Substitution position effect on photoluminescence emission and chain conformation of poly(diphenylacetylene) derivatives

Abstract

The significant variation in photoluminescence emission of poly(diphenylacetylene) derivatives according to the substitution position is due to the differences in the intramolecular pi-stack structure and chain conformation.

Highly Emissive, Water‐Repellent, Soft Materials: Hydrophobic Wrapping and Fluorescent Plasticizing of Conjugated Polyelectrolyte via Electrostatic Self‐Assembly

“…The shorter-lived species comes from a dense IaSS, which generates a nonradiative decay channel with a higher probability of π-electron communication, while the longer-lived species arises from a relaxed IaSS in a radiative emission decay process. [13] This TCSPC analysis well indicates that the larger number of hydrophobic tails can maximize the plasticizer effect on FL emission enhancement.…”

“…[12] The FL origin is now believed to be intramolecular excimer emission, which originates from the IaSS. [13] As a quite interesting feature of the IaSS, its molecular conformation is extremely variable based on its internal (length or substitution position of the side alkyl chain) or external (viscosity of solvent) environment, leading to significant changes in FL emission. [14] In a previous study, when SPDPA was combined with a cationic surfactant (O 1 M 3 AB, Figure 1) containing one long hydrophobic tail (O 1 , octadecyl group) in situ in a film, the polymer no longer dissolved in water and the FL was remarkably enhanced.…”

Remarkable Change in Fluorescence Emission of Poly(diphenylacetylene) Film via in situ Desilylation Reaction: Correlation with Variations in Microporous Structure, Chain Conformation, and Lamellar Layer Distance

“…Also, it should be noted that the intramolecular p-stack structure and chain conformation of PDPA are almost the same as those of the corresponding meta-substituted polymer (m-PTMSDPA), having a trimethylsilyl group on the meta position of the side phenyl ring. [5] According to a previous report, m-PTMSDPA also showed much weaker emission (F FL : 0.2%) at a longer wavelength (544 nm) relative to p-PTMSDPA. The emission property and electronic structure of m-PTMSDPA are closer to that of PDPA rather than p-PTMSDPA.…”

“…[4] Also, the side phenyl ring stack structure was significantly dependent on the substitution position of the trimethylsilyl group on the side phenyl ring. [5] The polymer having a trimethylsilyl group on the para position of the side phenyl ring showed a lower stack degree of the side phenyl rings as compared to the corresponding meta-substituted polymer. Thus, the para-substituted polymer showed greater emission efficiency than the meta-substituted polymer.…”

“…As for p-PTMSDPA, the dihedral angles between the two planes of the molecular backbone with the neighboring ipsocarbon of the p-trimethylsilylphenyl group are sequentially twisted with angles of þ63 AE 1, þ54 AE 3 and -107 AE 48 in a repetitive zig-zag pattern. [5] On the other hand, in the case of PDPA, the corresponding dihedral angles are fixed at 57 AE 0.38 in a helical manner. The side phenyl groups of PDPA are stacked one on top of the other, with a average distance of ca 2.4 Å between two phenyl rings.…”