# Photopolymerization of Styrene–Naphthalenediimide Monomer: Formation of Pattern and Electrochromism

## TL;DR

This paper describes a new electrochromic polymer made from a styrene–naphthalenediimide monomer that changes color and is stable over many cycles.

## Contribution

The study introduces a novel photopolymerization method for creating stable electrochromic polymer layers.

## Key findings

- The polymer exhibits a visible color change from transparent to green through reduction reactions.
- The electrochromic device showed stability over 500 redox cycles with fast switching times of 18 s and 6 s.
- Photopolymerization of the monomer is shown to be effective for generating electrochromic polymer layers.

## Abstract

The electrochromic naphthalenediimide (NDI) based monomer containing styrene pedant groups, which are capable of polymerization, was prepared, and the formation of its polymer via a photopolymerization reaction was described. Both the monomer and polymer exhibited a color change in the visible range from transparent or slightly yellow, respectively, followed by brown-red to green. This was the result of a two-step reduction reaction of NDI core to radical anion and dianion, respectively. The device constructed using the polymer as an active material was found to exhibit good electrochromic stability over 500 redox cycles. The switching times were calculated to be 18 s and 6 s for the coloration and bleaching steps, respectively. The presented results showed the usability of the photopolymerization of styrene-based monomers in the generation of the stable electrochromic layers of polymers.