Large Stokes-Shifted Photoluminescence of Sulfur-Containing Imide Compounds and Polyimides Induced by Transient Conformational Changes upon Excitation.

Authors

Hiroka Yamamatsu, Mayuko Nara, Shinji Ando

Published in

The journal of physical chemistry. B. Apr 22, 2025. Epub Apr 22, 2025.

Abstract

The optical absorption and photoluminescence (PL) properties of a series of sulfur-containing semialicyclic polyimides (S-PIs) were examined to develop thermally stable functional polymers with high glass transition temperatures, high optical transparencies, and large Stokes-shifted PL. These S-PIs were synthesized using tetracarboxylic dianhydrides, including thioether (-S-) linkages, such as 4,4-thiodiphthalic anhydride (SDPA), 4,4'-[p-phenylenebis(thio)]diphthalic anhydride (2SDEA), 4,4'-[p-thiobis(phenylene sulfanyl)] diphthalic anhydride (3SDEA), and trans-1,4-cyclohexanediamine (1,4-tDACH). In addition, the optical and PL properties of three types of imide model compounds (MCs) were investigated. All the S-PI films exhibited blue or green fluorescence (FL) under ambient conditions (in air at 295 K), weak room temperature phosphorescence (RTP) under vacuum, and bright green phosphorescence (PH) at lower temperatures (∼77 K). The intersystem crossing (ISC) rates at 77 K were significantly higher than those of the polyimides containing diphenyl-ether (-O-) linkages, primarily due to the enhancement of ISC by the heavy-atom effect of the sulfur atoms. MCs with multiple thioether (-S-) linkages exhibited a peculiar green or greenish-yellow FL with very large Stokes shifts in the CHCl₃ solution. This behavior was due to the transient conformational change from the kinked structure in the ground state to a skewed structure in the excited singlet state. In addition, all the MCs dispersed in a poly(methyl methacrylate) matrix exhibited distinctive RTP owing to the restricted conformational changes in the rigid matrix. These results provide effective guidelines for designing polymers exhibiting large Stokes-shifted FL and PH at longer wavelengths in the visible region.

PMID:
40261976
Bibliographic data and abstract were imported from PubMed on 23 Apr 2025.

Read full publication at:
Please sign in to see all details.

Stats

1-terrible, 9-excellent. How would you rate this publication? Sign in in to submit your rating.

Post a comment

You need to be signed in to post comments. You can sign in here.

Comments

There are no comments yet.