The complexity of biological processes manifests itself in many ways, with the most notable being the high level of dynamical control they possess. For the full potential of biological mimicry to be unlocked, it is essential for the scientific community to partake in an exhaustive search to understand the governing dynamics behind these biological processes. In this vein, this work investigates the bulk conductivity behavior of sodium polystyrene sulfonate (NaPSS) as a function of polymer (Cp) and salt (Cs) concentrations. This was carried out in an attempt to understand the individual contributions from each of the conducting species of a polyelectrolyte solution (chain, counter-ions, and/or salt) to the bulk conductivity in its most simple aqueous environment. The translocation behavior of NaPSS through α-hemolysin protein pores was also investigated. We demonstrate how single molecules of NaPSS, varying over two orders of magnitude in the degree of polymerization, can be pulled in aqueous media by an externally applied electric field through the α-hemolysin channel embedded in a lipid bilayer. We propose a two-barrier free energy landscape for polyelectrolyte translocation through α-hemolysin protein pores. Based on the proposed energy landscape, a detailed mechanism behind the array of interactions between a charged polymer and the α-hemolysin protein pore is described. Although the experimental setup and the measurement protocol are identical to the original investigation involving DNA, this work demonstrates that synthetic polymer translocation displays many significant distinguishing features when compared to the behavior of DNA or RNA. We have also investigated the sculpting of synthetic nanopores for translocation of bottle-brush polyelectrolytes towards understanding the transport behavior of more complex chain architectures. The use of synthetic nanopores allows for the custom tailoring of pore diameter, allowing for the translocation properties for a variety of chain architectures to be studied.

The glass transition temperature, the equilibrium modulus, the relaxation behavior in the glass transition region, and the swelling behavior in mixed solvents of two structurally different model network systems, the PPG-DRF system and the PIP-HDI system, were studied. These materials are important since they mimic the behavior of the theoretically described "perfect networks" closely. A range in material properties was induced by introducing stoichiometric imbalances and different molecular weights of the network components in the system. Several theories for each aspect of the properties of these two systems were tested against the experiment. It can be concluded that the PPG-DRF system behaves as a copolymer, following from the glass transition temperature and relaxation, and the swelling behavior. The end group contribution was important for the glass transition temperature. The PIP-HDI system does not behave as a copolymer. The Constrained Chain model was applicable to the equilibrium modulus data for both systems. The trapped entanglement contribution was not explicitly relevant. The swelling in mixed solvents could only be explained when azeotropic behavior of the solvent mixture is assumed.

The study of molecules in restricted geometries is an important topic in the chemical sciences. Surfaces and ultra-thin films are examples of restricted geometries because they alter the structure of the molecules confined due to the presence of an air interface. The structural changes that occur in these restricted geometries directly influence the fields of adhesion, coatings, lithography, photography, printing, filtration, transport properties, surfactants, sensors, microelectronics, electrodes, biology, biological compatibility and membrane function. The structure of ultra-thin polyurethane films is studied to determine effect of the air-polymer interface on the degree of phase separation and the orientation of the hard segments in both the hard and soft domains. External reflection infrared spectroscopy studies show that as the film thickness is decreased, the degree of phase separation decreased and the hard segments oriented into the plane of the film in both domains. The phase separation process in ultra-thin polyurethane films are also studied. The added free volume of the air-polymer interface allows phase mixing to occur at a much lower temperature than in the bulk. The isothermal phase separation of the ultra-thin films is characterized by a much lower Avrami coefficient than the bulk. A simulation of the phase separation process shows that the decrease in the Avrami coefficients can be attributed to the small film thickness compared to the hard domain size, the hard segment concentration change over the course of the phase separation and the disk like shape of the growing domains. In addition, the overall degree of phase separation observed in the ultra-thin films is kinetically controlled due to the directional grow of the disk like hard domains which is limited not by the amount of isotropic phase, but by the film thickness. Finally, the structures of insoluble monolayers at the air-water interface are studied. The frequency and approximate S to P dichroic ratio are used to characterize the structure of H(CH$\sb2)\sb{18}$OH as a function of area per molecule. F(CF$\sb2)\sb{8}$(CH$\sb2)\sb2$OH and F(CF$\sb2)\sb{10}$(CH$\sb2)\sb2$OH are also studied at the air-water interface. In both cases, the C-H stretching region indicated that the water surface is covered by a monolayer however only the longer fluorinated chain gives consistently useful information in the C-F stretching region. This is attributed to changes in the structure of the shorter chain amphiphiles just after they are spread at the air-water interface that the longer chain molecules do not exhibit.

