Surface tension driven flow is studied in films of viscous polymer liquid by monitoring the spreading of droplets or the capillary levelling of films with excess surface area. The research presented in this thesis is focused on three major themes where molecular details are important to flow: molecular anisotropy, interfacial friction, and the initial state of the film. The effect of molecular anisotropy is studied by examining the dynamics of partially wetting diblock copolymer droplets using optical microscopy. The shape of the droplets is measured as they evolve towards equilibrium. In this system, it is found that energy is dissipated at the base of the droplets. This is consistent with a reduced interfacial friction at the liquid-substrate interface. Flow dynamics are also found to depend on the symmetry of the initial film thickness profile. Thickness perturbations with different degrees of symmetry were created in an initially flat film using focused laser spike annealing. The films were allowed to flow under the driving force of surface tension, and using atomic force microscopy, the film thickness profile was measured as a function of time. We find the depth of the perturbations decreases as a power law in time, with a power law exponent that depends on the symmetry of the thickness perturbation. The role of interfacial effects are explored by studying the flow in a film with zero interfacial friction: a freely-suspended film. Flow is measured in films with no interfacial friction using a technique which creates a film with a sharp step in the initial thickness profile. The excess surface area at the edge of the step drives flow, and information about the dynamics of the fluid is obtained by measuring the width of the step over time with atomic force microscopy. We observe flow that is consistent with plug flow: where the velocity of the fluid in the plane of the film is constant along the direction perpendicular to the film. Finally, freely-suspended films provide a model system to study the nucleation and growth of pores in a membrane. By purposefully creating pores of different initial size, the critical radius for nucleation is measured as a function of the membrane thickness. The experimental results agree with a simple model in which the free energy cost at the perimeter of a pore is determined by the excess surface area due to the curved interface of the pore edge. / Thesis / Doctor of Philosophy (PhD)

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第13843号 / 工博第2947号 / 新制||工||1435(附属図書館) / 26059 / UT51-2008-C759 / 京都大学大学院工学研究科高分子化学専攻 / (主査)教授 金谷 利治, 教授 吉﨑 武尚, 教授 渡辺 宏 / 学位規則第4条第1項該当

No description available.

Conductive thin films of poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate (PEDOT-PSS) were created via layer-by-layer assembly. The PEDOT-PSS was used in an aqueous solution as an anionic polyelectrolyte, with both linear and branched polyethylenimine (PEI) and poly(allylamine hydrochloride) (PAH) in the positive aqueous solution. The electrical conductivity was varied by altering pH, concentration, polyelectrolyte, and doping the PEDOT with dimethylsulfoxide (DMSO). The most conductive 12BL samples were doped with 1wt% DMSO and have a sheet resistance of approximately 8kΩ/□. Despite exhibiting good initial conductivity, these PEDOT based thin films degrade under ultraviolet (UV) exposure. UV absorbing nanoparticles were added into the cationic solution in an effort to reduce UV sensitivity. The final bilayers of the films contained either colloidal titanium dioxide (TiO2) or carbon black (CB) and the films were exposed to a 365nm UV-light with an intensity of 2.16mW/cm2 for 9 days. The UV light at this intensity correlates to approximately four years of sunlight. The initial sheet resistances for all samples were similar, but the UV-degradation was reduced by a factor of 5 by utilizing TiO2 and CB in the final bilayers. In addition to being the most conductive after UV exposure, the TiO2 containing film was also 27% more optically transparent than the pure PEDOT films. These additional UV-absorbing nanoparticles extend the operational life of the PEDOT films and, in the case of TiO2, do so without any reduced transparency.

Conductive thin films of poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate (PEDOT-PSS) were created via layer-by-layer assembly. The PEDOT-PSS was used in an aqueous solution as an anionic polyelectrolyte, with both linear and branched polyethylenimine (PEI) and poly(allylamine hydrochloride) (PAH) in the positive aqueous solution. The electrical conductivity was varied by altering pH, concentration, polyelectrolyte, and doping the PEDOT with dimethylsulfoxide (DMSO). The most conductive 12BL samples were doped with 1wt% DMSO and have a sheet resistance of approximately 8kΩ/□. Despite exhibiting good initial conductivity, these PEDOT based thin films degrade under ultraviolet (UV) exposure. UV absorbing nanoparticles were added into the cationic solution in an effort to reduce UV sensitivity. The final bilayers of the films contained either colloidal titanium dioxide (TiO2) or carbon black (CB) and the films were exposed to a 365nm UV-light with an intensity of 2.16mW/cm2 for 9 days. The UV light at this intensity correlates to approximately four years of sunlight. The initial sheet resistances for all samples were similar, but the UV-degradation was reduced by a factor of 5 by utilizing TiO2 and CB in the final bilayers. In addition to being the most conductive after UV exposure, the TiO2 containing film was also 27% more optically transparent than the pure PEDOT films. These additional UV-absorbing nanoparticles extend the operational life of the PEDOT films and, in the case of TiO2, do so without any reduced transparency.

