The dynamics of the gas phase photopolymerization of acrolein on aluminum (Al), nickel (Ni), and gold (Au) substrates were studied in-situ and in real time using surface second harmonic generation (SSHG) and monitoring vapor pressure decay. The Al and Ni substrates had a significant effect on the apparent rate of polymerization. A dark reaction after irradiation occurred in the absence of metal (Al or Ni) substrates, but no dark reaction was observed when the metal substrates were present. The significant differences in the metal/monomer interactions during photopolymerization are indicated by SEMs of the polyacrolein, as well as evidence from FTIR-ATR spectra. The SSHG intensities from the Au, Al, and polyacrolein surfaces were obtained.

The purpose of research on metals (M) deposited onto self-assembled monolayers (SAMs) is to understand the interactions between the metal and eventually metal oxide overlayers on well-ordered organic substrates. Applications of M/SAM and inorganic/SAM research results to the understanding of real inorganic/organic interfaces in vacuum and under environmental conditions can potentially play a key role in the development of advanced devices with stable interfacial properties. The results of selected M/SAM studies to date are reviewed, and MISAM combinations ranked according to reactivity and penetration. Specific examples of reactive interfaces (Cu/COOH, Cr/several groups) and nonreactive interfaces with penetration (Ag/CH3, Ag/COOH) are used to illustrate the extremes.

The exposure of polycarbonate to an argon plasma is studied using in situ ellipsometry from the UV to the IR, nuclear magnetic resonance and light scattering measurements. An increase in the refractive index and the existence of two populations of different molecular weights show that structural changes occur in the polymer. They are correlated with modifications at the polymer unit scale, such as formation of new polar groups and decrease in dimethyl groups. Two simultaneous reaction mechanisms must be considered to account for these changes. The adhesion of a silica layer on treated polycarbonate is then discussed.

Adhesion at fiber-matrix interface in fiber-reinforced composites plays an important role in controlling the mechanical properties and overall performance of composites. Among the many available tests applicable to the composite interfaces, vibration damping technique has the advantages of being nondestructive as well as highly sensitive. We set up an optical system to measure the damping tangent delta of a cantilever beam, and correlated the damping data in glass-fiber reinforced epoxy-resin composites with transverse tensile strength which is also a qualitative measurement of adhesion at fiber-matrix interface. Four different composite systems containing three different glass-fiber surface treatments were tested and compared. Our experimental results showed an inverse relationship between damping contributed by the interface and composite transverse tensile strength.

Engineering liver tissue using hepatocyte transplantation may provide a new approach for treating a variety of liver diseases. However, techniques to transplant hepatocytes and promote their survival must be developed. We have developed systems to transplant hepatocytes on highly porous (95%), biodegradable sponges, and to regulate the survival of cultured hepatocytes by releasing specific growth factors in the cellular environment. Sponges were fabricated from poly (L, lactic acid) (PLLA) and polyvinyl alcohol using a particulate leaching technique. Epidermal growth factor and insulin, critical factors for hepatocyte growth and survival in culture, were incorporated into microspheres fabricated from poly (lactic-co-glycolic acid) (PLGA) utilizing a double emulsion technique. The incorporated factors were released in a controlled manner over one month in vitro, and the released factors maintained their biological activity, as measured by their ability to promote hepatocyte growth and survival in culture. The growth factor-containing microspheres could be transplanted with hepatocytes using the porous sponges, and the localized, sustained release of these factors improved hepatocyte engraftment 2-fold. These studies suggest that hepatocytecontaining tissues can be engineered using cell transplantation, and that regulating the microenvironment of transplanted cells can control their engraftment.