Reaction of poly(chlorotrifluoroethylene) (PCTFE) with trimethyl 4-lithioorthobutyrate and hydrolysis produces a surface containing carboxylic acids (PCTFE-CO$\sb2$H). The advancing water contact angle ($\Theta\sb{\rm A}$) varies from ${\sim56}\sp\circ$ at low pH to ${\sim30}\sp\circ$ at high pH. The receding water contact angle ($\Theta\sb{\rm R}$) is 0$\sp\circ$ at all pH values. PCTFE-CO2H could be reduced to the alcohol, creating a less hydrophilic surface $\rm (\Theta\sb{A}/\Theta\sb{R} = 62\sp\circ/22\sp\circ)$ or converted to the n-octyl ester, rendering a hydrophobic surface $\rm (\Theta\sb{A}/\Theta\sb{R} = 99\sp\circ/47\sp\circ).$ PCTFE reacts with acetaldehyde 3-lithiopropyl ethyl acetal at $-$78-$-$15$\sp\circ$C to introduce the acetal into the outer $\sim$30-1000 A of the surface (PCTFE-PEAA). Hydrolysis produces a hydrophilic $\rm (\Theta\sb{A}/\Theta\sb{R} = 67\sp\circ/17\sp\circ),$ alcohol-functionalized surface (PCTFE-OH) which was derivatized to prepare a series of linear hydrocarbon and fluorocarbon ester surfaces. Reactions with multifunctional reagents produced crosslinked surfaces. Gravimetric, XPS, ATR-IR and contact angles results are consistent with the proposed surface structures and high reaction yields. Water contact angles on the hydrocarbon ester surfaces range from 82$\sp\circ/46\sp\circ$ (acetate) to 108$\sp\circ/90\sp\circ$ (stearate), while those on the fluorocarbon esters range from 92$\sp\circ/51\sp\circ$ (trifluoroacetate) to 120$\sp\circ/69\sp\circ$ (perfluorodecanoate). Hexadecane contact angles and XPS results show that the stearate and perfluorodecanoate esters form ordered surfaces. Friction properties of these modified surfaces were also investigated. The effects of varying the ester chain length, crosslinking the surface and varying the modification depth were studied. Contrary to expectations, the perfluorinated surfaces exhibited greater friction than their hydrocarbon analogs. The results show that chemical interactions at the sliding interface have little influence on friction and that it is the deformation behavior of the polymer near the interface that dictates the magnitude of the energy losses. Mixed surfaces were prepared to study the effect of surface composition on wetting. Randomly mixed hydroxyl/hydrocarbon ester surfaces were prepared by kinetic control of the esterification of PCTFE-OH, while compositionally similar, patchy surfaces were prepared by kinetic control of the hydrolysis of PCTFE-Esters. Esterification of the alcohol groups in these two sets of mixed surfaces was utilized to prepare the corresponding hydrocarbon ester/fluorocarbon ester mixed surfaces. As expected, greater contact angle hysteresis was observed on the patchy surfaces.

This thesis describes the use of bisphenol a carbonate cyclic oligomers (BPACY) as novel building blocks for polymer blends. The objective of the initial phase of this research is to determine whether the thermodynamics of mixing are affected by changes in the topology of a mixture's components. The second phase of this research involves the in-situ polymerization of BPACY in miscible thermoplastic matrices. The thermodynamics of mixing have been shown to be quite sensitive to changes in the topology of blend components. Cyclic bisphenol a carbonate cyclic oligomers are miscible with a wider range of polystyrene molecular weights than are chemically equivalent linear oligomers. The Flory-Huggins mean field theory predicts the shape of phase boundaries quite well for linear polystyrene (PS) /linear polycarbonate (PC) blends as well as for linear polystyrene/cyclic polycarbonate blends. However, the interaction parameter was determined to be strongly dependent upon topology with $\rm\chi\sb{PS\sb{L}/PC\sb{C}}<\chi\sb{PS\sb{L}/PC\sb{L}}.$ This result has been explained in terms of a topological interaction unique to ring polymers which is expected to be quite general. The in-situ polymerization of BPACY/styrene-acrylonitrile copolymer (SAN) blends has been demonstrated to yield PC/SAN blends with morphologies unattainable via conventional melt blending. Extremely fine phase dispersion can be obtained by this method of blend preparation. The domain coarsening kinetics have been shown to be quite sensitive to the volume fraction of the dispersed phase. The "pinning" of domain coarsening, unique to polymer systems, can be attributed to the extreme barriers to diffusive coarsening mechanisms in these systems. Thus, phase coarsening is arrested when percolation ceases or domains no longer form local clusters. The dispersed phase size has been shown to have a dramatic effect on high stress deformation in systems where a brittle phase is dispersed in a more compliant ductile matrix. The increased ductility of blends with finer phase dispersions has been rationalized based on a lower tendency for smaller brittle phases to craze/crack in addition to the influence of complex local stress fields in heterogeneous materials.

