Controllable Blue Shift and Enhancement Emission during the Gradually Increasing Molecular Weight of Polyacrylamide.

Abstract

Nonconventional luminescent polymers have become research hotspots due to their advantages such as persistent room temperature phosphorescence (p-RTP) emission and strong film-forming properties. It has been proven that the molecular weight(MW) of such luminescent polymers has a significant impact on their emission over a large range, generally with a red shift as the MW increases. Herein, four controllable MW polyacrylamide (PAM) were prepared via Reversible addition-fragmentation chain transfer polymerization (RAFT) polymerization, and their photoluminescence quantum yield (PLQY) and p-RTP lifetimes gradually increase with the increasing MW. The emission of p-RTP gradually shifts blue with increasing MW, which is likely due to the gradually changing interactions between the electron rich portion in RAFT reagent and the increasing AM units in the molecular chain. These can be reasonably explained through small angle X-ray scattering (SAXS), the clustering triggered emission (CTE) mechanism and supported by theoretical calculations. Powder with controllable p-RTP capability has the potential for strategic anti-counterfeiting encryption. The above results not only promote the development of CTE mechanism towards more precise explanations, but also provide new ideas for the preparation of nonconventional luminescent polymers with controllable p-RTP emission performance. This article is protected by copyright. All rights reserved.