angle ¡-10o and surface energy ¡- 60 - 70 erg/cm2) have been accomplished by the Ion Assisted Reaction, in which Ar+ energetic ions are irradiated on polymer film under a constant blow of oxygen over the irradiated surface. Improvements in the wettability and surface energy are primarily due to the polar force and hydrophilic groups such as C=O, (C=O)-O, C-O, etc., which are formed during the bombardment with energetic ions, without surface damage to the surface of the polymer film. Characteristic of the IAR, current stage of commercialization, new research areas, etc. have been reviewed with significant results such as strong adhesions to PTFE, PE, Silicon Rubber, etc.
1) CLFA (French-German Laser Center), 16 bis av. prieur de la Côte d'Or, 94114 Arcueil Cedex, FRANCE
2) Laboratoire des Plasmas et des Traitements de Surface, ENSCP, 11 rue Pierre et Marie Curie, 75231 Paris Cedex, FRANCE
Excimer Laser Treatment of Polymers : Characterizations of The Surface Modifications And The Adhesion Properties of PET
The effects of an excimer laser treatment at fluences below the ablation threshold on PET were investigated. The purpose is to prepare the polymer surface before aluminium metallization. The role of the process parameters: laser wavelength (193 nm or 248 nm), laser fluence, surrounding gas treatment (He, air, O2 or O2-He mixtures) on the PET surface composition and properties were studied by XPS, wettability measurements with water, diodomethane and aqueous solutions of HCl or NaOH, SEM, AFM and 180° peeling test. Due to the competition of different chemical reactions occurring on the polymer surface during the UV photons irradiation, the surface oxidation or de-oxidation could be observed depending on the treatment conditions. At very low fluences, surface oxidation and acidic surface properties were evidenced but increasing the fluence tended to decrease the O/C ratio. Surface modifications of treated PET had consequences on the aluminium/PET adhesion ; results showed that surface oxidation (increase of O/C) is not the only factor for improved adhesion. Furthermore, low pressure plasma treatments are under investigation, in order to establish a comparison in term of PET surface fonctionalization and adhesion.
Polymer Surface Modification by Using Plasma Source Ion Implantation
The Plasma Source Ion Implantation (PSII) technique has been utilized to improve the hardness, friction, wear and corrosion properties of various material surfaces, and to substitute the doping steps in semiconductor manufacturing. Recently, our group investigated the use of PSII in the modification of polymeric materials. Synthetic polymers such as polyimide, polycarbonate, polystyrene, poly(ethylene terephthalate), and MPPO were used for investigations. They were implanted with different ion species such as Ar, Xe, N2, CH4, CF4, He, and O2 to render the surface more hydrophilic or hydrophobic. Hydrophobic recovery of PSII-treated polymers were observed as a function of aging time, temperature, and treatment parameters. Treatment parameters include kinds of gases, gas pressure, plasma power, pulse frequency, pulse width, ion energy, etc. In this study we also provide a method for surface modification of 3-dimensional bulk polymers, which is capable of implanting plasma ions into surface of 3-dimensional bulk polymer sample by mounting a metallic grid over a sample stage. Hydrophilic property and electrical property improvement was measured by water contact angle goniometer and high resistance electrometer, respectively. PSII-treated polymer surfaces were characterized by TOF-SIMS, XPS, AFM, and SEM.
Nanostructures Generated by Plasma-Enhanced Modification of Polymeric Surfaces
(Abstract not yet available)
M.J. Walzak; Surface Science Western. The University of Western Ontario.
London Ontario N6A 5B7. CANADA.
UV, and UV+ozone Surface Treatment of Synthetic Rubbers
Previous studies [1-3] showed the effectiveness of the UV treatment to enhance the adhesion of many polymers. However, no previous studies consider the use of that treatment in rubber materials. In this study two different SBS rubbers were exposed to UV radiation for different length of time. As a consequence of the treatment, ionization of air gave ozone, which concentration is critical to produce adequate effectiveness. Therefore, in this study the influence of the ozone concentration during UV treatment was also considered by treating the rubbers with only ozone and UV+ozone.
