This dissertation, studies two specific topics related to the research of surface science by employing the molecular dynamics (MD) approach, that of a water droplet deposited on a poly (methyl methacrylate) (PMMA) substrate and that of a single tricarboxylic acid derivative, 1, 3, 5-tri(carboxymethoxy) benzene (TCMB, C6H3(OCH2COOH)3 ) adsorbed on gold (100) and (110) surfaces. These can help engineers clarify the characteristics and phenomena of physical adsorption of the molecule, as well as contributing to the application of surface science. This work is divided into two parts. Effect of droplet size on the structural and dynamical behavior of a water droplet spreading on a PMMA amorphous surface: note that most experts prefer to consider a rigid model as the substrate in research of surface wetting because it is more efficient to run the MD simulation such that a long simulation can be accomplished in a short time. The results verify that the rigid model is not suitable to act as the PMMA substrate in simulation because it prevents the diffusion of PMMA molecules, which then affects the penetration behavior of water molecules in the droplet upon impact with the PMMA surface. Several sizes of water droplets are considered in order to understand the size influence of the droplet on the properties of water molecules and on the PMMA surface. The penetrated water molecules and the local roughness increase with a decrease in the size of the droplet, which also leads to a smaller contact angle of the water droplet on the PMMA substrate. When the droplet is composed of more than 1000 water molecules, the contact angle shows agreement with experimental results. As regarding the structure of the water molecule in the droplet on PMMA substrate, the average number of hydrogen-bonded penetrating water molecules is in inverse proportion to the size of the droplet By examining the velocity field, the regular motion of the water droplet is found during the equilibrium process and after the droplet reaches the equilibrium state. The diffusion of the water molecules shows a significant decrease for the penetrated water molecules and an increase as it gradually approaches the vapor/liquid interface. Finally, calculations at different regions are made for the vibration spectrum of the oxygen atom, life time, and the relaxation time of the hydrogen bond. The changes of the hydrogen-bond dynamics of the hydrogen bond are consistent with the change of the distribution of the hydrogen bond angle. Effect of surface structure on the structural and dynamical behavior of a tricarboxylic acid derivative molecule on Au surfaces: the dynamical behavior of the single tricarboxylic acid derivative, 1, 3, 5-tri(carboxymethoxy) benzene (TCMB, C6H3(OCH2COOH)3 ) on Au (100) and (110) surfaces by molecular dynamics simulation approach is studied to provide better understanding of surface diffusion. Four possible conformations of the adsorbed TCMB molecule on the Au surface are found, with differences arising from different numbers of CH2 groups adsorbed on the Au substrate. Both the number of CH2 groups in the TCMB molecule that interact with Au surface and the different geometric relationship between the TCMB molecule and the Au surface strongly affect the translational motion, rotational motion, interaction energy and the Lock-and-Key behaviors of the TCMB molecule. A poor complementarity between the TCMB molecule shape and atomic structure of the surface results in significant migration of the molecule and is therefore an unstable adsorption. These results will be useful for the design of a molecular monolayer.

<p>Biomaterials used for stabilization of compressed vertebraes due to osteoporosis, have mainly been based on resin materials, like PMMA (polymethyl methacrylate), but have recently expanded to consist of injectable ceramics, such as calcium-aluminate. In this in vitro study human osteoblast-like cells, MG-63, were cultured on three different injectable biomaterials based on: Ca-aluminate, Bis-GMA (bisphenol A-glycidylmethacrylate) and PMMA, to investigate the cellular response elicited by these materials. Cell proliferation was measured by the NucleoCounter® system, cell viability was investigated by LDH (lactate dehydrogenase) analysis, cell differentiation and mineralization was evaluated by mRNA gene expression of the osteoblastic markers: ALP (alkaline phosphatase), OC (osteocalcin) and COLL-I (collagen type I) by qPCR (quantitative polymerase chain reaction) analysis. Two control materials were used: TCP (tissue culture polystyrene, negative control) and PVC (polyvinyl chloride, positive control). The results showed that all the bone cement materials were non-toxic and biocompatible, i.e. they provided good cell viability and proliferation of the MG-63 cells. They are specific for bone cells, since they expressed high values of the osteoblast-specific differentiation markers, and are thus promising as injectable bone cement materials. Among the bone cements, Xeraspine appears to be the most biocompatible material for bone cells. It is followed by Cortoss and then Vertebroplastic.</p>

