Thesis (Ph.D.)--University of Delaware, 2009. / Principal faculty advisors: Michael H. Santare and Anette M. Karlsson, Dept. of Mechanical Engineering. Includes bibliographical references.

Styrene-4-vinylpyridinium ionomers of different architectures, random and ABA blocks, were synthesized and their thermal and dynamic mechanical properties investigated. / The Tg's of the random ionomers were found to increase regularly with increasing ion content, at a rate of about 3.5(DEGREES)C per mole % of ions. In contrast with other ionomeric systems studied before, however, these materials showed only one peak in their tan delta curves, associated with the Tg of the matrix. The absence of a second, high temperature peak suggests the absence of clusters in these vinylpyridinium ionomers, at least at temperatures above their Tg. The storage modulus curves were in agreement with this conclusion. / An elaborate polymerization line was constructed for the production of the block copolymers by living anionic polymerization; a basic design was modified considerably and two new units were completely designed in this laboratory. Only one Tg, associated with the Tg of the polystyrene phase, was observed in DSC measurements for the resulting ionomers. The glass transition of the ionic domains was detected in dynamic mechanical measurements as a shoulder on the low temperature side of the polystyrene transition. This unexpected low value for the Tg of the ionic domains was attributed to plasticization by water.

Conventional melt transesterification successfully synthesized high molecular weight segmented copolyesters.  The cycloaliphatic monomers 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO) and dimethyl-1,4-cyclohexane dicarboxylate (DMCD) afforded sterically hindered, ester carbonyls in high-Tg polyester precursors.   Reaction between the polyester polyol precursor and a primary or secondary alcohol at melt polymerization temperatures revealed reduced transesterification of the polyester hard segment as a result of enhanced steric hindrance adjacent to the ester linkages.  Subsequent polymerization of a 4,000 g/mol polyol with monomers comprising the low-Tg block yielded high molecular weight polymers that exhibited enhanced mechanical properties compared to a non-segmented copolyester control.  Atomic force microscopy uncovered unique needle-like, interconnected, microphase separated surface morphologies, and small-angle X-ray scattering confirmed the presence of bulk microphase separation. This new synthetic strategy enabled selective control of ionic charge placement into the hard segment or soft segment block of segmented copolyesters using melt transesterification.  The ionic placement impacted the microphase-separated morphology, which influenced its thermomechanical properties and resulting mechanical performance.  Melt transesterification of low-Tg, sodium sulfonated copolyesters achieved up to 15 mol% ionic content.  The 10 and 15 mol% sodium sulfonated copolyesters exhibited water-dispersibility, which enabled cation dialysis exchanges to divalent metal cations.  The sulfonated copolyesters containing divalent metal cations exhibited enhanced rubbery plateau moduli to higher temperatures.   Novel trialkylphosphonium ionic liquids chain extenders enabled the successful synthesis of poly(ethylene glycol)-based, cationic polyurethanes with pendant phosphoniums in the hard segments (HS).  Aqueous size exclusion chromatography (SEC) confirmed the charged polyurethanes, which varied the phosphonium alkyl substituent length (ethyl and butyl) and cationic HS content (25, 50, 75 mol%), achieved high absolute molecular weights.  Dynamic mechanical analysis (DMA) demonstrated the triethylphosphonium (TEP) and tributylphosphonium (TBP) polyurethanes displayed similar thermomechanical properties, including increased rubbery plateau moduli and flow temperatures.  Fourier transform infrared spectroscopy (FTIR) emphasized the significance of ion-dipole interaction on hydrogen bonding. Atomic force microscopy (AFM), small-angle X-ray scattering (SAXS), and wide-angle X-ray diffraction (WAXD) supported microphase separated morphologies in the trialkylphosphonium polyurethanes, despite the presence of ionic interactions. Sorption isotherm experiments revealed TBP polyurethanes displayed similar water sorption profiles to the noncharged analogue and lower water absorptivity compared to TEP.  The phosphonium polyurethanes displayed significantly improved tensile strain; however, lower tensile stress of the TEP polyurethane was presumably due to absorbed water.  In addition, we also explored applications of the trialkylphosphonium polyurethanes as nucleic acid delivery vectors and demonstrated their abilities to form colloidally stable polyplexes in salt-containing media. / Ph. D.

No description available.

Perfluorosulfonate ionomer (PFSI) membranes were annealed at elevated temperature for various periods of time in order to investigate the morphological effects of thermal treatments. For Nafion® 117, the DSC thermograms of Na+-, Cs+- and tetramethylammonium(TMA+)-form membranes show an endothermic peak develops upon annealing at 200ºC, indicating the development of crystallinity in the membrane. For these three samples annealed under same conditions, the heat of fusion (ΠH) values of the endothermic event increases with increasing counterion size. Larger tetraalkylammonium ions, tetraethylammonium(TEA+) and tetrapropylammonium(TPA+), result in no significant peak upon annealing at 200ºC. DSC thermograms of annealed Na+-form 3M Ionomer show no peak upon annealing and DSC thermograms of annealed TMA+-form 3M Ionomer show a very small peak that develops with annealing time at high equivalent weights. Annealed TMA+-form Dow Ionomer, which has a side chain shorter than both Nafion® and 3M Ionomer and a smaller mole% of side chains at the same equivalent weight, shows a relatively high ΠH value, which might also be related to its blocky nature. These results show that the isothermal crystallization kinetics of PFSI is affected by the counterion attached to the sulfonate group, the length of side chain, the mole% of side chains and the nature of the membrane. Water uptake analysis has been performed on annealed membranes, and the result shows that water uptake decreases with increasing degree of crystallinity. / Master of Science

No description available.