The surface modifications produced on the rubber surface were analyzed using contact angle measurements (water and ethylene glycol, 25ºC), IR-ATR spectroscopy (germanium crystal), SEM, XPS and AFM. Adhesion properties were measured using T-peel test (72h after joint formation and after ageing in weathering chamber). Failed surfaces were characterized using IR-ATR spectroscopy in order to more precisely assess the locus of failure in the joints. A polyurethane adhesive was used to produce the treated rubber/PU/leather joints.
The two materials used in this study were two styrene-butadiene-styrene rubbers, one of them containing 10wt% calcium carbonate as a filler. In both cases, the decrease in contact angles is more marked as the length of the UV treatment increased. Oxidation bands appear (1730, 1650 and 3400 cm-1) in the IR-ATR spectra as well as a decrease in the relative intensity of the C-C and C-H bands (2919 and 2851 cm-1). XPS spectroscopy showed that the surface oxidation is due to the relative increase in R-COO- and C=O functionalities with respect to C-O functionalities. as the length of the treatment increased. Apart from chemical modifications, the migration of the filler particles to the rubber surface as a result of the treatment has been observed from SEM and AFM images.
T-peel strength was improved when the rubbers were treated, mainly for the rubber containing calcium carbonate as a filler. Greater modifications were produced if the treatment is produced with UV+ozone.
1. I. Mathieson, R.H. Bradley, Int. J. Adhesion and Adhesives, 16, 1 (1996).
2. L.F. Macmanus, M.J. Walzak, N.S. McIntyre, Journal of Polymer Science: Part A, Polymer Chemistry, 37, 2489-2501 (1999).
3.A.S. Bhurke, P.A. Askeland, L.T. Drzal, Proceedings of the 23 rd Annual Meeting of the Adhesion Society, Feb 20-23, 2000 South Carolina, USA.
Asunción Martínez-García1, Ana Sánchez-Reche1, Santiago Gisbert-Soler1,
Carmen Cepeda-Jiménez2 and José Miguel Martín-Martínez2
1) AIJU. Toy Research Institute. Avda. Industria, 23. 03440 Ibi (Alicante). SPAIN.
2) Adhesion and Adhesives Laboratory. Department of Inorganic Chemistry. 03080 Alicante. SPAIN.
Improved Adhesion Properties of Eva Copolymers Containing CaCO3 as Filler by Treatment with Corona Discharge
EVA copolymers are commonly used in the footwear and toy industries. The formulation of those EVA copolymers contains several additives, fillers (mainly CaCO3) being one of the most common. In several applications, EVA copolymers must be joined to different substrates using adhesives. Because the EVA copolymers mainly contain polyethylene, they exhibit low surface energy and poor adhesion. In this study, corona discharge was selected as a surface treatment to improve the adhesion properties of different EVA copolymers. More precisely, two EVA copolymers (vinyl acetate content = 12, 20 wt%) containing different amounts of a natural ultramicronized calcium carbonate (5 to 20 wt% CaCO3) were treated with corona discharge and the nature of the surface modifications produced by the treatment were assessed. Furthermore, the adhesion to a polychloroprene adhesive was also studied.
EVA 20 copolymer containing different amount of CaCO3 as filler
Treatment of EVA 20 (i.e. EVA copolymer containing 20 wt% vinyl acetate) with corona discharge produces a decrease in water contact angle value (water, 25ºC), from 80º on the as-received to 50º on the corona discharge treated EVA 20; and the value is not depend on the CaCO3 in the EVA 20. The treatment produces C-O and C=O moieties on the most external surface, the concentration of these specimens is relatively similar independently of the CaCO3 in the EVA 20. The treatment also produces roughness and surface degradation, more pronounced in the samples containing 5 and 20 wt% CaCO3.
