Nanomaterial composites hold improvement potential for many materials. Improvements arise through known material behaviors and unique nanoscale effects to improve performance in areas including elastic modulus and damping as well as various processes, and products. Review of research spurred development of a load-stage. The load stage could be used independently, or in conjunction with an AFM to investigate bulk and nanoscale material mechanics. The effect of MWCNT content on structural damping, elastic modulus, toughness, loss modulus, and glass transition temperature was investigated using the load stage, AMF, and DMA. Initial investigation showed elastic modulus increased 23% with 1wt.% MWCNT versus pure epoxy and in-situ imaging observed micro/nanoscale deformation. Dynamic capabilities of the load stage were investigated as a method to achieve higher stress than available through DMA. The system showed energy dissipation across all reinforce levels, with ~480% peak for the 1wt.% MWCNT material vs. the neat epoxy at 1Hz. / ND NASA EPSCoR FAR0017788 / NDSU Development Foundation FAR0017503 / National Science Foundation (NSF) Grant# HRD-0811239 to the NDSU Advance FORWARD Program

The amorphous fraction of semicrystalline polymers has long been thought to be a significant contributor to creep deformation. In polyethylene (PE) nanocomposites, the semicrystalline nature of the maleated PE compatibilizer leads to a limited ability to separate the role of the PE in the nanocomposite properties. This dissertation investigates blown films of linear low-density polyethylene (LLDPE) and its nanocomposites with montmorillonite-layered silicate (MLS). Addition of an amorphous ethylene propylene copolymer grafted maleic anhydride (amEP) was utilized to enhance the interaction between the PE and the MLS. The amorphous nature of the compatibilizer was used to differentiate the effect of the different components of the nanocomposites; namely the matrix, the filler, and the compatibilizer on the overall properties. Tensile test results of the nanocomposites indicate that the addition of amEP and MLS separately and together produces a synergistic effect on the mechanical properties of the neat PE Thermal transitions were analyzed using differential scanning calorimetry (DSC) to determine if the observed improvement in mechanical properties is related to changes in crystallinity. The effect of dispersion of the MLS in the matrix was investigated by using a combination of X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Mechanical measurements were correlated to the dispersion of the layered silicate particles in the matrix. The nonlinear time dependent creep of the material was analyzed by examining creep and recovery of the films with a Burger model and the Kohlrausch-Williams-Watts (KWW) relation. The effect of stress on the nonlinear behavior of the nanocomposites was investigated by analyzing creep-recovery at different stress levels. Stress-related creep constants and shift factors were determined for the material by using the Schapery nonlinear viscoelastic equation at room temperature. The effect of temperature on the tensile and creep properties of the nanocomposites was analyzed by examining tensile and creep-recovery behavior of the films at temperatures in the range of 25 to -100 oC. Within the measured temperature range, the materials showed a nonlinear temperature dependent response. The time-temperature superposition principle was successfully used to predict the long term behavior of LLDPE nanocomposites.

