In-situ investigation of shear force induced solution phase transformation of ABA-type tri-block copolymers

Interplay between self-assembly and phase behaviors for block copolymer under external force is one of the significant research directions in materials science. Rheo-small-angle neutron scattering (Rheo-SANS) is a powerful in situ tool that enables the investigation of this subject. Herein, we present the installation and commissioning of the Rheo-SANS instrument, in conjunction with an Anton-Paar MCR 302e rheometer, at the small-angle neutron scattering beamline (BL01) of the China Spallation Neutron Source (CSNS). We provide a detailed description of the design, construction and technical specifications of the Rheo-SANS instrument. Taking advantage of this newly built Rheo-SANS facility, we are able to investigate the phase transformation behavior of block copolymer under external shear force, which is otherwise impossible for traditional characterization methods. We demonstrate through Rheo-SANS experiment that for block copolymer with small packing parameter (Pluronic F127), shear force can cause orientation of the Hcp phase in solid-like state. While in liquid-like state, shear force hardly orients the system. On the contrary, for block copolymer with large packing parameter (Pluronic L64), shear force can easily cause orientation of the lamella phase in liquid-like state, while in solid-like state, much large shear force is needed to induce the orientation of the lamella phase.