Master of Science (MS), Wright State University, 2007, Chemistry

Michael Simons. M.S., Department of Chemistry, Wright State University, 2007. Hydrophobically Modified Polyethyleneimines and Ethoxylated Polyethyleneimines. The modification of the commercially available polymers polyethyleneimines and ethoxylated polyethyleneimines took place with approximately a 3-10% alkylbromide modification followed by, in the case of the polyethyleneimines, a 2-hydroxypropyl modification, using propylene oxide, on the order of 65-70%. The objective was to increase the hydrophobicity of the polymer while keeping the cloud point above 60°C. Another approach taken was to form hydrophobic ethers from ethoxylated polyethyleneimine. We also added a 2-hydroxy ethyl group to a hexylated polyethyleneimine avoiding the use of ethylene oxide or drying EPI.

Committee: Eric Fossum (Advisor) Subjects: Chemistry, Polymer

PhD, University of Cincinnati, 2001, Arts and Sciences : Chemistry

Simulation of Crystallization in Random Ethylene/1-Hexene Copolymers Random ethylene/1-hexene copolymer chains were generated via Monte Carlo simulations. The comonomer distributions of the simulated chains and melting temperatures of real chains were used to compute the core crystallite thickness. Computed values of the core crystallite thickness matched values calculated from Raman Longitudinal Acoustic Mode (LAM) spectroscopy for some compositions; some computed and experimental values differed widely, presumably due to entanglements and high melt viscosity. Synthesis and Computer Simulation of Polydimethylsiloxane Networks Vinyl-terminated polydimethylsiloxysilane (PDMS) was endlinked with silanes having functionalities of 3, 4 and 40 - 50. SiH consumption was monitored before and after the gel point via Fourier-transform infrared spectroscopy (FTIR). Size exclusion chromatography (SEC) was used to determine the molecular weights of pre- and post-gel point sols. Gel samples were swollen in toluene so that cycle rank, the proportion of intramolecular bonds, could be estimated. Experimental values of sol molecular weight, gel mass fraction and cycle rank were compared to simulation results from MSI Polymer network modeling software. The experimental and simulation results showed that the gel point extent of reaction and gel point sol molecular weight are inversely proportional to the crosslinker functionality. Computed and experimental values of sol molecular weight were close to one another up to the gel point; after the gel point, the simulation values were slightly lower because the software does not account for entanglements and viscosity. The software also underestimated the gel weight fraction. This discrepancy may be partly due to the software's inability to account for entanglement of cyclic compounds which are not covalently attached to the network. Silicone Seal Compatibility with Organic Acid and Conventional Coolant Formulations Filled and unfille (open full item for complete abstract)

Committee: James Mark (Advisor) Subjects: Chemistry, Polymer

MS, University of Cincinnati, 2007, Arts and Sciences : Chemistry

A proposal was made that the effects of copper phthalocyanine pigment, known for its nucleating ability on polypropylene crystallization, should be different for the alpha and beta crystal phase and particle size differences. Crystallization effects of alpha phase and beta phase copper phthalocyanine pigment (alpha-CuPc and beta-CuPc respectively) on polypropylene were investigated using differential scanning colorimetry (DSC) and wide angle x-ray diffraction (WAXD). This study indicated that the pigment-polymer epitaxial relationship was the same for both pigments whereas their effects on the crystallization temperatures and crystallization rates differed. Both pigments equally influenced the b-axial spherulitic growth relative to the a-axis as indicated by peak intensity ratio reduction of the (110) to the (040) diffraction planes. The onset crystallization temperatures and temperatures at maximum heat-flow of the pigmented polypropylene samples were both higher than that of the unpigmented polypropylene control. The polypropylene containing the alpha-CuPc showed a 17C higher temperature at maximum heat-flow and a 50% increase in crystallization rate. The polypropylene containing the beta-CuPc showed a 10C higher temperature at maximum heat-flow and a 17% increase in crystallization rate. Consequently, the alpha-CuPc in this study was a more efficient nucleator than the beta-CuPc. It is presumed that this was due to the smaller particle size of the alpha-CuPc rather than the crystal phase. The effect on the epitaxial relationship appears to be the same for both pigment types.