The addition of fillers to a polymer matrix to endow soft materials with desirable properties has been a focused area of study over many decades and composite materials based on this idea are being increasingly incorporated into several end use products. Yet, almost always, the focus is on maximizing a particular property set for a unique polymer/filler combination for a specific application, which might not necessarily be translatable into another application. To exploit possible synergies, there is a need to develop materials that have the potential to perform multiple functions at the same time rather than a singular function. In this vein of thought, materials constructed using only polymer grafted nanoparticles (GNPs) have the potential to be one such class of materials as they have been shown to display a whole host of unique property sets – ranging from improved mechanical strength, enhancements in the gas and condensable penetrant transport properties, improvements in thermal conductivity, tunability of impact mitigation to more exotic behavior related to development of phononic bandgaps and quasi-crystalline materials. This thesis explores some of the structure-dynamics-property relations of some of the unique property sets described above and aims to provide insights into the nanoscale properties that lead to the improvements observed in macroscopic properties. In the first 2 chapters, we study the effect of tethering polymer chains to a spherical surface on the segmental and local vibrational dynamics of grafted polymer chains in an ensemble of GNPs. In the field of gas transport, the hopping motion of gas molecules inside a non-porous polymer matrix is facilitated by the motion of polymer segments, yet the understanding between the coupling of the two is very poor. By utilizing GNPs in which the diffusivity of gases is controlled by varying graft chain molecular weights, we can show that segmental dynamics of the polymer chains operating on a length scale of ~ 1 nm are positively correlated with the observed enhancements in diffusivities observed previously. We also propose that the inefficient packing of polymer chains leads to a decrease in the barriers of motion of the polymer segments, which is ultimately responsible for allowing penetrant molecules to move through the polymer phase much faster than a corresponding homopolymer melt. By utilizing a similar time and length scale approach, we can also explain the observed increases in thermal conductivities through the vibrational motion of polymer chains. This reaffirms the important role nanoscale polymer dynamics plays in both mass and thermal transport. In the next few chapters, we switch gears and focus on the microscopic structure and dynamics of the nanoparticles and how they impact the mechanical properties in suspensions. By studying the translational and vibrational motion of the GNPs, we find that the vibrational amplitude of a singular GNP decreases with increasing chain length all while the motion of the NP becomes faster, a phenomenon that we can associate with unjamming of the GNPs. This transition from jamming to unjamming is also visible in the local and long wavelength structure of the GNPs as well as the sound velocity through the material. Through these observations we can show that there is an intricate link between the structure and the relevant mechanical properties. Lastly, by building on the understanding laid out in the first few chapters, we propose that static features measurable through scattering are indicators of the enhanced transport properties of GNP based membranes. This also provides structural insights into the correlation between the structure of the polymer phase and the transport of penetrants. Each of the chapters touch upon a unique aspect of the structure and dynamics of different components of a GNP at different time and length scales, and how they are possibly linked to the several different property sets or dynamic features exhibited by the constructs, while also providing possible microscopic explanations for the same.

Thesis (M.S.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Mechanical Engineering, 2009.. / Includes bibliographical references.

Thesis (Ph. D.)--State University of New York at Binghamton, Materials Science and Engineering Program, 2009. / Includes bibliographical references.

