Nanoparticles reinforced polymer composite films have been widely studied for their enhanced mechanical, electrical and thermal properties compared with host polymer matrix. However, most research was conducted on incorporation of nanoparticles in polymer films to improve single property and there is a lack of research on the multifunctional polymer nanocomposite films. In this work, a scalable and continuous spray deposition process was developed for the production of nanoparticles reinforced multifunctional thermoplastic nanocomposite films. This process is capable of making a thin sheet of thermoplastic nanocomposites with high nanoparticle loadings. The smallest thickness can be 40um. The objective of this study is to design and optimize the thermoplastic nanocomposite films by utilizing nanoclay and helical carbon nanotube for multifunctional application: a) high electrical conductivity and thermal stability. Helical carbon nanotube paper based thermoplastic polyurethane nanocomposite films have been studied. The electrical conductivity and thermal stability of nanocomposite films increase a lot due to the incorporation of helical carbon nanotube paper with high electrical and thermal conductivity. The peculiar helical configuration of carbon nanotubes could greatly improve the interfacial bonding between carbon nanotubes and polymer matrix. b)High wear resistance and thermal stability. A nanoclay reinforced thermoplastic polyurethane nanocomposite coating was applied on the surface of leather. Due to the high hardness and thermal stability of nanoclay, the leather coated with nanocomposite film showed an improvement of wear resistance and thermal stability.

<p>The entrapment of biomolecules within TEOS-based sol-gel derived organic/inorganic nanocomposite materials has proven to be a viable platform for the development of biosensors and solid-phase biocatalysts. In this thesis, a series of organically modified silica materials were prepared by a two-step aqueous processing method that was suitable for biomolecule entrapment, and were formed as submicron thick films by dipcasting. Dispersed additives, such as polymers (Class I materials) and covalently bound additives, such as organically modified silanes (Class II materials), were used to modify the internal environment compared to the undoped matrices and to correlate the properties of entrapped enzymes.</p> <p>The morphology of organically modified silica materials could be modified through the use of either separate or co-hydrolysis of the silane precursors, with the later method generating optically transparent materials. Fluorescence microscopy revealed chemical heterogeneity in materials that appeared to be homogeneous by brightfield or SEM.</p> <p>Fluorescence emission studies of a solvatochromic dye entrapped within the film confirmed that the internal chemical environment of the films was strongly affected by doping with polymers and organosilanes. The films showed a rapid initial change in chemical properties owing to solvent evaporation, followed by a much slower evolution over several months owing to continued condensation reactions within the film.</p> <p>A reagentless biosensor was designed based on co-entrapment of an enzyme and a fluorescently labeled polymer. The enzymes urease and lipase were selected for this study as both catalyze reactions that alter the local pH. By co-entrapping pH sensitive fluorophores (SNARF-I and fluorescein) bound to a high molecular weight polymer, it was possible to detect the analytes urea and glyceryl tributyrate using changes in the fluorescence intensity (fluorescein) or emission ratio (SNARF-l). By tuning the polarity of the matrix it was possible to optimize the sensitivity of the sensing film for both the polar and non-polar analyte.</p> / Doctor of Philosophy (PhD)

The advancement in smart technologies for organic conducting polymers as flexible substrates in LEDs, PVs and solid state lighting necessitates the development of ultra-high barrier films to protect the devices from moisture and oxygen. The current encapsulation methodology of using layers of plastics and inorganic oxides has several deficiencies. Alternatively, the use of single layer of polymer nanocomposites is a promising substitute for these inorganic based encapsulation layers. The use of polymer materials have the advantage of flexibility, active electrodes printability and easy to make the devices for large area applications. The nano-fillers with high aspect ratio as nanocomposites ingredient in polymers reinforces its mechanical strength and also acts as a scavenging material for moisture and increases the residence time and/or for the penetrating moisture in the film. Chapter 1 gives the basic overview in the field of barrier technology films and coatings from polymers and inorganic oxide as either mono/multi layer hermetic encapsulation methods. The understanding of both chemistry and physics behind the moisture permeation and its interaction with the film material was discussed. The inclusion of functional nano-fillers as moisture trapping agents in the film provide better device protection achieved. The methods and instruments to measure such ultra-low permeation within the films are discussed. Finally, the advantage of polymer based nanocomposites for low-permeable films with existing materials