Committee: Dr. James Mark (Advisor) Subjects: Chemistry, Polymer

PhD, University of Cincinnati, 2006, Arts and Sciences : Chemistry

The purpose of this study is to use the layer-by-layer assembly (LbL) method to investigate the incorporation of ultra-thin insulating films into organic electronic device architectures and to improve the understanding of structure-property relationships as applied to how nanoscale architecture affects device performance. Initially, reflective Fourier transform infrared (FT-IR) spectroscopy is used to quantify the degree of cross-linking in poly(allylamine hydrochloride)/poly(acrylic acid) (PAH/PAA) polyelectrolyte multilayers with a change in their intrinsic ionic interaction (solution pH) and an increase in post-deposition heat-treatment temperature. The breakdown strength of these dielectric films is then analyzed as a function of their degree of cross-linking, layer morphology, and film thickness to determine their applicability for use in metallized polymer film capacitors. Similar efforts are then directed toward the incorporation of these dielectric layers into both semi-conducting and doped organic thin film transistors (TFTs). While a field effect is observed when using a semi-conducting active layer, an electrochemical effect involving water is responsible for a change in the conductivity of the active layer in doped organic TFTs (PEDOT:PSS secondary doped with ethylene glycol). Similar observations are also apparent when using a standard (less conductive) active layer, whether it is deposited by spin-coating or with LbL assembly, but their response upon exposure to different environments is unique.

Committee: Dr. Anna Gudmundsdottir (Advisor) Subjects: Chemistry, Polymer

MS, University of Cincinnati, 2005, Arts and Sciences : Chemistry

Polymer nanocomposites were successfully prepared by various methods, such as (i) in-situ silica formed in trans-1, 4 polybutadiene (tPBD) networks using a two-step sol-gel technique, (ii) polyaniline (PANI) prepared in end-linked poly(dimethylsiloxane) (PDMS) networks using an inverse emulsion polymerization, and (iii) polyisobutylene/Ti/silica, poly(ethyl oxide)/expanded graphite and PDMS/expanded graphite electrically conducting composites using mechanical blending. Structures of the polymer matrix were controlled by adjusting the degree of cross linking or the number average molecular weight. The dispersion of particles was confirmed by UV/Vis spectrophotometry, Fourier transform infrared spectrometry, wide-angle X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. Stress-strain measurements in continuous extension indicated good reinforcement, even at relatively low amounts of fillers. Thermal properties were analyzed by differential scanning calorimetry and thermogravimetric analysis. The content, particle sizes and degrees of dispersion of the nano particles were studied with regard to the pore dimensions of the polymer networks or the differences in polymer chain length as the results of different number average molecular weight. The correlation between properties and structure of polymer nanocomposites was evaluated, and possible reaction mechanisms were proposed.

Committee: Dr. James Mark (Advisor) Subjects: Chemistry, Polymer

MS, University of Cincinnati, 2004, Arts and Sciences : Chemistry

The purpose of this study was to decrease chemical permeation of model compounds through calcium alginate film by adding small amounts of Montmorillonite (MMT) clay. In order to ensure maximum effectiveness of the clay it is crucial for MMT to be sufficiently exfoliated. During exfoliation MMT platelets are separated, thus increasing surface area improving dispersion within the calcium alginate matrix. The extent of exfoliation was verified by Light scattering particle-sizing and X-ray diffraction. Sodium alginate polymer solutions were blended with 0 to10% pre-exfoliated MMT on a dry weight basis to investigate the effect MMT has on alginate permeability. The polymer blends were cast into thin films and dried. The sodium alginate films were crosslinked with calcium chloride solution forming the water insoluble calcium alginate. The MMT impregnated calcium alginate films were subjected to permeation study to determine model chemical permeation. A Hanson Research diffusion cell was used to study the model permeation of a chemical across the calcium alginate membranes. Ultraviolet (UV) absorbance was used to determine the concentration of the model chemical that crossed the alginate membrane. Benzaldehyde was used for the model chemical due to its high UV absorbance and favorable oil to water partition coefficient. Accumulated benzaldehyde concentrations were then used to calculate diffusion coefficients for benzaldehyde within each film. The results indicate exfoliated MMT addition decreased the permeability of calcium alginate polymer membranes. The data show that addition of 0.5% clay yields decreased permeation compared to nascent calcium alginate film by approximately 2.5X. MMT clay amounts above 3% show a complicated clay concentration dependence, but were generally smaller than those of a calcium alginate film with 0% clay.