The synthesis of ion containing copolymers by emulsion copolymerization of polar vinyl monomers with ionic vinyl monomers has been studied. The copolymerization of n-butyl acrylate with sodium-pstyrene sulfonate proved to be particularly rapid. With the proper choice of chain transfer agent soluble polymers with enhanced rubbery plateaus have been synthesized. The best conditions for the polymerizations were a reaction temperature of 70°C and reaction times up to 8 hours with TWEEN 20 used as the emulsifier. Analysis of the copolymer composition by UV spectroscopy, and potentionmetric titration was not possible due to the vastly different solubility characteristics of the components of this system. This prevented the use of homopolymer blends as standards for these techniques. The study of the copolymerization kinetics of this system was very difficult due to the coagulation of the polymer latex. The rate of copolymerization was nevertheless shown to be very rapid. The synthesis of the sulfonated styrene monomer by a literature procedure led to the formation of a covalent sulfonamide instead of the desired ionic sulfonate. This product was substantiated by l_H and 13_C NMR infrared, mass spectral, and melting point data. Study of the physical properties of these polymers by differential scanning calorimetry and thermal mechanical analysis showed them to have only a low temperature acrylate glass transition with an enhanced rubbery plateau due to the ionic pseudo crosslinking. Stress-strain measurements showed that this pseudo crosslinking gives enhanced tensile properties (modulus, tensile strength) in the ion-containing polymers. / M.S.

Orientador: Mario Fernando de Goes / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-14T19:35:08Z (GMT). No. of bitstreams: 1 Blatt_JoseAgostinho_M.pdf: 2893059 bytes, checksum: cf1ca8b9535f7d4b0b87c687c0e6f655 (MD5) Previous issue date: 2000 / Resumo: A proposta deste estudo foi avaliar a infiltração marginal em restaurações confeccionadas com cimento de ionômero de vidro convencional e resina composta modificada por poliácidos em cavidades de classe V preparadas sobre dentina normal e esclerosada. As cavidades foram preparadas usando brocas em aço "carbide" n° 330 montadas em alta rotação e sob constante refrigeração com ar/água, e padronizadas com 1,8 0,2 mm de diâmetro e 1,8 0,2 mm de profundidade na região abaixo do limite cemento-dentinário de 20 dentes molares humanos com as superfícies radiculares íntegras e idade acima de 50 anos e, em outros 20 dentes molares de humanos com idade abaixo de 30 anos. Os 20 preparos cavitários confeccionados nos dentes dos pacientes idosos foram divididos aleatoriamente e alocados nos grupos 1 e 2 com 10 dentes cada. Da mesma forma, os dentes dos pacientes jovens foram determinados para os grupos 3 e 4. As cavidades dos grupos 1 e 3 foram restauradas com o cimento de ionômero de vidro Fuji IX e as dos grupos 2 e 4 foram restauradas com a resina modificada por poliácidos F 2000. Os materiais foram manipulados de acordo com as instruções dos fabricantes. Em seguida, os dentes foram armazenados em água destilada a 37°C durante 24 horas. Após a armazenagem, as restaurações foram polidas usando a seqüência de discos Sof-Iex. Todas as superfícies dentais foram protegidas com esmalte para unha, deixando livre 1 mm ao redor da margem das restaurações. A seguir, os dentes foram imersos em solução aquosa de nitrato de prata 50% e armazenadas por 24 horas. Logo após, imersos em uma solução para revelação fotográfica sob exposição de luz fluorescente por 12 horas. Em seguida, todos os dentes foram seccionados longitudinalmente e cada secção foi polida com lixas d'água e pasta de diamante. A mensuração da penetração do corante foi feita em um microscópio comparador. O percentual de penetração da solução de nitrato de prata nas interfaces dentina-material restaurador foi obtido pela mensuração do comprimento total da infiltração do corante na interface dividido pelo comprimento total da cavidade e multiplicado por 100. Os valores percentuais obtidos foram submetidos à análise de variância e ao teste de Tukey em nível de 5% de significância. O valor percentual médio de penetração do nitrato de prata na interface dentina esclerosada e material ionomérico Fuji IX foi menor e estatisticamente significante em relação ao valor apresentado na interface dentina esclerosada e material resinoso F2000. O valor apresentado na interface entre o ionômero de vidro Fuji IX ou F2000 e dentina normal não mostrou diferença estatística entre si. / Abstract: he purpose of this study was to evaluate marginal infiltration in restorations prepared with conventional glass ionomer cement and composite resin modified by polyacids in cavities class V prepared on normal and sclerosed dentin. Cavities were prepared using number 330 "carbide" drills mounted in high rotation and under constant dry/water refrigeration, and standardized with a diameter of 1.8 :t 0.2 mm and a depth of 1.8 :t 0.2 mm., in the region below the cementoenamel junctions of 20 molar teeth human with intact radicular surfaces from patients of over 50 years old and in another 20 molar teeth humans of below 30 years. The 20 cavity preparations prepared on the teeth of elderly patients were divided randomly and placed in-groups 1 and 2 with 10 teeth in each. In the same way, the teeth from the young patients were determined by groups 3 and 4. The cavities of groups 1 and 3 were restored using the Fuji IX glass ionomer cement and those of groups 2 and 4 were restored using resin modified by F2000 polyacids. The materiais were used according to the manufacturer's instructions. Next, the teeth were then stored in distilled water at 37°C for 24 hours. After storage, the restorations polished using the Sof-Lex (3M) sequence of discs. Ali the dental surfaces were protected with nail enamel, leaving a 1 mm margin around the restorations. To follow, the teeth were then immersed in water solution of silver nitrate 50% and stored for 24 hours. Therefore, immersed in a solution for photographic exposure under florescent light for 12 hours. Next, ali the teeth were cross-sectioned longitudinally and each cross-section was polished using water abrasion and diamond paste. The stain penetration measurement was carried out using a comparatar microscope. The percentage of penetration of the silver nitrate solution on the dentin-restorative material interface was obtained by measuring the total length of the stain infiltration on the interface, divided by the total length of the cavity, and multiplied by 100. The percentage values obtained underwent variance analysis and the Tukey test at a levei of 5% significance. The average percent value of the silver nitrate penetration on the sclerosed dentin interface and Fuji IX ionomeric material was lower and statistically significant in relation to the value shown on the sclerosed dentin interface and F2000 resin material. The value of the interface between the Fuji IX glass ionomer ar F2000 and normal dentin did not show any statistical difference between them. / Mestrado / Mestre em Materiais Dentários