Addition of CaCO3 to EVA 20 increases the peel strength from 2.1 (as-received) to 3.6 kN/m (corona discharge treated). For CaCO3 content higher than 5 wt% similar peel strength values were obtained. In general, a cohesive failure in the EVA 20 is produced (assessed by IR-ATR spectroscopy and SEM of the failed surfaces), independently of the CaCO3 content in the EVA 20. EVA copolymers with different vinyl acetate content. The treatment with corona discharge decreases the water contact angle values, more noticeably by increasing the length of the treatment (or decreasing the speed of the counter-electrode). The peel strength values obtained with corona discharge treated EVA 12 containing 5 wt% CaCO3 increase more noticeably than for the EVA 20 + 5 wt% CaCO3 material, from 0.8 kN/m (as-received) to 2.5-2.9 kN/m (treated), the increase is independent of the length of treatment. Always a mixed failure mode was obtained, i.e. adhesional + cohesive failure in EVA 12.
UV Laser Induced Photo Chemical Surface Modification of Polymers -Hydrophilic Treatment of the Inner Pore Porous PTFE for Glaucoma-
The increased intraocular pressure with aqueous outflow failure causes glaucoma. In healthy human intraocular pressure is maintained at a normal physiological level, between 8 to 18mmHg. When pressure exceeds 21 mmHg, a diagnostic of glaucoma may be predicted.
We reported elsewhere upon a method of photochemical substitution of hydrophilic or lipophilic groups on fluorocarbon surfaces. The pore inner surface of porous PTFE was made hydrophilic using these techniques that were then applied to liquid separation filters. With this knowledge we were able to develop a device that regulate/control the flow rate of the aqueous humor at a low-pressure differential. BSS (Balanced Salt Solution) cannot penetrate PTFE 3µm pores even at 300mmHg pressure, but using 193nm photon radiation (1000 shots at 15 mJ/cm2) transformed the material allowing flow at pressure of 20 mmHg. It was also shown that BSS transmission flow rate was proportional to OH radical substitution density. Experimental results confirmed the processing method as aqueous flow began at 20 mmHg and animal studies showed treated samples to be biocompatible, therefore indicating the potential for this material to be used in intraocular pressure control implants.
Surface Graft Polymerization of Glycidyl Methacrylate onto (CHA-DBM) Biomatrix
Demineralised bone matrix (DBM) is a potent inducer of osteoblastic differentiation of mesenchymel cells into bone forming cells. Biomatrix was prepared in different compositions of coralline hydroxyapatite (CHA) and DBM. Surface modification of (CHA-DBM) biomatrix was carried out by grafting with GMA. The percent grafting and grafting efficiency was calculated and hence reaction condition was optimized. The crystal structure and phase purity was confirmed by X-ray diffraction method. The XRD profile of grafted CHA clearly indicated that the PGMA was intact well on the surface. Crystallinity of grafted CHA do not changed due to the grafting reaction, which implies that the PGMA chains were grafted on the surface of the apatite. The observed Bragg's peaks were indexed and crystallographic parameters were calculated. The lattice cell parameters, ao=bo= 9.4290 A and co=6.8867 A, were calculated by least square method and compared with JCPDS file no.9-432. The existence of grafted polymer onto biomatrix was identified by FT-IR spectrometer. The observed peaks at 871 and 845 cm-1 were due to the presence of oxirane ring of glycidyl group, which confirms the existence of PGMA chains in the grafted biomatrix. The modification of biomatrix further confirmed by SEM. Thermal stability of ungrafted and grafted biomatrix was analyzed by TGA and DSC. TG-trace has indicated no significant weight loss for CHA. However the observed weight loss for the biomatrix can be attributed to dehydroxylation and decomposition of PGMA. DSC traces of grafted biomatrix gave further confirmation of the thermal degradation of PGMA. In-vitro physiological stability was performed in different buffers of pH 7.4 at 37C and the results are discussed.
