Nanoscale surfaces were examined in order to determine the influence of surface curvature on polymer behavior at polymer-ceramic interfaces, as well as the influence of nanoparticles in cellulosic media. Poly(methyl methacrylate) and block copolymers thereof were adsorbed onto porous alumina substrates of various pore sizes in order to determine how polymer and copolymer adsorption behavior at nanoscale surfaces differs from adsorption onto flat surfaces. It was determined that chain density on concave surfaces dramatically decreases as curvature increases in much the same way that it does on convex surfaces (e.g. on the surface of nanoparticles), and physical models are provided to explain this similarity. Diblock copolymer adsorption is observed to vary dramatically with solvent quality and block asymmetry and can be correlated with the surface curvature very similarly to the adsorptive behavior of homopolymers on those same surfaces. The addition of nanoparticles to cellulosic media was investigated as a means to significantly modify the properties of cellulosic composites with minimal additions of nanoparticles. Although cellulose is among the most abundant polymers on earth, its primary uses are limited to bulk commodity goods, such as paper and textiles. This work demonstrates a simple means to control cellulosic fluid viscosity, thereby increasing the versatility of these biopolymers in additional applications with higher value-added potential. The formation of iron-cellulosic nanocomposites by the in-situ thermolysis of metal carbonyls to form metallic nanoparticles was performed and was analyzed by viscometry among other techniques. It was determined that the nanocomposites that were formed exhibited significantly increased viscosity, up to the point of gelation. Additionally, an introduction to the expansive field of nanocomposites is provided, including how and why composite properties change abruptly as filler size approaches the nanoscale. An extensive background on this diverse field as it relates to the current work is provided with an emphasis on cellulosic nanocomposites and the dependence of curvature on polymer-surface interactions. A detailed account of the experimental work relevant to this work is provided, including materials and characterization methods. Future work is proposed for both cellulosic nanocomposites as well as for curvature-dependent polymer adsorption. Finally, conclusions are drawn from the entire work and its implications to the greater field of nanocomposites.

The discovery of RNA interference and the increasing understanding of disease genetics have created a new class of potential therapeutics based on oligonucleotides. This therapeutic class includes antisense molecules, small interfering RNA (siRNA), and microRNA modulators such as antagomirs (antisense directed against microRNA) and microRNA mimics, all of which function by altering gene expression at the translational level. While these molecules have the promise of treating a host of diseases from neurological disorders to cancer, a major hurdle is their inability to enter cells on their own, where they may render therapeutic effect. Nanotechnology is the engineering of materials at the nanometer scale and has gained significant interest for nucleic acid delivery due to its biologically relevant length-scale and amenability to multifunctionality. While a number of nanoparticle vehicles have shown promise for oligonucleotide delivery, there remains a lack of understanding of how nanoparticle coating and size affect these delivery processes. This dissertation seeks to elucidate some of these factors by evaluating oligonucleotide delivery efficiencies of a panel of iron oxide nanoparticles with varying cationic coatings and sizes. A panel of uniformly-sized nanoparticles was prepared with surface coatings comprised of various amine groups representing high and low pKas. A separate panel of nanoparticles with sizes of 40, 80, 150, and 200 nm but with the same cationic coating was also prepared. Results indicated that both nanoparticle surface coating and nanoparticle hydrodynamic size affect transfection efficiency. Specific particle coatings and sizes were identified that gave superior performance. The intracellular fate of iron oxide nanoparticles was also tracked by electron microscopy and suggests that they function via the proton sponge effect. The research presented in this dissertation may aid in the rational design of improved nanoparticle delivery vectors for nucleic acid-based therapy.