Committee: Dr. James Mark (Advisor) Subjects: Chemistry, Polymer

PhD, University of Cincinnati, 2004, Arts and Sciences : Chemistry

The present study has developed a new method to prepare stable PDMS latexes suitable for spraying-coating drug tablets without the need for colloidal silica and organic tin catalyst. The approach taken consisted of preparing water-based emulsions of hydroxyl-terminated PDMS with sodium lauryl sulfate (SLS) as surfactant, and then cross linking on restriction of the pH of the system to the acidic range with HCl. Optimizing the coatings for drug-release applications requires a better understanding of their properties and thus clarification of the mechanism through which the cross-linking reaction takes place. The present study also approaches this goal by documenting the effects of anionic, cationic and nonionic surfactants at various concentrations, and in acidic, neutral, or basic media. Analytical methods were set up to monitor the transport of crosslinker from the water phase into the hydrophobic PDMS phase. A possible mechanism for the PDMS cross-linking reaction in emulsion without organic tin as catalyst has been developed. Additionally, to prepare coated tablets for controlled drug release studies, an economical and efficient lab-scale coating system has been developed. Furthermore, in-vitro evaluations were performed to study the effects of the amount of channeling agents, the addition of colloidal silica, and the pH of the dissolution media used. The study involved hydrochlorothiazide (as a marker drug) released from compressed tablets, which had been spray coated using PDMS latexes with various polyethylene glycols (PEG) loadings as channeling agents. The dissolution results showed that coated tablets containing up to 25% (w/w) PEG could have constant release rates. Higher amounts of PEG resulted in non-linear release patterns. Also, the addition of colloidal silica decreased the rates of drug release. Since the pH of dissolution media affected the structures of the exposed PDMS films, it had significant effects on the drug release behavior.

Committee: Dr. James Mark (Advisor) Subjects: Chemistry, Polymer

PhD, University of Cincinnati, 2003, Arts and Sciences : Chemistry

Poly(dimethylsiloxane) (PDMS) is a versatile silicone polymer studied very extensively for various applications. However, because of its mechanical weakness, it is filled with many different filler particles including SiO2, TiO2 and ZrO2. In the present research work, some specialty filler particles were generated by in-situ sol-gel method in PDMS networks. These composites were studied for their structure-property effects in relevance to their transparency, magnetic, electrical and mechanical properties. Structure-property and kinetic studies were performed on TiO2 and ZrO2 filled PDMS composites. Hydrolysis and condensation process was controlled by selecting alkoxides, with longer chain length and bulky side groups (titanium-2-ethyl hexoxide and zirconium butoxide). SAXS, SEM, Instron was used for characterizing these composites. Fe2O3 particles with different shapes and sizes were generated in-situ in PDMS networks using aqueous solutions of FeCl3 and HCl. Non-aqueous method and ferric acetylacetonate [Fe(acac)] however yielded higher amounts of filler. Magnetic and mechanical properties were studied using vibrating sampling magnetometer (VSM) and Instron respectively. Attenuated Total Reflectance (ATR), SEM and EDS. was used to determine the structure, shape and composition of the composite. Polyaniline (PANI) was generated in-situ from monomer aniline, by chemical oxidation in PDMS networks. The effects of temperature, dopant and oxidant were also studied. The structures of the PANIs were studied using ATR. Conductivity was measured using a four-point probe. Conductivity of this composite depends on the degree of oxidation and doping of the generated PANI. A novel approach along with a structure-property study for ZrO2 and TiO2 filled PDMS was performed. A small amount of a stannous compound mixed in alkoxide, dramatically reduced the time for particle generation. The composites were transparent, with ZrO2 filled having higher transparency than TiO2. SAXS data (open full item for complete abstract)

Committee: Dr. James E. Mark (Advisor) Subjects: Chemistry, Polymer

PhD, University of Cincinnati, 2002, Engineering : Materials Science

Systems with a hierarchical structure (henceforth referred to as complex systems) are ubiquitous in soft matter science. In many cases, scattering techniques have been used to unravel the structure of these complex systems and in turn have provided an understanding of some unique properties of these materials. Small Angle Neutron Scattering (SANS) is one such scattering technique and has been widely used in the study of polymeric materials due to a rare confluence of certain properties of both the radiation and polymeric systems, as further explained in the text. Two systems of significant scientific and technological importance which satisfy the aforementioned criterion for complexity are 1) the structure of equilibrium swollen polymer networks and 2) the structure of self-associating triblock copolymers in solution and the effect of anions on the structure. 1) A model to describe the different levels of structure exhibited in polymer networks swollen to equilibrium is described. The characteristic SANS pattern is attributed to stressed regions associated with the quenched topological constraints in the network. The model generalizes the idea of Pincus blobs, originally introduced to explain the behavior of a linear polymer chain obeying self avoiding walk statistics under tension, to non linear structural elements. Two characteristic lengths are identified, a gel tensile blob size and an extended structure length. Predictions are made relating these size scales to the system parameters. These predictions have been tested using SANS measurements. 2) Neutron scattering measurements were made on a triblock copolymer in solution as a function of temperature and concentration of several potassium salts. The self assembled aggregates of these triblock copolymers exhibit rich polymorphism, with the structure varying from spherical to cylindrical and finally the solution undergoing phase separation with an increase in temperature and/or salt concentration. The critical mi (open full item for complete abstract)