Poly(ß-hydroxybutyrate-co-ß-hydroxyvalerate) have been recently proposed as degradable biomaterials for drug delivery systems, sutures, bone plates and short-term implants. Three PIBF\HV (7, 14 & 22 % HV) films were analyzed for in vitro cytotoxicity and aqueous accelerated degradation, in vivo degradation and tissue reactions. The PHB/HV materials and extracts elicit few or mild toxic responses, do not lead in vivo to tissue necrosis or abscess formation, but provoke acute inflammatory reactions slightly decreasing with the time. The degradation of PHB/HV polymers present low rates in vitro as well as in vivo. The weight loss rate generally increases with the copolymer composition (HV content) and ranges from 0.15–0.30 (in vitro) to 0.25 %day (in vivo). Compositional and physico-chemical changes in PHB/HV materials were rapidly detected during the accelerated hydrolysis, but were much slower to appear in vivo. The structural and mechanical integrity of PHB/HV materials tend to disappear early in vitro as well as in vivo. After 90 wks in dorsal muscular tissues of adult sheep, there was no significant dissolution of the PHBiIV polymer, 50–60% of the initial weight still remaining. PHB/HV polymers are biodegradable materials, either by hydrolysis or implantation, but with extremely low dissolution or degradation rates.

Water is often the main cause of adhesion loss of a polymer coating/substrate system. The buildup of the interfacial water layer and the loss of adhesion of polymer-coated siliceous substrates exposed to liquid water has been investigated. The thickness of the interfacial water layer was measured on epoxy-coated SiO2-Si prisms using FTIR-multiple internal reflection (FTIR-MIR) spectroscopy. Adhesion loss on flat siliceous substrates was determined by a wet peel test on epoxy-coated SiO2-Si wafers and adhesion loss of composites was obtained by measuring the interlaminar shear strengths of epoxy/E-glass fiber composites. Both untreated and 0.1 % silane-treated substrates were used. Little water was observed at the interface of the silanetreated samples but about 10 monolayers of water have accumulated at the interface of the untreated samples after 100 h of exposure to 24°C water. Untreated, flat substrates lost most of their bonding strengths within 75 h of exposure but silane-treated specimens retained 80% of their adhesion after 600 h of exposure to 24°C water. Adhesion loss of untreated composites immersed in 60°C water was greater than that of treated samples; however, the rate of loss of both silanetreated and untreated composites was much lower than that of flat substrates. Adhesion loss was found to follow the same trend as interfacial water buildup.

It is now recognized that there is a region at the epoxy/adherend interface known as the interphase whose chemistry and structure are different from those of bulk epoxy. There is, however, no adequate understanding of its microstructure. This paper describes differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) studies of the interphase between an aromatic amine cured epoxy and alumina/oxidized-aluminum surfaces. DSC results show dramatic differences in resin-cure behavior in the presence of particulate alumina. TEM results on microtomed cross-sectional specimens of anodized aluminum wire embedded in epoxy show regions of incomplete epoxy infiltration and interfacial stress. RuO4 staining combined with high-angle annular-dark-field STEM imaging indicates that there are structural variations within the bulk epoxy at lengths of ∼10–30nm. The magnitude of these fluctuations decreases in the near the adherend interface, and there is a simultaneous variation in the average epoxy structure. A plausible interpretation of these observations is that the interphase region suffers a variation in curing-agent concentration of unknown magnitude and there is a higher concentration of homopolymerized epoxy there relative to the bulk.

The adhesion and thermal properties of optical ceramic structures bonded by a polymer interlayer are explored. The mechanical, adhesion and optical properties of the heterostructure are dependent on the thickness of the bond and on the residual thermal stresses developed during the bonding process. The thermomechanical properties of a bonded structure over a range of temperatures are investigated, focusing on the thermal expansion and operating temperature limits of the polymer bond. The temperature and stress histories during manufacturing are determined through both numerical modeling and experimental analysis. The effect of stress relaxation and initial stresses on the behavior of the bonding material are examined for different processing conditions. The bond material relaxation time constant, activation energy, viscosity, and shear modulus are approximated from observation of the temperature-dependent behavior of the structure.

