This research includes two topics. The first topic is prepared a series of poly(methyl methacrylate) (PMMA)-based copolymers through free radical copolymerizations of methyl methacrylate in the presence of the either 2 - vinyl - 4,6 -diamino - 1, 3, 5triazine(VDAT) or vinylbenzyl -thymine (VBT). Using 1H nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), we investigated the thermal properties and hydrogen-bonding interactions within blends of the two copolymers poly(2-vinyl-4,6-diamino-1,3,5-triazine-co-methyl methacrylate) (PVD AT-co-PMMA) and poly(vinylbenzylthymine-co-methyl methacrylate) (PVBT-co-PMMA). A large positive deviation in the behavior of the glass transition temperature determined by using the Kwei equation and DSC analyses indicated that strong multiple hydrogen-bonding interactions existed between the two copolymers. The FTIR and solid-state NMR spectroscopic analyses provided positive evidence for the presence of three hydrogen bonds between the diamino-1,3,5-triazine groups of PVDAT and thymine groups of PVBT. The second topic is synthesized a series of alkyne end-terminated poly(£^-Benzyl L-glutamate) (alkyne-PBLG), which was prepared by the ring-opening polymerization of the N-carboxyanhydride monomer of £^-Benzyl L-glutamate-carboxyanhydride. Then combination of the alkyne-PBLG with polyhedral oligomeric silsesquioxanes (POSS) with eight function groups are prepared through the click reation and formed a peptide-based block polymer with £\-helice and £]-sheet conformations. The thermal properties and structure of these polypeptides were characterized by using 1H NMR and FTIR. The FTIR, solid-state NMR and WXRD spectroscopic analyses provided evidence for the change of secondary structure between POSS and terminated peptide group, so that the conformation of £]-sheets and £\-helices would be influenced by the incorporation of POSS nanoparticle.

Angioplasty over the years has proven to be an excellent substitute for open heart surgery where an artery/vien, blocked by atherosclerosis, is expanded using a stent. Metallic and coated metallic stents have been used for angioplasty. Metal stents might induce blood clotting, release cytotoxic heavy metal ions which are potential inducers of allergies, clotting, immune reactions and hyperproliferation of smooth muscle cells and also lead to protein absorption which activates clotting factors. Biodegradable polymers have also been tried as stent materials, but the loss of radial strength over time is a big problem associated with them. The use of a hybrid stent, consisting of biodegradable polymer and biocompatible stainless steel, is proposed. The use of such a system would require excellent adhesion between the stent metal and the biodegradable polymer. This study presents the electrochemically induced micromechanical interlocking to enhance adhesion between 304 stainless steel and high density polyethylene. High density polyethylene was used instead of biodegradable polymer for initial investigation. Electrochemical etching on the stainless steel wire was accomplished by immersing a stainless steel wire in a sodium carbonate electrolyte while applying a known voltage through the wire. The electrochemical etching of the stainless steel wire resulted in pitting under suitable conditions. The etching time, voltage and electrolyte concentration were varied to achieve different pit sizes and pit distributions on the stainless steel wire. An image analysis was conducted using an image analysis software to find the exact pit size and pit distribution on the stainless steel wire from electrochemical etching. A statistical model based on design of engineering experiments was derived. Etched and the unetched wires were molded with high density polyethylene and a mechanical test was conducted to measure the force required to pull the wire out of the polymer and verified using calculations based on the pit size and pit distribution of the pits on the surface of the wire. Electrochemical etching produced burr free surface features. It was observed that the pH level in the electrolyte contributes to the pit size and pit distribution. The results of the statistical model were consistent with the experimental values and it was possible to optimize the electrochemical etching parameters for maximum pit size and pit distribution. It was also observed that while voltage and etching time contribute to pit size and pit distribution, the electrolyte concentration does not have significant effect on the pit size and pit distribution. The calculated pull out force and measured values were off by 22.7%. The lower value of calculated force could result from neglecting some of the smaller pits while performing the image analysis. The average adhesive strength of the etched samples was 276% higher than that of the unetched samples.

