Centrifugal Force-Induced Alignment in the Self-Assembly of Block Copolymers

Abstract

In this study, a facile method is introduced for fabricating unidirectional block copolymer (BCP) self-assembly patterns induced by centrifugal force. Centrifugal force can be easily applied and manipulated but has never been used to control the orientation of soft matter, including BCP. During centrifugal force-induced self-assembly, the centrifugal force acts as a shear force in the BCP film to effectively align the BCP domains without a guide template. The structural analysis shows the notable improvement in the degree of orientation as the shear stress increased. Moreover, the shear stress applied by the centrifuge is calculated and systematically controlled by adjusting the rotation speed, film thickness, and radial distance within the centrifuge. This approach offers an effective route to fabricating well-aligned nanopatterns from BCPs without a guiding template or complicated facilities.

Improved Exciton Bandwidth and Edge-On Oriented Ordering of Donor–Acceptor Copolymer Thin Films

“…The expected deterioration of BP (decrease of W-value) with increasing ω in low c-value films is due to the increased E induced entanglement during deposition of the well separated less entangled aggregates in solution, while the unexpected improvement of BP (increase of W-value) with increasing ω in high c-value films is due to the increased centrifugal force induced disentanglement during deposition of the large size overlapped and entangled aggregates in solution. 31,62,63 The radial distance average centrifugal force experienced by any aggregate during spin coating is related to its mass apart from the spinning speed. 63 It is well expected that the overlapped and entangled aggregates, which are known to form in the high c-value solution of high viscosity regime, will have effective mass (m*) much larger than that (m) of the well separated less entangled aggregates formed in the low c-value solution of low viscosity regime.…”

“…31,62,63 The radial distance average centrifugal force experienced by any aggregate during spin coating is related to its mass apart from the spinning speed. 63 It is well expected that the overlapped and entangled aggregates, which are known to form in the high c-value solution of high viscosity regime, will have effective mass (m*) much larger than that (m) of the well separated less entangled aggregates formed in the low c-value solution of low viscosity regime. 31,32 Such relatively large effective mass (m* ≫ m) along with the increasing ω creates a large centrifugal force on the entangled aggregates during spin coating to disentangle them.…”