Department of Mechanical, Industrial and Aeronautical Engineering MSc (Mechanical Engineering) / Aramid fibre reinforced epoxy composites were hybridised by the addition of electrospun PAN (polyacrylonitrile) and ECNF (electrospun carbon nanofibre) doped PAN nanomats. One of the major concerns in polymer composites is the effect of the interlaminar properties on the overall mechanical properties of the composite. Electrospun carbon nanofibres were used as doping agents within PAN nanofibres, and coated in between aramid epoxy laminates to improve the interlaminar properties. PAN nanomats and ECNF doped PAN nanomats were created by the use electrospinning on the surface of aramid fibre sheets. Multiscale hybrid aramid reinforced composites were then fabricated. Mechanical characterization was carried out to determine the effect of PAN and CNF doped PAN nanofibre mats on aramid fibre reinforced epoxy. It was found that PAN reinforced nanomats had improved the mechanical properties and more specifically, when doped by ECNFs, the volume fraction of ECNFs played a vital role. An addition of 1% vol. CNF doped 0.1% vol. PAN reinforcement within a 30% vol. aramid fibre composite (control composite), improved the tensile strength and elastic modulus by 17.3% and 730% respectively. The 0.5% vol. PAN reinforced AFC (aramid fibre composite) specimens revealed a major increase in the flexural strength by 9.67% and 12.1%, when doped by both 0.5% vol. ECNFs and 1% vol. ECNFs respectively. The 0.5% vol. CNF doped reinforcement increased the impact energy by over 40%, for both the 0.1% vol. and 0.2 % vol. PAN reinforced aramid hybrid specimens. The 0.5% vol. CNF doped 0.5% vol. PAN had increased by 30% when compared to a non-doped sample. Morphological studies indicated interlaminar shearing between plies was affected by CNF agglomerations. This was discovered when determining the impact properties of the multiscale doped hybrid composites. Electrospun nanofibres however, assisted in improving the interlaminar regions within aramid epoxy by mechanical locking within the epoxy, and creating an adhesive bond using Van der Waals forces and electrostatic charges between nanofibre and macro fibre. Hybridising aramid epoxy with the use of nanofibres assisted in improving various mechanical properties. Impact degradation was one disadvantage of hybridising using CNF doped PAN nanofibre reinforcements. / MT2017

Ph.D., Faculty of Science, University of the Witwatersrand, 2011 / ABSTRACT Page | iiAbstract i The deposition of carbon during catalytic reactions has a long history, with major efforts initially focused towards their prevention rather than synthesis. However the discovery of fullerenes and later that of carbon nanotubes by Iijima, shifted scientific focus towards the synthesis, characterization and application of carbon deposits. This renewed interest in carbon based materials, has revealed a universe of extraordinarily shaped carbon materials (SCMs) in the nano and micro range, from tubes and helices to horns and most recently graphene. It has been noted that there exists a relationship between the morphology of the carbon material and its inherent properties, making them highly prized for numerous technological applications. However before these carbon materials can be effectively exploited control over their selective synthesis is necessary, a problem that has been solved with only limited success. As such, there still exists a need to develop synthetic strategies that would yield shaped carbon materials selectively. More importantly, it is essential that a better understanding of the growth factors that lead to differently SCMs is obtained. In this study we have highlighted the parametric conditions for optimum growth of carbon helices, as well as that of carbon fibers with unique structure. We have found that catalyst morphology and the carbon source are key aspects, which control carbon material growth and morphology. The synthesis of carbon materials using bi and tri-metallic supported catalyst systems revealed that Cu was an effective promoter for obtaining helices, particularly at low temperatures (≤ 550 ˚C). On further investigation, Cu was shown to exhibit incredible carbon deposition capabilities at temperatures as low as 200 ˚C. Adjustments of the catalyst preparation conditions (support, metal counter ion, solvent and reduction temperature) and synthesis temperature, revealed that the yield and morphology of the carbon deposit could be altered to selectively produce both straight and helical carbon fibers. A TEM tomography study revealed that the copper particles that gave distorted decahedra formed helical fibers, while trigonal bi-pyramidal particles gave linear fibers. Various plate-like particles revealed that as the number of sides of a catalyst particle varied (3, 4, 5 or 6) there was a corresponding change in the Abstract Page | iv carbon fiber helicity. A relationship