This thesis research focuses on fundamental understanding regarding the morphological transitions of weak polyelectrolyte multilayers (PEMs) formed by the layer-by-layer (LbL) electrostatic assembly of oppositely charged polymers. he first part of this thesis focuses on patterning polyelectrolyte multilayers that are able to undergo transitions from continuous films to porous materials by using hydrogel stamps. The stamping process is able to locally etch and pattern the porous transition in the LbL films by using reactive wet stamping (r-WETS). It was found that r-WETS of PEMs can also enable the modification of chemical functionality. The second part is an investigation about morphological changes of weak polyelectrolyte multilayers assembled with PAH and PAA using r-WETS in which hydrogel stamp material was soaked into various salt solutions and then applied to the LbL films. Also, in this study we presented a novel strategy to create a continuous gradient structure in thickness or porosity along the lateral direction of the thin films using concentration gradient salt stamping. The third part is an investigation regarding the mechanism of the transition from a continuous morphology to a porous morphology within weak polyelectrolyte multilayers. These morphological changes were able to be created by both acidic and basic post-assembly treatments, showing various morphological transitions from the introduction of porosity to the collapse of these porous structures and the eventual dissolution of the films. A similar observation of morphological transitions in weak polyelectrolyte multilayers was obtained by applying an electric field to the films in the fourth part of this thesis. Exposure to an electric field resulted in the creation of a porous structure, which can be ascribed to local changes in pH and subsequent structural rearrangements of the weak polyelectrolyte constituents. The final part of this thesis is to make PEMs into nanostructured matrices for inorganic synthesis. Multilayers possessing ion-exchangeable carboxylic acid groups were used for binding metal catalysts such as platinum (Pt) nanoparticles (NPs) within the film. Therefore, polyelectrolyte multilayers were able to stabilize catalytic Pt NPs in order to increase the useful time of catalyst materials suitable for use in proton exchange membrane fuel cells.

Materiais auto-organizados constituídos de V2O5 xerogel, poli(etilenoimina) (PEI) e nanopartículas de carbono (NpCs) foram obtidos por meio da técnica camada-por-camada (LbL). A metodologia aplicada permitiu a obtenção de filmes finos com elevado controle de espessura além de permitir um crescimento linear dos filmes, denominados neste trabalho V2O5/PEI e V2O5/PEI/NpCs. Além disso, o desempenho eletroquímico dos materiais auto-organizados foi comparado a um eletrodo de V2O5. Análises de FTIR mostraram que interações específicas entre os grupos amina do PEI e os grupos carboxila do V2O5 são responsáveis pelo crescimento do filme. Estas interações permitem a formação de um campo eletrostático capaz de blindar as interações entre os íons lítio e os oxigênios da vanadila (V=O) e, por consequência, são responsáveis pelo aumento na mobilidade iônica dos íons lítio no interior da matriz hospedeira e, portanto, um aumento na capacidade de armazenamento de carga. Resultados obtidos através de medidas de carga/descarga mostram que o V2O5/PEI/NpCs apresenta uma melhor desempenho do que os demais materiais estudados neste trabalho. Estes resultados mostram que a capacidade específica do V2O5/PEI/NpCs foi de 137 mA h g-1 para a menor densidade de corrente aplicada e aproximadamente 1,6 vezes maior do que os valores de capacidade específica para os outros materiais para a maior densidade de corrente aplicada. Além disso, estas medidas permitiram a observação de uma menor variação na razão estequiométrica máxima (xmáx) em função das densidades de corrente aplicadas para os filmes auto-organizados, fato este relacionado a uma maior mobilidade iônica dos íons lítio no interior dessas matrizes. Os resultados obtidos a partir de espectroscopia de impedância eletroquímica (EIS) mostraram que a difusão dos íons lítio no interior das matrizes auto-organizadas é maior do que no caso do V2O5, cujos valores do coeficiente de difusão foram de 1,64 x 10-15, 1,21 x 10-14 e 2,26 x 10-14 cm2 s-1 para os filmes V2O5, V2O5/PEI e V2O5/PEI/NpCs, respectivamente. Sendo assim, o polímero e as NpCs promoveram novos caminhos condutores e permitiram a conexão elétrica entre camadas isoladas da matriz V2O5. Dessa forma, novos nanocompósitos foram obtidos visando demonstrar o método de auto-organização empregado para melhorar o transporte de carga em matrizes hospedeiras. / Self-assembled materials constituted of V2O5 xerogel, poly (ethyleneimine) (PEI), and carbon nanoparticles (CNPs) were obtained by the layer-by-layer (LbL) technique. The applied methodology permitted the obtainment of thin films with high thickness control and also permitted a linear growth of the films, which will be named V2O5/PEI and V2O5/PEI/CNPs. Besides, the electrochemical performance of the self-assembled materials was compared to a V2O5 electrode. FTIR analyses showed that the specific interactions between the amine groups of PEI and the vanadyl groups of the V2O5 are responsible for the film growth. These interactions permitted the formation of an electrostatic shield capable of hindering the interactions between the lithium ions and the vanadyl oxygen atoms (V=O) and are consequently responsible for the enhancement on the ionic mobility of the lithium ions within the host matrix, leading to a higher energy storage capability. Results obtained by the charge/discharge measurements showed that V2O5/PEI/CNPs presents a better performance than the other materials studied for this research. These results demonstrated that the specific capacity of the V2O5/PEI/CNPs was 137 mA h g-1 under the lowest current density applied and approximately 1.6 times higher than the specific capacity values obtained for the other materials under the highest current density applied. Moreover, it was observed that the variation of the maximum stoichiometric ratio (xmax) as a function of the current density is lower for the self-assembled materials than for the V2O5 electrode, which can be related to the higher ionic mobility of the lithium ion within the self-assembled materials. Electrochemical Impedance Spectroscopy (EIS) data demonstrated that the diffusion of the lithium ions within the self-assembled materials is higher than within the V2O5 electrode, and the diffusion coefficients were 1.64 x 10-15, 1.21 x 10-14 e 2.26 x 10-14 cm2 s-1 for V2O5, V2O5/PEI and V2O5/PEI/CNPs, respectively. Thus, the polymer and the CNPs provided new conducting pathways and connected isolated V2O5 chains in the host matrix. Therefore, novel spontaneous nanocomposites were formed, aiming to demonstrate the self-assembled method adopted for improving charge transport within host matrices.