Ce travail porte sur le greffage radicalaire de méthacrylate de méthyle sur un poly(éthylène-co-1-octène) par extrusion réactive. Le contrôle de l'architecture des copolymères greffés nécessite la compréhension des mécanismes réactionnels mis en jeu, à température et viscosité élevées. Grâce à une étude sur molécules modèles, les sites de greffage, les réactions gouvernant la masse molaire des greffons, ainsi que les réactions compétitives à l'origine de l'homopolymérisation ont pu être quantifiées. L'étude modèle, complétée par une simulation numérique, souligne la nécessité de diminuer la température du milieu réactionnel pour favoriser la réaction de greffage. Parallèlement, l'extrusion réactive confirme les tendances dégagées par l'étude modèle et met en évidence l'influence des conditions de mélange sur la morphologie. Enfin, l'utilisation de radicaux nitroxyles pour limiter la réaction d'homopolymérisation, n'améliore pas significativement l'efficacité du greffage.

A novel Poly (methyl methacrylate) Composites using Copper-4, 4'- Trimethylenedipyridine Metal-Organic Framework as Fillers (CTMOF) had been synthesized and analyzed. The CTMOF structure had been characterized by X-ray crystallography. The thermal and mechanical properties of CTMOF-PMMA composites had been examined via optical microscopy, differential scanning calorimetry (DSC), microhardness, and dynamic mechanical thermal analysis (DMTA). The results showed the increase of Glass transition temperatures and the improvement of mechanical properties of the PMMA composites as the concentration of CBMOF loading increased.

Laser micromachining has become increasing prominent in various industries given its speed, lack of tool wear, and ability to create features on the order of micrometres. Inherent stochastic variations from thermal ablation along with detrimental heat effects, however, limit the feasibility of achieving high precision. The high number of control parameters that make laser micromachining versatile also hinders optimization due to high exploration time. The introduction of high intensity nonlinear ablation leads to more precise cuts but at a much higher, often restrictive, cost. The work here shows that by combining an imaging technique frequently used in ophthalmology called optical coherence tomography (OCT) with a machining platform, in situ observation of ablation can be made. This combination, known as in-line coherent imaging (ICI), allows information to be gathered about the dynamics of the ablation process. Experimental results show that quality cutting of silicon can be achieved with thermal ablation and at a wavelength of 1070 nm. This result is surprising as silicon absorbs this wavelength very weakly at room temperature. It is shown here that a nonlinear thermal dependence in absorption allows a cascaded absorption effect to enable machining. With the aid of ICI, the model shown here is able to accurately predict the thermal ablation rate and help understand the ablation process. The high quality cutting achieved allows for a more cost efficient alternative to current techniques using ultraviolet diode-pumped solid state (UV DPSS) systems. Where thermal effects such as heat-affected zones (HAZ) cannot be overcome, high intensity nonlinear ablation allows the processing of lead zirconate titanate (PZT) for high frequency arrays (used in ultrasound applications) at speeds two orders of magnitude greater than found in the literature, and potential feature sizes (< 100 µm) in polymethyl methacrylate (PMMA) unachievable by thermal ablation. The ablation mechanism here is Coulombic explosion (CE), which is a non-thermal process. Coupled with demonstrated manual and automatic feedback abilities of ICI, the processes shown here may open up new avenues for fabrication. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2011-05-31 15:02:55.547

Dental implants are an effective alternative for the replacement of missing teeth. The success of the implant depends on how well a bone heals around the implant, a process known as osseointegration. However, excessive heat generated during the bone drilling will cause cell death and may prevent osseointegration of the implant, resulting in early failure. There are many factors which contribute to the heat generation during drilling. Experiments were carried out to investigate the affect of variable drilling factors on heat generation during drilling operation. Natural bone is not an ideal material for such research, as it varies widely in density and other parameters of interest.. It would be desirable to have a more uniform and consistent material to use in such studies. However, such a material must be similar to bone to allow the results to be extrapolated to the clinical situation. The current study describes and validates a model for use in such studies. Polymethylmethacrylate (PMMA) is the material chosen for our studies. A theoretical model was developed to study the effect of different drilling parameters on temperature rise during drilling operations. Comparison of observed results obtained from experiments was made with the results from theoretical study. Comparison of results for PMMA and human bone are also shown explaining how PMMA material can be substituted for human bone. The results suggest that the PMMA model is an acceptable surrogate for bone in such studies.