Two types of (polymer-imaging agent-drug) complexes were prepared and characterized. These included block and graft copolymer complexes with magnetite nanoparticles and manganese ions. Magnetite block ionomer complexes (MBICs) were formed through binding of a portion of the anionic segment of poly(ethylene oxide)-b-poly(acrylic acid) (PEO-b-PAA) block copolymers with the magnetite nanoparticle surfaces. The remainder of the carboxylic acids were utilized to bind with high concentrations of the cationic antibiotic gentamicin (31 wt%). A near zero-order release of gentamicin (pH 7.4 in PBS) that reached ~35 wt% of the initial gentamicin within 10 hours was observed, and this was followed by slower release of another 7 % by 18 hours. These nanoparticles were efficiently taken up by macrophages and appeared to enhance intracellular antimicrobial activities of gentamicin. To increase the complex sizes and NMR T2 relaxivities, amine functional MBICs (MBICs-NH2) were first assembled by adsorbing the polyacrylate block of an aminofunctional poly(ethylene oxide)-b-poly(acrylic acid)) (H2N-PEO-b-PAA) copolymer onto magnetite nanoparticles. Amines at the tips of the H2N-PEO corona were then linked through reaction with a PEO diacrylate oligomer to yield MBIClusters where the metal oxides in the precursor nanoparticles were distinctly separated by the hydrophilic polymer. These MBIClusters with hydrophilic intra-cluster space had transverse relaxivities (r2's) that increased from 190 to 604 s-1 mM Fe-1 measured at 1.4 T and 37°C as their average sizes increased. The clusters were loaded with up to ~38 wt% of the multi-cationic drug gentamicin. MRI scans focused on the livers of mice demonstrated that these MBIClusters are very sensitive contrast agents. These results indicate that these complexes could be potential theranostic agents for dual imaging and drug delivery. Manganese graft ionomer complexes (MaGICs) comprised of Mn ions and a novel polyaminobisphosphonate-g-PEO copolymer were developed for use as T1 weighted MRI positive contrast agents. The graft copolymers were prepared by free radical copolymerization of ammonium bisphosphonate methacrylate monomers with PEO-acrylate macromonomers. The complexes exhibited good colloidal stability without release of free manganese and did not show any in vitro toxicity against mouse hepatocytes. The T1 relaxivities of the MaGICs were 2-10 times higher than that of a commercial manganese based contrast agent MnDPDP. These MaGICs with encapsulated anticancer drugs including doxorubicin, cisplatin and carboplatin have encapsulation efficiencies of 80-100 %. Drug release was sustained and depended on environmental pH, drug structure and drug concentration in the MaGICs. Moreover, these drug-loaded complexes exhibited high anticancer efficacy against MCF-7 breast cancer cells. The prominent MRI relaxivities and high anticancer efficacy suggest that these MaGICs have potential as effective dual imaging and chemotherapeutic agents. / Ph. D.

No description available.