Materiais auto-organizados constituídos de V2O5 xerogel, poli(etilenoimina) (PEI) e nanopartículas de carbono (NpCs) foram obtidos por meio da técnica camada-por-camada (LbL). A metodologia aplicada permitiu a obtenção de filmes finos com elevado controle de espessura além de permitir um crescimento linear dos filmes, denominados neste trabalho V2O5/PEI e V2O5/PEI/NpCs. Além disso, o desempenho eletroquímico dos materiais auto-organizados foi comparado a um eletrodo de V2O5. Análises de FTIR mostraram que interações específicas entre os grupos amina do PEI e os grupos carboxila do V2O5 são responsáveis pelo crescimento do filme. Estas interações permitem a formação de um campo eletrostático capaz de blindar as interações entre os íons lítio e os oxigênios da vanadila (V=O) e, por consequência, são responsáveis pelo aumento na mobilidade iônica dos íons lítio no interior da matriz hospedeira e, portanto, um aumento na capacidade de armazenamento de carga. Resultados obtidos através de medidas de carga/descarga mostram que o V2O5/PEI/NpCs apresenta uma melhor desempenho do que os demais materiais estudados neste trabalho. Estes resultados mostram que a capacidade específica do V2O5/PEI/NpCs foi de 137 mA h g-1 para a menor densidade de corrente aplicada e aproximadamente 1,6 vezes maior do que os valores de capacidade específica para os outros materiais para a maior densidade de corrente aplicada. Além disso, estas medidas permitiram a observação de uma menor variação na razão estequiométrica máxima (xmáx) em função das densidades de corrente aplicadas para os filmes auto-organizados, fato este relacionado a uma maior mobilidade iônica dos íons lítio no interior dessas matrizes. Os resultados obtidos a partir de espectroscopia de impedância eletroquímica (EIS) mostraram que a difusão dos íons lítio no interior das matrizes auto-organizadas é maior do que no caso do V2O5, cujos valores do coeficiente de difusão foram de 1,64 x 10-15, 1,21 x 10-14 e 2,26 x 10-14 cm2 s-1 para os filmes V2O5, V2O5/PEI e V2O5/PEI/NpCs, respectivamente. Sendo assim, o polímero e as NpCs promoveram novos caminhos condutores e permitiram a conexão elétrica entre camadas isoladas da matriz V2O5. Dessa forma, novos nanocompósitos foram obtidos visando demonstrar o método de auto-organização empregado para melhorar o transporte de carga em matrizes hospedeiras. / Self-assembled materials constituted of V2O5 xerogel, poly (ethyleneimine) (PEI), and carbon nanoparticles (CNPs) were obtained by the layer-by-layer (LbL) technique. The applied methodology permitted the obtainment of thin films with high thickness control and also permitted a linear growth of the films, which will be named V2O5/PEI and V2O5/PEI/CNPs. Besides, the electrochemical performance of the self-assembled materials was compared to a V2O5 electrode. FTIR analyses showed that the specific interactions between the amine groups of PEI and the vanadyl groups of the V2O5 are responsible for the film growth. These interactions permitted the formation of an electrostatic shield capable of hindering the interactions between the lithium ions and the vanadyl oxygen atoms (V=O) and are consequently responsible for the enhancement on the ionic mobility of the lithium ions within the host matrix, leading to a higher energy storage capability. Results obtained by the charge/discharge measurements showed that V2O5/PEI/CNPs presents a better performance than the other materials studied for this research. These results demonstrated that the specific capacity of the V2O5/PEI/CNPs was 137 mA h g-1 under the lowest current density applied and approximately 1.6 times higher than the specific capacity values obtained for the other materials under the highest current density applied. Moreover, it was observed that the variation of the maximum stoichiometric ratio (xmax) as a function of the current density is lower for the self-assembled materials than for the V2O5 electrode, which can be related to the higher ionic mobility of the lithium ion within the self-assembled materials. Electrochemical Impedance Spectroscopy (EIS) data demonstrated that the diffusion of the lithium ions within the self-assembled materials is higher than within the V2O5 electrode, and the diffusion coefficients were 1.64 x 10-15, 1.21 x 10-14 e 2.26 x 10-14 cm2 s-1 for V2O5, V2O5/PEI and V2O5/PEI/CNPs, respectively. Thus, the polymer and the CNPs provided new conducting pathways and connected isolated V2O5 chains in the host matrix. Therefore, novel spontaneous nanocomposites were formed, aiming to demonstrate the self-assembled method adopted for improving charge transport within host matrices.

This thesis deals with solving of the Rubik's cube. It describes the Rubik's cube and the famous methods for its composition. The main goal of this work is to propose an evelutionary method that for any configuration of blocks will lead to its composition. The theis describes the problem encoding, the proposed evelutionary algorithm and its proper configuration and deployment. The achieved results are commented on and compared with other known mehtods in conclusions.