# Random Copolymerization: An Efficient Strategy for Significantly Enhancing Photothermal Performance Through Synergistic Open-Shell Radical and TICT Effects

## TL;DR

This paper introduces a new method to create efficient photothermal materials using random copolymers that combine donor and acceptor units to enhance performance.

## Contribution

A novel strategy using random copolymerization to synergistically enhance photothermal performance via open-shell radical and TICT effects.

## Key findings

- Random copolymers achieved a photothermal conversion efficiency of up to 58.5%.
- The PT temperature increased from 150 °C to 232 °C under laser irradiation.
- The materials showed good water evaporation rates.

## Abstract

Currently, photothermal (PT) polymers are gaining increasing attention in water evaporation, photocatalysis and photothermal therapy. However, high-performance PT polymers often require conjugated backbones and/or large fused units, which can impede non-radiative decay and lead to suboptimal PT performance. The development of general strategies for preparing high-performance PT polymers remains a significant challenge. In this paper, the high-performance donor–acceptor (D–A) random copolymers, named PBT4T-BBT-x (x = 0, 5, 10, 20 and 100), were fabricated by cross-mixing bithiophene donors with benzothiadiazole (BT) and benzodithiadiazole (BBT) acceptors. Notably, when the ratios of BT and BBT are finely tuned, the polymers exhibit significantly controllable open-shell radical effects and twisted intermolecular charge transfer (TICT) states. The synergistic effects of radicals and TICT states notably enhanced the PT performance of random copolymers. Specifically, when the proper ratios of BBT units are used, the photothermal conversion efficiency (PTCE) is remarkably increased from 21.7% to 58.5%, and the PT temperature obviously increases from 150 °C to 232 °C under 808 nm laser irradiation. Furthermore, the random copolymers exhibit good water evaporation rates. We propose that this strategy provides a valuable synthesis pathway for generating high-performance photothermal therapy and water evaporation materials.