Surface Modification of Coralline Hydroxyapatite By Grafting with GMA for Controlled Release of Antibiotic Drug
Surface modification of coralline hydroxyapatite (CHA) has gained much attention since surface properties of CHA play an important role in tissue regeneration by exposing its surface to body fluids when in use. CHA was prepared hydrothermally from marine coral and its surface was modified by grafting with polyglycidyl methacrylate (PGMA) using redox initiator in aqueous medium. The PGMA chains were grafted onto CHA backbone and subsequently coupled with antibiotic drug through epoxy functional groups present in the PGMA. The percent grafting and grafting efficiency was calculated and hence reaction condition was optimized. The crystal structure and phase purity was confirmed by X-ray diffraction method. The XRD profile of grafted CHA clearly indicated that the PGMA was intact well on the surface. Crystallinity of grafted CHA do not changed due to the grafting reaction, which implies that the PGMA chains were grafted on the surface of the apatite. The existence of polymer and antibiotic drug on the surface of CHA was identified by FT-IR spectrometer. The observed peaks around 870 and 845 cm-1 were due to the presence of oxirane ring of glycidyl group, which confirms the existence of PGMA chains on apatite lattice surface. The surface modification of grafted CHA was further confirmed by SEM. In-vitro drug release profile of grafted CHA indicated that the grafted CHA released drug in a zero order fashion for the prolonged period. The total amount of drug released from the grafted CHA was found to be 79% for the period of 21 days. This surface grafted CHA can also be act as a reservoir for the local antibiotic delivery and the material developed can be used in the treatment of infected and diseased bone.
Ramie Fiber/Soy Protein Interface
(Abstract not yet available)
Ultrathin Films from Fluorinated Polymers: Fabrication and Characterization
Langmuir-Blodgett films from polymers because of their superior thermal stability over films of low molecular weight amphiphiles and possibility of making ordered structures are finding more applications especially in the fields of electronics and optics [1-2]. Due to their low dielectric constant, fluorinated polymer films are finding uses in interlayer dielectrics , passivation and protective coatings in integrated circuit fabrication [3-4] . In this paper we report direct fabrication of LB films of fluorinated polymers and gas phase polymerization of tetrafluoropropylmethacrylate (TFPM).
Gas phase polymerization of TFPM was carried out in the presence of macroinitiator, poly(octadecene-co-maleic anhydride) modified with tert.-butylhydroperoxide . Film thickness can be controlled on different hydrophobic substrates varying the reaction time. Ultrathin films of some fluorine containing polymers were prepared by the Langmuir-Blodgett technique. The polymers were obtained from two main synthetic approaches: firstly, polyamide (PA-1) and polyimide (PI-1) were prepared from direct polycondensation of 4,4'- hexafluoroisopropylidenediphthalic anhydride and 4,4'-hexafluoroisopropylidene dianiline in N-Methyl-2-pyrrolidone (NMP). They form stable monolayers which have a collapse pressure of 62 mN/m and an area per r.u. of 0.10 nm² for PA-1 and for PI-1, the collapse pressure is 60 mN/m with an area per r.u. of 0.40 nm². Secondly, PAI-1 with fluorinated side chains were synthesized from poly(maleic anhydride-co-ethylene). They formed stable monolayers at an air/water interface too. For some of the polymers, the area per r.u. may be smaller as expected from their molecular structure.This may indicate that the orientation of polymeric monolayer structure is significantly different from monolayers of low molecular weight amphiphiles. LB films were characterized by infrared (IR) spectroscopy, ultraviolet - visible spectroscopy (UV), surface plasmon resonance (SPR) and atomic force microscopy (AFM) . Monolayer thickness varies between 1-2.6 nm, depending on the polymer. The dielectric constant for
PI-1 estimated from experimentally determined refractive index at 630 nm (n = 1.5447) using the Maxwell equation is 2.40. This result compares favourably with 2.39 earlier obtained in literature [6-7] at 10 GHz.
 G.G. Roberts (ed), Langmuir-Blodgett Films; Plenum Press: New York, 1990; Chapter 7.
 A. Ulman, An Introduction to Ultrathin Organic Films from Langmuir-Blodgett to Self-
Assembly; Academic Press: San Diego, 1991; Chapter 5.
 F.W. Mercer, T.M. Mckenzie, High perf. Polym., 1993, 5 , 97-106.
 Ha KiRyong, Kim Jong-Mok, J.F. Rabolt, Thin Solid Films ,1999, 347, 272-227.