between catalyst particle morphology and fiber morphology was thus established. TEM analysis also revealed that catalyst particles underwent rapid reconstruction during carbon fiber synthesis, and that the carbon source (gas environment) was influential in this reconstruction event. A NiOx (unsupported) catalyst was prepared and reactions with various substituted alkyne hydrocarbons were undertaken. Analysis revealed that different alkynes produced carbon fibers with varying morphologies. Using different alkynes in a sequential manner led to the formation of ‘co-block’ carbon fibers with an A-B-A-B... or A-B-C... morphology. Using different alkynes followed by acetylene led to the selective synthesis of straight, Y-junction or irregular carbon fibers. Accompanying these results was the observation that in each case the catalyst particle morphology was unique. Reaction of NiOx with trichloroethylene, in which trichloroethylene acted as a source of carbon for fiber growth, also restructured the Ni catalyst into a tetrahedral shape that gave tripod-like carbon growth. It was found that, substituted alkynes (and alkenes) provided a means for controlling catalyst particle morphology and hence carbon fiber morphology. The study has highlighted the relationship that exists between catalyst and SCM morphology, as well as the effect of hydrocarbons, not only as a source of carbon for SCM growth but also as a means of controlling catalyst morphology and SCM structures.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the Degree of Doctor of Philosophy. Johannesburg, 2015 / Bimetallic platinum nanoparticles were synthesized for application as anode catalysts for low temperature fuel cells such as direct methanol fuel cells (DMFCs). Two distinct synthesis procedures were used; namely conventional synthesis with post-synthesis heat treatment, and secondly polyol microwave-irradiation without further heat-treatment. The aim was to synthesize interesting and novel bimetallic nanostructures and relate their shape and morphologies to their methanol oxidation reaction (MOR) activities and their CO tolerance. Due to the high cost of the conventional synthesis processes as well as their use of harmful solvents, microwave-irradiation was explored as a possible synthesis procedure. It is a greener and more environmentally friendly approach with possibilities of mass production of the nanoparticles. For both the synthesis procedures, the reducing agent, the precursor salts, surfactants, pH of the solution and molar ratios were varied to determine the effect on the shape, size and ultimately the electrocatalytic activities of the Pt-Co and Pt-Ni nanoparticles. For the conventional synthesis procedure, the main parameter of comparison was the strength of the reducing agents, where NaBH4 and N2H4 were used under the same reaction conditions. In this study, the strength of the reducing agent affected the properties of the Pt-Co and Pt-Ni nanoparticles, such that, the stronger the reducing agent, the higher the degree of alloying and the more electrocatalytically active the materials. The drawback in the conventional synthesis was however low current outputs, in the microamps range, which necessitates a need to explore other synthesis procedures. Microwave-irradiation was thus used as an alternative synthesis procedure in an attempt to produce more active bimetallic platinum nanoparticles. Different reaction parameters were changed in this process to optimize the synthesis process, namely the pH of the solution, the amount of surfactant and the Pt-Ni molar ratio. In changing the reaction parameters, there was an observed change in the structure of the nanoparticles, with an average size in the order of 5 nm and different MOR activities. Furthermore, it was found that the activity was highest for the optimum amount of PVP and NaOH concentration of 500 mg and 1.0 M NaOH. In general, the MW synthesized nanoparticles achieved current values in the microamps to amps range, making it a more attractive synthesis procedure compared to the conventional method. The CO tolerance of the materials is an important aspect, as one of the main drawbacks of the commercial application of fuel cells is the propensity of Pt to get poisoned by CO during the methanol dissociation process. Therefore CO stripping measurements were performed on the MW-irradiated catalysts. The catalysts produced in this work showed good resistance towards CO. In general, the behaviours of the catalysts were dependent on the amount of surfactant and the molar ratio of the starting solution. The mechanism of CO tolerance in this case was determined as the bifunctional model, where the Ni-oxide and Ni-hydroxide species donate O to the electrooxidation of CO to CO2. In conclusion, the study of microwave-irradiated bimetallic nanoparticles performed here, resulted in highly active catalysts, which are even more active than commercial Pt/C nanoparticles.