Polymer waveguides present a potentially low cost alternative to electronics in communication systems. Polymers offer relatively straightforward and economical fabrication when compared to conventional materials. In this study, a fabrication process for Bragg gratings in polymer waveguides was developed. Waveguides were designed using finite-element analysis, patterned via e-beam lithography, and a detailed fabrication method was developed. Surface-Plasmon Resonance (SPR) is a widely accepted method for biological and chemical sensing. Measurement of bulk refractive index changes and specific surface binding is a crucial part in any biosensing. Design and fabrication of a novel self-referencing SPR sensor is described and its functionality is tested.

This thesis presents an investigation into the factors which control the gain and amplification properties in conjugated materials. Conjugated polymers and perylene dyes are highly fluorescent, are easy to process into thin films, and exhibit strong amplification over a broad gain bandwidth making them ideal for use in lasers and amplifiers. The stimulated emission created when thin films of the red emitting polymer poly(2-methoxy-5-(2'-ethylhexyloxy)- p-phenylenvinylene) (MEH-PPV) were photoexcited with high energy laser pulses was investigated. This was characterised by a dramatic narrowing of the emission spectrum which has been assigned to amplified spontaneous emission (ASE). The emission was found to have a gaussian profile and the gain coefficient was found to be 4 cm-1.The temperature dependence of the absorption, photoluminescence and ASE of films of MEH-PPV was measured. The effect of film morphology on the photophysical properties was investigated by using films cast from two spinning solvents, chlorobenzene (CB) and tetrahydrofuran (THE). Film morphology was found to greatly affect the temperature dependence. A particularly important property is the spectral position of the ASE and the factors which affect it. By controlling the film thickness close to the cut-off thickness for waveguiding in the polymer film it was shown that the peak position of the ASE could be tuned by 31 nm. Modelling of the waveguide modes in the polymer films was used to explain this effect. The cut-off wavelength for each film was measured and good agreement with the theory was found. In order to investigate ways in which energy transfer could be used to control the emission, two perylene dyes were used as a donor-acceptor pair in a host matrix of poly methymethacralate (PMMA). The position of the ASE was found to depend on the acceptor concentration. Measurements of the photoluminescence quantum yield and time-resolved luminescence measurements showed that the energy transfer coefficient was 5x10(^11)mol(^-1)d(^3)