The techniques of neutron and x-ray scattering have been used to study the morphology and crystallization behavior of polyethylene and blends of polyethylene. Synchrotron radiation was used to study the crystallization behavior of blends of high density polyethylene/ low density polyethylene (HDPE/LDPE) and linear low density/ low density polyethylene (LLDPE/LDPE). Simultaneous real time small and wide angle scattering from blends slowly cooled at (0.5$\sp\circ$C/min) seem to indicate that the lamellae are formed in bundles of primarily one component. For blends quickly cooled from the melt (quenched to 60$\sp\circ$C) on the other hand, the lamellae are randomly mixed together. HDPE/LDPE and LLDPE/LDPE blends show qualitatively the same crystallization behavior throughout the composition range except for 10%/90% LLDPE/LDPE. At this composition, extensive cocrystallization may be occurring in even slowly cooled samples. Small angle neutron and x-ray scattering was used to determine the location of the short chain branches in selectively deuterated LLDPE. Specially prepared LLDPE with the main chain deuterated was used in these experiments to provide contrast for neutron scattering. Despite density contributions to the neutron scattering from crystalline and amorphous regions, differences between the x-ray and neutron scattering suggest that the concentration of branches may be enhanced at the crystal- amorphous boundary. The extent of this branch-rich region was estimated to be about 30A. Lastly, the chain orientation of ultra high molecular weight PE (UHMWPE) was examined by small angle neutron scattering. A circularly averaging technique was applied in order to avoid sample alignment problems. Between extension ratios of 12 and 60, hot drawn (125$\sp\circ$C) gel crystallized UHMWPE does not show appreciable change in the perpendicular radius of gyration. However, changes in the asymptotic behavior of the scattering intensity from I $\sim$ q$\sp{-1.56}$ at 12x to I $\sim$ q$\sp{-1.2}$ at 60x indicate a change in geometry toward more rod like segments in the higher drawn material.

The effect of crosslinking on the phase stability and phase separation behavior of poly(vinyl methyl ether)/polystyrene semi-IPN was studied by light scattering. The cloud point temperature was measured as a function of degree of crosslinking and found to be constant within experimental precision. The result of this experiment was combined with a theoretical prediction of the phase diagram to determine conditions for the following experiment. Wide angle light scattering was used to quantitatively analyze the mechanism and dynamics of the thermally induced phase separation with respect to the crosslinking density and the thermal condition. An apparatus with a one dimensional diode array was used to simultaneously monitor a wide range of scattering angles. Analysis of the early stages of phase separation indicates that the spinodal temperature remained virtually constant whether or not crosslinks were present in the system. This was demonstrated to be consistent with theoretical prediction. However, the apparent diffusion coefficient decreased dramatically with the introduction of crosslinks thus the initial phase separation was slowed down significantly. The final scattering intensity was shown to decrease with increasing crosslinking density. The scattering vector dependence of the scattering intensity was negligible compared with its overall time dependence. A plateau region was observed for some of the scattering intensity data of the semi-IPN systems with respect to time. This indicates that the crosslinks restrict terminal phase contrast and not the size of phase.

