No description available.

No description available.

The research involved determining the processes that occur during dye diffusion thermal transfer printing. Dye diffusion printing is a novel method of printing photo quality graphics from a personal computer. The process involves two polymer films coming into contact, one containing a dye, and the diffusion of the dye from this donor sheet onto the receiving sheet using heating elements to drive the diffusion process. In this high temperature, high pressure, and short time scale regime undesirable adhesion between the two polymer sheets is observed. It is this adhesion and its mechanisms that were investigated. Several types of homopolymers were used in.an attempt to obtain information on the processes involved in the adhesion of the two films during the printing stage. Initially dyes were absent from the polymer films to examine the polymer adhesion alone. It was hoped that the principal factors involved in the unusual joint forming conditions could be explained. The unusual conditions are high heat (250°C) and short time span (10-15 milliseconds). Polystyrene, poly (methyl methacrylate) and poly (vinyl acetate) were chosen to determine the effect of Glass Transition Temperature (T g), surface energies and molecular weight on the polymer adhesion. Initial results showed that the adhesion was a complex system. but it became clear that the t g of the polymers and the presence of small molecules and contaminants· were very important. Work with commercial polymers was undertaken to transfer the knowledge gained from the homopolymers to the more complicated commercial systems using poly (vinyl. chloride) and poly (vinyl butyral). To expand the understanding of the results small molecules and dyes were added to these commercial polymers to examine their effects. The surface of the samples were analysed using X-ray Photoelectron Spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy (FTIR). This was used to determine if there was any migration of the small molecules to the surface of the polymer films. It was also useful in indicating the location of the dyes and how much penetration into the polymers is achieved by them. Atomic Force Microscopy (AFM) was implemented to analyse the surface morphology and gave an insight into the mechanism of the small molecule migration. The conclusions drawn were that the presence of small molecules had significant affect on the adhesion of the polymers. Compatible small molecules would act as plasticisers and lower the T g of the polymers giving rise to higher adhesion. Small molecules that were incompatible were found to migrate to the surface in large quantities and would act as weak boundary layers, significantly reducing the adhesion. Work in this area has shown that an autolayering mechanism is occurring that may be useful in producing a release mechanism for the commercial products.

No description available.

Amphiphilic polymers are a subset of macromolecules that exhibit both hydrophobic and hydrophilic moieties within their covalently bonded structures. Because of the differing solubilities of the contrasting regions of the amphiphilic polymers, they exhibit an inherent ability to self-assemble in the solution phase where one block exhibits poor compatibility with the solvent. And by tuning the composition, size and shape of the polymers, a variety of morphologies of the assembly in solution were observed, like spherical micelle, vesicle, rod-like and lamellar. The propensity to self-assemble to complex structures makes them promising candidates in wide varieties of applications, for example, drug delivery, gene transfection, catalyst, and sensing. Nowadays, most of the researches of amphiphilic polymers have been focused on simple linear di-block copolymers. Amphiphilic non-linear architectures, like dendrimers, star polymers, hyperbranched polymers, brush polymers and cyclic polymers, have been proved to exhibit unique properties compare to their linear analogs, such as lower critical micelle concentrations and better-assembled strengths because the structures are covalently tethered together. These unique properties make them a particularly attractive vehicle in drug/gene delivery. However, investigations of the amphiphilic homopolymers are limited and the majority of work have been done is focused on charged polymers, anionic or cationic. The amphiphilic ionic homopolymers largely relied on the pH of the solution to assemble into complex morphologies, perturbation of pH could result in deformation of assemblies and pro-release of encapsulate. Also, extremely severe pH environment prohibit the usages of the amphiphilic polymers in biological systems. Well defined non-ionic amphiphilic linear homopolymers bearing hydrophobic decyl groups and hydrophilic tri(ethylene glycol) monomethyl ether groups was synthesized by atom transfer radical polymerization technique and the structures were confirmed by NMR and GPC. The low polyedispersity polymers, were found to readily self-assembled to form micelles in non-polar organic phase and reverse micelles in polar aqueous phase. The assemblies were studied with UV-vis spectroscopy, fluorescence spectroscopy, dynamic light scattering, and transmission electron microscopy to determine the critical micelle concentrations and assembly size in both conditions. The synthesis towards more complex architectures of the homopolymers was also investigated. / acase@tulane.edu

