Polymers

In spite of the vast research on polymer-based tissue regeneration, extensive studies to develop an elastic and cell-promoting polymer biomaterial are still ongoing. However, using a renewable resource and a simple, environment-friendly synthesis route to synthesize an elastic polymer has not been successfully achieved yet.
The objective of this work was to develop an elastic polymer for tissue engineering and drug delivery applications by using non-toxic, inexpensive and renewable monomers. A new nature-derived renewable material, xylitol, was used to synthesize an elastic polymer with the presence of a crosslinking agent, dodecanedioic acid. Here a simple melt condensation polymerization method was used to synthesize the poly(xylitoldodecanedioic acid)(PXDDA). The physicochemical and biological properties of the new PXDDA polymer were characterized. Fourier transform infrared (FTIR) confirmed the formation of ester bonding in the polymer structure, and thermal analysis demonstrated that the polymer was completely amorphous. The polymer shows high elasticity. Increasing the molar ratio of dodecanedioic acid resulted in higher hydrophobicity and lower glass transition temperature. Further, the polymer degradation and in vitro dye release studies revealed that the degradation and dye release from the polymer became slower when the amount of dodecanedioic acid in the composite increased.

The objective of this thesis is to develop a new experimental method to characterize
the diffusion of water in polymer resins, based on the evolution in the volume of water
droplets as a function of time. A finite element model is established to model the mass
transport of water droplet through evaporation and diffusion processes. Diffusivity of water
into polymer resins is then extracted by matching the volume variation of the simulated
water droplet to the experimental results. Capability of this method is demonstrated by
determining the diffusivity of water into void-free epoxy and epoxy samples with voids.
Diffusion coefficient value obtained from this method agrees with data from conventional
water immersion method. The significantly small scale of the water droplet (less than 10
microliter) allows rapid characterization of diffusivity in hours instead of months as
typically required by the conventional immersion method. The method developed here provides a useful tool for rapid and effective characterization of diffusivity of water in
polymer substrates and can be extended to other substances as well.

The association between cytotoxicity and cell cycle perturbation caused by cisplatin and two platinum (II) polyamines, containing a methotrexate or a 2-chloro-p-phenylenediamine component, was investigated in human ovarian carcinoma cells (CAOV3), murine Balb 3T3 fibroblasts and Chinese ovarian hamster cells by flow cytometric DNA/protein, DNA/RNA and DNA degradation assays. Continuous in vitro drug exposure caused a time- and dose-dependent suppression of growth. Flow cytometric analysis revealed a multiplicity of cytokinetic perturbations, the most important of which was Go/G1 depletion and S phase arrest. The latter correlated with inhibition of DNA synthesis and subsequent inhibition of RNA and protein synthesis. Prolonged S phase arrest concomitant with DNA degradation, followed by RNA and protein degradation, resulted in cell death via apoptosis. The platinum polymers appear to be effective in vitro chemotherapeutic agents. The study of cytokinetic perturbations is useful in determining the relative potency of antitumor drugs and in monitoring drug effectiveness during treatment.

Molecular architecture has been used to develop new materials with our knowledge of Bis(arylimino)isoindoline (BAII). Ni(BAII)2,\ Ni(NBAII)2 and Cu(NBAII)(OAc) complexes were prepared and studied using their Crystal packing diagrams and data in order to evaluate $\pi$-overlapping. It is believed that $\pi$-overlapping will occur in complexes with mono BAII substituted complexes and not di-substituted. The first steps have been made in the development of a polymeric BAII complex with the production of an oligomeric BAII (GBAII). The GBAII complex was analysis using a molecular device approach with the use of NMR instrumentation.

Poly(magnesium acrylate) and poly(zirconyl acrylate) have been formed by chelating the magnesium ion and the zirconyl ion onto poly(acrylic acid). The PAA is usually neutralized by addition of sodium hydroxide before the synthesis process. The structures and characterisitics of these polymers are studied by various analytical methods such as thermal analysis, elemental analysis, infrared spectroscopy, and mass spectroscopy. The formation of these polymers is verified and their structures are determined. In addition, a preliminary attempt was carried out to make an advanced structural ceramic from a mixture of poly(magnesium acrylate) and poly(zirconyl acrylate).