Committee: Dr. Gregory Beaucage (Advisor) Subjects: Chemistry, Polymer

PhD, University of Cincinnati, 2002, Arts and Sciences : Chemistry

This work focused on examining the structure – property relationships of filled and unfilled elastomers and plastics. Some of the factors that influence the final properties of these systems are: molecular weight, % isotactic pentad content, shape and structure of the filler particles, surface modification of the filler particles, polymer – filler interaction, particle size, pore size, surface area, etc. The five parts in this dissertation are as follows: Chapter 1: Thermal and mechanical tests of thermoplastic elastomeric polypropylenes (EPP) prepared by the metallocene catalysts showed that they were multiphase, tough elastomeric materials. The moduli and strengths of the unfilled EPPs increased with increase in % isotactic pentad content and increase in molecular weight. Preliminary tests on filled EPPs showed that layered silicates (clays) gave better reinforcement than silica fillers because of the higher aspect ratio of the former. Chapter 2: The mechanical properties of poly (methyl acrylate) composites prepared by using a silane coupling agent designed to suppress the bonding between the silica and the elastomeric matrix were much poorer than those of the corresponding composite having a silane giving strong interfacial bonding, and thus documenting the effects of these interactions on the reinforcement of a typical elastomeric material. Chapter 3: The polystyrene/Vycor blends and pseudo interpenetrating polymer networks (PIPN) did not exhibit any reinforcing ability due to the large particle size of the Vycor filler. The PS/zeolite PIPNs showed reinforcement whereas the PS/zeolite blends did not. The PIPN samples gave larger tensile strength values relative to the corresponding blends. This could possibly be due to increased interfacial interactions in the PIPNs. Chapter 4: Poly(dimethylsiloxane) (PDMS) composites, reinforced by in situ silica precipitation, were prepared by a two – step process. Ultraviolet/visible spectroscopy was used to make quantitativ (open full item for complete abstract)

Committee: Dr. James E. Mark (Advisor) Subjects: Chemistry, Polymer

PhD, University of Cincinnati, 2001, Arts and Sciences : Chemistry

This work focused on examining and characterizing the reinforcement of thermoset and thermoplastic elastomers, such as natural rubber, epoxidized natural rubber and elastomeric polypropylene. The reinforcement was achieved through the formation of composites of these elastomers with reinforcing fillers by applying some of the latest techniques. One of the techniques is the combination of elastomeric materials with thermosetting resins, specifically natural rubber and cardanol-formaldehyde resins, to improve mechanical properties, such as toughness and thermal properties, such as high-temperature resistance. The natural product cashew nut shell liquid was used to obtain the cardanol, which was then used to prepare cardanol-formaldehyde (CF) resole and novolak resins. The curing behavior of systems containing natural rubber and cardanol-formaldehyde resins was established. The incorporation of cardanol-formaldehyde resins into natural rubber provided significant improvements in tensile strength, while maintaining the thermal stability of the elastomer. Various nanocomposites of epoxidized natural rubber, cis-1,4 polyisoprene and elastomeric polypropylene were successfully prepared by using montmorillonite clays as a reinforcing filler. Conditions were established for dispersing clay nanolayers into these elastomers. The clay filler-elastomer and clay filler-filler interactions were studied by using dynamic mechanical analysis. Such interactions were found to strongly depend on the clay organic modifiers and the polarity of the elastomers was found to have a major effect on the final properties of these nanocomposites. The dispersion of clay fillers into the elastomer matrix was examined by X-ray diffraction techniques. Mechanical property measurements showed that several organo-clays provided very strong reinforcing effects. For non-polar elastomers, organo-modified clays were found to behave more like "carbon black". For polar elastomers, the intercalation of the ela (open full item for complete abstract)