<p> This thesis presents a study on silane based polymerization in two parts. </p> <p> In Part A, diphenylvinylsilane (1) underwent oligomerization with initiation by azo(bisisobutyronitrile) (AIBN) or benzoyl peroxide (BPO). The vinyl groups were preferentially consumed under either set of conditions. Several products were isolated; these included oligomers 3, an AIBN adduct 4, a dimer 5, and a trimer 6. The residual SiH moieties could be subsequently coupled hydrosilylatively with alkynes or vinylsilicones. The efficiency of the radical reactions was very low. 15% starting material was recovered even with 200 mol% of initiating radicals added to the reaction mixture. The relative radical reactivities of the two functional groups is discussed.</p> <p> In Part B, 1 was radically copolymerized with styrene and methyl methacrylate (MMA). From the results of infrared and 1H NMR it was determined that 1 participated in copolymerization via a vinyl type polymerization and not in the form of a hydrogen-transfer type polymerization. Residual SiH groups along the backbone of the polymer remained reactive. A vinylsilicone and 9-vinylanthracene were grafted onto the copolymer from MMA and 1 by hydrosilylation and radical methods, respectively.</p> / Thesis / Master of Science (MSc)

ABSTRACT Light emitting diodes of non-fully conjugated coil-like homopolymers and fully conjugated rigid-rod homopolymers with electron withdrawing or donating group were studied. A series of Poly[2,2-(m-2-X-phenylene)-4-4¡A-hexafluoroisopropane- bibenzoxazoles] (6F-PBO-X, with X = amine, hydrogen and nitro) and poly-p-(2-X- phenylene)-benzobisoxazole (PBO-X, with X = amine, hydrogen and nitro) were synthesized for light emitting diode applications to observe electroluminescence emission affected by electron withdrawing or donating group. All polymers were fabricated identically to form bi-layer light emitting diodes. In the devices, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonite)(PEDOT:PSS) was applied to be a hole transport layer; indium tin oxide (ITO) was the anode; and aluminum was the cathode. Devices of the non-fully conjugated coli-like polymers (6F-PBO-X) and the fully conjugated rigid-rod polymers (PBO-X) all showed threshold voltage about 4 V. In the electroluminescence (EL) spectrum, the maximum intensity of non-fully conjugated polymer (6F-PBO-X) with amine (-NH2), hydrogen (-H) or nitro (-NO2) functional group was at 499 nm, 505 nm and 515 nm, respectively, showing a 20 nm wavelength shift. From ¡VNH2, -H and ¡VNO2 groups, their Commission International de l`Eclairage (C. I. E.) coordinates were (0.30, 0.46), (0.34, 0.45) and (0.40, 0.46), respectively. The EL maximum intensity for fully conjugated rigid-rod polymer PBO-X was at 521 nm (-NH2) and 474 nm (-NO2) showing a 50 nm wavelength shift. Their C. I. E. coordinates were (0.42, 0.45) and (0.25, 0.38), respectively. This is attributed to the fully conjugated, collinear, coplanar, rigid-rod polymers (PBO-X) backbone readily affected by the push-pull functional groups showing a large red shift.