A dissertation submitted to the Faculty of Science of the University of Witwatersrand, Johannesburg, in full fulfilment of the requirements for the degree of Master of Science. May 2017 / Nanomaterials (NMs) have been shown to exhibit unique physical and chemical properties that are highly size and shape-dependent. The ability to control synthesis of nanoparticles (NPs) with particular shapes and sizes can lead to exciting new applications or enhancements of current systems in the fields of optics, electronics, catalytics, biomedicine and biotechnology. Due to increased chemical pollution as well as health concerns, biological synthesis of NMs has quickly emerged as potentially being an eco-friendly, scalable, and clean alternative to chemical and physical synthesis. In this study, the inference that the heavy metal-resistant bacteria, Paenibacillus castaneae, has the propensity to synthesize metal NPs was validated. NP formation was achieved after the exposure of bacterial cell biomass or cell-free extracts (CFE) to excess metal ion precursors in solution. These include lead nitrate and calcium sulphate dehydrate, gold (III) chloride trihydrate and silver nitrate, respectively. All reactions were incubated at 37 °C for 72 h at 200 rpm and observed for a colour change. UV–visible (UV-Vis) spectral scans (200 nm – 900 nm) were measured on a Jasco V-630 UV-Vis spectrophotometer. For scanning electron microscopy (SEM), samples were fixed, dehydrated and loaded onto carbon-coated aluminium stubs. The stubs were then sputter-coated with either Au/Pd or Cr and analysed on the FEI Nova Nanolab 600 FEG-SEM/FIB. Size distribution analysis was done using transmission electron microscopy (TEM) using the FEI Tecnai T12 TEM and Image J software. Powder X-ray diffraction measurements were carried out on a Rigaku Miniflex-II X-ray diffractrometer. Colour changes indicative of the synthesis of PbS, Au and Ag NPs were observed as a white precipitate (PbS), purple (Au) and yellow-brown (Ag) colour, respectively. This was confirmed by absorbance peaks at 325 nm and 550 nm (PbS), 595 nm (Au) and 440 nm (Ag) from UV-Vis analyses. Exposure of P. castaneae biomass and CFE to PbS ions in solution resulted in the production of nanospheres, irregularly-shaped NPs, nanorods, nanowires as well as large nanoflowers. Exposure of P. castaneae biomass to Au3+ ions in solution produced Au nanospheres, nanotriangles, nanohexagons, nanopentagons and nanopolyhedrons. Ag/AgCl NP production occurred using both the P. castaneae biomass and CFE, and resulted in the synthesis of nanospheres only. This is the first report of the biosynthesis of such a diverse set of anisotropic NPs by P. castaneae. It is also the first instance in which anisotropic PbS nanorods and nanowires, 3-D Au nanoprisms as well as “rough” Ag/AgCl nanospheres were bacterially produced. This study serves as an eco-friendly approach for the synthesis of NPs that is a simple yet amenable method for the large-scale commercial production of nanoparticles with technical relevance. This in turn expands the limited knowledge surrounding the biological synthesis of heavy metal NMs. / MT 2017

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfillment for the degree of Master of Science in Chemistry, 2017 / The aim of this study was to synthesize helical carbon nanofibers with controlled diameter by using copper nanoparticles contained inside hollow carbon sphere. In this work, different methods have been explored to synthesize copper nanoparticles contained inside mesoporous hollow carbon spheres in order to minimize the sintering effect of the copper nanoparticles. Mesoporous hollow carbon spheres were used not only as a support for the copper nanoparticles but to stabilize and disperse these nanoparticles to prevent the formation of aggregates. Mesoporous hollow carbon spheres were synthesized using a hard templating method, in which mesoporous silica spheres or polystyrene spheres were used as a sacrificial template. Carbon nanofibers with different morphologies, including straight and helical fibers were obtained by a chemical vapor deposition method where acetylene was decomposed over copper nanoparticles contained inside mesoporous hollow carbon spheres catalyst at 350 °C. The synthesized carbon nanofibers were grown on the surface of the mesoporous hollow carbon spheres as the methods used to synthesize the catalyst failed to incorporate copper nanoparticles inside the spheres. Differences in the diameter of the straight and helical carbon nanofibers were observed from both catalysts. This supports the important effect of particle size on influencing the shape of the synthesized carbon nanofibers. / XL2018