M.Sc. / Carbon nanotubes (CNTs) have been of utmost scientific interest since their discovery in 1991 by a Japanese physicist - Sumio Iijima. This is due to their extraordinary properties which make them one of the most promising options for the design of novel ultrahigh strength polymer nanocomposites. It is believed that the high aspect ratio, mechanical strength, and high electrical and thermal conductivity of these CNTs will enhance the performance of many polymer / CNT nanocomposites and open up new applications. However, poor dispersibility and lack of interfacial adhesion of the CNTs in the polymer matrix have remained a challenge towards fabrication of these nanocomposites. This has been due to the atomically smooth surface of the nanotubes and their intrinsic van der Waals forces which make them chemically inert. This study was aimed at exploring this concept by using novel phosphorylated multiwalled carbon nanotubes (p-MWCNTs) and polyvinyl chloride (PVC) polymer. Phosphorylation of MWCNTs has been successfully achieved in our laboratories, with the p-MWCNTs showing improvement in thermal stability. PVC on the other hand, is the world’s second largest thermoplastic material and has physical properties that are key technical advantages for its use in various and diverse fields such as building and construction, electronics, food packaging and in medical applications. A novel solvent-free method was used to synthesize p-MWCNTs / PVC nanocomposites. MWCNTs were synthesized by nebulized spray pyrolysis, a modification of catalytic vapour deposition and purified by soxhlet extraction using toluene. This method proved to be convenient and economical, producing a high yield of carbon nanotubes. The MWCNTs were phosphorylated with alkylazido phosphonate compounds through a 1,3-dipolar cycloaddition reaction between the phosphonate azides and the C=C bonds of the MWCNTs, with nitrogen loss occurring upon thermolysis. These p-MWCNTs were then melt compounded with PVC to form the p-MWCNTs / PVC nanocomposites. vii The phosphorylation of the MWCNTs and their dispersion in the PVC matrix were characterized by FTIR, SEM, TEM and Raman spectroscopy. Thermal analysis of the nanocomposites by TGA and DSC showed an enhanced thermal stability when comparing the nanocomposites with neat PVC. The modulus of the MWCNTs / PVC nanocomposites increased whilst there was a reduction in their tensile strength, indicating a decrease in polymer toughness.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The main aim of this study was to use poly (ethylene-co-vinyl alcohol) (EVOH) as vehicle to incorporate nanofillers into low density polyethylene (LDPE). For this purpose, chitin and cellulose nanowhiskers were prepared through a process of acid hydrolysis and then incorporated into different EVOH copolymers with varying ethylene contents by means of two different experimental methods, namely solution casting and electrospinning. The extremely small dimensions of nanowhiskers make it difficult to observe the degree of dispersion in the electrospun fibers using methods such as transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Fluorescence microscopy was therefore investigated as an alternative characterization technique to obtain better results with regard to tracking the filler dispersion. TEM analysis proved to be the most successful method for observing the dispersion of nanowhiskers for solution cast EVOH nanocomposites as well as electrospun EVOH nanocomposites. Clear differences between EVOH composites with low nanowhisker and high nanowhisker loading were observed in TEM images for these nanocomposites. Thermal analysis of solution cast as well as electrospun fibers were carried out using techniques such as differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). These results revealed changes in crystallization behaviour as well as changes in thermal stability of the EVOH nanocomposites compared to the pure polymer matrix. The incorporation of cellulose and chitin nanowhiskers indicated a general increase in percentage crystallization which probably resulted from the nanowhiskers acting as nucleating agents and therefore increasing the crystallization of most EVOH nanocomposites. The thermal stability is observed to increase as the cellulose nanowhisker loading is increased. This increase in thermal stability proved to be partly attributed to the presence of sulphuric acid which were not completely removed during dialysis of cellulose nanowhiskers. Neutralisation of cellulose nanowhiskers and the treatment with a strong base was therefore further investigated to improve degradation within the EVOH nanocomposites during thermal treatment. The last step in this study involved the incorporation of electrospun EVOH nanofibers containing cellulose nanowhiskers into LDPE in order to improve the mechanical properties. The tensile strength and Young’s modulus of these LDPE nanocomposites were seen to improve quite significantly while a decrease in elongation at break was observed. / AFRIKAANSE OPSOMMING: Die hoofdoel van hierdie studie was om poliëtileen (ko-viniel alkohol) (EVOH) as voertuig te gebruik om nanofillers in lae digtheid poliëtileen (LDPE) te inkorporeer. Kitien en sellulose nanokristalle is vir hierdie doel geproduseer deur middel van ʼn suurhidrolise proses en daarna in verskillende EVOH-kopolimere met verskillende etileeninhoude geïnkorporeer met behulp van twee verskillende eksperimentele metodes, naamlik ʼn drogings- en elektrospinproses. Die uiters klein dimensies van die nanokristalle maak dit uitdagend om die mate van verspreiding van die nanokristalle binne in die elekrogespinde vesels waar te neem m.b.v. metodes soos transmissieelektronmikroskopie (TEM) en skandeerelektronmikroskopie (SEM). Fluoressensie is dus as ʼn moontlike alternatiewe karakteriserings tegniek bestudeer om beter