PEM (Proton Exchange Membrane) fuel cell is one of the most important green energy, because it has high energy density, lifetime, small and light.etc advantages. Nafion , the major material for PEM now, However, has some disadvantages such as high cost ($600¡V1000/m2) and limited choices for operation temperature about 25¢J~80¢J. Consequently, there is an increasing interest in the development of alternative ionomer membranes with lower cost, and higher proton conductivity, and that are more easily processed. Here we present polymeric membranes made of sulfonic Poly(arylene ether)s (PAEs) which is achieved by nucleophilic displacement reactions of dihalo or dinitro compounds with alkali metal bisphenolates and direct polymer sulfonation was carried out in heterogeneous media using chlorosulfonic acid as both solvent and sulfonating agent. In our PAEs which has high Tg values about 225¡ã250¢XC depends on the barriers to rotation along the main polymer chain. And weight losses above 500 ¢XC by thermogravimetric (TGA) analysis, indicative of their high thermal stability. After FTIR analysis we preparation sulfonated polymer successfully by using chlorosulfonic acid as sulfonating agent. Thermogravimetric analysis (TGA) studies were carried out to investigate the thermal stability of sulfonated PAEs (Td≈ 500¢XC). The proton conductivity of polymer s(DFB+M3) sulfonated with chlorosulfonic acid about 10-6¡ã10-7S cm-1 .Compared with Nafion membrane measured in the same condition, the conductivity of our membrane is smaller than 3~4 order. In the future, it is possible to improve the conductivity of our membrane with optimization.

We have two topics, In the first study, we synthesized three low-molecular-weight poly(glutamate)s¡Xpoly( £^-methyl l-glutamate) (PMLG), poly( £^-ethyl l-glutamate) (PELG), and poly( £^-benzyl l-glutamate) (PBLG)¡Xthrough living ring-opening polymerization of their £\-amino acid-N-carboxyanhydride derivatives and then blended them with phenolic resin to control the secondary structures of these polypeptides. Each of the three binary blends exhibited a single glass transition temperature (differential scanning calorimetry) and solid state nuclear magnetic resonance (NMR) spectroscopy], characteristic of a miscible system. The strength of the inter-associative interactions depended on the nature of the hydrogen bond acceptor groups, increasing in the order phenolic/PELG > phenolic/PMLG > phenolic/PBLG, as evidenced through analyses using Fourier transform infrared (FTIR) spectroscopy and the Painter¡VColeman association model. The fractions of £\-helical conformations (measured using FTIR and solid state NMR spectroscopy) of PMLG and PELG decreased initially upon increasing the phenolic content, but increased thereafter; in contrast, the fraction of £\-helical conformations of PBLG increased continuously upon increasing the phenolic contents. Using variable-temperature infrared spectroscopy to investigate the changes in the conformations of the secondary structures of the peptide segments in these three binary blends, we found that the £\-helical conformation in these three blend systems correlated strongly with the rigidity of side chain groups, the strength of the intermolecular hydrogen bonding with the phenolic resin, the compositions of phenolic resin, and the temperature. More interestingly, the content of £\-helical conformations of the polypeptides in these phenolic/PBLG blends increased upon increasing the temperature. The second topic is synthesized low-molecular-weight poly( £^-benzyl l-glutamate) (PBLG) through living ring-opening polymerization of their £\-amino acid-N-carboxyanhydride derivatives and blended them with poly( styrene¡^(PS), poly (acetoxystyrene) (PAS) and poly(vinyl phenol) (PVPh) to control the secondary structures of these polypeptides. DSC have been used to investigate the miscibility of. FTIR spectroscopies and wide-angle X-ray diffraction (WXRD) spectroscopic analyses provided evidence for the change and specific interactions between (PS, PAS and PVPh) and PBLG. That the secondary structures of polypeptides can be altered through blending with other different Specific Interactions, mediated by hydrogen bonding, dipole¡Vdipole, and £k¡X£k Interaction, we investigate strong Specific interactions was found between the side-chain esters of PAS, PVPh, but not found between PBLG and PS, because more weakly with the aromatic rings of PS through intermolecular £k¡X£k interactions, so that this latter system is phase separated.

