| dc.description.abstract | In this study, we have investigated the solution behaviours of PS24k-P4VP9.5k(TOB)0.7 in o-xylene by means of small-angle X-ray scattering. We found three regions of structural evolution depending on polymer concentrations in o-xylene. At low concentrations (0.12.5 mass%) PS24k-P4VP9.5k(TOB)0.7 forms micelles whereas at medium concentrations (510 mass%), single chains comprised of supramolecular PSP4VP/TOB complex are dispersed in o-xylene. By contrast, as PS24k-P4VP9.5k(TOB)0.7 becomes higher than a critical concentration (> 10 mass%), the single chains of supramolecular complex can self-assemble to form an ordered structure. FTIR data demonstrate that TOB molecules exhibit a high tendency to selectively bind with the P4VP block because of hydrogen bonds. As a result, the selective addition of TOB within the P4VP block reduces the χPS – P4VP (the Flory-Huggins interaction between the PS and P4VP) so that the molecular micelles (formed by the aggregation of the whole PS-b-P4VP chain molecules) dissolute to form free single chains comprised of supramolecular PSP4VP/TOB complex. Because the free single chains add flexibility in self-assembly in thin film nano-structures, spin-coating from an o-xylene solution of 5 mass% of PS24k-P4VP9.5k(TOB)0.7 followed by solvent annealing in saturated vapour of a PS-selective solvent can lead to an ordered array of nanodomains in thin films. The reason is that at high vapor pressure, TOB molecules preferentially form homeotropic-oriented nematic phase within the P4VP domain, which improves the long-ranged ordering of self-assembled nanodomains in thin films. By contrast, upon solvent annealing in unsaturated vapour of a non-selective solvent, TOB molecules intend to form a column phase within the P4VP matrix. Since the column phase of TOB causes planar inter-domain interfaces between PS and P4VP blocks, the PS nanocylinders embedded with the P4VP9.5k(TOB)0.7 matrix exhibit a hexagonal shape. Moreover, the formation of the TOB column phase also increases rigidity in the PS cylinders. As a result, any defects, such as dislocations as well as disclinations, may cause high entropic penalty. In order to release this penalty around the effects, the PS nanocylinders tend to rupture, giving rise to polygrains of short PS cylinders within the P4VP/TOB matrix.
For potential applications, we used deposit and scrape wet polymer solutions onto substrates under shearing fields to form thick films. Then isothermal annealing at a high temperature was imposed onto the films to induce highly-oriented arrays of parallel nanocylidrical nanodomains. Interestingly, after the scraped films were subjected to solvent annealing in vapor of a non-selective solvent,we obtained high arrays of hexagonal-packing perpendicularly-oriented hexagonal-shaped cylinders. | en_US |