are briefly discussed in this chapter. In this thesis, we employed both thermoplastic and thermoset polymer nanocomposites as encapsulation layer for device sealing. The use of ion-containing polymers (ionomers) as a sealant layer was also studied. Chapter 2 presents the detailed experimental procedures with materials and methods used in this thesis along with the synthesis methodologies to make films from the polymer. In chapter 3, we used cyclic olefin copolymer COC (copolymer of ethylene and norbornene) as an encapsulation layer with silica and layered silicate nano-fillers. The compatibility between hydrophilic silica and hydrophobic COC was achieved by maleic anhydride grafted PE with anchoring on COC as a compatibilizer and then silica filler was added to make the nanocomposite films. FTIR spectroscopy confirms the bond formation of silica with COC/MA-g-PE. The mechanical (tensile and DMA) and thermal studies (DSC) suggested that there is an improvement observed when adding silica/silicate layers in the polymer matrix with increased tensile strength, storage modulus and Tg. The calcium degradation test show enhanced performance towards moisture impermeation in the film. Chapter 4 deals with the synthesis of PVB based nanocomposite film with silica/layered silicate as nanofillers in the base matrix with varying degree of acetalization in the film. The FTIR and NMR spectroscopy show the evidence for acetal link formation in the in-situ synthesized PVB with silica/silicate nanofillers with three different acetyl contents. The tensile and DMA studies show the observed improvement in mechanical strength (increased tensile strength, storage modulus) were due to the intercalation of clay galleries during PVB formation and the interaction of silica particles interactive bond formation with –OH groups of PVA in PVB. The higher clay/silica particles show agglomerated nature and reduction in film strength. Thermal studies (DSC) show that there is an improvement observed in Tg when adding silica/silicate layers in the polymer matrix with moderate to low acetal content. The calcium degradation test show enhanced performance towards moisture impermeation in the film. Chapter 5 describes the inclusion of ionic groups (ionomers) in PVB and its effects on moisture permeation and mechanical properties. PVB ionomer was synthesized using formyl benzene 2-sulfonic acid sodium salt and 2-carboxy benzaldehyde (both sulfonic and carboxylic acid sources) as co-aldehyde with butyraldehyde and PVA. These acid groups were neutralized with potassium, magnesium and zinc ions. The level of acid content in the films was maintained between 6 to 28 mol percent. The sulfonic acid films with zinc and magnesium ions of 14 mol% exhibit good mechanical strength and low moisture permeation. Chapter 6 deals with the epoxy terminated silicone polymer nanocomposites as moisture barrier coatings for device encapsulation. Both silica and clay silicate layers were used to reinforce the silicone matrix. The silica nanoparticles were grafted with amino-silane groups, this would help in better mixing of silica particles in the silicone matrix due to the amine groups interaction in curing with epoxy groups. The calcium degradation test was used to determine the WVTR of the nanocomposites and device encapsulation was employed to estimate the degradation after exposure to ambient environment. Chapter 7 presents the concluding remarks of the results presented. The benefits as well as limitations of the polymer nanocomposite film and the future developmental work to be carried out are discussed in this chapter.

The ultra high barrier films for packaging find applications in a wide variety of areas where moisture and oxygen barrier is required for improved shelf-life of food/beverage products and for microbial free pharmaceutical containers. These materials also find applications in micro electro mechanical systems such as ICs, and for packaging in industrial and space electronics. Flexible and portable organic electronics like OLEDs (Organic Light Emitting Diodes), OPVDs (Organic Photo Voltaic Devices) and dye sensitized solar cells (DSSCs) have a good potential in next generation solar powered devices. In fact, organic insulators, semiconductors, and metals may be a large part of the future of electronics. However, these classes of materials are just an emerging class of materials mainly because of their life time constraints. Thus significant research is required to bring them into the forefront of electronic applications. If the degradation problems can be diminished, then these polymers could play a major role in the worldwide electronic industry. A flexible polymer film itself cannot be used as an encapsulation material owing to its high permeability. While a glass or metal substrate possesses ultra high barrier properties, it cannot be used in many electronic applications due to its brittleness and inflexibility. Polymer/ nanocomposites based hybrid materials are thus a promising class of material that can be used for device encapsulation. Chapter I summarizes some of the recent developments in the polymer/nanocomposites based materials for packaging and specifically its use in flexible as well as portable organic electronic device encapsulation. While the development of low permeable encapsulant materials is a chemistry