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. / A comprehensive experimental study on alternating current (AC) electrical transport in the three forms of carbon nanotubes (CNTs) and nanodiamond films is presented. It is termed dynamic electrical transport to differentiate it from direct current measurements, which may be referred as static transport. The results and analysis are based on the scattering parameter measurements of a few horizontally aligned single, double, multi-walled carbon nanotubes and nanodiamond films. Which were measured in the frequency range 10 MHz to 65 GHz, at room and cryogenic temperatures using a vector network analyser. The work is motivated by the fact that AC transport in 1D systems has not been fully studied and is not well understood. From direct current measurements, it is known that one dimensional (1D) electrical transport is very different from its two or three dimensional counterpart. This is because adding an electron to a 1D system tends to affect the whole system in ways which to date cannot be fully explained theoretically. CNTs present an ideal platform to study the AC or dynamic transport behaviour of 1D systems because of the high mobility and electrical conductivity at nano-scale. Therefore from the AC complex impedance and conductance, this work demonstrates quantum effects of collectively excited strongly interacting electrons (Luttinger Liquid), which had been predicted theoretically but not observed experimentally using this technique. Ballistic transport at room temperature is also demonstrated by setting the stimulus frequency higher than the scattering rate in the CNTs. A crossover from capacitive to inductive behaviour in the imaginary component of impedance has been shown by improving the CNT-electrode coupling. Furthermore the effect of metal contacts on microwave/ radio frequency transmission is also demonstrated. The results are consolidated by RF simulations, as strong conclusions are drawn. Studies on the dynamic transport in nanodiamond films revealed a crossover from the insulating to semi-metallic regime by nitrogen incorporation. The crossover is explained by considering the changes of the grain boundary morphology. This work shows that AC transport in polycrystalline nanodiamond films is similar to DC transport.

M.Sc., Faculty of Science, University of the Witwatersrand, 2011 / In this dissertation, the synthesis of nitrogen doped carbon nanotubes (N-CNTs) was performed successfully, using a floating catalyst chemical vapour deposition (CVD) method. Fe(CO)5 was utilized as the catalyst and acetonitrile and toluene as nitrogen and carbon sources respectively. Two different procedures were used to add reagents to the reactor: an injection method and a bubbling method. The effect of nitrogen concentration and physical parameters such as reaction temperature, gas flow rate on the morphology, crystallinity and thermal stability of the tubes was studied. The synthesized materials were characterized by means of Raman spectroscopy, TGA and TEM analyses. The presence of nitrogen was confirmed by the presence of the bamboo formations in the tubes by TEM. A comparison of the data from the numerous reactions revealed that N-CNTs can be made from Fe(CO)5 and acetonitrile. Further the main conclusions achieved using the injection method were: i) the maximum number of tubes with bamboo structure were made using on acetonitrile concentration of 15%, ii) The best growth temperature to make N-CNTs was 850 oC, iii) An increase in acetonitrile concentration decreased the yield of NCNTs and iv) Tubes with the narrowest outer diameters were made using an acetonitrile concentration of 15%.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the Degree of Master of Science. Johannesburg, 2015. / Fly ash is a by-product generated during the combustion of coal for electricity gen- eration. Previous studies have shown that various waste fly-ashes (Japanese, Saudi Arabian, and Australian) contain trace quantities of transition metal elements which can be used in the synthesis of shaped carbon nanomaterials. A survey of the litera- ture has shown that no attempts to correlate the composition of a particular coal fly ash and the type or quantity of carbon nanomaterials (CNMs) that can be synthesized has been made. Neither has the effect of leached fly ash been tested for the synthesis of CNMs. Hence a study on the effect of the chemical composition of South African fly ash (collected from ESKOM’s Duvha power station in Mpumalanga) upon the chemical vapour deposition (CVD) synthesis of carbon nanostructures is justified. Untreated and chemically treated fly ash samples were used as catalysts in the CVD method to