Orientador: Watson Loh / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-07T11:45:40Z (GMT). No. of bitstreams: 1 Anselmo_AleteiaGarcia_M.pdf: 1348079 bytes, checksum: 03480ee468bf0185ae57c464c2020046 (MD5) Previous issue date: 2006 / Resumo: Neste trabalho estudou-se a partição do poli (óxido de propileno), PPO, poli (N - isopropilacrilamida), PNIPAM, poli (N-vinil-2- pirrolidona), PVP, e poli (óxido de etileno), PEO em sistemas líquidos bifásicos, entre as fases aquosa e orgânica (CHCI3, CH2Cl2 e C6H5CI). Os resultados obtidos indicaram que a partição do PPO, polímero hidrofóbico, é preferencial para as fases orgânicas em todos os sistemas bifásicos estudados, enquanto que para os polímeros hidrofílicos, tais como, o PVP e PNIPAM, a partição ocorre preferencialmente para a fase aquosa. As entalpias de transferência, da fase aquosa para a fase orgânica para estes polímeros, foram determinadas através da técnica de titulação calorimétrica isotérmica e revelaram que para todos os sistemas estudados o processo de transferência é endotérmico. Isto sugere que a solvatação dos polímeros pela fase aquosa é mais energética que quando comparada com a solvatação dos polímeros pela fase orgânica, e que, portanto, para o PPO, o processo de transferência é entropicamente dirigido. Spitzer e colaboradores observaram resultados similares para a partição do poli (óxido de etileno), PEO, em sistemas bifásicos contendo CHCl3 e CH2Cl2, (Spitzer et aI.; J. Phys. Chem. B 2002, 106, 12448). Em comparação com o PEO, os valores de entalpia de transferência obtidos para o PPO são mais positivos, o mesmo pode ser observado para o coeficiente de partição. A partição do PPO pode ser explicada em termos de efeito hidrofóbico, o qual propõe a liberação das moléculas de água que estariam solvatando o polímero quando este é transferido para a fase orgânica. / Abstract: In this work the partitioning of poly (propylene oxide), PPO, poly (Nisopropylacrylamide), PNIPAM, poly (vinyl pyrrolidone), PVP and poly (ethylene oxide), PEO between aqueous and organic phases (CHCI3, CH2Cl2 and C6H5CI) was investigated. The results reveal that for all biphasic systems the partitioning of PPO, a hydrophobic polymer, to organic phase is predominant, while for PVP and PNIPAM, hydrophilic polymers, partitioning is always preferential towards the aqueous phase. The enthalpies of transfer for these polymers from aqueous to organic phases were calorimetrically determined and revealed an endothermic process for all the systems investigated, suggesting that solvatation of polymers in aqueous phase is more energetic than organic phase and, therefore, the process of transfer must be entropically driven for PPO. Spitzer and coworkers observed similar results for the partitioning of PEO in biphasic systems containing CHCl3 and CH2Cl2, (Spitzer et aI.; J. Phys. Chem. B 2002, 106, 12448). In comparison with PEO, the enthalpies of transfer of PPO are more positive, the same being observed for the partition coefficients. These data indicate that partitioning of PPO can be explained within the framework of the hydrophobic effect, whereby water molecules that were originally solvating the polymer are released when this is transferred to the organic phase. / Mestrado / Físico-Química / Mestre em Química

Amphiphilic tri- and penta-block copolymers containing a polyurethane central block with pendant carboxylic acid groups flanked by hydroxyl functional polyether tails were synthesized. Our intention was to investigate the activities of these copolymers as dispersants for magnetite nanoparticles in biological media. A benzyl alkoxide initiator was utilized to prepare poly(ethylene oxide) (BzO-PEO-OH), poly(propylene oxide) (BzO-PPO-OH) and poly(ethylene oxide-b-propylene oxide) (poly(BzO-EO-b-PO-OH)) oligomeric tail blocks with varying lengths of PEO and PPO. The oligomers had a hydroxyl group at the terminal chain end and a benzyl-protected hydroxyl group at the initiated end. The polyether oligomers were incorporated into a block copolymer with a short polyurethane segment having approximately three carboxylic acid groups per chain. The block co-polyurethane was then hydrogenated to remove the benzyl group and yield primary hydroxyl functionality at the chain ends. End group analysis by 1H NMR showed the targeted ratio of PEO to PPO demonstrating control over block copolymer composition. Number average molecular weights determined by both 1H NMR and GPC were in agreement and close to targeted values demonstrating control over molecular weight. Titrations of the pentablock copolymers showed that the targeted value of approximately three carboxylic acid groups per chain was achieved. Heterobifunctional poly(ethylene oxide) (PEO) and poly(ethylene oxide-b-propylene oxide) (PEO-b-PPO) copolymers were synthesized utilizing heterobifunctional initiators to yield polymers having a hydroxyl group at one chain end and additional moieties at the other chain end. For PEO homopolymers, these moieties include maleimide, vinylsilane, and carboxylic acid functional groups. Heterobifunctional PEO oligomers with a maliemide end group were synthesized utilizing a double metal cyanide coordination catalyst to avoid side reactions that occur with a basic catalyst. PEO oligomers with vinylsilane end groups were synthesized via alkoxide-initiated living ring-opening polymerization, and this produced polymers with narrow molecular weight distributions. Heterobifunctional PEO-b-PPO block copolymers were synthesized in two steps where the double metal cyanide catalyst was used to polymerize propylene oxide (PO) initiated by 3-hydroxypropyltrivinylsilane. The PPO was then utilized as a macroinitiator to polymerize ethylene oxide (EO) with base catalysis. Heterobifunctional PEO and PEO-b-PPO block copolymers possessing carboxylic acid functional groups on one end were synthesized by reacting the vinyl groups with mercaptoacetic acid via an ene-thiol addition. / Ph. D.