There are three novel 2-trifluoromethyl-activated bisfluoro monomers have been successfully synthesized in this study, and the nomenclatures are shown as follows: 4,4¡¦¡¦¡¦¡¦-Difluore-3,3¡¦¡¦¡¦¡¦-bis(trifluoromethyl)-2¡¦¡¦,3¡¦¡¦,5¡¦¡¦,6¡¦¡¦-triphenyl(M4), 4,4¡¦¡¦¡¦¡¦-Difluore-3,3¡¦¡¦¡¦¡¦-bis(trifluoromethyl)-2¡¦¡¦,3¡¦¡¦,5¡¦¡¦-triphenyl(M3), 4,4¡¦¡¦¡¦¡¦-Difluore-3,3¡¦¡¦¡¦¡¦-bis(trifluoromethyl)-2¡¦¡¦,3¡¦¡¦-triphenyl(M2). Through polymerization with 1,1-dihydroxydiphenyl cyclododecane the monomers M2, M3 and M4 were accordingly converted into poly(arylene ether)s P2-1,1C, P3-1,1C and P4-1,1C, respectively. These polymers exhibit weight-average molecular weight up to 2.25¡Ñ105g/mol. The molecular weight were investigated and confirmed by MASS and GPC. The molecular structures were investigated and confirmed by NMR and FTIR. The UV-VIS absorption and photoluminescence spectra measurement of all the monomers and polymers in dilute solutions and in solid state were conducted. The results show that all monomers and polymers in dilute solutions have no absorption in the vision light region of spectrum. The absorption spectra of polymer thin films showed high optical transparency up to 90%. The photoluminescence spectra of all monomers and polymers in dilute solutions and thin film emits light with high intensity and wavelength in region of 350~380nm. Thermal analysis studies were conducted with TGA, DSC, TMA and crystal property study was performed by XRD. The results show that these polymers did not show melting but showed ultrahigh Tg values ranging from 270~330¢XC in DSC and TMA measurements, so it indicated that three polymers were not crystalline materials. Outstanding thermal stability is over then 440~ 460¢XC for 5% weight loss in TGA under nitrogen atmosphere. So it could make manufacture in higher temperature and have higher thermal stability. With optical properties of polymer thin films, we utilized Ellipsometer to measure refractive index and the results showed no birefringence for these polymers. The polymer thin films show low polarity and high hydrophobicity could be attested by the measured results of contact angle and surface energy. The HOMO and LUMO energy level of monomers are both measured by Cyclic Voltammetry and theoretical calculation. The absorption spectra of polymer thin films showed no absorption in the visible light region of the spectrum i.e., having a high optical transparency. All above stated material properties are good for doing as a plastic substrate of devices or panel display.

The behavior of polymeric systems confined into thin films is a situation that has numerous practical consequences. One particular application in which the properties of thin polymer films is becoming crucially important is in the design, formulation, and processing of photoresists for semiconductor microlithography. As devices continue to be scaled down into the nano-regime, the microelectronics industry will ultimately rely upon a molecular understanding of materials for process development. The majority of these devices are now confined in planar geometries; thus, thin films have played an ever-increasing role in manufacturing of modern electronic devices. This movement towards thinner resist films creates larger surface to volume ratios, and hence thin films can exhibit thermodynamic, structural, and dynamic properties that are different from those of the bulk material. It is thus extremely important to understand the properties of polymers when confined in such geometries for various applications including resists for lithographic patterning. In present work, the influence of a variety of factors including film thickness, molecular weight, and substrate interactions on the polymer thin film physical properties such as the glass transition temperature, coefficient of thermal expansion, dissolution rate, and diffusion coefficient was studied in detail using a combination of experimental characterization and molecular modeling simulation techniques.

Structure and dynamics of nanoconfined glass-forming oligomers and diblock coplymers (BPCs) are investigated by a combination of infrared transition moment orientational analysis (IR-TMOA), positron annihilation lifetime spectroscopy (PALS), grazing incidence small angle X-ray scattering (GISAXS), atomic force microscopy (AFM), scanning electron microscopy (SEM) and broadband dielectric spectroscopy (BDS). The oligomers probed are the van der Waals type, tris(2-ethyhexyl)phosphate (TEHP) and the self-associating molecules of 2-ethyl-1-hexanol (2E1H). Symmetric and asymmetric poly(styrene-b-1,4-isoprene) P(S-b-I) are studied for the case of BCPs. The samples are confined either in one-dimensional (1D) in form of thin films or in 2D (nanopores) geometrical constraints. The molecular order of TEHP in nanopores as studied by IR-TMOA shows that about 7% of the molecules are preferentially oriented perpendicular to the long axis of the pores due to their interaction with the pore walls. PALS results reveal that 2E1H confined in nanopores exhibit larger free volume with respect to the bulk. In thin films (1D), P(S-b-I) having volume fraction of isoprene blocks f(PI)= 0.55 exhibits randomly oriented lamellae and their thicknesses are directly proportional to the film thickness d(film). For f(PI) = 0.73, perpendicular cylinders with respect to the substrate are observed for d(film)>50 nm but they lie along the substrate plane when d(film) < 50 nm. In AAO pores (2D) with average pore diameter d(pore) of 150 nm, straight nanorods are formed which change to helical structures in 18 nm pores. Molecular dynamics of 2E1H and TEHP constrained in nanopores (2D), is influenced by the interplay between confinement and surface effects. Confinement effects show up as an increase in the structural relaxation rate with decreasing pore sizes at the vicinity of the glass transition temperature. This is attributed to the reduced packing density of the molecules in pores as quantified by PALS results for 2E1H. Whereas the orientation and morphologies of the domains in P(S-b-I) and the chain dynamics of isoprene chains are influenced by the finite--size and dimensionality of confinement, the segmental motion, related to the dynamic glass transition (DGT) of both styrene and isoprene blocks remains unaffected-in its relaxation time-within experimental accuracy. Effects of nanoscale confinement on the molecular dynamics therefore depend on a number of factors: the type of molecules (polymers, low molecular liquids), interfacial interactions and the dimensionality of the constraining geometries.