Investigations focused on the lower critical solution temperature (LCST) exhibited by poly(N-isopropylacrylamide) (PNIPAAM) in aqueous solution. The perturbation of this transition by the addition of cosolutes and by copolymerization was examined through the application of microcalorimetry, fluorescence spectroscopy, surface tensiometry, and cloud point measurements. Cosolutes employed included polar solvents, inorganic salts, amphiphiles, and other macromolecules. Copolymerization incorporated very small amounts (less than 2 mol %) of fluorescent derivatives or N-hexadecylacrylamide (HDAM). The microcalorimetric method was established through analyzing endotherms observed upon heating various samples of PNIPAAM and other polymers that exhibit LCSTs in aqueous solution; comparisons were made with classical cloud point curves. The properties of ternary solutions were then determined. Substituting miscible polar solvents for water lead to the phenomenon of cononsolvency. Transitions present in water-methanol mixtures were quantitatively related to those found by Hirotsu in crosslinked gels of PNIPAAM. The effects of low concentrations of poly(vinyl methyl ether) (PVME) and polyacrylamide were briefly studied. The influence of PNIPAAM on the association of amphiphiles characterized by a wide range of head group and tail structures was measured. Changes in critical surfactant concentrations and bilayer transition endotherms were correlated with reciprocal effects on the LCST of PNIPAAM to establish a hierarchy of complexation strengths. Use of free probes was complemented by applying fluorescent amphiphiles and polymer-bound fluorophores. This last approach was applied not only as an environmental micropolarity sensor but also in nonradiative energy transfer experiments. Solutions of PNIPAAM/HDAM copolymers were concluded to be micellar via the above methods. Solubilization sites of probes were estimated based upon their sensitivity to the LCST. Adding amphiphiles and varying polymer concentration also aided in establishing a microheterogeneous state.

The structure and permeability of phosphatidylcholine bilayer membranes prepared in the presence of azobenzene and spirobenzopyran modified poly(methacrylic acid) and poly(2-ethylacrylic acid) were studied as a function of the isomeric state of the bound chromophores. Poly(methacrylic acid) modified with 10.4 mole% azobenzene units (PMAZ) and poly(2-ethylacryIic acid) modified with 4 mole% azobenzene units (PEAZ) were prepared by free radical polymerization of the corresponding acrylic acid with N-4-(phenylazo)phenyl methacrylamide. Poly(methacrylic acid) modified with 1.5 mole% spirobenzopyran units (PMSP) and poly(2-ethyIacryIic acid) modified with 5.2 mole% spirobenzopyran (PESP) units were prepared by first incorporating pendant nitrosalicylaldehyde units into the polymer with subsequent conversion to the spirobenzopyran units. Each of these polymers undergoes a transition from a collapsed coil to an expanded chain and this transition is unaffected by the conformation of the pendant chromophore. The ability of these polymers to associate with phosphatidylcholine bilayer membranes is dependent upon the nature of the chromophore. With PMAZ and PEAZ a greater extent of polymer-lipid association was detected when the azobenzene was in the trans conformation as compared to the cis azobenzene conformation. For PMSP and PESP greater association was detected when the chromophore was in the spiropyran conformation as compared to the merocyanine form. Larger extents of association were observed as broadening of the vesicle phase transition. The change in polymer-lipid association is attributed to the difference in polarity of the two forms of the chromophores. The permeability of the membranes could be sensitized to light only in the presence of PEAZ and PESP. With PEAZ the permeability of the membranes could be reversibly photomodulated.

The structural reorganization of vesicle membranes that occur due to a pH dependent complexation of the membranes with poly(2-ethylacrylic acid) (PEAA) was investigated. The kinetics of the reorganization were examined by monitoring the changes in the turbidity of vesicle suspensions that occurs during the reorganization. The response of the rate of reorganization to pH, temperature, and membrane composition was studied. It was found that the reorganization behaved similarly to the solubilization of phosphatidylcholine vesicle by apolipoproteins. Permeability changes accompanying the process were recorded by monitoring the fluorescence changes of vesicle suspensions containing a fluorescent marker. The rate of change in permeability was found to be fast relative to the rate of structural reorganization. PEAA was labeled with the dansyl chromophore. Fluorescence microscopy was used to visualize the interaction of the labeled polymer (DnsPEAA) with egg yolk phosphatidylcholine vesicles. Adsorption of DnsPEAA onto vesicle surfaces produced a concentration of fluorescence on the vesicles. Following acidification of these samples, vesicles reorganized into many smaller particles with a diffusion of fluorescence. The reorganization was sensitized to the presence of glucose by incorporating the enzyme, glucose oxidase, into vesicles suspensions containing PEAA. The rate of permeability increase of membranes could be controlled by adjusting the concentrations glucose, enzyme, oxygen and PEAA.