 C. Anders, R. Gärtner, V. Steinert, B.I. Voit, S. Zschoche, J.M.S.-Pure Appl. Chem.,
 T. Matsuura, S. Ando, S. Sasaki ,Synthesis and properties of partially fluorinated
polyimides for optical applications in G. Hougham, P. E. Cassidy, K. Johns, T.
Davidson (eds.), Fluoropolymers 2-Properties, Kluwer Academic/Plenum Publishers:
New York, 1999, pp 305-350.
 A.K. St. Clair, T.L. St. Clair, W.P. Winfree, Polym. Mater. Sci. Eng. 1988, 59, 28-32.
Flame Treatment of Polymer Surfaces: An Overview
(Abstract not yet available)
Improving the Ultrasonic Weld Strength of Polypropylene by Bulk Material and Surface Modification Methods Including Excimer Laser Irradiation
The objective of this work was to compare methods of surface and bulk material modification for optimized ultrasonic welding of polypropylene. The methods considered included the following: Improving the joint design by joint interface orientation; Modification of surface polarity by grafting monomers onto polypropylene backbone; Thermal and chemical surface pretreatment; Surface pretreatment by excimer laser ablation. The weld joint tensile strength was chosen as the optimization criterion for ultrasonic welding. The thermal properties, weld morphology, and the weld strength were correlated by Differential Scanning Calorimetry (DSC), and Scanning Electron Microscopy (SEM). Grafting of maleic anhydride onto the backbone of polypropylene (PP-g-MA) increased its weld strength by 41% in comparison to pure PP due to increased polarity, reduced melting temperature (Tm), and reduced heat of melting (DHm). Consequently, PP-g-MA melted and diffused more easily during ultrasonic welding.
Excimer laser ablation surface treatment increased the weld strength 200% for PP and 65% for PP-g-MA in comparison to the untreated material. Irradiation led to the degradation of the polymer by the disruption of its linear structure. As a result, oxygen in air could react with the radical ends to produce oxidation products, increasing the surface polarity. Furthermore, subsequent to laser irradiation, the required melt flow velocity, Vm, was attained by the molten PP, which was necessary to obtain acceptable strength in the joint plane. By solvent etching with xylene at 100 oC, subsequent to thermal treatment at 200 oC for 25 seconds, the weld strength increased 173% for PP and 63% for PP-g-MA, in comparison to the untreated material. Compared to the untreated material, thermal treatment (25 seconds at 200 oC) followed by etching with chromic/sulphuric acid at 70 oC resulted in increases of 100% for PP and 15% for PP-g-MA in their weld strengths. Based on our DSC results, the melting temperature (Tm), and the heat of melting (DHm), were reduced as result of thermal and chemical treatment and excimer laser irradiation. Our SEM observations revealed that thermal and chemical surface treatment and excimer laser irradiation roughen the weld surface, increase local melt flow and diffusion, resulting in higher mechanical adhesion. These processes also induce a cleaning action to remove surface contaminants. Joint design is also a crucial factor in ultrasonic welding. By tapering the weld-line, we created a small initial contact area at the ends of the weld line, thus concentrating the ultrasonic energy and decreasing the total time needed for melting. By using a 10 degrees weld-line in top-half of the specimen, the weld strength increased 98% for PP and 60% for PP-g-MA, in comparison to our standard (0o) specimens.