<p>Polymer thin films have been developed in numerous industrial fields due to their cost efficiency and productivity. A primary step in developing new products is characterizing the properties of polymer thin films before implementing them in various applications. Many studies have been conducted to determine the physical properties of polymer thin films but there is still a need to further understand and characterize their mechanical and interfacial properties. Although there are standard testing methods to assess the mechanical and interfacial properties of thin films, they can be challenging to use due to the geometrical and physical limitations of polymer thin films. Hence, there is a need to develop a new approach for mechanical and interfacial characterization that has high sensitivity and can be broadly applied.</p> <p>In this work, wrinkling and delamination of a glassy thin film on an elastomeric substrate, a well-defined and understood surface buckling instability, is adopted to investigate the interfacial and mechanical properties of a glassy polymer thin film on a soft elastomeric substrate. This new characterization tool utilizes the transition from thin film wrinkling to delamination (W2D) from the elastomeric substrate to subsequently measure the elastic modulus and the adhesion strength of a glassy polymer thin film, which is difficult to characterize simultaneously with conventional techniques due to the brittleness of glassy thin films. Furthermore, the dependency of the elastomer’s bulk mechanical properties on adhesion strength was investigated by expanding on the W2D technique. Further exploiting the W2D technique, the delamination propagation rate of a thin film debonding from a substrate is used to understand how the bulk mechanical properties of the substrate affect the adhesion energy, termed the strain energy release rate (G), of a thin film on an elastic substrate. Additionally, a new method for determining the axial fracture mechanism and axial modulus of cellulose nanocrystal (CNC) films has been developed by visualizing in-situ deformation and surface instabilities (wrinkling). Lastly, new experimental approaches were developed to understand the mechanical behavior of polymeric thin films using a common test method. The effect of temperature on the adhesion and mechanical behavior of polymeric thin films was studied by developing a double lap shear fixture and temperature stabilization platform. Through these newly developed or revised characterization approaches, measurement of the physical and mechanical properties of polymer thin films that are commonly difficult to measure have been overcome. </p>

La miniaturisation est un paramètre important lors de la fabrication d’un dispositif. Les films minces de polymère, qui sont des composants essentiels de beaucoup d’entre eux, montrent des propriétés anormales quand leur épaisseur est réduite jusqu’à produire un film confiné. Ce travail est dédié à la compréhension des effets de confinements et des propriétés des films ultra-minces de polymère. Dans un premier temps, nous avons observé l’évolution de la densité des films de polymère en fonction de leur épaisseur au moyen de nanoparticules d’oxyde de cérium adsorbées sur les surfaces polymères. La deuxième étude a mis en évidence les domaines de stabilité/instabilité de tels films, ce qui a conduit à une méthode pour fabriquer des films stables de moins de 7 nm d’épaisseur grâce au rinçage avec un solvant adéquat. Dans l’étude suivante, il a été montré qu’il y avait une influence significative du solvant utilisé pour le rinçage sur les caractéristiques de la couche résiduelle de polymère. Pour finir, la température de transition vitreuse de la couche résiduelle de polymère a été étudiée, montrant l’existence de deux températures de transition vitreuse, indiquant deux états physiques de la couche de polymère résiduelle. Au final, ce travail contribue à une meilleure compréhension de la densité, stabilité et des propriétés de transition vitreuse des films minces de polymère confinés par leur épaisseur. / Size reduction is one of the very important factors considered during the device fabrication. Polymer thin films, which is a crucial component of many devices, shows numerous anomalous behaviors when they are confined by their thickness. This work is dedicated to understand the confinement effects and properties of ultrathin polymer films. At the very outset we observed the density evolution of polymer films with the film thickness by means of adsorbing ceria nanoparticles onto the polymer surfaces. The second study threw light on the stability/instability domains of such films, which led to a method for fabricating stable films which are less than 7nm, by means of rinsing with a good solvent. In the following study, it was found that there is a significant influence of solvent used rinsing on the characteristics of the polymer residual layer. Finally the glass transition behavior of the polymer residual layer was analyzed, which showed multiple glass transition temperatures, that points to the existence of two physical states in the polymer residual layer. Altogether, this work contributes towards a better understanding of the density, stability and glass transition properties of polymer films confined by their thickness.