The need to tailor release-rate profiles from polymeric microspheres remains one of the leading challenges in controlled drug delivery. Microsphere size, which has a significant effect on drug release rate, can potentially be varied to design a controlled drug delivery system with desired release profile. In addition, drug release rate from polymeric microspheres is dependent on material properties such as polymer molecular weight. Mathematical modeling provides insight into the fundamental processes that govern the release, and once validated with experimental results, it can be used to tailor a desired controlled drug delivery system. To these ends, PLG microspheres were fabricated using the oil-in-water emulsion technique. A quantitative study that describes the size distribution of poly(lactide-coglycolide) (PLG) microspheres is presented. A fluid mechanics-based correlation that predicts the mean microsphere diameter is formulated based on the theory of emulsification in turbulent flow. The effects of microspheres’ mean diameter, polydispersity, and polymer molecular weight on therapeutic drug release rate from poly(lactide-co-glycolide) (PLG) microspheres were investigated experimentally. Based on the experimental results, a suitable mathematical theory has been developed that incorporates the effect of microsphere size distribution and polymer degradation on drug release. In addition, a numerical optimization technique, based on the least squares method, was developed to achieve desired therapeutic drug release profiles by combining individual microsphere populations. The fluid mechanics-based mathematical correlation that predicts microsphere mean diameter provided a close fit to the experimental results. We show from in vitro release experiments that microsphere size has a significant effect on drug release rate. The initial release rate decreased with an increase in microsphere size. In addition, the release profile changed from first order to concave-upward (sigmoidal) as the microsphere size was increased. The mathematical model gave a good fit to the experimental release data. Using the numerical optimization technique, it was possible to achieve desired release profiles, in particular zero-order and pulsatile release, by combining individual microsphere populations at the appropriate proportions. Overall, this work shows that engineering polymeric microsphere populations having predetermined characteristics is an effective means to obtain desired therapeutic drug release patterns, relevant for controlled drug delivery.

The increasing prevalence of diabetes and the severity of long-term complications have emphasized the need for continuous glucose monitoring. Optically-based methods are advantageous as they have potential for noninvasive or minimally invasive detection. Fluorescence-based affinity assays, in particular, can be fast, reagentless, and highly specific. Poly(ethylene glycol) (PEG) microspheres have been used to encapsulate such fluorescently labeled molecules in a hydrogel matrix for implantation into the body. The matrix is designed to retain the sensing molecules while simultaneously allowing sufficient analyte diffusion. Sensing assays which depend upon a spatial displacement of molecules, however, experience limited motility and diminished sensor response in a dense matrix. In order to overcome this, a process of hydrogel microporation has been developed to create cavities within the PEG that contain the assay components in solution, providing improved motility for large sensing elements, while limiting leaching and increasing sensor lifetime. For an implanted sensor to be successful in vivo, it should exhibit long-term stability and functionality. Even biocompatible materials that have no toxic effect on surrounding tissues elicit a host response. Over time, a fibrous capsule forms around the implant, slowing diffusion of the target analyte to the sensor and limiting optical signal propagation. To prevent this biofouling, a thermoresponsive nanocomposite hydrogel based on poly(N-isopropylacrylamide) was developed to create a self-cleaning sensor membrane. These hydrogels exist in a swollen state at temperatures below the volume phase transition temperature (VPTT) and become increasingly hydrophobic as the temperature is raised. Upon thermal cycling around the VPTT, these hydrogels exhibit significant cell release in vitro. However, the VPTT of the original formula was around 33-34 degrees C, resulting in a gel that is in a collapsed state, ultimately limiting glucose diffusion at body temperature. The hydrogel was modified by introducing a hydrophilic comonomer, N-vinylpyrrolidone (NVP), to raise the VPTT above body temperature. The new formulation was optimized with regard to diffusion, mechanical strength, and cell releasing capabilities under physiological conditions. Overall, this system is a promising method to translate a glucose-sensitive assay from the cuvette to the clinic for minimally invasive continuous glucose sensing.

This thesis presents a novel method for the preparation of quantum dot-thermoresponsive polymer nanocomposite hydrogels. The quantum dots (QD’s) were synthesized in a microwave reactor using a high temperature organometallic synthesis procedure. The initial hydrophobic surface layer on the QD’s was coated with an amphiphilic polymer to enable phase transfer from non-polar solvent to water followed by physical immobilization of the QD’s in the thermoresponsive polymer hydrogel by photopolymerization. Their temperature dependent emission properties were investigated as a function of concentration of the incorporated QD’s. The resultant temperature dependent changes in the position of the peak emission wavelength of the QD-polymer nanocomposite hydrogels were found to be due to the change in the physical environment causing increased interaction between the embedded amphiphilic polymer coated QD’s and/or due to aggregation of QD’s. This change in peak emission position was found to be reversible in the temperature range from 29 to 37 °C.