In recent years an increased use of polymers has occurred to modify asphalt binders, mainly to decrease pavement rutting but also to improve binder failure strain in direct tension. Whereas all of these effects positively impact the durability of polymermodified pavements, a need exists to quantify these improvements and the duration in the presence of oxidative aging. This research evaluated the durability of polymer modified asphalt (PMA) through a number of determinations that included the characterization of the original binder property and pavement-aged binder for modified and unmodified binders. Changes in styrene-butadiene-styrene (SBS) polymer modified binder properties from oxidation were analyzed using dynamic shear rheometry, ductility, and force ductility. Previous literature reports using size exclusion chromatography showed that degradation of the molecular weight profile of SBS accompanied the loss of PMA ductility. Yet base binder embrittlement also occurred, as evidenced by ductility and force ductility. Testing aged PMA binders at higher temperatures to soften the base binder restored the polymer modulus to the force ductility measurements as did blending with a softer deasphalted oil. These measurements indicate that the more significant cause of PMA degradation with aging is base binder embrittlement rather than polymer degradation. Sixteen pavements in 11 Texas Districts, plus four MnRoad pavements were evaluated in order to obtain a more detailed profile of binder oxidation in pavements. Slices of each core provided detail on binder oxidation and air voids. The data confirm that binders can oxidize at least several inches into the pavement. However, oxidation also can be significantly slowed, apparently by very low accessible air voids. Interestingly, the data indicate that the air voids that are relevant to the binder at a specific depth of the pavement are those in the immediate vicinity of the binder; low air voids above or below the binder do not seem to significantly affect the binder oxidation rate. Furthermore, that binders oxidize inches below the surface shows that temperature conducts well into the pavement, consistent with a heat conduction model that is used to calculate ground temperatures as a function of depth.

Organic semiconductors have generated huge interested in recent years for low-cost and flexible electronics. Current and future device applications for semiconducting polymers include light-emitting diodes, thin-film transistors, photovoltaic cells, chemical and biological sensors, photodetectors, lasers, and memories. The performance of conjugated polymer devices depends on two major factors: the chain conformation in polymer film and the device architecture. Highly ordered chain structure usually leads to much improved performance by enhancing interchain interaction to facilitate carrier transport. The goal of this research is to improve the performance of organic devices with the nanoimprint lithography. The work begins with the controlling of polymer chain orientation in patterned nanostructures through nanoimprint mold design and process parameter manipulation, and studying the effect of chain ordering on material properties. After that, step-and-repeat thermal nanoimprint technique for large-scale continuous manufacturing of conjugated polymer nanostructures is developed. The actual chain orientation of molecular groups in polymer micro- and nanostructures patterning by nanoimprint is complicated. However, this information is crucial for intelligently controlling the electrical and photophysical properties of conjugated polymers by nanoimprint. Systematic investigation of polymer chain configuration by Raman spectroscopy is carried out to understand how nanoimprint process parameters, such as mold pattern size, temperature, and polymer molecular weight, affects polymer chain configuration. The results indicate that chain orientation in nanoimprinted polymer micro- and nanostructures is highly related to the nanoimprint temperature and the dimensions of the mold structures. The ability to create nanoscale polymer micro- and nanostructures and manipulate their internal chain conformation establishes an original experimental platform that enables studying the properties of functional polymers at the micro- and nanoscale and understanding their fundamental structure-property relationships. In addition to the impact on basic research, the techniques developed in this work are important in applied research and development. Large-area conjugated polymer micro- and nanostructures can be easily fabricated by thermal step-and-repeat nanoimprint for organic flat-panel displays, organic circuits and organic solar panels. The ability to manipulate chain orientation through nanoimprint presents a new route to fine-tune the electrical and photophysical properties of conjugated polymers, which can lead to improved performance for all organic electronics. The techniques developed here also allow for easy incorporation of other micro- and nanoscale soft functional polymers in miniaturized devices and systems for new applications in electronics, photonics, sensors and bioengineering.

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A BCB Polymer/Ta2O5/SiO2 antiresonant reflecting optical waveguide (ARROW) at quasi-antiresonant condition is presented. The waveguide consists of the SiO2 second cladding, the Ta2O5 first cladding, and the BCB core. The lateral guiding of the ARROW waveguide was formed by reactive ion etching based on SF6 and O2 mixtures (SF6 : O2 =1.5 : 1). A metal layer Ni/Cr thin films were used as the etch mask to avoid cracking of the mask caused by large thermal expansion coefficient of the BCB Polymer. The waveguide losses were measured by the cut back method. Large dry-etching aspect ratio of the BCB polymer to the etch mask was obtained. For TE polarized light, the propagation loss of the waveguide was 1.12 dB/cm at 1.3£gm. The propagation loss for TM polarized light was 2.56 dB/cm.