synthesize CNMs. In the latter case selective leaching experiments were conducted on the fly ash samples under acidic, basic and neutral conditions. Op- timal CNM synthetic conditions were achieved by initially flowing H2 gas to re- duce the metal oxides within the fly ash catalyst followed by the introduction of the carbon source (C2H2) at a temperature range of 600 - 800 ◦C. All samples were quantitatively and/or qualitatively characterized. Inductively coupled plasma optical emission spectrometry (ICP-OES) and X-ray fluorescence (XRF) techniques were used to quantify the metal ions which were removed from the fly ash samples. Fur- thermore, qualitative studies were conducted with (PXRD, and laser Raman spec- troscopy), morphological and surface area characterization techniques (SEM, TEM and BET) were used to investigate the synthesis of CNMs from the untreated and chemically treated fly ash samples. Results have shown that carbon nanofibers (CNFs) of different geometric morpholo- gies were synthesized at an optimal yield temperature of 700◦C. A combination of smooth, thin, wide, spiral platelet-like, stacked cup, and fishbone morphologies were reported when the untreated fly ash catalyst was used. Fly ash catalysts under acidic, basic and neutral treatments showed CNFs of varying sizes and specific morpholo- gies. Smooth graphitic platelet-like, stacked cup and platelet-like CNFs were re- ported when the fly ash catalyst was leached with neutral, basic and acidic solutions. Carbon nanofibre sizes with the IG ID ratios were reported as follows 115 nm (1.092), 52 nm (0.799), and 200 nm (0.960) under neutral, basic and acidic mediums respec- tively. Surface areas (41, 14 and 7) m2/g for the CNFs that were synthesised from the neutral, basic and acidic treated fly ash catalysts were related to the selective leaching of metals. The quality and quantity of CNFs obtained under acidic medium were associated with the leaching of iron (5.6%), cobalt (1.7%), calcium (20.4%), copper (12.5%), chromium (4.6%), magnesium (23.3%), manganese (15.2%) and nickel (2%) from the fly ash catalyst. Under a basic medium only chromium (0.2%), calcium (0.3%) and copper (7.4%) were removed. Significantly the best quality of CNFs was ob- tained when fly ash was treated under neutral conditions. Metal ions such as: cal- cium (3.7%), copper (3.8%), chromium (0.1%), and magnesium (1.3%) were mod- erately removed from the ash matrix. Therefore, composition and quantity of the fly ash catalyst had an effect on the synthesis of CNFs.

SC-15 epoxy is used in many industrial applications and it is well known that the mechanical and viscoelastic properties of epoxy can be signicantly enhanced when reinforced with nanofillers. In this work, SC-15 epoxy is reinforced by loading with magnetically-active nanofillers and cured in a modest magnetic field. Because of the signicant magnetic response of the nanofillers, this is a low cost and relatively easy technique for imposing a strong magnetic anisotropy to the system without the need of a superconducting magnet. It is also found that this method is an effective way of enhancing the mechanical properties of epoxy. Three systems were prepared and studied. The first is a dilute system of various concentrations of Fe2O3 nanoparticles in SC-15 epoxy. The second system is a combination of Fe2O3 nanoparticles and chemically-functionalized single-walled carbon nanotubes (SWCNT(COOH)s) in SC-15 epoxy. The third is a dilute system of SWCNT(COOH)s decorated with Fe3O4 particles t hrough a sonochemical oxidation process in SC-15 epoxy. Samples have an initial cure of 6 hrs in a magnetic led of 10 kOe followed by an additional 24 hours of post curing at room temperature. These are compared to the control samples that do not have initial field curing. Tensile and compressive stress-strain analysis of the prepared systems shows that mechanical properties such as tensile strength, tensile modulus and compressive strength are enhanced with the inclusion of these nanofillers. It is also found that there is an anisotropic enhancement of these properties with respect to the imposed curing field. An interesting phenomenon is observed with the increase in modulus of toughness and fracture strain with nanotube inclusion. / These parameters are drastically enhanced after curing the systems in a magnetic field. While there is a modest shift in glass transition temperature during viscoelastic analysis, the thermal stability of the created systems is not compromised. Results of these mechanical enhancements will be compared with other nanoloading techniques from literature. / by Olga Malkina. / Thesis (Ph.D.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web.

