Sub-10 nm Structures Constructed by a Rod-Coil Block Copolymer

Block copolymers (BCPs) can self-assemble into various nanostructures, with periodic sizes generally around 20-100 nm. In order to obtain self-assembled structures with even smaller sizes, it is necessary to design high-χ BCPs. It is known that the properties of rod blocks and coil blocks are quite different. Theoretically, microphase separation will occur when χN value is greater than 5 for rod-coil BCPs. Therefore, ordered structures can be formed even when the total polymerization degree is small. In this work, BCPs containing polydimethylsiloxane (PDMS) as a coil block and a rod block, poly[4'-(methoxy)-2-vinylbiphenyl-4-methyl ether] (PMVBP), are synthesized. Small-angle X-ray scattering (SAXS) is used to characterize the bulk self-assembled structures of the BCPs. PDMS-b-PMVBP can form structures including lamellae (LAM), a bicontinuous phase, and hexagonally packed cylinders (HEX). In addition, a LAM structure with a minimum periodic size of 9.34 nm is obtained. Using temperature-dependent SAXS, the order-disorder phase transition temperature (T_ODT) of PDMS-b-PMVBP is obtained, and the interaction parameter χ at room temperature (25 °C) is calculated to be a high value of 0.632.