Committee: Dr. James E. Mark (Advisor) Subjects: Chemistry, Polymer

Doctor of Philosophy, The Ohio State University, 2008, Chemistry

Single-site metal alkoxides are used to catalyze the controlled ring-opening polymerization (ROP) of lactides and other cyclic esters. In this study, a new trispyrazolylborate ligand, Tp*, containing a 3-substituted pyrazole with ─CMe2CH2OMe group has been synthesized. By synthesizing this new ligand we aimed that this ligand can form a pocket around Ca2+ in order to protect the metal center against ligand scrambling, transesterification, or deactivation by impurities, such as water. First, the synthesis of 3-(2-methoxy-1,1-dimethylethyl)pyrazole, pz*H is described together with its reactions with the borohydrides MBH4, where M = Li, Na, and K, under melt conditions. At 180°C, this procedure leads to a mixture of products for M = Li, and at higher temperatures, a derivative LiTp'pz*H is isolated, wherein a B-H bond and a methyl group have been eliminated and a B-O bond has been formed. For M = Na, the reaction proceeds to give NaTp* but at higher temperatures NaB(pz*)4 is obtained. The reactions involving KBH4 and pz*H yield the dinuclear complex K2(Tp*)2pz*H. The reaction between NaTp* and TlOAc in dichloromethane at room temperature gives TlTp* along with NaOAc. TlTp* reacts with methyllitium in diethylether to give LiTp* and thallium metal, and, similarly, TlTp*and KH react in THF to give KTp* and Tl(0). In addition, the heavier alkaline earth metal iodides (Tp*MI where M = Ca, Sr and Ba) were synthesized by using TlTp* and the corresponding metal diiodide, MI2 in THF. However, Tp*MgI and Tp*ZnI were obtained from the reaction of MI2 and NaTp* in THF and dichloromethane, respectively. The reaction between Ca[N(SiMe33)](THF)2 and TlTp*yieldsTp*Ca[N(SiMe3)]2-via [CaTp*]+{Ca[N(SiMe3)2)3]}-.-Heating-Tp*CaN(SiMe3)2-gives-CaTp*2-by disproportionation. Whereas MgTp*2 is prepared from MgBu2 and TlTp* in THF. Both CaTp*3 and MgTp*2 exist as salts in the solid state: [Tp*M]+[Tp*], but in solution the CaTp*3 undergoes dynamic Tp* exchange on the NMR time-scale. Slower liga (open full item for complete abstract)

Committee: Malcolm Chisholm (Advisor); James Cowan (Other); T. RajanBabu (Other) Subjects: Chemistry, General; Chemistry, General; Chemistry, Inorganic; Chemistry, Polymer

Doctor of Philosophy, The Ohio State University, 2006, Chemistry

End-free cyclic polymers are attracting considerable attention recently in both academic and industrial areas. Cyclic esters and cyclodepsipeptides, as analogues of naturally available ionopores, represent one important branch of such polymers. Herein, a series of polymer-supported metallated catalysts PS-C6H4CH2NHM, where M = –Li(LiBu)x (x~4), –MgMe and –ZnEt have been synthesized. The catalysts were applied in ring opening of lactide and 2,5-morpholinediones and the formation of oligo cyclic lactides (MeCHC(O)O)n (An) and oligo cyclodepsipeptides [MeCHC(O)OCHRC(NH)O]n (AB), where R = CH3, iPr, CH2iPr and PhCH2. For lactide, the reactivity of the catalysts follow the order of Li > Mg > Zn. Addition of NaBPh4 to a heated system containing cyclic polymers preferentially removes the 18-membered rings from solution. For lactide this is shown to form the basis for chemical amplification from a dynamic combinatorial library and lactide can be converted to A6 in > 80% yield. Epimerization resulted in optically inactive materials. Isomers of A6, including 6 pairs of enantiomers and 2 meso- isomers were isolated from their sodium-bound mixture A6NaBPh4 and characterized. For A6NaBPh4 with the isomer (SRSRSR)- A6, each molecule acts as a m,h3,h3-ligand by binding to two sodium cations with its three ketonic oxygens and each sodium atom is bound to two A6 molecules, thus forming infinite chains in the solid state. The 6S-A6 isomer was shown to form a salt (A6)2NaBPh4 where each A6 molecule acts as an c3–O donor. In the presence of NaBPh4 and 4-dimethylaminopyridine (DMAP), 6-membered cyclic esters [R1CHC(O)OR2CHC(O)O], where R1 = H, CH3, R2 = H, CH3 yield ring-chain equilibra to give sodium-bound 18-membered rings. The complex [CH2C(O)O]6NaBPh4·2CH3CN contains both m,h1,h1- and m,h3,h3-[CH2C(O)O]6 molecules that bridge sodium atoms and form infinite chains.