Nesta tese foi explorado o controle de arquitetura molecular pelo uso das técnicas de Langmuir-Blodgett (LB) e automontagem (LBL) para produzir filmes nanoestruturados de azopolímeros e azocorantes de baixa massa molecular. A primeira contribuição foi a síntese química de azopolímeros, nos quais os grupos azo são ligados covalentemente a uma cadeia polimérica. Para produção de filmes LBL, que requer compostos solúveis em água, fez-se a sulfonação do PAZO (poli(p-azofenileno)) resultando no PAZOS (poli(p-azofenileno sulfonado)). Este azopolímero conjugado apresentou luminescência em solução, confirmando cálculos teóricos, mas não em filmes LBL com poli(alilamina) (PAH). Os filmes LBL são condutores elétricos quando dopados com iodo e têm propriedades de birrefringência opticamente induzida. A fotoindução da birrefringência com laser linearmente polarizado foi muito lenta, com tempos consideravelmente maiores que em outros filmes LBL, devido não só às interações eletrostáticas, mas também à rigidez da cadeia conjugada. Outro polímero sintetizado foi o DR19CL-IPDI, que é solúvel em clorofórmio e foi utilizado para fabricação de filmes de Langmuir e LB. Os filmes LB só puderam ser produzidos utilizando a estratégia de co-espalhamento com estearato de cádmio (CdSt). Os experimentos de birrefringência opticamente induzida indicaram que os filmes LB de DR19CL-IPDI/CdSt têm maior birrefringência que os outros azopolímeros derivados de poliuretanos, pois o seu máximo de absorbância coincide com o comprimento de onda do laser de escrita. Por outro lado, a birrefringência residual, após desligamento do laser, foi menor que em sistemas similares porque a relaxação do azocromóforo é facilitada devido a este polímero possuir menor temperatura de transição vítrea. Ainda com filmes de Langmuir, utilizamos a espectroscopia de UV-VI in situ para analisar os filmes de HPDR13 (poli 4\'-2-(metacriloiloxi)etiletilamino -2-cloro- 4-nitroazobenzeno)). Em acordo com as isotermas de pressão de superfície, os resultados indicaram que com maiores temperaturas de subfase, as cadeias de HPDR 13 ganham flexibilidade e são mais bem empacotadas, ocupando menor área por molécula. A importância do controle da arquitetura molecular foi demonstrada no estudo da birrefringência fotoinduzida e formação de grades de relevo de superfície (SRG) nos filmes LBL de azocorantes com quitosana e em filmes do azopolímero PS119 com dendrímeros DAB (Polipropilenimina). Os filmes LBL de quitosana com o corante SunsetYellow (SY) possuem birrefringência espontânea devida a uma organização molecular proveniente da técnica de automontagem. Para os filmes Ponceau S (PS), a birrefringência pode ser fotoinduzida e a dinâmica depende do pH utilizado na fabricação do filme, devido a alterações nas interações intermoleculares. A estrutura interna do filme LBL de dendrímero DAB teve grande efeito na adsorção de PS119, que aumentou com a geração, de 1 para 5. A maior adsorção do dendrímero G5 foi atribuída ao maior número de sítios ionizados para interagir com os azocromóforos do PS119. Entretanto, a birrefringência fotoinduzida foi maior para os filmes LBL com dendrímeros de menor geração, pois os filmes de geração maior apresentam maior interpenetração entre as camadas. Esta restringe a mobilidade dos cromóforos, gerando menor birrefringência. Esta explicação foi corroborada pela observação de maiores amplitudes das SRG, 31 nm e 5nm, para filmes de 35 bicamadas de PS119/DAB G1 e PS119/DAB G5, respectivamente. Estas grades foram formadas por transporte de massa causado por efeitos fotônicos, sendo observadas só para luz com polarização p e não s / In this thesis we exploit the control of molecular architecture provided by the Langmuir-Blodgett (LB) and layer-by-layer (LBL) techniques to produce nanostructured films from azobenzene-containing