Perylene diimide-based supramolecular polymer with temperature-sensitive ratiometric fluorescence responsiveness in solution and gels

Abstract

A novel amphiphilic fluorescence building block with perylene diimide (PDI) as the core and quadruple H-bonding groups (UPy) as wings (UPy-PDI-UPy) has been synthesized. It shows interesting thermo-responsive ratiometric dual-emission properties in both aqueous solution and the hydrogel state. Further contrast experiments with two other analogous derivatives, namely UPy-TPDI-UPy and TEG-PDI-TEG, indicated that the presence of supramolecular aggregation induced an emission enhancement effect between the UPy-PDI-UPy molecules, attributed to the synergetic effect of intermolecular intrinsic π-π stacking, the hydrophobic effect and highly directional quadruple H-bonding. In DMF/H2O (v:v = 1:1), UPy-PDI-UPy self-assembles into nanoparticles with obvious ratiometric fluorescence responsiveness towards temperature in the range of 20-80 °C. Moreover, UPy-PDI-UPy can form a thermo-responsive hydrogel by dispersing in PEG-containing aqueous solution. The hydrogels show a temperature-dependent ratiometric dual-emission with a narrow responsive range of 20-39 °C and an excellent renewable property. This innovative research helps to fabricate novel responsive luminescent materials by using the supramolecular self-assembly behavior.