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Showing 1 to 10 of 10 (0.051 seconds)Spelling suggestions: "subject:"thin apolymer films"" "subject:"thin apolymer wilms""
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Surface and interface properties of industrially relevant polymersMaccarini, Marco January 2002 (has links)
No description available.
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Shear Deformation in Thin Polymer Films as a Probe of Entanglement in Confined SystemsSi, Lun January 2003 (has links)
We present the results of our study of the shear deformation zone in free-standing thin polymer films as a probe of entanglement in confined systems. A stretching system was used to uniaxially strain thin polystyrene (PS) films. Atomic force microscopy was used to measure the thicknesses of the shear deformation zone (SDZ), hc, and the film thicknesses h. The maximum extension ratio 2 - h/hc, was measured as a function of film thickness. The results show that A increases with the decreasing film thickness which implies an increase in the entanglement molecular weight in confinement. The same experiments were carried out for thin PS film with different molecular weights. A tentative model was developed to explain the experimental results and found to be in good agreement with the data. More exciting is the fact that the model predicts a scaling dependence on the polymer molecular weight which was also observed. / Thesis / Master of Applied Science (MASc)
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Measuring material properties of thin films with DIC and tearing test of laminateNilsson, Peter January 2017 (has links)
Thin polymer materials are today widely used in industry and production. An ordinary food package can have around six different layers of materials laminated together to obtain the desired protection. To obtain an efficient usage of these materials simulations are often required. But the simulations require precise and good material models and properties. To obtain these properties through standard tests are difficult as normal strain gauges or extensometers can’t be used. Much research has been done on this kind of material. But still, the knowledge of the behaviour in certain cases is limited. One such area is the tearing of a laminated material. The first objective of the work is to test a new measurement method, Digital Image Correlation (DIC), for thin polymer films and test if the method is applicable. DIC is a non-contact measurement technique that measure the deformation of a stochastic pattern. The strain is then calculated from this deformation. These strains can then be used to obtain material properties and behaviour. The second objective is to test the tearing behaviour of a laminate. The material used is a laminate between a PET (100 μm) and LDPE (25 μm) film. When testing the single layers they were carefully delaminated with a plexiglass staff. As the material can be anisotropic the materials were tested in five directions: Machine Direction (MD); 22,5˚; 45˚; 67,5˚ and Cross Direction (CD). The work and tests were performed at BTH Campus Gräsvik. An experimental setup for DIC with the usage of chalk spray and backlight was tested. Five tests were performed with and without DIC pattern. It was calculated that the DIC specimens were within standard deviation of the reference tests. GOM Correlate was used to evaluate the strains and visualise the distribution. The strains obtained were also used to calculate the true stress of the specimens and estimate the Poisson’s ratio. Through testing it was concluded that the tearing of the laminate led to delamination in one of the legs. The delamination always appears in the leg where the LDPE film will experience tensile forces. The crack also angels towards 45˚. By testing single layers it was found that the PET film angles when teared, likely caused by the anisotropy of the material. An experimental setup for the use of DIC for thin polymer has been developed. This method can be used for future measurements and improvement of material models. The behaviour of laminated tearing was observed and some conclusions could be drawn about its behaviour. However, a lot more work is required on this subject.
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SURFACE AND INTERFACE STRUCTURE OF DIBLOCK COPOLYMER BRUSHESAkgun, Bulent 02 October 2007 (has links)
No description available.
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The effect of temperature on the solvent removal from solution-cast thin polymer filmsPowers, Gerald, W. January 1988 (has links)
No description available.