materials, azopolymers and low molecular weight azodyes. The first contribution was associated with the chemical synthesis of azopolymers, in which azochromophores were attached to polymer chains. For LBL film fabrication, which requires water-soluble materials, the sulfonation of the polymer PAZO (poly(p-azophenylene)) led to PAZOS (sulphonated poly(p-azophenylene)) This conjugated azopolymer was luminescent in solution, confirming theoretical predictions, but not in LBL films when alternated with poly(allylamine hydrochloride) (PAH). The latter LBL films displayed electric conductivity when doped with iodine and were also amenable to photoinduced birefringence. The writing of information with a linearly polarized laser was very slow, with writing times considerably longer than for other LBL films due not only to the electrostatic interactions in the film but also to the rigidity of the conjugated chain. The other polymer synthesized and characterized here was DR19CL-IPDI, which is soluble in organic solvents and was used to fabricate Langmuir and LB films. The LB films could only be produced by employing the strategy of co-spreading with an amphiphile, in this case DR19CL-IPDI mixed with cadmium stearate (CdSt). Experiments with photoinduced birefringence in the LB films of DR19CL-IPDI/CdSt indicated higher birefringence than in other polyurethane-based azopolymers because the laser wavelength almost coincides with the wavelength for maximum absorbance. On the other hand, the residual birefringence - after the writing laser was switched off - was smaller than in those similar systems because azochromophore relaxation is facilitated in DR19CL-IPDI due to its lower glass transition temperature. Still with regard to Langmuir films, we have introduced the in situ UV-VIS. spectroscopy technique to analyze films of HPDR13 (poly 4 ’-2-(methacryloyloxy)ethylethylamino -2-chloro-4-nitroazobenzene). Consistent with the pressure-area isotherms, the results from this spectroscopy indicated that at higher subphase temperatures the HPDR13 chains gain flexibility and the molecules can be packed in a more condensed manner, leading to a smaller occupied area per molecule. The importance of molecular architecture control was demonstrated in the study of photoinduced birefringence and formation of surface-relief gratings in LBL films consisting of azodyes alternated with chitosan, and the azopolymer PS119 alternated with DAB (polypropylenimine) dendrimers. In the chitosan LBL films, those containing the azodye Sunset Yellow (SY) exhibited spontaneous birefringence owing to the anisotropy in molecular organization imparted by the LBL technique. For Ponceau S (PS) films, birefringence could be photoinduced with the dynamics of writing depending on the solution pH employed for film fabrication, owing to changes in the intermolecular interactions. The internal structure of LBL films from DAB dendrimers had a large effect on the adsorption of PS119, which increased with the generation, from 1 to 5. The more effective adsorption for G5 dendrimer was due to a larger number of ionized sites for interacting with the azochromophores of PS119. In contrast, the photoinduced birefringence was higher for LBL films of the low generation G1 dendrimer, which was explained by the stronger interpenetration between adjacent layers in the higher generation dendrimers. In LBL films from PS119/DAB G5, this interpenetration restricts the chromophore mobility, leading to a smaller birefringence. Consistent with this explanation, higher amplitudes were obtained for 35-bilayer films of PS119/DAB G1 (31 nm) in comparison with films from PS119/DAB G5 (5 nm). These gratings were formed with mass transport arising from a light-driven mechanism, as photoinscription was only successful with p-polarized light and not with s-polarized light