Packed beds find extensive application in a wide variety of industries to cany out a large number of diverse processes. The main objective of the present work is to develop models to predict the arrangement of particles and based on them, to determine and evaluate the structural characteristics of packed beds. These problems have received only a limited attention in the literature. As a first attempt, spheres of uniform size are considered. Beds of aspect ratio up to 2 (referred to as low aspect ratio beds) are analyzed by application of principles of analytical geometry. Expressions are derived for the location of particles and for the structural characteristics of the beds, both of which show periodicity. This leads to the concept of a unit cell which is the repetitive section of the bed whose characteristics are the same as those of the complete bed. The beds fall into three distinct groups — those with aspect ratio between 1 and l√3⁄2, between 1√3⁄2 and 2, and with aspect ratio 2. Equations are distinct for each group. The aspect ratio shows marked influence on the structural characteristics of the beds. Agreement of the predictions on the overall void fraction with the available experimental data is excellent. Radial void fraction profiles are estimated by defining a concentric cylindrical channel (CCC) of an arbitrary thickness and with the cylindrical surface through the radial position of interest located at the middle of the CCC, and by accounting for the solid volumes of all the segments (in this CCC) of spheres with centers lying within a distance of a particle radius on either side of the cylindrical surface. The curved boundaries of the sphere segments are rigorously accounted for. The results show that the entire bed is filled with variations in the void fraction, starting from a value of unity at the wall and zero (or close to zero) towards the axis of the bed. Monte Carlo model for the simulation of high aspect ratio beds has not proved successful even with any of a wide variety of distribution functions for the coordinates of the sphere dropping point. With uniform distribution, the only distribution used in all the reports so far, and with normal distribution, there is not even a qualitative agreement with the reported data on void fraction variations. Distributions with asymmetric density functions such as exponential, Weibull, gamma and beta, show considerable improvement; beta distribution being the best. However even the best results with beta distribution show satisfactory agreement with the experimental data only up to about 2dp from the wall. Simulations with the cluster growth model, modified to account for the confining nature of the wall, lead to more satisfactory results. The proposed algorithm consists of building up the cluster, sphere by sphere, by calculating all possible interior and wall sites for placing an incoming sphere in a stable and non-overlapping position on the current cluster. A preference parameter is defined to place the new sphere at locations along the cross section of the column at which the experimental void fraction profiles show prominent minima, that is, locations around which the bed has relatively high solid volume. Void fraction profiles in beds of various aspect ratios simulated by this model show good agreement with the corresponding experimental data. The structural characteristics of the high aspect ratio beds thus simulated are evaluated. The number of spheres per unit length, Ni is correlated with the aspect ratio. It becomes proportional to the square of the aspect ratio, with the proportionality constant being close to 0.9, for aspect ratios greater than about 10. This follows since in these beds the overall void fraction becomes constant at 0.4. Majority of the spheres have contacts (with neighboring spheres) between 4 and 7, with the lower and upper limits for the coordination number being 2 and 9. The radial profile of the average coordination number (averaged over the height of the bed at the given radial position) shows small oscillations about a mean value of about 6 over almost the entire bed cross section starting from a distance of about ldp from the wall. At a distance of 0.5dp from the wall the predominant number of contacts is four while the mean value is about 4.3. The overall coordination number (averaged over the entire bed) shows inverse dependence on the aspect ratio. For random packings, that is, as the aspect ratio becomes infinity, the overall coordination number tends to six which corresponds to regular cubic arrangement. Cumulative number fraction, CNf is a global measure of the arrangement of spheres in beds of high aspect ratio. Its radial variation shows four distinct regions whose locations are independent of the aspect ratio The CNf values in each region are correlated with aspect ratio The correlations combined with that of NL lead to a very useful and effective model for predicting void fraction profiles in a bed of any specified aspect ratio The validity of the predictive model is demonstrated

<p>The relationship between the amount and conformation of apolymer at the solid-liquid interface, and the resultinginteraction forces between two such surfaces has beeninvestigated. With a degree of control of the polymerconformation, by varying the temperature, solvent quality,polymer charge density etc, it has been possible to measure andinterpret the resulting changes in the surface interactions.The recurring themes of dynamics and hydrodynamics have beencontinually considered due to the large range and viscoelasticnature of the polymeric systems.</p><p>The polymeric systems investigated in this thesis are, poly(N-isopropylacrylamide), poly (12-hydroxystearate) and a seriesof AM-MAPTAC polyelectrolytes with variable chargedensities.</p><p>Adsorption and conformation of polymers have beeninvestigated by the novel QCM instrument. By comparison tosimultaneously measured energy loss information, a greaterunderstanding of the conformation of the polymer has beengained, both as a function of layer build-up during initialadsorption, and as a result of induced conformational changes.Comparing the results to<i>in situ</i>surface plasmon resonance and subsequent x-rayphotoelectron spectroscopy measurements, the relativeconcentration of polymer within the layer is determined. Inaddition, efforts have been made to extend the scope of thetechnique, in such ways as measuring with QCM as a function oftemperature and deriving viscoelastic properties. The later isstill to be achieved in absolute terms for polymer layers inliquid environments, yet both the principle and experimentalcapabilities have been shown.</p><p>Normal interaction forces have been measured as a functionof solvation of the polymer layer, for both adsorbed andgrafted polymer layers. For fully solvated (steric) polymerlayers, which can act as colloidal stabilisers, the dynamics ofthe repulsive force, including hydrodynamics have beeninvestigated. The same has been achieved for collapsed polymerlayers, in which the dynamic adhesion has also beeninvestigated. The effect on the adhesion of three differentdynamic mechanisms has been determined (which, like the surfaceforces, depend on the polymer conformation andviscoelasticity). These dynamic mechanisms are based onbridging forces, polymer entanglement and a viscoelastic‘bulk’response from the surface layers.</p><p>Lateral or friction measurements have also been completed.The effect of load and rate have been investigated as afunction of both the polymer charge density and the underlyingsubstrate, which result in a variable conformation and bindingstrength to the substrate. This has resulted in a complexaddition of numerous mechanisms, the dominant mechanism beingdetermined by the binding strength to the surface, polymerconformation and viscoelasticity. The results have shown thatadsorbed polymer layers can be used to both increase anddecrease friction, and to change the direction of the ratedependence.</p>

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 66-69). Also available on the World Wide Web.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

This dissertation involved a theoretical and experimental investigation of the adhesive forces between spherical particles of four different diameters and two selected flooring materials under different air velocities. Previous theoretical work and experiments described in the literature tended to be conducted with idealized surfaces, and therefore have limited applicability to indoor environments. Controlled experiments were designed, constructed and executed to measure the air velocity required to overcome adhesion forces. The diameters of the particles investigated were 0.5, 3.0, 5.0 and 9.9 [mu]m, and the flooring materials were linoleum and wooden flooring. The critical velocity, the flow at which 50% of the particles detached, is presented as a function of particle diameter for each surface. The measured values were then compared to empirical and theoretical models as well as to a scaling analysis that considers component forces that act on a particle-surface system. The results suggest that critical velocity decreases with increasing particle diameter and that existing models have limited applicability to resuspension from flooring materials. / text