Fatigue cracking is one of the fundamental distresses that occur in the life of a Hot Mix Asphalt Concrete (HMAC) pavement. This load induced distress leads to structural collapse of the entire pavement ultimately and can only be remedied by rehabilitation. There is the need, therefore, for a total understanding of the phenomenon to be able to counter its occurrence. The fatigue resistance of hot mix asphalt concrete (HMAC) has been estimated using approaches ranging from empirical methods to mechanistic-empirical methods to purely mechanistic methods. A continuum mechanics based approach called the Calibrated Mechanistic with Surface Energy (CMSE) measurements was developed at Texas A&M University and recommended after comparison with other approaches in predicting fatigue lives of two Texas HMAC mixtures. The CMSE approach which includes fundamental material properties such as fracture, aging, healing, and anisotropy has been shown to effectively model the parameters that affect the performance of HMAC pavements exposed to repetitive traffic loads. Polymer modified asphalt (PMA) improves pavement performance by providing additional resistance to the primary distresses in flexible pavements, including permanent deformation or rutting, thermal cracking, and fatigue cracking. In this research, the CMSE approach was utilized to estimate the fatigue resistance of HMAC fabricated with asphalts modified with Styrene-butadiene-Styrene (SBS) co-block polymer. These HMAC mixtures were fabricated from materials used on three different road sections in Texas and one test pavement in Minnesota. The CMSE approach was validated as an effective approach for estimating the fatigue resistance of HMAC mixtures with PMA. The effect of oxidative aging on the fatigue resistance of the HMAC mixtures was also verified. Oxidative aging of the mixtures resulted in a corresponding decrease in mixture fatigue resistance. In addition, for two HMAC mixtures with the same binder content and aggregate gradation, the mixture with the softer of the two Performance Grade (PG) binders exhibited greater fatigue resistance. The use of the Utility Theory revealed the possible effects of aggregate geometric properties on the HMAC mixture properties and consequently on their fatigue resistance.

The objective of this research was to determine the effect of thermal cycling combined with mechanical loading on the development of microcracks in M40J/PMR-II- 50, the second generation aerospace application material. The objective was pursued by finding the critical controlling parameters for microcrack formation from mechanical stress-thermal cycling test. Three different in-plane strains (0%, 0.175~0.350%, and 0.325~0.650%) were applied to the composites by clamping composite specimens (M40J/PMR-II-50, [0,90]s, a unitape cross-ply) on the radial sides of half cylinders having two different radii (78.74mm and 37.96mm). Three different thermal loading experiments, 1) 23oC to –196oC to 250oC, 2) 23oC to 250oC, and 3) 23oC to -196oC, were performed as a function of mechanical inplane strain levels, heating rates, and number of thermal cycles. The apparatus generated cracks related to the in-plane stresses (or strains) on plies. The design and analysis concept of the synergistic stress-thermal cycling experiment was simplified to obtain main and interaction factors by applying 2k factorial design from the various factors affecting microcrack density of M40J/PMR-II-50. Observations indicate that the higher temperature portion of the cycle under load causes fiber/matrix interface failure. Subsequent exposure to higher stresses in the cryogenic temperature region results in composite matrix microcracking due to the additional stresses associated with the fiber-matrix thermal expansion mismatch.

Accurate constitutive modeling of polymeric fibers presents a difficult and distinct challenge. While significant progress has been made in constructing models applicable for small strains and limited strain-rate and temperature regimes, much less has been made for more general conditions. This is due in part to the complexity of polymeric behavior. In this work, experimental results of uniaxial extension tests on Polyethylene terephthalate (PET) were obtained from Dr. S.Bechtel, were analyzed, and were formulated into a new model which explains the behavior of PET at different temperatures and strains. The biggest impediment in the determining the behavior of polymeric was the difference in the behavior of PET above and below its glass transition temperature. Consequently, well established (from microstructural considerations) constitutive models and concepts for rubber elasticity and plasticity were not directly transferable to modeling PET fibers. In the model, the PET fibers were assumed to be constituted by amorphous and crystallization segments and the response of the material during stretching was the combined response of simultaneous stretching of the amorphous and the crystalline segments. The strengthening mechanism is due to orientation of the amorphous segments during stretching. The model involves a friction element which took account of the plastic behavior below the glass transition temperature. The model was used to predict the response of PET at different temperatures and the results from the model showed good agreement with the experimental data. The results from the research will be further used to increase the overall efficiency of the fiber drawing process.

Phase selective soluble polymers are useful in organic synthesis because they simplify purification and separation processes. Such selective soluble polymers enable the use of Green chemistry principles to be utilized as ways to simplify catalyst, reagent, and product recovery. Polyisobutylene oligomers serve as examples of such polymers. Vinyl terminated polyisobutylene (PIB) oligomers can be easily transformed into a variety of end-functionalized PIB oligomers. Previous work has shown that PIB oligomers possess nonpolar phase selective solubility that allows them to be used as polymer supports for ligands and catalysts in liquid/liquid biphasic systems. This dissertation focuses on the use of PIB oligomers as supports for a salen Cr(III) complex, a Hoveyda-Grubbs 2nd generation catalyst, and a N-heterocyclic carbene. The syntheses of these PIB-supported ligands and catalysts are simple and straightforward. The synthetic products and the intermediates in these syntheses can all be readily analyzed and monitored by conventional spectroscopic methods. The activity of the PIBsupported catalysts is shown to be analogous to that of other soluble polymer supported catalysts or their non-supported analogs. The PIB-bound catalysts can be separated from products by a latent biphasic, liquid/liquid extractions, or product self-separation systems. The recovered PIB-bound catalysts can then be recycled multiple times.