Molecular dynamics and formation of domains in block copolymers studied by high and low resolution NMR / Dinâmica molecular e formação de domínios em copolímeros em bloco estudados por RMN de alta e baixa resolução

AUTOR(ES)

Wesley de Souza Bezerra

FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

09/04/2012

RESUMO

The main objective of this dissertation is the use of NMR methods to characterize the phase separation and, to some extent, the dynamics of the molecular segments in block copolymers. In the first part, NMR Spin Diffusion methods were explored in order to evaluate their performance as well as the main experimental difficulties. For that, a reference tri-block polymer SEBS (styrene-block-butadiene-block-styrene), which had a well known morphology, was used. The experimental tests were carried out in NMR equipments with magnetic field of 0.47 T and 9.4 T and at low filed an alternative proposal for data analysis was used. A already shown in the literature, the results indicated that , despite being possible to accomplish these experiments in low field, the data analysis become more intricate due to the shorter T1 values at this magnetic field, requiring the use of numerical simulations, which make the method more model dependent. The second part was dedicated to the study of copolymers consisting of Polyoxyethylene (PEO) or Polyethylene Glycol (PEG-low molecular weight PEO) and polystyrene (PS) as well as copolymers based on PS and Poly acrylates with PEO branches (PMAPEG -Poly Methyl Acrylate Polyethylene Glicol). In these studies, 1H and 13C NMR methods as function of temperature were used to characterize the main dynamic transitions in the PEO chains. It was shown that, despite similar dynamic behavior was observed in all samples, the PS-PMAPEG copolymers present a smaller degree of motional heterogeneity, which was attributed to the similar local packing of the PMAPEG chains. Using Spin diffusion NMR information about the morphology of the samples were obtained, showing evidences of phase separation and domain formation in all samples, being the regularity of the domain related with the sample composition. The average domain sizes were estimated.

ASSUNTO(S)

block copolymers copolímeros em bloco difusão de spins nmr pmapeg pmapeg poe poe rmn spin diffusion

Documentos Relacionados

• Vegetable oil quality analisys of intact seeds through low resolution NMR
• USO DA RMN DE BAIXA RESOLUÇÃO NA AVALIAÇÃO DA DINÂMICA MOLECULAR DO Origanum vulgare
• Análise da qualidade de carne bovina por ressonância magnética nuclear em baixa resolução
• Avaliação da qualidade de frutas por Ressonância Magnética Nuclear em baixa resolução
• Avaliação da qualidade interna de banana por RMN em baixa resolução.