Committee: Malcolm Chisholm (Advisor) Subjects: Chemistry, Polymer

Doctor of Philosophy, Case Western Reserve University, 2008, Macromolecular Science

In this dissertation, a systematic investigation of the chemical durability study of perfluorinated sulfonic acid (PFSA) ionomers for polymer electrolyte membrane fuel cell (PEMFC) was conducted. Low molecular weight model compounds with various structural characteristics were employed as analogs to different moieties that are present in the ionomers. Model compounds and ionomers were degraded by hydroxyl radicals, which are the attacking species present in a running fuel cell. The hydroxyl radicals were created by Fenton's reagents, ferrous ion and hydrogen peroxide, or by direct UV photolysis of hydrogen peroxide. Fluoride release was measured and considered to be the measurement of chemical degradation of model compounds and ionomers. Degradation products from model compound systems and ionomer systems were identified by liquid chromatography-mass spectrometry (LC-MS) and 19F nuclear magnetic resonance (NMR) experiments. Certain intermediate radical species that are present during the degradation were trapped by using stable radical solutions of 4-hydroxy-2,2,6,6-tetramethyl-piperidinooxy (4-hydroxy-TEMPO), followed by identification using LC-MS. The results from model compound systems revealed that: carboxylic acid groups are extremely labile toward the reaction with hydroxyl radicals, fluoroethers moieties can be cleaved by hydroxyl radicals, and the mechanistic steps involved in the ether cleavage reaction are proposed. The results from ionomer systems, i.e. commercial Nafion® ionomer and 3M ionomers, showed good agreement with the conclusions reached from model compound systems. After degradation, low molecular weight fragments formed through the side chain cleavage from the fluoroether branching points of ionomers were identified by LC-MS. The proton conductivity of various ionomers also decreased after degradation.

Committee: David Schiraldi (Advisor) Subjects: Chemistry, Polymer

Doctor of Philosophy, Case Western Reserve University, 2008, Macromolecular Science

A water soluble polyelectrolyte, PPDSA [poly( p-phenylene-2,5-disulfonic acid)], was synthesized using Ullmann coupling between DBBDSA (1,4-dibromo-2,5-benzenedisulfonic acid). For the design of PPDSA, two concepts were adopted: highly sulfonated and rigid rod liquid crystalline polymer. It has a high ionic exchange capacity, 8.46meq/g, and the positions of the sulfonic acids on its backbone were well controlled. Its solution properties were studied using viscosity, rheometric measurements, and optical polarizing microscopy. Due to the rigid rod structure, its reduced viscosities increased at low concentration under all conditions. PPDSA solutions showed shear rate dependent viscosity, and concentrated solutions were lyotropic with a typical nematic structure using crossed polarization. PPDSA 1H-NMR spectra had many overlapping peaks that were analyzed by deconvolution. The highest number average degree of polymerization was 142. But, 1H-NMR spectra are not fully understood due to the local organization in solution. However, 13C-NMR showed a linear para-coupled PPDSA structure with only three 13C resonances. PPDSA membrane properties were characterized as a function of temperature and relative humidity. Its water contents per acid group were about two water molecules more than that of Nafion between 15 and 75%RH at room temperature. DSC results showed that at least 8.45 H 2O per sulfonic acid were strongly bound in the polymer. The PPDSA hexagonally packed nematic liquid crystal polydomain structure with frozen-in free volume is a possible reason for the high water retention. This was suggested based on WAXD, 2D X-ray and dimensional changes. The inter-chain distance increased from ~8 to ~11A as humidity increased. The structure consists of nano-size channels lined with sulfonic acids. The free volume in the polymer was shown by the fact that the absorbed water had a density of about 1.23g/cc. Its conductivities were extremely high at low humidities, ~0.01 S/cm at 1 (open full item for complete abstract)

Committee: Morton Litt (Advisor) Subjects: Chemistry, Polymer

Doctor of Philosophy, Case Western Reserve University, 2008, Macromolecular Science