Poly(N-isopropylacrylamide) (PNIPAM), a temperature responsive polymer, undergoes a phase change at a lower critical solution temperature (LCST) in aqueous solutions. For PNIPAM this temperature is 32 °C in water. Below the LCST, the polymer is readily solvated by water. As the temperature of the solution increases, the polymer undergoes a phase transition so that above the LCST it is no longer water soluble. The LCST of PNIPAM may be changed by the addition of salt solutions from the Hofmeister series which will follow the Hofmeister effect for salting-in and salting-out the polymer. Temperature responsive polymers may be grafted to a surface in a variety of methods to create responsive thin films that exhibit a change in wettability. The surface wettability is directly related to the polymers ability to be solvated in its coil conformation. When PNIPAM is grafted to a surface, the surface becomes alternatively hydrophobic and hydrophilic in response to both temperature and the anions in the Hofmeister series which take the surface either above or below the LCST of PNIPAM. The synthesis of responsive nanocomposite grafts was successfully applied to glass slides and three-dimensional surfaces, porous glass frits which were capable of controlling the passive flow rate. The nanocomposite graft was assembled in a covalent layer-by-layer approach to create more chemically robust surfaces, and also to incorporate nanoparticles into the graft for increased surface roughness and therefore improve wettability response. Because of a much greater inherent roughness to a glass frit, characterization of the polymers and nanoparticles was performed before they were covalently bound to the surface. The final product, a functionalized frit with a PNIPAM/SiO2 nanocomposite graft, was analyzed by observing changes in the passive permeation rate of the frit between water and salt solutions. These changes in flow were indicative of the surface bound PNIPAM changing between its hydrophilic and hydrophobic conformation in response to water and concentrations of kosmotropic salts such as sodium sulfate and sodium citrate. In addition to the solute response, the frit was also determined to be responsive to temperature and concentration. Water exhibited a passive flow rate 1000 times faster than a kosmotropic salt but had a similar flow rate to that a chaotropic salt. By measuring the flow rate of 0.5 M Na2SO4 at ~7 °C in a cold room and at room temperature it was observed that sodium sulfate in the cold room passed through the frit at a rate 100 times faster than at room temperature. Because of the hysteresis of PNIPAM documented in literature, washing procedures were kept consistent between experiments to achieve more reproducible results. It was concluded that the frits were temperature responsive and had relative standard deviations below 25 percent for flow rates on a single frit. However, standard deviations of flow rates between frits were higher. This was likely due to a combination of factors, such as the frits’ pore size range of 10 μm resulting in the possibility of varied degrees of functionalization of each frit.

Research on nanofluids has been undertaken for several years because of the reported enhancements of thermal properties such as thermal conductivity and enhanced heat transfer performance in laminar flow. Nanofluid is the fluid where nanoparticles are dispersed in a base fluid. Thermal conductivity and viscosity are considered to be the most prominent factors in the efficient use of nanofluids. A change in thermal conductivity and viscosity also changes the convective heat transfer coefficient. Nanoparticles can be metallic or non-metallic and also can have different shapes. In this study, Poly-Alpha-Olefin (PAO) has been used as a base fluid with Alumina (Al2O3) nanoparticles. Poly-Alpha-Olefin is commonly used for engine lubrication in military applications and cooling in electronic and industrial devices. Several nanofluid samples were made by METSS Corp. in Ohio, USA using different dispersants, different base fluids and different morphology of alumina nanoparticles. The mass fraction of nanoparticles is from 2.5 to 20 percent. The thermal properties of each sample such as thermal conductivity and viscosity have been measured. Thermal conductivity of nanofluids and pure base fluids were both measured and the thermal conductivity enhancement has been calculated. Also, the heat transfer coefficient has been determined for laminar flow under constant heat flux conditions. Results indicate that all the tested nanofluids and base fluid samples show a Newtonian behavior. Among the nanofluid samples, NF-048, which contains non-spherical Alumina nanoparticles exhibits the greatest thermal conductivity enhancement when compared to pure PAO. Heat transfer tests were conducted with pure PAO and NF-048, and an enhancement in convective heat transfer coefficient was observed. The thermal conductivity of NF-048 increases with temperature, which is consistent with heat transfer results. Furthermore, the percentage enhancement in convective heat transfer coefficient was shown to increase non-linearly with the axial distance in the heat transfer section. NF-048 exhibits a lower Re (Reynolds number)*Ra (Rayleigh number) than pure PAO under laminar flow constant heat flux conditions indicating that nanoparticle morphology and composition are the two main factors responsible for convective heat transfer enhancement at low Reynolds number.