Acrylic bone cements are one of the most important biomaterials used in orthopaedic surgery and dental applications to fill the cavities or provide mechanical interlock between prosthesis and the bone. Their biocompatibility can be increased by addition of different materials into the formulation, such as hydroxyapatite. Besides all the advantages, bone cements have several drawbacks including tissue necrosis, chemical necrosis, shrinkage of the cement and aseptic loosening. Therefore painstaking research and study are carried out on development of new formulations to improve mechanical and thermal properties as well as biocompatibilities. In this study, bone cements with different compositions were prepared and new formulations were examined to improve mechanical properties and to reduce maximum curing temperature. It was observed that addition of hydroxyapatite, while keeping polymer-to-monomer ratio constant at 2.0, decreased curing temperature and increased compressive strength about 11% (Group-C) when hydroxyapatite addition was 12%. Further addition of hydroxyapatite destroyed homogeneity of the cement dough and made it difficult to handle. The composition which contains 8% hydroxyapatite was chosen as the optimum composition in respect of mechanical properties with 102.62&deg / C curing temperature. In order to decrease the curing temperature ammonium nitrate this gives endothermic reactions with water, was added into the formulations. Addition of 0.5 g NH4NO3 decreased curing temperature from 94&deg / C to 79.3&deg / C while compressive strength kept in acceptable range with 95.99 MPa. Experiments demonstrated that the proposed formulation is acceptable for workability, homogeneity, mechanical strength and thermal properties. Further studies especially on curing temperature and biocompatibility should be achieved.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2018-01-23T13:48:58Z No. of bitstreams: 1 ErikDosSantosSilva_TESE.pdf: 6543895 bytes, checksum: 29c9b0e4741aa669a76be6f191b18cf7 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2018-01-24T14:05:43Z (GMT) No. of bitstreams: 1 ErikDosSantosSilva_TESE.pdf: 6543895 bytes, checksum: 29c9b0e4741aa669a76be6f191b18cf7 (MD5) / Made available in DSpace on 2018-01-24T14:05:43Z (GMT). No. of bitstreams: 1 ErikDosSantosSilva_TESE.pdf: 6543895 bytes, checksum: 29c9b0e4741aa669a76be6f191b18cf7 (MD5) Previous issue date: 2017-08-30 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / A pesquisa em nanocomp?sitos de pol?meros e s?lica tornou-se foco de muitos pesquisadores nos ?ltimos anos devido ?s excelentes propriedades apresentadas quando comparadas aos componentes individuais. Neste trabalho foi realizado um tratamento de modifica??o superficial da s?lica com 3-aminopropiltriet?xisilano (APTES) para incorpora??o na blenda poli(metacrilato de metila)/poli(estireno-co-acrilonitrila) (PMMA/SAN) por meio de processamento em extrusora dupla rosca. Foi avaliado o efeito da adi??o de nanopart?culas de s?lica com e sem modifica??o superficial na estrutura e propriedades da blenda PMMA/SAN, com objetivo de promover melhores propriedades mec?nicas, sem comprometer a transpar?ncia dos materiais produzidos. Os materiais foram caracterizados por medidas de ?ndice de fluidez (MFI), ensaios mec?nicos de tra??o uniaxial, flex?o em 3 pontos, dureza Rockwell M (HRM) e Shore D, impacto Izod, reometria de placas paralelas, microscopia eletr?nica de transmiss?o (MET), ensaios de abras?o e risco. Os resultados reol?gicos indicaram que houve rea??o entre as nanopart?culas de s?lica tratadas com os pol?meros puros e com a blenda PMMA/SAN, mostrando-se uma t?cnica ?til para avaliar poss?veis rea??es durante o processo de extrus?o. Os nanocomp?sitos apresentaram um decr?scimo nas propriedades de resist?ncia m?xima ? tra??o, resist?ncia ao impacto e alongamento na ruptura, se comparado a blenda PMMA/SAN, que apresentou sinergismo nas propriedades de resist?ncia m?xima ? tra??o e alongamento na ruptura. Entretanto, as propriedades dos nanocomp?sitos com nanopart?culas de s?lica modificadas foram superiores aos nanocomp?sitos sem tratamento. A adi??o de s?lica tratada promoveu um aumento no m?dulo de elasticidade, dureza, abras?o e risco dos nanocomp?sitos produzidos. / Research on nanocomposites of polymers and silica has become the focus of many researchers in recent years because of the excellent properties presented when compared to individual components. In this work a surface modification treatment of silica with 3-aminopropyltriethoxysilane (APTES) was carried out for incorporation in the poly(methyl methacrylate)/poly(styrene-co-acrylonitrile) (PMMA/SAN) blend by processing in a twin screw extruder. The effect of the addition of silica nanoparticles with and without surface modification on the structure and properties of the PMMA/SAN blend was evaluated, aiming to promote better mechanical properties without compromising the transparency of the materials produced. The materials were characterized by flow index measures (MFI), mechanical tests of uniaxial traction, 3-point flexure, Rockwell M hardness (HRM) and Shore D, Izod impact, parallel plate rheometry, transmission electron microscopy (TEM), abrasion and scratch tests. The rheological results indicated that there was a reaction between the silica nanoparticles treated with the pure polymers and with the PMMA/SAN blend, showing a useful technique to evaluate possible reactions during the extrusion process. The nanocomposites showed a decrease in the properties of maximum tensile strength, impact strength and elongation at break when compared to PMMA/SAN blends, which showed synergism in the properties of maximum tensile strength and elongation at break. However, the properties of the nanocomposites with modified silica nanoparticles were superior to the nanocomposites without treatment. The addition of treated silica promoted an increase in the modulus of elasticity, hardness, abrasion and scratch of the nanocomposites produced.