resultate rakende die verspreiding van die nanokristalle te kan waarneem. In hierdie studie is gevind dat TEM-analise die suksesvolste metode was om die verspreiding van nanokristalle te bestudeer en dit geld vir beide die gedroogte en gespinde EVOH-nanosamestellings. Duidelike verskille is waargeneem vir monsters wat hoër en laer nanokristalinhoude gehad het. Saambondeling van die nanokristalle kom duideliker voor by dié wat ʼn hoër inhoud van nanokristalle bevat. Termiese analises van gedroogte EVOH-nanosamestellings en ook die gespinde nanosaamgestelde vesels is uitgevoer d.m.v. tegnieke soos differensieëlskandeerkalorometrie (DSC) en termiese-gravimetriese analise (TGA). Die resultate wat verkry is vanaf die bogenoemde tegnieke het bewys dat daar verandering in die kristallisasie, sowel as die degradasie temperatuur, van die EVOH-nanosamestelling is. Die byvoeging van sellulose en kitien nanokristalle het ʼn algemene verhoging in die persentasie kristallisasie van die EVOH-nanosamestelling te wee gebring. Die byvoeging van nanokristalle tree waarskynlik gedeeltelik op as kernvormings agent vir die EVOH-molekules. TGA analises toon dat die termiese stabiliteit van die EVOH-nanosamestelling verhoog met die byvoeging van nanokristalle. Die teenwoordigheid van die sulfaatgroepe wat nie heeltemal verwyder is tydens die wasproses nie, is bewys om gedeeltelik verantwoordelik te wees vir die verhoging in termiese stabiliteit van die EVOH-nanosamestellings. Die neutralisasie en behandeling van die nanokristalle met ʼn sterk basis is dus verder ondersoek om die degradasie van die EVOH-nanosamestellings tydens verhitting te verbeter. Die laaste stap in hierdie studie het behels dat elektrogespinde EVOH vesels wat verskillende hoeveelhede sellulose nanokristalle bevat, geïnkorporeer is in LDPE ten einde die meganiese eienskappe te verbeter. Die treksterkte en die Young’s modulus het met ʼn beduidendende hoeveelheid verbeter terwyl die verlenging by breekpunt verlaag het. / National Research Foundation

L'objectif de cette thèse a été l'optimisation de la synthèse et des performances catalytiques des matériaux lamellaires au W et Mo dans les réactions d'oxydation de plusieurs composés organiques en présence d'H2O2. Le travail réalisé au cours de cette thèse est le développement de nouveaux catalyseurs hétérogènes pour la réaction d'oxydation qui est réalisée sélectivement en systèmes catalytiques homogènes, mais pour un développement durable, la catalyse hétérogène demeure beaucoup plus porteuse d'avenir au niveau industriel. La réaction d'oxydation de composés soufrés a un grand intérêt, en particulier dans l'élimination des composés organiques soufrés (thiophènes, sulfures) contenus dans les carburants et les coupes pétrolières, réalisée dans des conditions douces de température et pression, en présence de l'eau oxygénée. Les objectifs principaux de cette étude ont été les suivants: 1. élaboration des matériaux catalytiques : a) préparation des précurseurs de type hydrotalcites (HDL) à base de Mg-Al-NO3, Mg-Al-terephthalate et Ni-Mg-Al-NO3. b) préparation des matériaux hybrides par intercalation des espèces de Mo et W par deux voies de synthèse : réaction d'échange anionique et synthèse hydrothermale. 2. caractérisation de la structure, la texture et la nature des sites catalytique par différentes techniques : DRX, adsorption d'azote, ATG, spectroscopie Raman et UV-Vis, MEB etc. 3. applications de ces catalyseurs à la réaction d'oxydation des composes soufrés (sulfures, thiophènes, sulfoxydes), epoxydation de cyclooctene et oxydation d'anthracène. Les catalyseurs ont été stables au recyclage et aucun phénomène de leaching n'a été observé. / The objective of this thesis was the optimization of the synthesis and catalytic performances of nanocomposites materials containing W and Mo in the oxidation with H2O2 of a wide range of model organic compounds. The work achieved during this thesis is the development of new heterogeneous catalysts for the oxidation reaction who is carried out selectively in homogeneous catalytic systems, heterogeneous catalysis is still much more promising in future. The oxidation reaction of sulfur compounds has great interest, especially in the removal of organic sulfur compounds (thiophene, sulfide) contained in fuels and petroleum fractions, performed in mild conditions of temperature and pressure in the presence of H2O2. In this study were as follows : 1. elaboration of materials : a) preparation of precursors of type hydrotalcites (HDL) based on Mg-Al-NO3, Mg-Al-Ni-terephthalate and Mg-Al-NO3. b) preparation of hybrid materials by intercalation species of Mo and W by two synthetic routes : reaction of anion-exchange and hydrothermal synthesis. 2. characterization of the structure, texture and nature of catalytic sites by different techniques : XRD, nitrogen adsorption, TGA, Raman spectroscopy and UV-Vis, SEM, etc. 3. application of these catalysts in the reaction of oxidation of sulfur compounds (sulfides, thiophenes, sulfoxides), epoxidation of cyclooctene and oxidation of anthracene. The catalysts were stable under operating conditions.