Metal/Polymer systems have potential applications as interconnect materials in integrated circuits. Polymers with low dielectric constants, if used as interlayer dielectric, can reduce the RC time constant. Device speed can be doubled if a polymer can replace the present dielectric material, SiO2. However, the problem of weak metal/polymer adhesion must be understood and resolved. In situ deposition and analysis are the most controlled means to study an interface formation process. However, for practical reasons, i.e., application, time, cost, and flexibility, it is critical to study metal/polymer interface ex situ. X-ray Photoelectron Spectroscopy (XPS), can be used to determine the composition and bonding structures of buried interfaces. This is achieved by examining peeled surfaces, thin overlayer, and lowenergy- ion sputtered surfaces. The possible adhesion mechanism or failure mode is determined by correlating XPS results with adhesion strength. Based on these results, adhesion enhancement methods, such as substrate surface treatments, can be formulated. The product of these treatments can be evaluated using the same analysis. These techniques for studying buried interfaces using XPS are reviewed and results of their applications to the metal/Teflon AF 1600 interface is presented.

The adhesive strength of polyimide thin films on an alumina substrate has been studied by the pull test. Polyimide thin films were cured at various temperatures from 300 to 400°C, followed by etching in an oxygen plasma for 3 min. After metallization with chromium and copper, the pull test was carried out. It is found that the adhesive strength increases with an increase of the cure temperature. However the strength deteriorates noticeably at the cure temperature of 400°C. A possible reason for this is the variation of chemical states in the polyimide thin films.

This paper describes a method for estimating the effective sticking probability for plasma enhanced chemical vapor deposition (PECVD) of hexamethyldisiloxane (HMDSO) using SiO2 and polymerized siloxanes deposited on specially prepared trench structures. Comparison of the data with direct Monte-Carlo simulation curves provides information about the incorporation probability relative to film growth. It is shown that besides variation in gas chemistry, the choice of trench and film dimensions influences the step coverage. The sticking probability is shown to increase with oxygen flow rate by about 30%, from 0:1 to 10:1 02:HMDSO flow ratio. This flow rate dependence is found to be consistent with work performed on tetraethoxysilane.

Applications of Fourier transform infrared (FTIR) spectroscopy for probing polymer-metal interfaces are described with examples of polyimide (PI)-metal systems relevant to electronics packaging and poly(phenylene vinylene) (PPV) derivatives used in electroluminescent devices. Emphasis is placed on the detection and interpretation of interfacial reactions that influence performance characteristics (e.g., adhesion, stability, and light emission) of polymer-metal structures. In situ infrared reflection absorption spectroscopy (IRRAS) is used to explore the formation of PI-on-metal interfaces, the hydrolytic stability of such interfaces, and the reactivity of PPV systems when exposed to ultraviolet light and oxygen. Differences between polymer-on-metal and metal-onpolymer interfaces are discussed. Models of the infrared optical processes in the thin film composites are used to distinguish between chemical and optical effects. The FTIR observations are supported by additional spectroscopic characterizations, specifically ex situ X-ray photoelectron spectroscopy (XPS).

The chemical and electronic properties of aluminum/poly(p-phenylenevinylene) (PPV) interfaces were studied in situ using x-ray photoelectron spectroscopy (XPS). It was observed that the aluminum atoms react with the oxygen-containing groups present as impurities on the surface of PPV to form Al-O-C linkages. The Al atoms also interact with the wrsystem of the polymer as indicated by changes in the valence band. Contrary to to recent suggestions (Ettedgui et al.) the relation between surface oxygen content and band bending is not straightforward, as shown by deposition on PPV surfaces prepared by two different synthetic routes.

