There has been growing interest in designing and development of suitable micro or nano drug delivery system with the ability to target site specifically and release the payload in a predetermined fashion. Recently a new type of system called polyelectrolyte microcapsules and thin films have been proposed and developed for applications such as, biomedical devices to micro sensing and drug delivery. Owing to its advantages of mild preparation conditions, multifunctionality, with programmable characteristics and to encapsulate large amount of materials, it has shown immense potential. In the present research, multilayer polyelectrolyte thin films composed of Poly(methacrylic acid) (PMA) and Poly (vinyl pyrrolidone) (PVP) were deposited on the flat substrates using layer by layer (LBL) technique. The film growth and its deconstruction under physiological conditions were characterized using UV Visible spectrophotometer and Scanning Electron Microscopy (SEM). Hollow microcapsules composed of PMA and PVP were also produced with the help of sacrificial silica template using the same LBL adsorption technique. After coating the desired number of PVP and PMA layers, the colloidal template was removed with a buffer system composed of Hydrofluoric acid (HF) and Ammonium fluoride (NH4F). The obtained capsules were characterized for its surface morphology using SEM and Atomic Force Microscopy (AFM). The hydrogen bonding in capsule formation was confirmed by Fourier Transform Infrared Spectroscopy (FTIR). Encapsulation and release with the microcapsules was carried out using Rifampicin (Antitubercular drug) as a model drug. The interaction of empty and drug loaded capsules with Mycobacterium Smegmatis cell line was investigated. It was found that the empty capsules did not affect the cell growth indicating their biocompatibility. Confocal microscopy studies with Doxorubicin (anticancer drug), which is a naturally fluorescent molecule, showed the drug is indeed encapsulated inside the hollow capsule. From the above studies, it was concluded that polyelectrolyte capsules have the potential to be used for delivering drugs.

In der vorliegenden Arbeit wurde das Phasenverhalten von harten Hantelteilchen (Dumbbells) als Funktion des Aspektverhältnisses (L*, der Quotient aus dem Abstand der Massenzentren zum Durchmesser der Kugel) und der Volumendichte untersucht. Bragg-Reflexe weisen darauf hin, das harte Dumbbells mit L* < 0.4 einen Phasenübergang von einer Fluid-artigen Phase zu einem plastischen Kristall zeigen. Die experimentellen Phasendiagramme bei L* ~ 0.24 und L*~ 0.30 sind vergleichbar mit Vorhersagen aus Monte Carlo-Simulationen. Rheologie Messungen zeigen, dass harte Dumbbells verschiedene Gleichgewichts- und Nichtgleichgewichtsphasen annehmen. Suspensionen von harten Dumbbells im Zweiphasenbereich zeigen ein einziges Fließgrenzen-Ereignis, wohingegen in der plastischen Kristallphase zwei Fließgrenzen-Ereignisse beobachtet werden. Diese, im Folgenden als „double yielding“ bezeichneten Ereignisse, hängen mit der Kristallisation der Suspensionen von harten Dumbbells zusammen. Die entsprechende Strukturentwicklung wurde mit rheo-SANS-Experimenten untersucht und mithilfe von BD Simulationen interpretiert. Es konnte gezeigt werden, dass die plastische Kristallphase polykristallin im Ruhezustand ist. Unter schwacher Scherung wird eine fcc-Schwerzwilling Struktur ausgebildet. Bei hoher Scherung formt sich eine teilweise orientierte Struktur aus gleitenden Schichten. Zwischen diesen beiden Strukturen existiert eine ungeordnete Übergangsphase. Die Scher-induzierte Strukturausbildung eintspricht dem „double yielding“ Ereignis der kristallinen harten Dumbells. Es wurde gezeigt, dass ein größeres L* (L* < 0.4) die Strukturentwicklung unter Scherung qualitativ nicht beeinflusst. Aufgrund verlangsamter Dynamik in der Nähe des Glasübergangs sind lediglich stärkere oder längere Oszillationen von Nöten, um Scher-induzierte Kristallisation zu erzeugen. Im zweiten Teil dieser Arbeit werden Systeme aus hohlen Kugeln und „Janus“-Dumbbells vorgestellt, die als kolloidale Modellsysteme dienen können. / In the present work the phase behaviour of hard dumbbells has been explored as a function of aspect ratio (L*, the center to center distance to the diameter of one composed sphere) and volume fractions using thermosensitive dumbbell-shaped microgels as the hard dumbbell model system. A fluid-to-plastic crystal phase transition indicated by Bragg reflections has been observed for L* < 0.4. The experimental phase diagrams at L* ~ 0.24 and L* ~ 0.30 are comparable to the theoretical prediction of the Monte Carlo simulations. Rheological measurements reveal that the hard dumbbells in the biphasic gap show the yielding behaviour with a single yielding event, while two yielding events have been observed for the plastic crystalline phase. The two yielding events, referred to as the double yielding behaviour, are proved to be related to the crystallization of hard dumbbells. The underlying structural evolution has been investigated by rheo-SANS experiments and the scattering data has been interpreted by BD simulations. It is demonstrated that the plastic crystal structure of the hard dumbbells is polycrystalline at rest, which has been induced into the twinned fcc structure at low strain, the partially oriented sliding layers at high strain and the intermediate state at the strain in-between. The shear-induced structural evolution corresponds to the double yielding events of the fully crystallized hard dumbbells. Additionally, we prove that the increase of L* (L* < 0.4) does not change the structural evolution of the sheared hard dumbbells. Only more extensive or longer oscillations are required to form the shear-induced crystal structures due to the slowdown of the dynamics in the vicinity of the glass transition. In a second part, the work of this thesis is extended to hollow systems composed of hollow spheres and hollow Janus dumbbells that can be used as model systems to probe phase behaviour of hollow capsules.