The common discotic mesogen molecules are known to have a flat structure, comprising a rigid core, e.g., polynuclear aromatic structure, and a ring of four to nine flexible aliphatic side chains. We take the electron deficient heterocyclic hexaazatriphenylene (HAT) as our central core and readily synthesized by the condensation of hexaketocyclohexane with the respective 1,2-bis-alkoxy-4,5-diaminobenzene. The new molecules with electron deficient discotic liquid crystal properties are successfully.

In this paper, we discuss the effect of the hydrogen-bonding on the photoluminescent(PL) properties of 1-pyrenecarboxylic acid (PCA)/ poly(methyl methacrylate) (PMMA). Isolated fluorophore can be obtained when PCA molecules were blended and septrated by PMMA, i. e. excimer emission can be more efficiently prevented. With the use of non-solvent, toluene, in the preparation step, excimer emission of PCA can be more effeiciently prevented as compared to the good solvent, tetrahydrofuran(THF). With a high PMMA/PCA ratio of 1000/1, emission spectra show no sign of excimer formation. Intermolecular hydrogen bonding between PMMA and PCA helps to prevent the excimer formation. Solvents used in the preparative state play important role on the final PL properties of the solid film. In the blend, partial carbonyl groups in PMMA band with carboxylic acid group in PCA, this causes the appearance of a stretching band at 1718 cm-1 in infrared spectroscopy. The hydrogen-bond interactions help to the prevention of excimer formation in the PMMA/PCA blending systems.

Poly(ethylene succinate) (PES), poly(trimethylene succinate) (PTS) and their copolyesters (PETSAs) with various compositions were used to investigate the structure-property relationship. The results of intrinsic viscosity and GPC have proven successful in preparing high molecular weight polyesters. The chemical compositions and the sequence distribution of co-monomers in the copolyesters were determined by NMR spectroscope. The distributions of ES unit and TS unit were found to be random. Their thermal properties were characterized using differential scanning calorimeter (DSC). The thermal stability of polyesters was analyzed by thermogravimeter (TGA) and polarized light microscope (PLM) under nitrogen. The results of TGA show that all of the samples have similar thermal stability (Tstart : 246¡Ó3 ¢XC), but the thermal degradation temperature of PES and PETSA(95/05) are 213 and 200 ¢XC, respectively, estimated from the isothermal growth rates after pre-melting at various temperatures. The degradation temperature analyzed by PLM is more sensitive than that obtained from TGA. The incorporation of 5 mol% of TS units into PES significantly reduces the thermal stability of PES. In addition, wide-angle X-ray diffractograms (WAXD) were obtained for polyesters which were crystallized isothermally at a temperature 5~10 ¢XC below their melting temperatures. The results of WAXD and DSC indicate that the incorporation of TS units into PES significantly inhibit the crystallization behavior of PES. In the second part of this study, PES and PETSA(95/05) were studied in detail. The crystallization kinetics and the melting behavior were investigated by using DSC in both conventional mode and modulated mode (TMDSC). The reversing, total, and non-reversing heat flow curves were analyzed. The Hoffman-Weeks plots gave an equilibrium melting temperature of 112.7 and 108.3 ¢XC for PES and PETSA(95/05), XI respectively. Only one crystal form was found from WAXD for specimens crystallized isothermally at various temperatures. Based on the WAXD patterns, DSC and TMDSC thermograms, multiple endothermic melting peaks can be explained by two mechanisms, melting-recrystallization-remelting and dual morphologies. PLM was used to study the growth rates and morphology of the spherulites. The growth rates measured in isothermal conditions were very well comparable with those measured by the non- isothermal procedure. In addition, the temperature range of growth rates detected by the non- isothermal procedure is wider than that by the isothermal method, which is time consuming. The regime II®III transition of PES was estimated at ~ 71 ¢XC which is very close to the literature values, and that of PETSA(95/05) was found at ~ 65 ¢XC.