This thesis aims to produce functional polymer fibres and films using liquid crystal networks or photoembossing. The work focuses on visual effects in fibres, optical sensing properties and, actuation and morphing properties. In the first part we focused on changing the perception of textiles by generating structural colours based on diffraction and/or reflection of light. For the former, a micro-structuring technique is combined with a contactless patterning technique: pulsed holography. The results show that diffractive features could be generated on static or moving polymer films allowing for large area patterning. The use of a contactless patterning technique also suggests its potential application for curved surfaces such as fibres. In the second approach, reflective colours are generated using a self-organising cholesteric liquid crystal (CLC) coating. The coating is applied in a one step process though spray coating of a liquid crystal monomer mixture on the polymer substrate followed by photopolymerization. Reflectivity measurements and optical microscopy show that a well-defined liquid crystalline and planar alignment is obtained. In the case of films, a strong angular dependent reflection is obtained. In comparison fibres shown lower reflectivity with an angular dependent colour in a single dimension along the fibre direction which originates from the planar cholesteric alignment on a curved surface. The second part of the project was aimed at detecting strain optically in polymer films and fibres. Here, we used the same process to produce reflective films and studied the optical response to uniaxial deformation. Results showed a colour shift as function of strain that was dependent on the mechanical behaviour of the substrate giving real time information of the deformation in the substrate. In the final part the thesis, we explored shape change in response to light of a bilayer photoresponsive film for adaptive textile applications. Here we showed that bending could be generated by coating a photoresponsive LC layer on an oriented polymer substrate. Bending is attributed to a photo induced contraction that occurs in the coating. The resulting response was strongly dependent on the substrate thickness and stiffness, thermo-mechanical properties and the concentration of chromophore in the LC layer.

M. Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / The world is continuously losing the battle against superbugs (resistant bacteria towards commonly used antibiotics), hence there is an urgent need to develop novel antibacterial agents. In this study, green synthesized silver nanoparticles (AgNPs) and eucalyptus oil, were incorporated into the polymer blend fibres of polyvinyl alcohol (PVA) and cellulose nanocrystals (CNC’s). Various techniques were used to characterize the AgNPs, PVA/CNC polymer fibres, and PVA/CNC incorporated with AgNPs/eucalyptus oil. The morphology of AgNPs synthesized using an increasing concentration of the Citrus sinensis peels (CSP) extract was obtained from transmission electron microscopy (TEM). AgNPs synthesized using 1 and 2 % m/v (CSP) were agglomerated and whereas those synthesized using 3 % m/v of the extract were spherical with an average particle size 10 ± 1.2 nm. UV/Visible absorption spectra for all the synthesized AgNPs exhibited a surface plasmon resonance (SPR) peak at around 400 nm which is a characteristic peak of silver. Significant shifts in the absorption peaks or maxima were observed to signify changes in the shape and size of the nanoparticles. Scanning electron microscopy (SEM) was used to study the morphology of the fabricated polymer fibres. The Addition of CNC’s to PVA resulted in an increase in fibre diameter due to an increase in viscosity of the solution. An increase in the concentration of silver nanoparticles and the eucalyptus oil in the PVA/CNC resulted in a decrease in fibre diameter due to an increase in conductivity of the material. The fibres with AgNPs were smooth while the ones with the eucalyptus oil were beaded. X-ray diffraction (XRD) showed the presence of the AgNPs in the polymer fibres and Fourier transform infrared (FTIR) showed the presence of the functional groups that are available in the eucalyptus oil. The antibacterial efficiency of the PVA/CNC incorporated with AgNPs, eucalyptus oil, and the mixture of AgNPs and the eucalyptus oil was investigated using S. aureus and K. pneumoniae. All the materials showed significant inhibition of the growth of the selected bacterial strains. PVA/CNC polymer fibres incorporated with AgNPs showed higher antibacterial activity compared to PVA/CNC polymer fibres incorporated with eucalyptus oil.