The Effects of Excimer Laser Irradiation on Biaxially Oriented Polypropylene Adhesive Tape
We investigated the geometrical effects produced by excimer laser irradiation on the surface of a biaxially oriented Scotchpro® polypropylene (PP) film adhesive tape bonded over a glass substrate by its pressure sensitive hot melt rubber resin, and related these changes in shape to the laser parameters of energy, repetition rate, and number of pulses. Furthermore, we were able to relate the ablation geometry to the stretching effects on the PP film, as well as to the layering effects when this adhesive tape was bonded in multi layer configuration. Excimer laser irradiation in single-spot mode demonstrated that the ablation depth, the ablated area, and the relocated material were directly proportional to the laser energy, the number of pulses, and the repetition rate. Moreover, the relocated material behavior provided information that could be used as an indirect measure of heat flow. The stretching of the tape resulted in more ablated area in the (stretched) strength direction than in transverse direction when an elliptical ablation pattern was used with its minor axes aligned along these two directions. The curing time for the adhesive influences the ablation geometry as follows: the ablation depth is inversely proportional to the cure time, the ablated area is independent, and the relocated material is directly proportional. Ablation of multi-layer configurations revealed a crater shape, and those systems with more layers had deeper tape ablation, smaller ablated area, and greater relocated material. The first layer of tape adjacent to the glass substrate always swelled the most. Increases in the thickness of the system resulted in material aggregation in the relocated material zone and decreased swelling. The percentage of the adhesive contribution to the composite tape thickness increased after the ablation process. The reduction in the ablation of the glass substrate with increasing number of the tape layers was more significant in its depth direction than the planar dimensions. The effects on samples irradiated in back-to-back spot mode from the PP backing side (front-shot experiments) revealed that the ablation threshold of the polypropylene for 1000 mJ/cm2 laser energy and 3 Hz repetition rate is around 8 pulses. Below the ablation threshold, tensile properties suffered an immediate reduction after irradiation by a single pulse, a recovery with an additional pulse, followed by continued and substantial reduction with higher number of pulses.
New Surface Chemistries and Surface Chemical Patterning by Plasma Polymerisation
The use of low power plasma affords a high degree of functional group and structural retention in the plasma deposition of a number of compounds (e.g. acrylic acid, alkyl methacrylates, allyl amine etc.) This is demonstrated by XPS and ToFSIMS. These functional groups can be used to control biological processes at the solid/liquid interface, e.g. protein adsorption and cell attachment and spreading. Examples of each will be given.
The sequential deposition of a non-functionalised (e.g. hydrocarbon) compound and a functionalised compound (e.g. acrylic acid, allyl amine) through EM grids has been used to create surface chemical patterns on polymer sheets (micron-scale). The fidelty of these patterns is demonstrated by means of imaging XPS and ToFSIMS. These patterns have been used to spatially control protein adsorption and cell attachment and spreading.
Why Do Aqueous Lacquers Adhere on Pre-treated Polyolefin Surfaces ?
In the last decades an enormous number of studies were carried out to understand and explain the mechanism of lacquer adhesion on polyolefin surfaces. First investigations have shown that it is absolutely necessary to pre-treat polyolefin surfaces to reach a satisfactory adhesion between the polymer and an aqueous lacquer. Therefore, different more or less surface sensitive techniques have been developed and industrially applied to modify polyethylene and polypropylene for colouring and joining processing. Well known and important for technologies are flaming and low-pressure plasma treatments using different reactive or non-reactive gases. The use of these techniques opened the way to the broad application of aqueous lacquers in the automotive industries and to banish lacquer systems containing environmental non-healthy solvents. In addition, polymer/lacquer joints made from pre-treated polyolefins and aqueous lacquers are characterized by excellent long-time qualities.
Plasma-treated and flamed polyolefin surfaces have been multifariously studied by surface sensitive spectroscopy and thermodynamic methods. Reactions on the surface during the pre-treatment procedures, the molecular build-up of the pre-treated surfaces as well as their wetting behaviour are well investigated and understood. For pre-treated polyolefins spectroscopic data have been compared with wetting and electrokinetic results to derive models for their adhesion to an aqueous lacquer. According to these well-established and successfully used models, flaming and plasma treatments increase the surface polarity by introduction of functional groups containing oxygen or nitrogen. The raised surface polarity improves the wetting behaviour towards water and should induce strong acid-base interactions between the polymer surface and wetting lacquer molecules. This widespread model has frequently been discussed and published.
