Photophysical properties of N‐acylated linear polyethylenimine and dehydroalanine main‐chain polymers containing carbazole or pyrene groups in side chains

Abstract

SynopsisA comparison of the UV absorption spectra of a carbazole-substituted N-acylated linear polyethylenimine (PEI) (5,6) with its monomer (1,2) and dimer (3,4) model compounds shows the presence of local conformational order of the carbazole groups in 3, 5, and 6 since these compounds exhibit hypochromism. The UV absorption spectra of carbazole-substituted N-acylated dehydroalanine main-chain polymer (PDA) (12, 13) and monomer (10, 11) model compounds indicate that the extent of local conformational order of the carbazole groups is reduced in 12 and 13 compared to that in 5 and 6. The UV absorption spectra of a pyrenesubstituted PEI (9) and PDA (15) and those oftheir monomer model compounds (7,14) indicate that the extent of local conformational order of the pyrene groups is greater in 9 than in 15 and furthermore the pyrene-substituted polymers (9,15) show more local conformational order than analogous carbazole-substituted polymers (5, 12). The emission spectra of 5 and 12 show carbazole monomer emission, while those of 9 and 15 are dominated by pyrene excimer emission. The formation of excimer emission is more efficient in 9 than in 15. Fluorescence lifetime measurements indicate interactions of excited carbazole groups in 5 and 13 but not in 12. The quenching of carbazole fluorescence by dimethyl terephthalate is more efficient in 5 than that in 12, indicating more efficient transfer of electronic energy in 5. These measurements show that the PEI mainchain polymers are conducive to interactions of the pendant groups.

Optoeletronic properties of poly(N‐alkenyl‐carbazole)s driven by polymer stereoregularity

“…The optical properties of all these synthesized stereoregular polymers were deeply investigated. In particular, some articles report that polymers containing carbazole pendants do not exhibit excimer emission, at least in diluted solutions, except when the carbazole chromophores are directly bound to the polymer backbone . Consistently with these observations, the fluorescence spectra of diluted solutions of our synthesized stereoregular polymers collected at room temperature do not exhibit excimer emission, but only the monomer fluorescence is observed.…”

“…In particular, some articles report that polymers containing carbazole pendants do not exhibit excimer emission, at least in diluted solutions, except when the carbazole chromophores are directly bound to the polymer backbone . Consistently with these observations, the fluorescence spectra of diluted solutions of our synthesized stereoregular polymers collected at room temperature do not exhibit excimer emission, but only the monomer fluorescence is observed. Conversely, we found that all our synthesized stereoregular polymers in the solid state as thin films, show both sandwich‐like and “partially overlapped” excimer emissions .…”

Energy migration in poly(N‐vinyl carbazole) and its copolymers with methyl methacrylate: Fluorescence polarization, quenching, and molecular dynamics

“…Fluorescence quenching has been used to measure intramolecular transfer and energy‐migration processes in polymer systems dispersed in dilute fluid solutions,1–3 including Cz containing polymers 8, 16, 37, 38. If an individual excited species is quenched by a collision with a quencher Q, the steady‐state Stern–Volmer quenching constant, K SV , provides a measure of the efficiency of quenching by where F 0 and F are the values of a relevant fluorescence parameter (fluorescence quantum yield, ϕ, intensity, I, or lifetime, τ) in the absence and presence of a given concentration of quencher [Q], k Q is the second‐order quenching constant, and τ 0 is the excited‐state lifetime in the absence of a quencher.…”

“…Despite the obvious importance of the photoconductive polymer in the solid state, the photophysics behavior of poly( N ‐vinyl carbazole) (PVCz) is more often examined in dilute solution 12–14. Examples of photophysical studies on polymers having a lower local volume fraction of carbazole (Cz) are poly[2‐(9‐carbazolyl)ethyl methacrylate];9 poly[2‐(9‐carbazolyl)ethyl acrylate];15 carbazole‐substituted, N ‐acrylated, linear poly(ethyleneimine) and dehydroaniline main‐chain polymers;16 polymers containing trans ‐1,2‐biscarbazolylcyclobutane in the main chain or as pendant substituents;17 and oligoethers such as poly[9‐(2,3‐epoxypropyl)carbazole] and poly[1,2‐epoxy‐6‐(9‐carbazolyl)‐4‐oxahexane]epoxypropyl)carbazole] 8…”

An experimental and theoretical study of the carbazole to carbazole intramolecular energy transfer in N‐vinylcarbazole/vinyl tert‐butyl‐benzoate copolymers of different molar compositions

“…In a rigid medium and in the absence of any other extrinsic cause, the degree of depolarization of the fluorescence depends on the extent of energy transfer 28, 29. On the other hand, the increase in the sphere action of a dynamic quencher due to IET, which is quantified by the bimolecular quenching constants, allows us to evaluate parameters like the singlet energy migration coefficient and the excitation diffusion length of migration 22, 28, 29, 47–49…”