Polyelectrolyte multilayer formation is achieved by alternate adsorption of oppositely charged polymers in a layer-by-layer (LbL) fashion from dilute polyelectrolyte solutions. This dissertation examines the formation, growth, structure, and morphology of polyelectrolyte multilayers by utilizing molecular dynamics (MD) simulations and polyelectrolyte spin assembly (PSA) experiments employing a spin-coating radial flow. Application of multilayers as substrates for biomineralization of hydroxyapatite (HA) and silica is also examined. MD simulations of assembly of flexible polyelectrolytes into multilayers were performed at a charged planar surface from dilute polyelectrolyte solutions. These simulations show that multilayer growth proceeds through surface overcharging, chain intermixing, and a linear increase in polymer surface coverage at each deposition step. The strong electrostatic attraction between oppositely charged polyelectrolytes at each deposition step is a driving force behind the multilayer growth. Polymer surface coverage and multilayer structure are each strongly influenced by the charge fraction of polyelectrolytes, as well as the strength of electrostatic and short-range interactions. Experimental results from PSA elucidated the synergistic effect of the spin-speed and the solution ionic strength on the growth and morphology of multilayers. The growth rate and polymer surface coverage of multilayers shows a non-monotonic dependence on solution ionic strength, first increasing and then decreasing as the solution ionic strength is increased. This is a manifestation of two competing mechanisms responsible for multilayer formation in agreement with Flory-like theory of multilayer formation from polyelectrolyte solutions under flow. At low salt concentrations, the electrostatic interactions control the multilayer assembly process while, at high salt concentrations, the multilayer assembly it is dominated by shear flow. For applications of multilayers in bi (open full item for complete abstract)

Committee: Patrick Mather (Advisor) Subjects: Chemistry, Polymer

Doctor of Philosophy, Case Western Reserve University, 2007, Macromolecular Science

Polypropylene (PP) and polystyrene (PS) nanolayer films were prepared. The crystal structure of extremely thin PP layers confined between PS layers was studied. Changes in structure were observed as the PP layer thickness decreased to the nanoscale. A dispersion of isotactic polypropylene (PP) particles was produced by interfacial-driven breakup of PP nanolayers. Particle size analysis indicated that breakup of PP microlayers produced a bimodal particle size distribution. A population of submicron particles formed due to the Rayleigh instability, and a second population of large particles formed by relaxation. Breakup of 12 nm layers resulted in primarily submicron particles, which crystallized into smectic form by homogeneous nucleation at 40 degreeC. The fraction of PP as submicron particles dropped dramatically as the layer thickness increased to 40 nm. Fractionated crystallization gave rise to four crystallization exotherms at higher temperatures, which represented fractionated crystallization of the large micron-sized particles in the PP alpha form. The effect of a particulate nucleating agent on crystallization of polypropylene (PP) in particles was found to be vastly different the effect of a sorbitol nucleating agent. A new class of hierarchically structured polymer optical materials was demonstrated that possess an internal refractive index gradient. The structure of the polymer material is analogous to the layered structure found in biological optical materials. Any practical refractive index distribution can be achieved with this flexible technology within the refractive index range of available coextrudable optical materials. An important application demonstrated for these materials is the construction of a bio-inspired GRIN lens. Lenses with gradients in both the radial and axial directions were fabricated. Materials with gradients with delta n ~ 0.17 have been made and larger index ranges are possible. Experimentally, these lenses were shown to have th (open full item for complete abstract)

Committee: Anne Hiltner (Advisor) Subjects: Chemistry, Polymer

Doctor of Philosophy, Case Western Reserve University, 2005, Macromolecular Science

