Formation of Organic-Inorganic Hybrid Materials by Sequential Vapor Infiltration

With the advance of technology, new challenges and new problems, raise the need for the new materials. Organic-inorganic hybrid materials aim to solve some of these problems by incorporation of the organic and inorganic components at very fine scales. Using sol-gel chemistry and metal organic frameworks, many functional hybrid materials have been introduced in the literature for long time. New techniques such as molecular layer deposition (MLD) and layer-by-layer (LbL) film formation have also been presented recently to meet new technological demands such as precise thickness control and conformality. Sequential vapor infiltration (SVI) is also one of the recent techniques that forms hybrid materials by heterogeneous reactions, taking place between a solid phase polymer and gas phase organometallic precursor.;SVI is conducted in an atomic layer deposition (ALD) reactor, using common ALD precursors, has advantage of being a solvent free technique. However being a batch process, limits the technique in terms of high throughput production and detailed understanding of the mechanism is necessary in order to overcome this problem. To this day, studies on SVI mechanism are very limited and one of the aims of this work is to improve the understanding mechanism of SVI. In this work, process parameters of SVI, such as temperature, pressure, exposure conditions and different substrates has been studied. It has been found that temperature has a profound effect on the mechanism of SVI and this effect is attributed to the mechanism being a combination of diffusion and chemical reaction. At high temperatures in general low mass gain observed is an effect of quick barrier layer formation at the surface of the polymer, which prevents further diffusion of the prescursors. Pressure effect at low temperatures was also less pronounced comparing to high temperatures. Furthermore in this work SVI process was conducted at atmospheric pressure for the first time, showed promising results for roll-to-roll application of the process. It is also shown that, at atmospheric pressure reduced diffusivity of the precursor in the reactor chamber can enable effective patterning of SVI on the substrate. Effect of exposure conditions on SVI showed significant dependence on the substrate chemistry. SVI on polyethylene terephthalate (PET) substrates showed amount of the precursor in the reactor chamber, holding time, and number of cycles are all interrelated to each other. However, the reaction extent in polyamide 6 (PA6) substrates showed primary dependence on the amount of the precursor in the reactor.;During the mechanistic SVI analysis on PET it is discovered that the optical properties of fibers changed by incorporation of alumina. PET shows weak photoluminescence due to UV light absorption by aromatic units on the backbone of the polymer. It is shown that SVI hybrid materials can intensify the photoluminescence intensity of the PET up to 13 times. This phenomenon further analyzed by internal quantum efficiency analysis which showed the efficiencies is increasing up to ~24% indicating not only the luminescence increases in the material but also the mobility of the charge carriers are also increased. Higher charge carrier mobility of a semiconductor material can also increase the photocatalytic activity of it. As a demonstration of the photocatalytic activity of hybrid materials, silver and gold particles were deposited onto SVI treated fabrics out of aqueous metal salt solutions. It is also presented that by controlling the light exposure of the substrate selective photoreduction of these particles is also possible, which is promising for flexible electronic applications.;A detailed analysis of photoluminescence structure analysis showed that SVI mainly takes place in amorphous regions of the polymer and the increased emission is due to amorphous hybrid material. Thermal analysis of SVI treated PET fabrics revealed that temperature stability of the substrates are increased with hybrid materials formation.