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Snakes and Labyrinths: Adhesion-Induced Fingering Instabilities in Thin Elastic FilmsDavis-Purcell, Benjamin 11 1900 (has links)
Fingering instabilities can be observed when studying many different phenomena and display elegant pattern formation. Adhesion-induced fingering instabilities, discovered in the early 2000s, are instability patterns that arise when elastic films are sandwiched between two rigid surfaces. In this thesis we investigate this adhesion-induced fingering instability in thin elastic films. This work builds upon previous research into this instability. Experiments based on studies in the literature were performed to further examine past results; general scaling rules were confirmed, but discrepancies between current and past data show that there is still much to understand theoretically. We also perform novel experiments to elucidate the effects of strain on the instability pattern. It is found that the pattern aligns with the direction of strain in a thin film. We provide a theoretical model to explain this result. / Thesis / Master of Science (MSc)
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Influence de la méthode de préparation sur la dynamique de relaxation des polymères en films minces / The influence of sample preparation on the relaxation dynamics of supported polymer thin filmsKchaou, Marwa 25 January 2016 (has links)
L'objectif principal de cette thèse est de mettre en évidence l'effet de la méthode de préparation sur la dynamique de relaxation des polymères en films minces. Nous nous sommes focalisés en particulier sur l'importance de la maîtrise du taux d'évaporation du solvant lors de la préparation des films, en termes de contrôle de la magnitude des contraintes résiduelles et les conséquences engendrées sur les propriétés physiques. Dans un premier temps, nous exposons la problématique de déviation des propriétés de polymères en films minces et le lien avec la technique de préparation. Nous décrivons un moyen simple permettant de contrôler le taux d'évaporation du solvant en ajustant la concentration de la solution et la vitesse de rotation de la tournette. Les expériences de démouillage nous ont permis de suivre l'effet du taux d'évaporation du solvant sur les propriétés viscoélastiques des polymères près de la Tg. Les résultats obtenus sur des films minces de polystyrène mettent en évidence le rôle de la méthode de préparation sur la probabilité de rupture des films, les temps caractéristiques de relaxation, la dynamique de démouillage et la magnitude des contraintes résiduelles. Dans une seconde partie, nous présentons également une expérience basée sur la propagation des fissures dans les films minces vitreux. Une simple observation microscopique, ainsi que des imageries en AFM permettent de prouver le rôle du taux d'évaporation du solvant lors de la préparation. Enfin, nous explorons une nouvelle approche expérimentale portant sur la possibilité d'investigations en temps réel et lors de démouillage la relaxation moléculaire des chaînes dans les films minces par des mesures diélectriques directes. Nous avons réussi à prouver non seulement un rôle de la méthode de préparation des films mais également que la restauration du comportement du polymère en volume « bulk » est possible en fonction du temps quelques soient les paramètres du film. Nous confirmons ainsi que les propriétés anormales observées dans les films minces spin-coatés sont dictées par l'état métastable provoqué par la méthode de préparation / The aim of this work is to highlight the influence of the sample preparation on the relaxation dynamics of supported polymer thin films. We focus in particular on the importance of tuning the solvent evaporation rate during films preparation, in terms of controlling the magnitude of residual stresses, and the impact on the physical properties. Firstly, we expose the deviation of the polymer behavior in thin polymer films related to the preparation technique. Then, we describe how the solvent evaporation rate can be precisely tuned by varying the concentration of the solution and the rotation rate of the spin coater. Dewetting experiments allowed us to investigate the effect of the solvent evaporation rate on the viscoelastic behavior of the polymers near the Tg. The probability of films rupture, the characteristic time, dewetting dynamics and the magnitude of residual stresses are deduced to prove the impact of sample preparation. In the second part, we present cracks propagation experiments in glassy thin films. A simple microscopic observation, as well as AFM imaging are used to emphasize the role of the solvent evaporation rate during the preparation. Finally, we present a new experimental approach to investigate in real time and during dewetting the dynamics of polymers in thin films by direct dielectric measurements. We have successfully proved not only the impact of sample preparation but also the restoration of the bulk behavior of polymers is possible during the time whatever the film parameters. We therefore confirm that the anomalous properties observed in spin-coated films are governed by the metastable state induced by the sample preparation
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Molecular Transport in Polyelectrolyte MultilayersPahal, Suman January 2016 (has links) (PDF)
Layer-by-layer assembly of polyelectrolytes is a simple technique based on the self-assembly of polycations and polyanions mainly by electrostatic interactions, which has gained considerable scientific interest for its versatility of applications. Ease of fabrication process, inexpensive approach and use to coat surfaces with various geometries prompts the researchers to select this technique not only for the surface modification applications but also to study the processes which exploit the 3D matrix properties of polyelectrolyte multilayer films (PEMs). Recent advances have been made where PEMs coatings have been utilized for their bio-applications like drug delivery and in tissue engineering for modifying the biomaterial's surfaces. In the field of drug delivery and tissue engineering the location and availability of the constituent molecules is very important, which is defined by their ability to diffuse through the encapsulating material or reservoir. So the main objective of this thesis is to understand the transport of molecules in ultrathin Polyelectrolyte Multilayer Films in lateral as well as transverse direction to the substrate. To study this transport behaviour in PEMs, we have employed various strategies which can enhance or suppress the diffusivity across PEMs. Thus, understanding the diffusion at nanoscale resolution will lead us to design better host materials for loading of drugs and growth factors for various biomedical applications.
