Density‐Dependent Emission Colors from a Conformation‐Switching Chromophore in Polyurethanes

Abstract

Achievingf ull-color emission from as ingle chromophore is not only highly desirable from practical considerations,but also greatly challenging for fundamental research. Herein, we demonstrated the density-dependent emission colors from as ingle boron-containing chromophore,f rom which multi-color fluorescent polyurethanes were prepared as well. Originating from its switchable molecular conformations, the emission color of the chromophore was found to be governed by the packing density and strongly influenced by hydrogen bonding interactions.T he chromophore was incorporated into polyurethanes to achievef ull-color emitting materials;t he emission color was only dependent on the chromophore density and could be tuned via synthetic approach by controlling the compositions.The emission colors could also be modulated by physical approaches,including by swelling/deswelling process,compression under high pressure, and even blending the fluorescent polyurethane with nonemitting ones.

Positional Isomerism-Mediated Copolymerization Realizing the Continuous Luminescence Color-Tuning of Liquid-Crystalline Polymers

“…To address the abovementioned issue, it is of significance to explore a new method for modulating emission colors based on the well-defined LC structure as a slight change in packing structure may give rise to unpredictable color alteration. − Random copolymerization of mesogens of different kinds has been demonstrated to be a simple yet effective synthetic method that can be used to tailor the LC properties. − Although copolymerization of different color-coded fluorophores has achieved variable emissions, − it is still rather difficult to achieve in ordered LC systems. The immiscibility of these common fluorophores may induce certain nanoscale phase separation or packing structural uncertainty due to the large differences in molecular dimension, geometry, etc. , Thus, it is desirable to explore suitable mesogenic fluorophore pairs, which should not only exhibit substantially different emissions but also have similar molecular architectures to facilitate mutual interaction and homogeneous coassembly into defined LC structures.…”