M. Tech. (Department of Chemistry, Faculty of Applied and Computer Science): Vaal University of Technology / Here, we report the synthesis and characterization of silver (Ag) and silver selenide (Ag2Se) nanoparticles using the metal-organic route method. This method involves the reduction of selenium powder and silver nitrate in the presence of trioctylphosphine as a solvent. Tri-n-octylphosphine oxide (TOPO) and hexadecylamine (HDA) were used in the study as capping molecules. The optical properties of the as-prepared nanoparticles were studied using UV-Visible and photoluminescence spectroscopy (PL). Transmission electron microscopy (TEM) and X-ray powder diffraction (XRD) were used to study the structural properties. The effect of capping molecules and temperature were investigated on the growth of the nanoparticles. The prepared nanoparticles seem to depend on the reaction temperature were the increase in temperature led to an increase in particle sizes. The growth of the as-prepared TOPO-capped Ag2Se nanoparticles was influenced by temperature, this was evident when the temperature was increased, the nanoparticles evolved from sphere to hexagonal shape. TOPO-capped nanoparticles showed the tendency of agglomeration with increase in temperature compared to HDA-capped nanoparticles. The X-ray diffraction results showed peaks which were identified as due to α-Ag2Se body centered cubic compound for both TOPO/HDA-capped Ag2Se nanoparticles. Some evidence of impurities were observed in the XRD analysis and indexed to metallic silver. HDA-capped Ag nanoparticles were found to be affected by temperature variation. The prepared nanoparticles were characterized with UV-Vis spectroscopy and transmission electron microscopy. XRD analysis was not performed due to small yield obtained. The absorption spectra of HDA-capped Ag nanoparticles at different temperatures show a surface Plasmon resonance (SPR) band in the regions 418 - 428 nm. Uniform spherical shapes were obtained for both 130 and 190 °C and fewer particles were obtained at 160 °C. The synthesis of TOPO–capped Ag nanoparticles was unsuccessful since none of the particles were isolated from the solution due to its lower capping ability or it may be that TOPO is binding too strongly to Ag. The polymer nanofibres were electrospun using electrospinning technique. Parameters such as concentration and voltage were investigated. These parameters significantly affect the formation of fibre morphology. PVP and PMMA polymers were used for this study. The electrospun composite fibres were characterized using UV-Visible spectroscopy, scanning electron microscopy (SEM), Thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and Fourier transformer infrared (FTIR) spectroscopy. The SEM results show that increasing the polymer concentration resulted in increased fibre diameters. Hence increasing the voltage decreases the fibre diameters. Ag2Se nanoparticles were incorporated into PVP and PMMA and electrospun using electrospinning to produce composite fibres. Their addition into PVP polymer fibres improved the fibre’s uniformity and further decreased their diameters. The SEM of composite fibres for PMMA is not shown. The absorption bands for PVP composites fibres show a blue shift from the pure Ag2Se nanoparticles, whereas the one for PMMA show a red shift from the pure Ag2Se nanoparticles. Both the composite fibres for PVP and PMMA show a blue shift from the bulk of Ag2Se. The XRD analysis of the composite fibres shows no significant effect upon addition of Ag2Se nanoparticles on the amorphous peak of the PVP polymer, whereas on the PMMA, it shows peaks which were due to the face centered cubic phase of Ag. The FTIR spectra of the composite fibres and pure polymers (PVP and PMMA) gave almost identical features. TGA curves show no significant effect on the thermal properties of the PVP polymer and its composites, however, on the PMMA composite fibres it show an increase in the thermal stability of the polymers upon addition of Ag2Se nanoparticles. The study was based on silver nanoparicles and its antibacterial activities. One of the synthetic challenges for silver nanoparticles is their solubility and yield. Selenide was introduced in the study to improve such shortcomings of silver nanoparticles and also for possible improved properties, chemical stability and increased activity against bacteria. The selenide group on the metal also provides stronger chemical interaction between the nanoparticles and the polymer. Therefore, the intension was to use these nanoparticles into polymer fibres for potential use in wound dressing.