No description available.

Well-defined heterobifunctional homopolyethers and amphiphilic block copolyethers containing a variety of functionalities were designed, synthesized, and characterized via GPC and 1H NMR. These have included controlled molecular weight cholesterol-PEO-OH, mono- and trivinylsilyl-PEO-OH, monovinylsilyl-PEO-PPO-OH, monovinylsilyl-PEO-PPO-PEO-OH, maleimide-PEO-OH, stearyl alcohol-PEO-OH, propargyl alcohol-PEO-OH, trivinylsilyl-PPO-OH, trivinylsilyl-PPO-PEO-OH, and benzyl alcohol-initiated poly(allyl glycidyl ether)-OH. The focus of polymers utilized in this study involved the mono- and trivinylsilyl polyethers. The vinylsilyl endgroups on these materials were functionalized with various bifunctional thiols through free radical addition of SH groups across the vinylsilyl double bonds. The resultant end-functional polyethers were adsorbed onto magnetite nanoparticles and the stabilities of the polymer-magnetite complexes were compared as a function of the type of anchoring moiety and the number of anchoring moieties per chain. Anchoring chemistries investigated in this work included carboxylates, alkylammonium ions, and zwitterionic phosphonates. The anchor group-magnetite bond stability was investigated in water and phosphate buffered saline (PBS). Through these studies, the zwitterionic phosphonate group was shown to be a better anchoring group for magnetite than either carboxylate or ammonium ions. Tri-zwitterionic phosphonate anchor groups provided stability of the complexes in PBS for a broad range of polymer loadings. Thus, investigations into the stability of polyether-magnetite complexes in PBS focused on hydrophilic zwitterionic phosphonate-PEO-OH and amphiphilic zwitterionic phosphonate-PPO-b-PEO-OH oligomer coatings on the surface of magnetite. Superparamagnetic magnetite nanoparticles are of interest as potential contrast-enhancement agents for MRI imaging. Thus, transverse NMR relaxivities of these complexes were studied as a function of chemical composition and nanostructure size and compared to commercial contrast agents. The amphiphilic polyether-magnetite nanoparticles were shown to be stable in both aqueous media as well as physiological media and have much higher transverse relaxation values, r2, than those of commercial contrast agents and other materials in the literature. / Ph. D.

The composition and stability of polymer-magnetite complexes is essential for their use as a treatment for retinal detachment, for drug targeting and delivery, and for use as a MRI contrast agent. This work outlines a general methodology to design well-defined, stable polymer-magnetite complexes. Colloidal modeling was developed and validated to describe polymer brush extension from the magnetite core. This allowed for the observation of deviations from expected behavior as well as the precise control of polymer-particle complex size. Application of the modified Derjaguin-Verwey-Landau-Overbeek (DLVO) theory allowed the determination of the polymer loading and molecular weight necessary to sterically stabilize primary magnetite particles. Anchoring of polyethers to the magnetite nanoparticle surface was examined using three different types of anchor groups: carboxylic acid, ammonium, and zwitterionic phosphonate. As assessed by dynamic light scattering (DLS), the zwitterionic phosphonate group provided far more robust anchoring than either the carboxylic acid or ammonium anchor groups, which was attributed to an extremely strong interaction between the phosphonate anchor and the magnetite surface. Coverage of the magnetite surface by the anchor group was found to be a critical design variable for the stability of the zwitterionic phosphonate groups, and the use of a tri-zwitterionic phosphonate anchor provided stability in phosphate buffered saline (PBS) for a large range of polymer loadings. Incorporation of an amphiphlic poly(propylene oxide)-b-poly(ethyelene oxide) (PPO-b-PEO) diblock copolymer attached to the magnetite surface was examined through colloidal modeling and DLS. The relaxivity of the complexes was related to aggregation behavior observed through DLS. This indicated the presence of a hydrophobic interaction between the PPO layers of neighboring complexes. When this interaction was large enough, the complexes exhibited an increased relaxivity and cellular uptake. Thus, we have developed a methodology that allows for design of polymer-magnetite complexes with controlled sizes (within 8% of predicted values). Application of this methodology incorporated with modified DLVO theory aids in the design of colloidally stable complexes with minimum polymer loading. Finally, determination of an anchor group stable in the presence of phosphate salts at all magnetite loadings allows for the design of materials with minimum polymer loadings in biological systems. / Ph. D.

