Synthesis and Optoelectronic Properties of Nonpolar Polyrotaxane Insulated Molecular Wires with High Solubility in Organic Solvents

Abstract

Hydrophilic polyanionic conjugated polyrotaxanes are readily synthesized in water by Suzuki coupling, but their high polarity and ionic nature limit the potential applications of these materials. Here, we demonstrate three methods for transforming these polar polyelectrolytes into nonpolar lipophilic insulated molecular wires. A water‐soluble polyfluorene‐alt‐biphenylene β‐cyclodextrin (CD) polyrotaxane was converted into nonpolar derivatives by methylation of the carboxylic acid groups with diazomethane and conversion of the hydroxyl groups of the CDs to benzyl ethers, trihexylsilyl ethers, benzoyl esters, and butanoate esters to yield polyrotaxanes that are soluble in organic solvents such as chloroform and cyclohexane. Elemental analysis, NMR spectroscopy, and gel permeation chromatography (GPC) data support the proposed structures of the organic‐soluble polyrotaxanes. The extents of reaction of the polyrotaxane CD hydroxyl groups were 55% for trihexylsilyl chloride/imidazole; 81% for benzyl chloride/sodium hydride; 72% for benzoyl chloride/pyridine/4‐dimethylaminopyridine; and 98% butanoic anhydride/pyridine/4‐dimethylaminopyridine. Alkylation, silylation, and esterification increase the bulk of the encapsulating sheath, preventing interstrand aggregation, increasing the photoluminescence efficiency in the solid state and simplifying the time‐resolved fluorescence decay. The organic‐soluble polyrotaxanes were processed into polymer light‐emitting diodes (PLEDs) from solution in nonpolar organic solvents, thereby excluding ionic impurities from the active layer.

Ultrafast All-optical Switching and Laser Action in Rotaxane

“…The positive band in both cases is attributed to the stimulated emission (SE), which spectral position matches with the photoluminescence spectra of the polymers [3]. The negative part of the spectrum for the neat polymer shows two well pronounced minima.…”

High-Efficiency All-Solution-Processed Light-Emitting Diodes Based on Anisotropic Colloidal Heterostructures with Polar Polymer Injecting Layers

“…The same colour scheme applies to the whole figure. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Importantly, the functionalization with the polar side chains does not interfere with the conjugated π-orbitals of the polyfluorene backbone and thus leads to no modification in the position of the HOMO and LUMO levels 57,58 . As a result, all polymers exhibit comparable absorption spectrum typical of polyfluorenes 28 , with low energy absorption band at approximately 395 nm 56,58 , as shown in Fig.1g together with the optical properties of the CdSe/CdS DiRs.…”

“…1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Importantly, the functionalization with the polar side chains does not interfere with the conjugated π-orbitals of the polyfluorene backbone and thus leads to no modification in the position of the HOMO and LUMO levels 57,58 . As a result, all polymers exhibit comparable absorption spectrum typical of polyfluorenes 28 , with low energy absorption band at approximately 395 nm 56,58 , as shown in Fig.1g together with the optical properties of the CdSe/CdS DiRs. In these heterostructures, similar to zero-and bi-dimensional core/shell CdSe/CdS systems 59 , the large (400 meV) energy offset between the CdSe and CdS valence bands along with the essential alignment of the conduction band energy ( Fig.1d) leads to the formation of a quasi type II heterojunction 49 where the hole wave function is localised inside the CdSe dot while the electron wave function spreads over the rod region within the attractive Coulomb potential of the hole.…”

Self-assembly of Functional Molecular Shuttles Based on Organic Conjugated Molecules

“…This encapsulation can lead to desirable properties such as enhanced environmental stability and increased photoluminescence (PL) and electroluminescence efficiencies. Anderson et al [36] have demonstrated that silylation, alkylation, and esterification of water-soluble polyrotaxane IMWs can give materials with modified organic solubility and enhanced backbone insulation. The properties of the lipophilic polyrotaxanes reflect an increased level of backbone insulation, and enhanced PL efficiency.…”