The synthesis of polymers which contain vanadocene in the polymer backbone is accomplished by interfacial condensation reactions with the appropriate diols, diacids, and diamines. Structural characterization is accomplished by using FTIR and HREI-MS spectroscopic methods. Weight average molecular weights were determined using light scattering photometry for products which are soluble. Molecular weights for the products vary from 3500 to 15,000 Daltons. The structural characterization results are consistent with the proposed structures.

Ruthenium-containing polymers derived from cis-dichloro-bis(2-2'-bipyridine) ruthenium and selected diamine-containing dyes have been synthesized. These polymeric products were characterized using FTIR, UV-Vis spectroscopy, light scattering photometry, and mass spectral analysis. Thermal degradation studies of these products are also presented.

Within solid-state chemistry, coordination polymers have gained interest for use in various applications such as sensing, catalysis, display technology, hydrogen storage, etc. The use of lanthanide ions in these materials provides a mean of exploring how structure may affect luminescence efficiency. In this study, the photophysics of several lanthanide benzenecarboxylates was studied. This data combined with data from other coordination polymers created in our lab indicate that the established guidelines for producing highly efficient materials may not correlate directly from solution to the solid state and that structure may also play a role.

An experimental investigation was undertaken to determine the effects of marine environmental exposure on the mechanical properties of vinylester resins (VE510A and VE8084) and carbon fiber/VE510A vinylester composites. The effect of carbon fiber sizing on the composite strengths was also examined. Neat resins were exposed to marine environments until moisture content reached a point of saturation after which they were tested in tension, compression and shear. Compared to the baseline dry specimens, specimens subjected to moisture showed overall increased ductility and a reduction in strength. Dry and moisture saturated composite specimens were tested in tension and compression in different orientations. Longitudinal specimens were tested in in-plane shear and interlaminar shear. Composites with F-sized carbon fibers displayed overall higher strength than those with G-sized fibers at both dry and moisture saturated conditions. An analysis of moisture absorption of the composites was performed which vii shows that the moisture up-take is dominated by the fiber/matrix region which absorbs up to 90% of the moisture. The composites experienced reduced strength after moisture absorption. The results revealed that the fiber sizing has stronger effect on the fiber/matrix interface dominated strengths than moisture up-take.

A dual inclusion strategy for textile polymers has been investigated to increase elastic energy storage capacity of fibers used in high velocity impact applications. Commercial fibers such as Spectra and Dyneema are made from ultra high molecular weight polyethylene (UHMWPE). Dynamic elastic energy of these fibers is still low therefore limiting their wholesale application without a secondary metallic or ceramic component. The idea in this investigation is to develop methodologies so that the elastic energy of polyethylene based fibers can be increased by several folds. This would allow manufacturing of an all-fabric system for high impact applications. The dual inclusion consists of a polymer phase and a nanoscale inorganic phase to polyethylene. The polymer phase was nylon-6 and the inorganic phase was carbon nanotubes (CNTs). Nylon-6 was blended as a minor phase into UHMWPE and was chosen because of its large fracture strain - almost one order higher than that of UHMWPE. On the other hand, CNTs with their very high strength, modulus, and aspect ratio, contributed to sharing of load and sliding of polymer interfaces as they aligned during extrusion and strain hardening processes. A solution spinning process was developed to produce UHMWPE filaments reinforced with CNTs and nylon-6. The procedure involved dispersing of CNTs into paraffin oil through sonication followed by dissolving polymers into paraffin-CNT solution using a homogenizer. The admixture was fed into a single screw extruder for melt mixing and extrusion through an orifice. The extrudate was rinsed via a hexane bath, stabilized through a heater, and then drawn into a filament winder with controlled stretching. In the next step, the as produced filaments were strain-hardened through repeated loading unloading cycles under tension.