The superior material properties of polymer/clay nanocomposites have attracted much research interests in the past years. The hypothesis of polymer stiffening in the vicinity of the nano-c1ay described using the "core-shell" model has not been fully investigated yet. The investigation of the interfacial region by atomic force microscopy (AFM) has provided us with details of the physical state of this region. It was found that the polymer stiffening region could extend as far as 200nm and 100nm from the face and the edge of a nano-clay respectively. Two different degrees of polymer stiffening have been observed from AFM micrographs with the help of amplitude and phase contrasting techniques. The temperature dependant property of the stiffened polymer has been studied using a heating stage, which showed the stiffened polymer was softened with increasing temperature between the studied range, 60°C and 91°C. The relative polymer crystallinity derived from the X-ray diffraction (XRD) data showed a general trend that increases with the clay content, regardless of the clay modification. However, an exception has been observed with the set of bi-axially drawn specimens, of which the highest polymer crystallinity was found to be the neat polymer when compared with the nanocomposites counterpart. It is believed that the presence of nano-c1ay particles restricted the reorientation of the polymer chains upon stress. From the in situ isothermal investigation of polymer crystal growth, it has been found the crystal grown from a nano-clay particle is larger than that from the bulk. This indicated that the crystallisation began at a lower temperature. The nano-clay and polymer crystal orientations have been further studied with X-ray texture analysis. It was found that the polymer chains were not completely aligned alone the extrusion direction as expected. Also, from the annealed specimens it was found that the orientation of the nano-clay particles had been influenced by the relaxation of the polymer chains.

Submitted in fulfillment of the academic requirements of the degree of Master of Applied Sciences in Chemistry, Durban University of Technology, Chemistry Department, Durban, South Africa, 2016. / Cellulose is a sustainable, abundant biopolymer derived from a variety of living species such as plants, animals, bacteria and some amoebas. An attractive source of cellulose for industrial uses is agricultural waste, as this use does not jeopardize food supplies and improves the local rural economy. Sugarcane bagasse (SCB) is one of the main biomass wastes from sugar production and represents 30–40 wt % of sugar production waste. In 2008, South Africa produced on average 22 million tons of sugar cane each season from 14 sugar mill supply areas which resulted in 7,9 million tons of “waste” bagasse. In this study cellulose nanocrystals were prepared from soda pulped sugarcane bagasse by acid hydrolysis followed by separation using centrifugation, ultrasonication and dialysis. Transmission Electron Microscopy (TEM) images showed nanocrystals of approximately 300 nm in length and 20 nm in width. Thermogravimetric Analysis and Differential Thermogravimetry (TGA and DTG) profiles of FD CNC, MCC and Pulped bagasse all had characteristic onset and decomposition temperatures indicating a change in the structure after chemical treatments. Particle size distribution measurements corroborated with the TEM and FE - SEM results and showed that the majority of the nanocrystals were in the 100 – 300 nm range. Attenuated Total Reflectance – Fourier Transform Infra Red (ATR - FTIR) analysis showed functional group changes as the amorphous regions of the polymer were removed revealing the ordered crystalline portions. These were further confirmed by an increase in the Lateral Orientation Index (LOI) of the samples as the nanocrystals were isolated. X - Ray Diffraction (XRD) Crystallinity Index (CrI) calculations showed a steady increase in the crystallinity of the materials from pulped bagasse to MCC to FD CNC. / M