The goal of this work is to examine the applicability of the Lauritzen-Hoflinan (LH) surface nucleation theory to the crystallization kinetics of poly(ε-caprolactone), PCL. This theory has successfully predicted a number of experimental observations such as the temperature dependence of spherulitic growth rates and the inverse relation between undercooling and the lamellar thickness. Claims have appeared in the literature that analysis of growth rate data using the LH theory does not yield physically meaningful parameters. This work will show that the lateral and fold interfacial free energy parameters, σ and σₑ, found by analysis with the LH theory are related to the chemical structure of the polymer chain in the case of PCL. The fold interfacial free energy is related to the chain stiffness, and a recent proposal relates σ to the characteristic ratio, C_∞. This work will examine the validity of the proposed relationship for the case of PCL. The effect of polymer chain architecture on the crystallization behavior was also investigated. The crystallization behavior of poly(ε-caprolactone) was compared and contrasted to that of a triblock copolymer containing (ε-caprolactone) blocks. / Ph. D.

Superparamagnetic nanoparticles have potential applications in targeted drug delivery and as magnetic resonance imaging contrast agents. Magnetite clusters are of particular interest for these applications because they provide higher magnetic flux (under a magnetic field) than individual magnetite nanoparticles, are biocompatible, and their size and compositions can be controlled. This thesis involves the controlled synthesis and characterization of clusters composed of magnetite nanoparticles stabilized with an amphiphilic block copolymer. It outlines a method to design and form well-defined and colloidally stable magnetite clusters. A Multi Inlet Vortex mixer (MIVM) was used because it is a continuous process that yields particles with relatively narrow and controlled size distributions. In the MIVM, four liquid streams collide under turbulent conditions in the mixing chamber where clusters form within milliseconds. The formation of magnetite clusters was studied in the presence of amphiphilic block copolymers containing poly (ethylene oxide) to provide steric stabilization and control of size distributions using flash nanoprecipitation. First, the mixer was tested using β-carotene as a model compound to form nanoparticles stabilized with an amphiphilic triblock copolymer poly(propylene oxide)-b-poly(ethylene oxide) (F127) at different Reynolds numbers and supersaturation values. Size analysis was done using dynamic light scattering and nanoparticle tracking analysis techniques. The cluster structure was studied using electron microscopy and magnetite compositions were measured using thermogravimetric analysis. Finally, the stability of magnetite clusters was studied over time and the effect of an applied magnetite field on the colloidal stability was investigated. / Master of Science

Copolymers that contain terminal or pendent functional groups have great potential in the biomedical area due to their biocompatibility and tunable properties.1-3 In this research, two vinyl functional epoxides, vinyldimethylsilylpropyl glycidyl ether (VSiGE) and ethoxy vinyl glycidyl ether (EVGE), were synthesized. These heterobifunctional monomers were polymerizable via the epoxide groups and can be functionalized via thiol-ene reactions through the pendent vinyl groups. A series of amphiphilic block copolyethers based on poly(ethylene oxide) and poly(1,2-butylene oxide) that incorporate VSiGE or EVGE were synthesized and characterized. The vinyl ether and vinyl silane functional groups were functionalized after polymerization and the functional polymers formed pH-sensitive micelles in aqueous medium. The copolyethers were loaded with ritonavir yielding well-controlled nanoparticles. Poly(L-glutamic acid) is comprised of naturally occurring L-glutamic acid repeating units that are linked together with amide bonds. In this research, we have prepared magnetic block ionomer complexes based on poly(ethylene oxide)-b-poly(L-glutamic acid) copolymers. This is of interest due to the biocompatibility and biodegradable nature of the poly(L-glutamic acid) component of the backbone. Allyl- and thiol-functional poly(ethylene oxide)-b-poly(L-glutamic acid) copolymers were also synthesized and coated onto the surface of iron oxide nanoparticles. Allyl- and thiol-tipped single particles were reacted with each other to prepare magnetic clusters. Transverse relaxivities of the clusters were found to be significantly higher than that of single particles. One major problem in commercial development of therapeutic proteins is their poor transport across cellular membranes and biological barriers such as the blood-brain barrier (BBB). One solution to this problem is to modify proteins with amphiphilic block copolymers such as PEO-b-PPO-b-PEO, Pluronics®. However, it isn't possible to independently tune the two PEO block lengths with commercial Pluronics® since a difunctional PPO macroinitator is utilized to grow both PEO blocks simultaneously (HO-EOn-b-POm-b-EOn-OH). Another challenge is introducing functional group which allows post-polymerization functionalization for specific applications. In this study, a series of heterobifunctional asymmetric amino-EOn1-b-POm-b-EOn2-OH block copolymers (APs) with different molecular weights of each block were synthesized and the amino terminal group was conjugated to an antioxidant enzyme, Cu/Zn superoxide dismutase (SOD1). The conjugates were characterized and their cellular uptake was investigated. / Ph. D.