En microélectronique, les techniques actuelles de fabrication des supercondensateurs requièrent le développement de motifs nanostructurés de surface spécifique élevée. Nous nous intéressons à une alternative émergeante aux techniques classiques ‘top-down’ de fabrication des masques de gravure : les mélanges d’homopolymères. En effet, deux polymères avec des chimies différentes sous forme de films minces peuvent conduire à une séparation de phase avec des domaines cylindriques de taille sub-micrométrique. Une gravure cryogénique au travers de ces masques produit une nanostructuration avec une importante surface spécifique. Les travaux de cette thèse ont porté sur la réalisation des films minces et sur la compréhension des mécanismes d’obtention de la morphologie finale. Une étude a été menée sur les solvants de dépôt et d’exposition pour déterminer leur influence sur les morphologies. Les paramètres influençant la taille des motifs sont ensuite étudiés. Des domaines de moins de 100 nm ont été obtenus. Finalement, l’étude d’une méthode alternative de dépôt par dip-coating a permis l’obtention d’une grande variété de morphologies en une seule étape et pour une même solution. Ces travaux se sont ensuite orientés sur la réalisation des motifs en gravant par plasma le silicium au travers de ces masques. Deux procédés ont été retenus, adaptés et optimisés afin de réaliser des gravures profondes sans défaut. Le procédé STiGer aniso permet de les obtenir et ce, avec la meilleure répétabilité. Un autre axe, portant sur l’optimisation de la sélectivité en modifiant la nature du masque, a été développé. Une sélectivité de 70 : 1 est obtenue pour un masque de poly(styrène) marqué au Ru. / In microelectronics, current techniques for supercapacitors manufacturing requires the development of nanostructured patterns with high specific surface. We are interested in an emerging alternative approach to conventional 'top-down' fabrication techniques based on blends of homopolymers. Indeed, two polymers with different chemistries in thin films can lead to phase separation with cylindrical domains of sub-micrometer size. A cryogenic plasma through these masks can produce nanostructuration with a high specific surface. The work of this thesis focused on the realization of thin films and on the understanding of the mechanisms to obtain the final morphology. A study on solvent deposition and exposure was led to determine their influence on the morphologies. The parameters influencing the size of the domains are then studied. Domains of less than 100 nm were obtained. Finally, the study of an alternative method of deposition by dip-coating enabled to obtain a variety of morphologies in one step and for the same solution. This work was then directed towards the realization of structured surfaces by plasma etching of the silicon through this masks. Two methods were used, adapted and optimized to achieve deep etched without default. The process StiGer aniso allows to obtain this and with better repeatability. Another axis is developed. It is focused on the optimization of the selectivity by modifying the nature of the mask. We succeed in obtaining a selectivity of 70: 1 with a mask of poly(styrene) stained by Ru.

We perform Monte-Carlo simulations of a binary, strongly separated mixture of A- and B-type homopolymers with some amount of random AB copolymers added. The interface is analyzed and the interface tension is calculated using the model of capillary waves. We can clearly demonstrate that random copolymers are localized at real, fluctuating interfaces between incompatible polymer species and micellization is not favored over adsorption. Our study proves that random copolymers are potential candidates for compatibilization of polymer-polymer mixtures. By simulating random copolymers in a one-component bulk and comparing their free energy to the copolymers adsorbed at the two-phase interface we show that the adsorption is thermodynamically stable. We use scaling arguments developed for ideal and non-fluctuating interfaces to rationalize the simulation results and we calculate the reduction of interface tension with increasing amount of the adsorbed copolymers.

Organic semiconducting polymers are widely employed in organic electronics such as organic photovoltaics (OPVs), organic field-effect transistors (OFETs) and organic light emitting diodes (OLEDs). Their remarkable mechanical and charge transport properties as well as solution processability allow low-cost fabrication of light-weight and flexible devices. Among them indacenodithiophene (IDT)-based materials are promising candidates for application in organic electronics. Due to their low energetic disorder, extended conjugation and high electron density the IDT-based polymers show high field-effect mobilities and high absorption coefficients. However, their synthesis suffers from long reaction sequences and is often accomplished using toxic materials. Commercialization requires development of more efficient and sustainable reaction pathways to ease tailoring of structures and to limit molecular defects. Herein, the development of new synthetic pathways towards IDT-based polymers is presented in which all C-C coupling steps are achieved by C-H activation – an atom-economic alternative to conventional transition-metal catalyzed cross couplings. Two different strategies were established to synthesize a series of well-defined IDT-based homo- and copolymers with different side chain patterns and varied molecular weights. The first way starts by synthesis of a precursor polymer and subsequent cyclization affording IDT homopolymers. In the second approach, cyclized IDT monomers were prepared first and then polymerized using direct arylation polycondensation (DAP) yielding IDT homo- and copolymers. The synthetic pathways were optimized in terms of maximizing molecular weights and limiting defect structures. While the first pathway enables synthesis of well-defined homopolymers, the latter is the method of choice for preparation of IDT-based copolymers in high yields and adjustable molecular weights. The polymers were further characterized in detail by optical, thermal, electrical and morphological analyses. OFETs as well as all-polymer solar cells (all-PSCs) were fabricated to investigate the influence of structural modifications and molecular weight on their optoelectronic performance. Thus, this thesis provides a comprehensive study of the structure-property correlations of IDT-based polymers and simplified synthetic protocols for the design and preparation of donor-acceptor copolymers in the future.