Although lacquer adhesion seems to be well understood and the technologies are established, there remain some problems concerning pre-treatment and lacquer adhesion. Flaming and plasma processing are additional steps in technologies. Often, they work discontinuously and increase production costs. Therefore, several efforts have been made to develop polyolefins containing polar groups that can migrate to the surface. We have also tried to develop such materials. We produced batches from polypropylene containing amino, alcohol, and carbonic acid groups, respectively. Then, the batches were blended with bare polypropylene. We have shown that, under certain conditions, the polar groups can migrate to the surface and enrich there. XPS, ToF-SIMS, streaming potential and contact angle measurements have shown a polypropylene surface comparable to a plasma treated or flamed polypropylene surface. But all of our experiments the adhesion of our blend surfaces with a simple aqueous lacquer was not satisfying. Under mild external stress we observed a delamination of the dried lacquer layer.
The frustrating results were the reason to focus the scientific interest on the molecular mechanism of lacquer adhesion. We studied lacquer's interaction on thin films made from self-assembled monolayers of differently w-functionalized thioalkanes as well as several model polymers. Here, we observed that lacquer adhesion does not depend on the kind and number of offered functional groups. In addition, good adhesion was observed on rather non-reactive polymers, like polycarbonate. Obviously, the acid-base model does not explain the adhesion between polyolefins and aqueous lacquer systems. DSC measurements have shown that a certain degree of compatibility between the two interacting phases must be ensured. On the basis of these results we have explained lacquer adhesion on plasma treated and flamed polyolefins.
Low-Molecular-Weight Oxidized Materials on Flame- and Corona-Treated Polypropylene Film
Flames and corona discharges are the two most widely used methods of modifying the surface properties of polypropylene (PP) films. Although both flames and coronas oxidize PP surfaces, there are significant differences in the surfaces generated by the two processes. Perhaps the most significant difference between flame and corona treatments is in the tendency to form water-soluble, low-molecular-weight oxidized materials (LMWOM).
In this study, we used contact-angle measurements, atomic force microscopy (AFM), and x-ray photoelectron spectroscopy (XPS or ESCA) to characterize flame- and corona-treated biaxially oriented PP films. While the surface of flame-treated PP is highly oxidized, no LMWOM is formed. By contrast, corona-treated PP forms copious amounts of LMWOM at lower overall levels of surface oxidation. The topography and stability of the treated films are strongly influenced by this difference.
The different surface modifications obtained with flame and corona treatments can be explained by examining the role of gas-phase atomic oxygen in the two processes. In flames, the concentration of atomic oxygen is low so that there is little scission of the PP chains and no formation of LMWOM. In corona discharges, however, higher concentrations of atomic oxygen causes considerable scission and LMWOM formation.
The Surface Modification of Polyimide- Copolymer Tetrafluorethylene with Hexafluorpropylene Film Using High-Voltage Pulsing Dielectric Barrier Discharge
The polyimide-(poly)tetrafluoroethylene film on both sides was modified using high-voltage (10 kV) pulsing dielectric barrier discharge in air in atmospheric pressure. The frequency was 10 - 30 kHz. Immediately after the modification, the contact angle of a water drop was measured with a contact angle meter. The raw PTFE had a water (glycerine) contact angle of approximately 1110 (900), polyimide - 750 (540). The minimum contact angle of a water (glycerine) drop on the modified surface was approximately 890(660) - for PTFE and 500 (440) - for polyimide.
To describe the surface energy (Es), a polar (gp) and dispersive (gd) component, the Fowkes equation has been used. The raw: for PTFE Es =44,3 mJ/m2 (gd =43,5 mJ/m2 ; gp =0,76 mJ/m2); for polyimide Es =49,3 mJ/m2 (gd =17,7 mJ/m2 ; gp =31,5 mJ/m2). Modified: for PTFE: Es =30,1 mJ/m2 (gd =30,0 mJ/m2 ; gp =0,1 mJ/m2); for polyimide: Es =45,7 mJ/m2 (gd =40,7 mJ/m2 ; gp =5,0 mJ/m2).
The maximal adhesion (420g/cm) is reached at time of discharge action on surface 10 seconds.
The ability of polymeric films to welding is maintained approximately one year.