problem, an engineering/instrumentation problem is the development of an accurate technique that can measure the low levels of permeability required for electronic application. Therefore, there is a keen interest in the development of an instrument to measure permeability at these limits. The existing techniques to measure the low permeabilities of barrier films, their importance and accuracy of measurements obtained by these instruments have been briefly discussed in this chapter. Different polymer based hybrid composite materials have been developed for the encapsulation of organic devices and their materials properties have been evaluated. Broadly, two diverse strategies have been used for the fabrication of the composites: in-situ curing and solution casting. Chapters II, III and IV discuss the fabrication of nanocomposite films based on in-situ curing while chapter V discusses fabrication based on solution casting. In chapter II, amine functionalized alumina was used as a cross-linking agent and reinforcing material for the polymer matrix in order to fabricate the composites to be used for encapsulation of devices. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were used to elucidate the surface chemistry. Thermogravimetric and CHN analysis were used to quantify the grafting density of amine groups over the surface of the nanoparticles. Mechanical characterizations of the composites with various loadings were carried out with dynamic mechanical analyzer (DMA). It was observed that the composites have good thermal stability and mechanical flexibility, which are important for an encapsulant. The morphology of the composites was evaluated using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The work presented in chapter III is a technique based on grafting between surface decorated γ-alumina nanoparticles and the polymer to make these nanocomposites. Alumina was functionalized with allyltrimethoxysilane and used to conjugate polymer molecules (hydride terminated polydimethylsiloxane) through platinum catalyzed hydrosilylation reaction. As in the previous chapter, the surface chemistry of the nanoparticles after surface modification was characterized by different techniques (FTIR, XPS and Raman). The grafting density of alkene groups over the surface of the modified nanoparticles was calculated using CHN analyzer. Thermal stability of the composites was also evaluated using thermogravimetric analysis. Nanoindentation technique was used to analyze the mechanical characteristics of the composites. The densities of the composites were evaluated using density gradient column and the morphology of composites was evaluated using SEM. All these studies reveal that the composites have good thermal stability and mechanical flexibility and thus can be potentially used for encapsulation of organic photovoltaic devices. In addition, rheological studies of the composites were carried out to investigate the curing reaction. The platinum-catalyzed hydrosilylation reaction was studied using both DSC and rheological measurements. The competitive reactions occurring in the system was also monitored in real time through DSC and rheology. Based on the curing curves obtained from these two studies, the mechanistic detail of the curing process was proposed. In addition, swelling studies and contact angle measurements of the composites were also carried out to determine the capability of these materials as encapsulants. Chapter IV deals with a thermally stable and flexible composite that has been synthesized by following a hydrosilylation coupling between silicone polymer containing internal hydrides and mesoporous silica. The results of the characterization of the composites indicates that the composites are thermally stable, hydrophobic, flexible and can be potentially used for encapsulating flexible electronic devices. Chapter V discusses the solution casting method for the development of composites. This chapter is divided into two parts: Part I discusses the synthesis and characterization of flexible and thermally stable composites using polyvinyl alcohol as the base polymer matrix and reactive zinc oxide nanoparticles as the dispersed phase. Various studies like thermal analysis, mechanical analysis, surface analysis and permeability studies were used to characterize the composite films for their possible use as a passivation material. The material was used to encapsulate Schottky structured devices and the performance of these encapsulated devices under accelerated weathering was studied. Part II of this chapter discusses the fabrication of hybrid organic/inorganic based polymer-composite films, based on polyvinylbutyral (PVB) and organically modified mesoporous silica. PVB and amine functionalized mesoporous silica were used to synthesize the composite. An additional polyol (‘tripentaerythritol’) component was also used to enhance the –OH group content in the composite matrix. The thermal, barrier and mechanical properties of these composites were investigated. The investigation of these films suggests that these can be used as a moisture barrier layer for encapsulation. Chapter VI gives the concluding remarks of the results presented. The advantages as well as disadvantages of the in-situ cured and solution casted films and the scope for future work is discussed in this chapter.

