Order-Order Phase Transitions Induced by Supercritical Carbon Dioxide in Triblock Copolymer Thin Film

ANABELLA A. ABATE; GIANG T. VU; C. PIQUERAS; M.C DEL BARRIO; L. GÓMEZ; FRIEDERIKE SCHMID; D. A. VEGA

MACROMOLECULES

AMER CHEMICAL SOC

Año: 2019

0024-9297

We study the influence of supercritical carbon dioxide (Sc CO2) on the phasebehaviour of a cylinder forming polystyrene-block-polybutadiene-b-polystyrene (SBS)triblock copolymer thin film. Solvent annealing with Sc CO2 can produce patternswith long range order but these patterns become unstable for thin films with smallthickness. These results are in good agreement with self-consistent mean field calculations,which indicate that a dewetting transition occurs for thicknesses below the radiusof gyration of the molecule. After decompression and solvent extraction, the initiallyswollen polymer nanostructure suffers a strong reduction in the average domain spacing,which has a deleterious effect on the degree of order in the resulting pattern. Both,experiments and Cahn-Hilliard simulations suggest that during decompression the patternsuffers an order-order instability where the change in the lattice structure affectsmore profoundly short- than long-range order.