Cette thèse est consacrée à la mécanique et à la mécanique statistique de biofilaments/biopolymères et de leur modèle le plus répandu le Worm-Like Chain (WLC) qu’il s’avère nécessaire d’étendre. Nous étudions WLC à 2-d en présence d’obstacles plus proches que la longueur de persistance. Nous caractérisons le mouvement aux temps courts par des simulations numériques complétées par des calculs analytiques. Des concepts similaires servent à décrire des ADN greffés balayés par le front d’une vésicule en cours d’étalement, l’adhésion de la vésicule est promue par des paires biotine/streptavidine qui contraignent les molécules d'ADN sur des chemins étroits où ils peuvent être imagés. Les microtubules (MT) ici stabilisés au taxol, présentent par contre certains comportements qui échappent au WLC et doivent être ramenés à leur structure interne : i)les déflexions latérales d’un MT attaché par un bout correspondent à une longueur de persistance apparente qui augmente avec la longueur ii) les MT adoptent des formes super-hélicoïdales. Ces deux points sont établis au moyen d’analyses de forme des MT. Des transitions de forme corrélées le long du MT mises en évidence sont compatibles avec un modèle basé sur la bistabilité du dimère de tubuline. Finalement un modèle de chaîne super-hélicoïdale comprenant une courbure et une torsion spontanées élargi le WLC. Confiné à 2-d, HWLC peut adopter un état fondamental circulaire ou sinueux caractérisé par le nombre de points d’inflexion où se concentre la torsion (twist-kink). Dans le cas circulaire, il existe des états métastables proches, à petit nombre de twist-kinks, hyperflexibles. / This PhD is devoted to the mechanics and statistical mechanics of biofilaments and their most widespread model, the Worm-Like Chain (WLC) model, which, as it turns out, needs to be extended. We study the WLC in 2-d in the presence of obstacles closer than their persistence length. We characterize the short time motion by numerical simulations complemented by analytical calculations. Similar concepts serve to describe grafted DNAs swept by the front of a spreading vesicle whose adhesion is promoted by biotin/streptavidin bonds, which constrain the DNAs on narrow paths where they can be imaged. Microtubules (MT), here stabilized by taxol, show features which cannot be rationalized by the WLC and shall be related to their internal structure : i)lateral deflections of a clamped MT correspond to an effective persistence length growing with the MT size ii) MT adopt super-helical shapes. These two points are proven by refined image analysis. We analyze shape transitions correlated along the MT which are compatible with a model based on dimer bi-stability. Finally, a super helical chain model (HWLC) allowing for spontaneous curvature and twist is developed which extends the WLC. When confined to 2-d, the HWLC can adopt a ground state which is circular or wavy with inflection points where twist accumulates, so-called twist-kinks. In the circular case there exist close metastable states, with a small number of twist-kinks, which are hyperflexible.

Plasma treatment of polypropylene fibers presents a new progressive method, how to increase the utility properties of these fibers. The thesis is focused on verifying the effect of surface treatment of polypropylene fibers in concrete with low-temperature plasma discharge in the normal atmosphere. The paper describes the procedure for treatment of polypropylene fibers with low-temperature plasma and evaluate the impact of this adjustment on the volume changes of cement composites. It should also be emphasized that the thesis is focused on the initial volume changes, ie volume changes in the early stages of solidification and only for your own mixture, which is not considered an external load. Subsequently, the experimental verification of the effect of the addition made commercially available fibers and fibers treated plasma volume changes to a selected physico-mechanical properties of the test compounds.

This PhD is devoted to the mechanics and statistical mechanics of biofilaments and their most widespread model, the Worm-Like Chain (WLC) model, which, as it turns out, needs to be extended. We study the WLC in 2-d in the presence of obstacles closer than their persistence length. We characterize the short time motion by numerical simulations complemented by analytical calculations. Similar concepts serve to describe grafted DNAs swept by the front of a spreading vesicle whose adhesion is promoted by biotin/streptavidin bonds, which constrain the DNAs on narrow paths where they can be imaged. Microtubules (MT), here stabilized by taxol, show features which cannot be rationalized by the WLC and shall be related to their internal structure : i)lateral deflections of a clamped MT correspond to an effective persistence length growing with the MT size ii) MT adopt super-helical shapes. These two points are proven by refined image analysis. We analyze shape transitions correlated along the MT which are compatible with a model based on dimer bi-stability. Finally, a super helical chain model (HWLC) allowing for spontaneous curvature and twist is developed which extends the WLC. When confined to 2-d, the HWLC can adopt a ground state which is circular or wavy with inflection points where twist accumulates, so-called twist-kinks. In the circular case there exist close metastable states, with a small number of twist-kinks, which are hyperflexible.