In this work nanocomposites based on chitosan or carboxymethylcellulose, and different kinds of clays were prepared using polyethyleneglycol (PEG) as plasticizer. The samples obtained were characterized by Fourier Transformed Infrared Spectroscopy (FTIR), X-Ray Diffraction, Thermal Analysis (TGA/DTG/DSC) and by mechanical characterization with the aim of investigate the interactions between chitosan and clay. From the analysis of the XRD spectrum, it was observed that the so produced nanocomposites presented na intercalated structure. The results obtained from TGA / DTG / DSC techniques showed that a reduction in the thermal stability and glass transition of the produced material occurred. The nanocomposites obtained from biopolymer/sodium bentonite (QuiBen) with PEG 5 % showed better mechanical properties in comparison to the pristine biopolymers due to the enhancement of their ntercalation into the silicate galleries. / Neste trabalho foram preparados nanocompósitos baseados em quitosana ou carborximetilcelulose e diferentes tipos de argilas usando polietileno glicol (PEG) como plastificante. As amostras obtidas foram caracterizadas através de espectroscopia de infravermelho (FTIR), difração de raios X (DRX), análises térmicas (TGA/DTG/DSC), e através de técnicas de análise de tensão e deformação com o objetivo de avaliar as interações entre os biopolímeros, o plastificante e as argilas. Através da analise dos espectros de DRX, foi observado que os nanocompósitos produzidos apresentaram estrutura intercalada. Os resultados obtidos através das técnicas de TGA/DTG/DSC mostraram que houve uma diminuição na estabilidade térmica e na temperatura de transição vítrea do material produzido. Os nanocompósitos obtidos a partir dos biopolímeros/Bentonita sódica com 5 % de PEG apresentaram melhores propriedades mecânicas do que os biopolímeros puros, devido a intercalação dos mesmos nas lamelas da argila.

Binary mixtures of polymers and soft nanocolloids, also called as polymer nanocomposites are well known and studied for their enormous potentials on various technological fronts. In this thesis blends of polystyrene grafted gold nanoparticles (PGNPs) and polystyrene (PS) are studied experimentally, both in bulk and in thin films. This thesis comprises three parts; 1) evolution of microscopic dynamics in the bulk(chapter-3),2) dispersion behavior of PGNPs in thin and ultra thin polymer matrices (chapter-4) 3) effect of dispersion on the glass transition behavior (chapter-5). In first part, the state of art technique, x-ray photon correlation spectroscopy is used to study the temperature and wave vector dependent microscopic dy¬namics of PGNPs and PGNP-PS mixtures. Structural similarities between PGNPs and star polymers (SPs) are shown using small angle x-ray scatter¬ing and scaling relations. We find unexpected (when compared with SPs) non-monotonic dependence of the structural relaxation time of the nanoparticles with functionality (number of arms attached to the surface). Role of core-core attractions in PGNPs is shown and discussed to be the cause of anomalous behavior in dynamics. In PGNP-PS mixtures, we find evidence of melting of the dynamically arrested state of the PGNPs with addition of PS followed by a reentrant slowing down of the dynamics with further increase in polymer frac¬tion, depending on the size ratio(δ)of PS and PGNPs. For higher δ the reen¬trant behavior is not observed with polymer densities explored here. Possible explanation of the observed dynamics in terms of the presence of double-glass phase is provided. The correlation between structure and reentrant vitrifica¬tion in both pristine PGNPs and blends are derived rather qualitatively. In the second part, the focus is shifted to miscibility between PGNPs and polymers under confinement i.e., in thin films. This chapter provide a compre¬hensive study on the different parameters affecting dispersion viz., annealing conditions, fraction of the added particles, polymer-particle interface and more importantly the thickness of the films. Changes in the dispersion behavior with annealing is shown and the need for annealing the films at temperatures higher than the glass transition temperature of the matrix polymers is clearly elucidated. Irrespective of the thickness of the films( 20 and 65 nm) studied, immiscible particle-polymer blends unequivocally prove the presence of gradi¬ent in dynamics along the depth of the films. To our knowledge for the first time, we report results on confinement induced enhancement in the dispersion of the nanoparticles in thin polymer films. The enhanced dispersion is argued to be facilitated by the increased free volume in the polymer due to confinement as shown by others. Based on these results we have proposed a phase diagram for dispersibility of the nanoparticles in polymer films. The phase diagram for ultra thin films highlights an important point: In ultra thin films the particles are dispersed even with grafting molecular weight less than matrix molecular weight. In the third part, we have studied the glass transition of the thin films whose structure has been studied earlier in the earlier part. Non-monotonic variation in glass transition with the fraction of particles in thin films has increased our belief on the gradient in the dynamics of thin polymer films. En¬hanced dispersion with confinement is captured with the enhanced deviation in glass transition temperature of ultra thin films. Effect of miscibility param¬eter on Tgis studied and the results are explained with the subtle interplay of polymer-particle interface and confinement.