Synthesis and Self-Assembly of an Amphiphilic Poly(phenylene ethynylene) Ionomer

Abstract

We have synthesized a conjugated amphiphilic polyelectrolyte, a poly(phenylene ethynylene) (PPE), and the structurally analogous neutral polymer. The solution-phase aggregation of the uncharged PPE can be reversibly controlled by varying the solvent polarity and concentration, while the charged polymer appears to self-assemble at any concentration in compatible solvents. These conclusions are based on a combination of absorption and photoluminescence spectroscopy and dynamic light scattering. Photoinduced absorption spectroscopy was also employed to investigate interchain electronic communication and the photoinduced production of free charge carriers. The uncharged PPE had a relatively high polaron yield, indicating pi-stacking of adjacent PPE chains and efficient exciton splitting, while the charged polymer did not produce polarons, indicating that the polymers are not pi-stacked despite their tendency to form aggregates. This is most likely due to the presence of the cationic trimethylammonium side chains which force neighboring polymer chains too far apart to achieve effective pi-orbital overlap. Polarons were observed in both polymers after chemical doping with iodine. The ability to control aggregation and interchain electronic communication could be a useful tool in designing nanostructured electronic materials.

Toward a Highly Sensitive Fluorescence Sensing System of an Amphiphilic Molecular Rod: Facile Synthesis and Significant Solvent-Assisted Photophysical Tunability

“…The slight red shift of the emission maximum from 450 to 465 nm could be attributed to the existence of the more extended polymer chains in the medium range of THF/H 2 O ratio at which both side groups could be well dissolved. 12 A similar change was observed during the process of titrating water into the polymer solution in 99.9% of THF (Figure 5b). However, less amount of water was needed to complete the whole transformation, which was consistent with the results obtained from polymer emission spectra in the THF/H 2 O mixed solvent as shown in Figure 4.…”

“…30 These advantages will not be simultaneously achieved in the case of having oligoethylene glycol side groups, which is soluble in both water and polar organic solvents, 14,25,30 or assembling hydrophilic and hydrophobic groups on the para-position of the same phenyl ring. 12,30 Compared to other literature reports about the solvent tunability, such as in phenyleneethynylene or fluorenephenylene systems having only hydrophilic side groups, 6,26,27 this molecular design should offer enhanced solvent tunability due to the existence of the hydrophobic side groups.…”

Ultrafast photoinduced electron transfer in conjugated polyelectrolyte–acceptor ion pair complexes

“…Their attempts to detect the polaron signals of the polyelectrolyte were unsuccessful due to the lack of effective interchain interactions. 68 The primary objective of this work was to study the mechanism of quenching of a water-soluble PPE-based conjugated polyelectrolyte by electron acceptors, with the aim to observe the CT state and its spectral properties and dynamics. For all three CPE/acceptor mixtures, a considerable red-shift in the absorption was readily observed in the steady-state absorption spectra and their intensities are comparable to the main band of CPE.…”

Influence of Air Flow on Luminescence Quenching in Polymer Films towards Explosives Detection Using Drones

“…In Figure 2 a, we show the HOMO and LUMO energy levels and bandgap energies of the PEE polymer obtained from DFT simulations (Orca 4.2.0) using the B3LYP method with a 6-31G basis function. In the PEE polymer that we used, the attached side chains were slightly different from the PPE polymers previously studied [ 15 , 19 , 34 , 35 , 36 ]. Figure 2 b shows the decrease in the theoretically expected bandgap of the polymer as the number of repeating units increased from 1 to 9, reflecting the increased delocalization of the electronic wave function.…”