Self-Assembling Semiconducting Polymers—Rods and Gels from Electronic Materials

Abstract

In an effort to favor the formation of straight polymer chains without crystalline grain boundaries, we have synthesized an amphiphilic conjugated polyelectrolyte, poly(fluorene-alt-thiophene) (PFT), which self-assembles in aqueous solutions to form cylindrical micelles. In contrast to many diblock copolymer assemblies, the semiconducting backbone runs parallel, not perpendicular, to the long axis of the cylindrical micelle. Solution-phase micelle formation is observed by X-ray and visible light scattering. The micelles can be cast as thin films, and the cylindrical morphology is preserved in the solid state. The effects of self-assembly are also observed through spectral shifts in optical absorption and photoluminescence. Solutions of higher-molecular-weight PFT micelles form gel networks at sufficiently high aqueous concentrations. Rheological characterization of the PFT gels reveals solid-like behavior and strain hardening below the yield point, properties similar to those found in entangled gels formed from surfactant-based micelles. Finally, electrical measurements on diode test structures indicate that, despite a complete lack of crystallinity in these self-assembled polymers, they effectively conduct electricity.

Fluorescent micellar nanoparticles by self-assembly of amphiphilic, nonionic and water self-dispersible polythiophenes with “hairy rod” architecture

“…A similar behaviour was also recently reported for some conjugated polyelectrolytes. 59 To prove the self-assembling of the amphiphilic synthesized polythiophenes in water and to characterize the formed micellar nanoparticles in terms of size and shape, 1 H-NMR spectroscopy, DLS, SEM and AFM techniques were complementary used. While the 1 H-NMR highlights the presence of the nanoparticles and DLS allow for their dimensional analysis in the solvated state, the microscopic investigations (SEM and AFM) give an image of their shape and size in dried state, even if the PEG corona in dried state is collapsed and consequently in a different conformation.…”

Long-lived photoinduced polaron formation in conjugated polyelectrolyte-fullerene assemblies

“…The particular materials used in this study are a combination of a conjugated polyelectrolyte, poly(fluorene-alt-thiophene) (PFT) (10), and several regioisomers of the charged fullerene derivatives C 60 - N,N -dimethylpyrrolidinium iodide [C 60 (PI) n ], where n is the number of charged pyrrolidinium iodide groups (11) (Fig. 1, A to C).…”

“…PFT is a water-soluble semiconducting polyelectrolyte whose bis-alkylated sp 3 -hybridized fluorenyl carbon forms a wedge-shaped monomer that facilitates the assembly of the charged polymer into rod-like micelles (Fig. 1B); details of how this polymer assembles have been published previously (10). Because of the charged nature of the polymer, the electron acceptor(s) must also carry cationic charges to avoid heterocoagulation.…”

“…PFT is a blue-absorbing polymer with an absorption maximum at 430 nm in water and little to no absorbance above 550 nm (10). The color change from yellow to green was confirmed to arise from the appearance of the PFT hole polaron (P + ) by comparing steady-state data (Fig.…”

3,4-Ethylenedioxythiophene (EDOT) End-Group Functionalized Poly-ε-caprolactone (PCL): Self-Assembly in Organic Solvents and Its Coincidentally Observed Peculiar Behavior in Thin Film and Protonated Media

“…However, it is also important to emphasize that the fluorescence traces of the EDOTMeOH initiator, which were registered in the same solvents, were monomodal but broad and non-symmetrical ( Figure S3D ), with a blue-shifted λ max em at 350 nm and 325 nm (see also Table S3 ) compared to EDOT-PCL . The possible explanations for all phenomena described above are as follows: (i) the blue-shifting of λ max em registered in the polar ACN solvent could be due to the stabilization of the ground state of EDOT-PCL, which has an increased polar character than the excited state; (ii) the bimodal shape and presence of the red-shifted peaks in both the investigated solvents, (the last one being a mark for the formation of the nanoparticles/micelle-like particles [ 55 , 72 , 77 ]), could be proof of the self-assembling nature of EDOT-PCL in the solution; (iii) the increased values of apparent hydrodynamic diameter (D h ) of the self-assembled structures in ACN in comparison with those formed in Chl, experimentally determined (vide infra) could be the reason for the observed fluorescence intensity decrease in this solvent. This behavior followed the well-established phenomenon of the dependence of fluorescence intensity on particle size [ 7 , 55 ].…”