Energy Transfer Dynamics in a Series of Conjugated Polyelectrolytes with Varying Chain Length

Abstract

A time-resolved and steady state photophysical study of a family of conjugated polyelectrolytes (CPEs) with variable chain lengths (ranging from 8 to 108 polymer repeat units per chain) is reported. The CPEs investigated are poly(phenylene ethynelene)s substituted with two carboxylate groups per polymer repeat unit to provide water and methanol soluble conjugated polyelectrolytes. Steady state and ultrafast time-resolved fluorescence and anisotropy measurements were performed to explore the role of chain lengths on the energy transfer processes. We find that the CPEs aggregate under almost all conditions, with the degree of aggregation depending on the length of the conjugated polyelectrolyte chains. These CPEs are highly rigid and planar and present a very small loss of anisotropy during their emission lifetime.

Enhanced exciton migration in electrospun poly[2-methoxy-5- (2′-ethylhexyloxy)-1,4- phenylenevinylene]/poly(vinyl pyrrolidone) nanofibers

“…Exciton migration is usually modeled with Förster energy transfer through nonradiative dipole-dipole coupling, which depends on the transition dipole orientations. 19 Comparing to film sample, ordered orientation in ES nanofibers should benefit the exciton migration between local aggregations due to enhanced dipole moment coupling. High level orientation of the polymer backbones along the fibers axis was demonstrated by Kakade et al 20 via several methods such as polarized Raman spectroscopy and x-ray diffraction studies.…”

Fluorescence spectral shape analysis for nucleotide identification

“…A kinetic model is proposed to assign these 2 lifetimes to different kinetic pathways. In Tables 2 and 3, the decay component (τ 2 ) of P-C-3 is assigned to the rapid energy transfer from isolated polymer chains which have no interchain π-electron delocalization, to aggregated chains where π-electron density is delocalized by interchain interactions (16). The assignment well explained the decrease in τ 2 and the increase of the amplitude A 2 in Table 2, after the addition of nucleotides which promote the formation of aggregates.…”

“…This kinetic model links the long lifetime component (τ 1 ) to the fluorescence emission and other decay channels in isolated chains. After excitation, energy is transferred from the high-energy sites to energy traps before emitting or decaying nonradiatively (16,34). The variation of the long lifetime component (τ 1 ) between different P-C-3/nucleotide complexes implies that the conformations of isolated chains are also affected by interactions with nucleotides, which influence the fluorescence shape together with the formation of aggregates.…”

“…The development of single-molecule spectroscopy (14) and ultrafast time-resolved techniques (15,16) has revealed that the fluorescence spectral shape is dependent upon polymer chain conformation and the emission of multiple segments with different energy gaps (17), which can provide useful structural information about the polymer's surroundings. Charged side chains and a hydrophobic backbone make the conformation of CPEs sensitive to electrostatic, hydrophobic, and steric interactions (7,16), which make them good candidates for use as broad-spectrum biosensors (18)(19)(20)(21). In 2014, Wu reported an array with 6 different CPEs for protein recognition and distinction via fluorescence correlation spectroscopy signal (22).…”

Polarizing polymer solar cells based on the self-organization of a liquid crystalline polymer

“…This result may be due to the anisotropy of long range ordering in oriented PBTTT. Exciton transfer in a polymer has been modeled with a Förster energy transfer through nonradiative dipole-dipole coupling [22]. In our oriented PBTTT sample, the high level of orientation of the polymer backbones (the dipole direction) along the x-direction enhanced the dipole moment coupling, which favors the transfer of parallel-polarized excitons between the local aggregations.…”