Effect of Nanoparticle Inclusions and Solvent Annealing on Block Copolymer Morphology

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Palta, Deepali
Bucknall, David G.
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Using block copolymers for large-area periodic structure fabrication is of great interest because of the potential for low fabrication costs and simplicity of the processing. The concept is that by selective inclusion of the nanoparticles into one of the blocks of a self-assembling copolymer, the nanoparticles are forced into a defined spatial arrangement determined by the phase morphology of the copolymer. Although copolymers can form well defined structures, they inherently have a 'polycrystalline' structure in the bulk, meaning that there is no long-range order of the domains. This thesis addresses both the effect of inclusion of the nanoparticles and the long range ordering of block copolymer domains. The first part of the thesis focuses on the study of the effect of nanoparticle inclusions on the phase morphology of the poly(styrene-butadiene) diblock and poly(styrene-butadiene-styrene) triblock copolymers. For gold inclusions, it was found that even at relatively low concentrations of inclusions (less than 1 wt./vol.%) the block copolymer phase morphology is altered from that of the native copolymer. By contrast to the block copolymer-gold system, no significant changes in bulk morphology is observed for similar fullerene concentrations. In the second part of the thesis, the evolution of the order in cylinder forming poly(styrene-butadiene-styrene) triblock copolymer thin films as a function of the type of solvent vapor, exposure time to the saturated vapors and substrate surface energy is discussed. Solvent vapors of dimethoxyethane, ethyl acetate and cyclohexanone were found to be the most effective for our polymer films. Solvent vapors differing in their selectivity towards the block copolymer domains have different kinetics of ordering which is explained in terms of the difference in the interaction of the solvent between the two different copolymer blocks.
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