The use of metal-ligand binding as the driving force for the self-assembly polymerizations of a ditopic ligand offers a facile route to the preparation of organic/inorganic hybrid materials. Such metallo-supramolecular polymers potentially offer the functionality of the metal ion along with the processibility of a polymer. This thesis reports the preparation and investigation of a series of metallo-supramolecular polymers prepared from different (macro)monomer units, which consist of flexible alkyl and alkyl ether cores. Attached to either end of these flexible chains is the terdentate ligand 2,6-bis-(benzimidazolyl)-4-oxypyridine. Addition of a metal ion (e.g. Fe(II), Co(II), Zn(II) or Cd(II)), which can bind to the ligand in 1:2 ratio, to a solution of the (macro)monomer results in the self-assembly of linear supramolecular polymers. Viscosity studies demonstrate the formation of self-assembling aggregates and mechanically stable films can be obtained by solution casting these solutions. A series of studies (including DSC, DMA, TGA and WAXD) were carried out in order to examine the solid state properties of films. The metallo-supramolecular polymers which have large poly(tetrahydrofuran) cores form thermoplastic elastomeric films in which the ionic blocks and soft poly(tetrahydrofuran) segments are phase separated. It was also possible to prepare gel-like metallo-supramolecular polymers from one of the monomer units mixed with a lanthanoid metal (e.g. La(III), Eu(III)) and a transition metal ion (e.g. Co(II) or Zn(II)). Such materials show dramatic reversible responses to a variety of stimuli, including thermal, mechanical, chemical and light. The nature of the response can be controlled by the nature of the combination of transition metal ion and lanthanoid metal ion used. These metal-ligand studies influenced the development of ligand-containing cyclic precursors that could be functionalized for reversible cyclization using imine and metathesis chemistry. This l (open full item for complete abstract)

Committee: Stuart Rowan (Advisor) Subjects: Chemistry, Polymer

Doctor of Philosophy, Case Western Reserve University, 1995, Macromolecular Science

A method for the synthesis of 3,4-dihydro-3-pentafluorophenyl-2H-1,3-benzoxazine in a high yield derived from pentafluoroaniline is described. The synthesized compounds are characterized by Fourier-Transfer Infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (1H NMR), size exclusion chromatography (SEC) and normal-phase high performance liquid chromatography (HPLC), The synthesis of 3,4-dihydro-2H-3-pentafluorophenyl-1,3-benzoxazine by the condensation of pentafluoroaniline with formaldehyde and bisphenol-A is monitored in 1,4-dioxane solution at 75°C by attenuated total reflection Fourier transform infrared (ATR-FTIR) technique using a liquid cell. It is found that the pH value of the reaction medium is the controlling factor in term of the yield. A strongly acidic condition is necessary for the synthesis of similar compounds from other very weak amines having a pK a lower than 3. In the presence of trace amount of HCl, the synthesis of benzoxazine includes a two step reaction. The formation of 1,3,5-tripentafluorophenylperhydro-1,3,5-triazine are involved in the first step of the reaction, which can be completed almost immediately after the addition of acid. The reaction between the acid-promoted cleavage of the perhydrotriazine and derivative of b isphenol-A and formaldehyde is the rate limiting reaction. The methods to synthesize 3,4-dihydro-1,3-benzoxazine by thermal reaction of paraformaldehyde, phenol and amine in the absence of solvent are developed. The reaction of solventless synthesis of 3,4-dihydro-2H-3-(4-methyl)phenyl-1,3-benzoxazine has been monitored by means of normal phase HPLC, FTIR and proton NMR at different reaction temperature in a closed and an open system respectively. The thermal transitions involved in this heterogeneous system resulted from both physical phase changes and chemical reactions are described in detail by differential thermal analysis (DTA). The role of the decomposition of paraformaldehyde in the whol (open full item for complete abstract)

Committee: Hatsuo Ishida (Advisor) Subjects: Chemistry, Polymer

Doctor of Philosophy, Case Western Reserve University, 1994, Macromolecular Science

This triblock polymer adsorbed strongly on the biomaterial surfaces in the aqueous condition through the hydrophobic interaction between the hydrophobic surface and the hydrophobic segment in the triblock polymer. The adsorbed triblock polymer exhibited fairly stable and significant protein resistance on PE surfaces Blood compatibility is a major concern in the development of synthetic biomaterials since most synthetic polymers will induce thrombosis formation on their surfaces once contact with blood or tissue. The objective of this thesis is to develop surface modification procedures for existing biomaterials, that will specifically inhibit the surface induced thrombosis and extend the lifetime of blood-contacting biomedical implants and devices. Three approaches have been developed to prepare the nonthrombogenic interfaces for biomaterials and devices. The first approach involved the surface modification of biomaterials by radiofrequency plasma discharge. Two plasma polymer thin films (approx. 110 nm) were deposited on PE. Plasma polymer modified polyethylene surfaces exhibited significant water contact angle hysteresis and a much lower value of advancing water contact angle than that of unmodified polyethylene. Interfacial reduction of the plasma modified surfaces by an aqueous solution of sodium borohydride converted surface carbonyl groups into hydroxyl groups which served as active sites for further derivatization and heparin immobilization.

Committee: Roger Marchant (Advisor) Subjects: Chemistry, Polymer