Plasma polymerized acetylene films contained mono- and di-substituted acetylene groups, aromatic groups, and carbonyl groups which resulted from reaction of residual free radicals with oxygen when the films were exposed to the atmosphere. There was some evidence for formation of acetylides in the interphase between the films and the substrates. Reactions occurring in the interphase between the plasma polymerized films and natural rubber were simulated using a model rubber compound consisting of a mixture of squalene, zinc oxide, carbon black, sulfur, stearic acid, diaryl-p-diphenyleneamine, and N,N-dicyclohexylbenzothiazole sulfenamide (DCBS). Zinc oxide and cobalt naphthenate reacted with stearic acid to form zinc and cobalt stearates. The stearates reacted with the benzothiazole sulfonamide moiety of DCBS and with sulfur to form zinc and cobalt accelerator complexes and perthiomercaptides. The complexes and perthiomercaptides reacted with squalene and the plasma polymer to form pendant groups which eventually disproportionated to form crosslinks between squalene and the primer. Migration of double bonds during reaction of the model rubber compound with the films resulted in formation of conjugated double bonds in squalene.

We investigated the role of coupling agents with respect to the relative durability of glass fiber/epoxy matrix composites exposed to water, which degrades both glass fibers and the fiber-matrix interface. Interface chemistry was tailored by coating fibers with mixtures of different coupling agents. Single-fiber fragmentation test results showed little decrease in the strengths of the interface and a slight decrease in fiber strengths upon exposure to water. XPS results showed expected variations in surface composition. Contact angle measurements demonstrated variations in surface hydrophobicity as coupling agent mixtures were changed.

Functionalized block copolymers were synthesized as adhesion promoters using Ring-Opening Metathesis Polymerization (ROMP). They were designed for glass/epoxy and copper/epoxy interfaces. The former contained triethoxysilane groups in the first block and secondary amine groups in the second. The latter contained imidazole groups in the first and amine groups in the second block. These block copolymers were shown to form ordered monolayers on the respective glass and copper surfaces using neutron reflectivity. Adhesion measurements showed an enhancement of adhesion after application of these block copolymers.

The present work was aimed at the development of new organosilicate polymeric composite, based on polydimethylphenylsiloxane/polyurethane (PDMPS/PU) miscible blend, filled with silicates and metal oxides. Considerable improvement of mechanical and corrosion-protective properties due to introduction of polyurethane has been observed. Coatings with sufficient thermostability (up to 300°C) have been obtained in the case of 20% polyurethane content, related to amount of binders. The effects coating heat treatment temperature and curing conditions on adhesion of metal/composite interface have been studied. Surface energy characteristics of this coating have been obtained and were correlated with its microstructure, determined from Scanning Electron X-ray Microprobe Analyses. Recently developed composite appeared to show increased durability in atmosphere operation conditions.

Toray M40 graphite fiber / Epon 828 epoxy resin single fiber composites with both sized and unsized fibers were exposed to distilled water at 50°C and 100°C, 10% NaOH and HCl aqueous solutions at 50°C, and air at 100°C. Micro Raman spectroscopy was used to measure the strain and interfacial shear stress profiles as a function of environmental exposure. It was found that the degradation mechanism is primarily a mechanical failure of the fiber/matrix interface.

Here we investigated the interactions of phenol resin precursor and calcium aluminates, in relation to a recently innovated cement based material having a high flexural strength of more than 120MPa. An anhydrous phenol resin precursor was used as the binder and water was not contained in the initial composition.

The method of processing consists of mixing of the cement, the phenol resin precursor, and small amounts of N-methoxymethyl 6-nylon and glycerol under high shear. Addition of the 6-nylon and glycerol was necessary to produce viscoelastic cement paste through a twin roll mill. Setting of calendered sheets takes place during the heat curing at 200° C. The best combination for high flexural strength among all the cements tested is the mixture of calcium aluminate cement and the resole type of phenol resin. Resulting outstanding affinity suggested specific interactions between the phenol resin and calcium aluminate.

We here propose the interaction evidence of phenol moiety-calcium aluminate, based on the experimental data of differential scanning calorimetry and conduction calorimetry.