Properties of a Surface of Polyolefines And Elastomers, Modified Ions of an N+ and Ar+
The rubbers (on a bottom butadiene - nitril of caoutchoucks) and polyethylene (PE) film was modified by ions Ar+ and N+ (Å = 1,5 ¸ 2,5 keV, fluence J = 8 - 12 A/m2), generated in ionic radiant. To describe the surface energy (Es), a polar (gp) and dispersive (gd) component, the Fowkes equation has been used. The greatest values (Es= 60 mJ/m2) are reached at modified by ions of nitrogen. At duration of handling greater time t = 50 s, there is an essential drop of a surface energy stipulated by diminution polar component.
The extreme character of dependence of a surface energy from duration of handling is exhibited and at action of ions on a film PE. During a storage a surface energy impinges with 60 up to 25 mJ/m2, that it is possible to explain by course of relaxation processes on a surface and in surfaces layer, diffusion of atoms of the nitrogen which has not entered in connection with molecules of polymer, formation on a surface of adsorptive beds of a moisture and other linkings.
1. Department of Physics
2. Department of Chemical Engineering, National University of Singapore, Kent Ridge, Singapore 119260
Plasma-Induced Grafting of Poly(ethylene glycol) onto Fluoropolymer Microporous Membranes for Reduction in Protein Adsorption
Fluoropolymer (FP) microporous membranes with surface immobilized poly(ethylene glycol) (PEG) were prepared by the argon plasma-induced direct grafting of PEG. The PEG was pre-coated on the pristine or plasma-pre-activated membrane surface, including the pore surfaces, by dipping the membrane in a PEG/CHCl3 solution prior to the argon plasma exposure. The microstructure and composition of the PEG-grafted FP (PEG-g-FP) membranes were characterized by attenuated total reflectance (ATR) FTIR, X-ray photoelectron spectroscopy (XPS), and thermogravimetric (TG) analysis. A moderate radio-frequency (RF) plasma power and plasma treatment time led to a high concentration of the grafted PEG polymer. The morphology of the modified membranes was studied by scanning electronic microscope (SEM). The flux decreased with increasing surface concentration of the grafted PEG polymer while the pore size remained almost unchanged. Protein adsorption experiments revealed that the PEG-g-FP membranes with a high PEG graft concentration exhibited good anti-fouling property.
1) Department of Chemistry and Laboratory for Surface Modification, Rutgers, The State University of New Jersey, Piscataway NJ 08854
2) Bell Laboratories, Lucent Technologies, 600 Mountain Avenue, Murray Hill, NJ, 07974
XPS and HR-FESEM Studies on the Interfaces of Au/CuPc vs. Au/FCuPc
Organic semiconductors have attracted a growing interest since the early fifties. Organic semiconductors are the core materials for constructing thin field-effect transistors (FETs), which comprise the basic building blocks for microelectronics. Copper phthalocyanine (CuPc) is a p-channel material, while copper hexadecafluorophthalocyanine (FCuPc) is found to function as an air-stable n-channel semiconductor. Gold is a good material for source and drain electrodes in organic transistors because it is chemically inert and allows excellent ohmic contacts with many organic semiconductors.
In our studies, ultrathin films of Au have been grown on both CuPc and FCuPc samples at room temperature and annealed thereafter. X-ray photoelectron spectroscopy (XPS) and high-resolution field emission scanning electron microscopy (HR-FESEM) have been performed on these ultrathin-film-covered samples. Our XPS measurements, performed for various Au film thicknesses (from 0.3 to 3.0 Angstrom), show that Au deposited on the CuPc surface does not react with the CuPc, but there is evidence for possible charge transfer from Au atoms to the four aromatic rings of FCuPc. The post-annealing procedure (annealed at ~125oC for 1 hour) enhances charge transfer at the interfaces of Au/FCuPc, while it does not cause any chemical reactions at the interfaces of Au/CuPc. Studies of the morphology of Au overlayers (from 5 to 120 Angstrom thick) using HR-FESEM complement the XPS measurements. The images show that the Au atoms tend to form bigger clusters with lower cluster density on CuPc surfaces than on FCuPc surfaces. This may indicate a higher diffusivity for Au on CuPc than on FCuPc, perhaps because of a stronger interaction between Au and FcuPc.