Crystallization in diblock copolymer thin films at different degrees of supercooling

Abstract

The crystalline structures in thin films of polystyrene-b-poly͑ethylene oxide͒ ͑PS-b-PEO͒ diblock copolymers were studied in dependence on the degree of supercooling. Atomic force microscopy showed that the crystalline domains ͑lamellae͒ consist of grains, which are macroscopic at low and intermediate degrees of supercooling, but of submicrometer size for strong supercooling. Using grazing-incidence wide-angle x-ray scattering, we could determine the grain orientation distribution function which shows that the chain stems are perpendicular to the lamellae at low supercooling, but tilted at intermediate and strong supercooling. These results suggest that, at intermediate and strong supercooling, the crystalline PEO lamellae do not grow homogeneously, but by the formation of small crystallites at the growth front.

Orientation Control and Crystallization in a Soft Confined Phase Separated Block Copolymer

“…AFM has been successfully employed to study diblock copolymers [39][40][41] , for example allowing direct visualization of crystallization in both cylindrical and spherical microdomains 42 .…”

Morphology of Semicrystalline Diblock Copolymer Thin Films upon Directional Solvent Vapor Flow

“…The flat square-shaped crystals are formed by a reorganization process of the film so that PS chains flip to the top of the PEO crystals during the crystallization step. The crystallization process of the PEO in the thin PEO containing DBC films has previously been observed [36,37] and dewetted polymer film were also obtained (see Figure 2a). In contrast, for the thicker film (87 nm), aggregates of crystalline PEO (Figure 2b) grow from a sheaf-like central structure and behave similar to those known for spherulite crystals of pure PEO films.…”

“…The GIXRD Bragg peak we have observed in case of the 65 nm thick film is thus assigned for the (120) plane of an oriented PEO monoclinic crystal and suggests that the c-axis of the unit cell is oriented perpendicular to the film surface. [37] The chains are packed regularly together along the c-axis and perpendicular to the cylinder axis (as shown schematically in Figure 6). …”

“…Recently, it has been reported [37,43] that for lamella forming P(S-b-EO) diblock copolymer the crystal orientation (the c-axis of the PEO crystals) can change from random to perpendicular, then to inclined, and finally to parallel with respect to the lamellar surface, depending on the crystallization temperature. With respect to the surface plane in our sample, the perpendicular orientation of the PEO crystalline stems should be considered as an average orientation due to the tethering of the confined PEO block at the interface.…”

Formation and thermal stability of liquid phase in layered film systems

“…A C C E P T E D ACCEPTED MANUSCRIPT 2 The value of supercooling is affected by many factors, among which the determinative ones are often all sorts of impurities [4][5][6], which are the potential centers of crystallization. To get rid of them there are different ways of cleaning them up and of multiple melting of the materials under study that can be combined with containerless techniques in zero gravity or electrostatic levitation [7].…”