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Characterization of heterogeneous diffusion in confined soft matterTäuber, Daniela 26 October 2011 (has links) (PDF)
A new method, probability distribution of diffusivities (time scaled square displacements between succeeding video frames), was developed to analyze single molecule tracking (SMT) experiments. This method was then applied to SMT experiments on ultrathin liquid tetrakis(2-ethylhexoxy)silane (TEHOS) films on Si wafer with 100 nm thermally grown oxide, and on thin semectic liquid crystal films. Spatial maps of diffusivities from SMT experiments on 220 nm thick semectic liquid crystal films reveal structure related dynamics. The SMT experiments on ultrathin TEHOS films were complemented by fluorescence correlation spectroscopy (FCS). The observed strongly heterogeneous single molecule dynamics within those films can be explained by a three-layer model consisting of (i) dye molecules adsorbed to the substrate, (ii) slowly diffusing molecules in the laterally heterogeneous near-surface region of 1 - 2 molecular diameters, and (iii) freely diffusing dye molecules in the upper region of the film. FCS and SMT experiments reveal a strong influence of substrate heterogeneity on SM dynamics. Thereby chemisorption to substrate surface silanols plays an important role. Vertical mean first passage times (mfpt) in those films are below 1 µs. This appears as fast component in FCS autocorrelation curves, which further contain a contribution from lateral diffusion and from adsorption events. Therefore, the FCS curves are approximated by a tri-component function, which contains an exponential term related to the mfpt, the correlation function for translational diffusion and a stretched exponential term for the broad distribution of adsorption events. Lateral diffusion coefficients obtained by FCS on 10 nm thick TEHOS films, thereby, are effective diffusion coefficients from dye transients in the focal area. They strongly depend on the substrate heterogeneity. Variation of the frame times for the acquisition of SMT experiments in steps of 20 ms from 20 ms to 200 ms revealed a strong dependence of the corresponding probability distributions of diffusivities on time, in particular in the range between 20 ms and 100 ms. This points to average dwell times of the dye molecules in at least one type of the heterogeneous regions (e.g. on and above silanol clusters) in the range of few tens of milliseconds.
Furthermore, time series of SM spectra from Nile Red in 25 nm thick poly-n-alkyl-methacrylate (PnAMA) films were studied. In analogy to translational diffusion, spectral diffusion (shifts in energetic positions of SM spectra) can be studied by probability distributions of spectral diffusivities, i.e. time scaled square energetic displacements. Simulations were run and analyzed to study contributions from noise and fitting uncertainty to spectral diffusion. Furthermore the effect of spectral jumps during acquisition of a SM spectrum was investigated. Probability distributions of spectral diffusivites of Nile Red probing vitreous PnAMA films reveal a two-level system. In contrast, such probability distributions obtained from Nile Red within a 25 nm thick poly-n-butylmethacrylate film around glass transition and in the melt state, display larger spectral jumps. Moreover, for longer alkyl side chains a solvent shift to higher energies is observed, which supports the idea of nanophase separation within those polymers.
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Characterization of heterogeneous diffusion in confined soft matterTäuber, Daniela 20 October 2011 (has links)
A new method, probability distribution of diffusivities (time scaled square displacements between succeeding video frames), was developed to analyze single molecule tracking (SMT) experiments. This method was then applied to SMT experiments on ultrathin liquid tetrakis(2-ethylhexoxy)silane (TEHOS) films on Si wafer with 100 nm thermally grown oxide, and on thin semectic liquid crystal films. Spatial maps of diffusivities from SMT experiments on 220 nm thick semectic liquid crystal films reveal structure related dynamics. The SMT experiments on ultrathin TEHOS films were complemented by fluorescence correlation spectroscopy (FCS). The observed strongly heterogeneous single molecule dynamics within those films can be explained by a three-layer model consisting of (i) dye molecules adsorbed to the substrate, (ii) slowly diffusing molecules in the laterally heterogeneous near-surface region of 1 - 2 molecular diameters, and (iii) freely diffusing dye molecules in the upper region of the film. FCS and SMT experiments reveal a strong influence of substrate heterogeneity on SM dynamics. Thereby chemisorption to substrate surface silanols plays an important role. Vertical mean first passage times (mfpt) in those films are below 1 µs. This appears as fast component in FCS autocorrelation curves, which further contain a contribution from lateral diffusion and from adsorption events. Therefore, the FCS curves are approximated by a tri-component function, which contains an exponential term related to the mfpt, the correlation function for translational diffusion and a stretched exponential term for the broad distribution of adsorption events. Lateral diffusion coefficients obtained by FCS on 10 nm thick TEHOS films, thereby, are effective diffusion coefficients from dye transients in the focal area. They strongly depend on the substrate heterogeneity. Variation of the frame times for the acquisition of SMT experiments in steps of 20 ms from 20 ms to 200 ms revealed a strong dependence of the corresponding probability distributions of diffusivities on time, in particular in the range between 20 ms and 100 ms. This points to average dwell times of the dye molecules in at least one type of the heterogeneous regions (e.g. on and above silanol clusters) in the range of few tens of milliseconds.
Furthermore, time series of SM spectra from Nile Red in 25 nm thick poly-n-alkyl-methacrylate (PnAMA) films were studied. In analogy to translational diffusion, spectral diffusion (shifts in energetic positions of SM spectra) can be studied by probability distributions of spectral diffusivities, i.e. time scaled square energetic displacements. Simulations were run and analyzed to study contributions from noise and fitting uncertainty to spectral diffusion. Furthermore the effect of spectral jumps during acquisition of a SM spectrum was investigated. Probability distributions of spectral diffusivites of Nile Red probing vitreous PnAMA films reveal a two-level system. In contrast, such probability distributions obtained from Nile Red within a 25 nm thick poly-n-butylmethacrylate film around glass transition and in the melt state, display larger spectral jumps. Moreover, for longer alkyl side chains a solvent shift to higher energies is observed, which supports the idea of nanophase separation within those polymers.
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