Self-assembling and phase behavior of block copolymer melts and solutions

VEGA DA

Laboratório Nacional de Luz Síncrotron (LNLS). Campinas, Brasil.

Simposio; 17 Reunión de la Sociedade Brasileira de Cristalografia. Simpósio sobre Estrutura de Polímeros.; 2005

Sociedade Brasileira de Cristalografia

Charla invitada As a consequence of their ability to self assemble into nanoscale ordered structures block copolymers have received great attention in recent years. For components which are sufficiently dissimilar, microphase separation occurs, into morphologies such as spheres or cylinders of the minor component in a matrix of the majority block. Here we studied a matched diblock/triblock mixture in a selective solvent, that is, a styrene–isoprene (SI) diblock and an SIS triblock of nearly double the diblock molecular weight in squalane, a branched saturated hydrocarbon that is a good solvent for isoprene and a nonsolvent for styrene. A midblock- hydrogenated derivative of the SIS triblock [styrene-(ethylene-alt-propylene)-styrene; SEPS] is examined for comparison. At low polymer concentrations, the SAXS patterns can be quantitatively described by a model for the scattering from a liquid-like arrangement of hard spheres, as expected for disordered micelles. A transition from disordered micelles to an ordered (BCC) array occurs at approximately 13 wt % total polymer. We have also studied monolayer films of diblock copolymers. Two dimensional block copolymer systems are periodic on a 40 nanometer length scale and cover square centimeters so that large regions free of edge defects are available for investigation and application by lithographic processes.