Non-Volatile, Multi-Level Optical Information Storage of Block Copolymer Structural Color

Abstract

Structural colors (SCs) of photonic crystals (PCs) have attracted much attention due to their broad applications in the field of displays, sensors, and media boards. Compared with different PCs, the block copolymer (BCP) based PCs has an easy processing route due to the self-assembled microstructure of BCP. Here, we demonstrate a non-volatile, multi-level optical information storage of BCP SC. Our method is based on the controlled cross-linking of the BCP PC's microdomains resulting from the photo-thermal conversion. The process of photo-thermal writing is accomplished by time, power, and position controlled near infrared (NIR) laser exposure on a poly (styrene-block-quaternized 2-vinyl pyridine) (PS-b-QP2VP) PC on a photo-thermal conversion layer consists of poly (3,4-ethylenedioxythiophene) doped with tosylate. The localized heat arising from the NIR-to-thermal conversion of the photo-thermal conversion layer is exerted on the BCP PC with alternating in-plane PS and QP2VP lamellae stacks. Thermal cross-linking consequentially occurs between quaternized pyridines due to heat transfer, which results in a programmed SC upon reading process with a swelling agent, ethanol. The degree of cross-linking of QP2VP domains is dependent upon laser-power and exposure time, allowing for multi-colored recording of SC per single spot, giving rise to a novel multi-level optical recording media based on BCP SC.