Highly Luminescent CB[7]‐Based Conjugated Polyrotaxanes Embedded into Crystalline Matrices

Abstract

they pose significantly lower risks to environment and health compared to other optical materials such as cadmiumbased quantum dots [10] and lead-based perovskites. [11] Despite the potential of conjugated polymers, a decrease in the fluorescence quantum yield (QY) and a low emission stability in their solid state turn out to be an important bottleneck. These problems mainly arise from the changes in the polymer morphology upon film casting, which affects the inter and intrachain interactions. To decrease these interactions and consequently, achieve higher QYs in solid films, various approaches have been adopted including the utilization of nonradiative energy transfer to light-emitting polymers [12,13] and the incorporation of the polymers into inorganic nanoparticles. [14][15][16] Alternatively, chemical entities such as dendrones have been attached to the polymer backbone in order to weaken the π-π stacking.[17] Insulation of the conjugated polymer backbones via rotaxanation, which can be considered as threading the polymer chain using a macrocyclic ring, also steps forward as a promising solution. [18][19][20] In the literature, cyclodextrins and cucurbit[n]urils (CB[n]) have been shown to successfully isolate the polymer backbone leading to enhanced fluorescence QY. [21][22][23][24][25][26] For instance, our group has recently demonstrated fourfold increase in the fluorescence QY of poly(9,9′-bis(6″-(N,N,N-trimethylammonium)hexyl)fluorene-alt-co-thiophenelene) accompanied by blue-shifted fluorescence spectrum and prolonged fluorescence lifetime after threading with CB7. [27] Despite the improvements in the QY of polyrotaxane solutions, their solid films still suffered from decreased fluorescence QY. Therefore, a solution to maintain the fluorescence QY is of significant importance for their use in solid-state lighting.A possible solution to this problem might come from the research on the colloidal quantum dots, which similarly suffered from decreasing QYs in their solid films. Otto et al. [28] showed that the quantum dots in water can be successfully incorporated into crystalline salt matrices. Later, this approach was shown to improve the fluorescence QY, [29] and emission stability. [30,31] Moreover, this method was also extended to nonionic crystals including sucrose [32] and anthracene [33] and to quantum dots in nonpolar solvents [30,34] and applied in lightemitting diodes (LEDs) [31] and sensors. [35] Recently, our group has evaluated the potential of this technique by incorporating π-Conjugated Polyrotaaxanes π-Conjugated polymers suffer from low quantum yields (QYs) due to chainchain interactions. Furthermore, their emission in solid films is significantly quenched due to aggregation leading further decrease in QY. These are the two main issues of these materials hampering their widespread use in optoelectronic devices. To address these issues, here the backbone of poly(9,9′-bis (6″-(N,N,N-trimethylammonium)hexyl)fluorene-alt-co-thiophenelene) is isolated by threading with cucurbit[7]uril (CB7). Su...

Suppressing Solid-State Quenching in Red-Emitting Conjugated Polymers

“…Similarly to what is observed for Φ F , the weighted-average fluorescence lifetimes (τ AVG ) (Table ) decrease when going from solution to thin film for all polymers. A similar observation has been previously reported for other “shielded” conjugated polymers. , However, we note that τ AVG in thin film decreases to a different extent than is seen in the values of Φ F . The possibility of interchain in addition to intrachain exciton transfer to either emissive or trap sites, in the solid state, could potentially account for this.…”

“…A similar observation has been previously reported for other "shielded" conjugated polymers. 35,36 However, we note that τ AVG in thin film decreases to a different extent than is seen in the values of Φ F . The possibility of interchain in addition to intrachain exciton transfer to either emissive or trap sites, in the solid state, could potentially account for this.…”

Supramolecular Assemblies of Cucurbiturils with Photoactive, π‐conjugated Chromophores

“…A proof-of-principle lightemitting diode is constructed by employing their powders as color converters. [42] 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 As it is mentioned earlier, conjugated polyrotaxanes or polypseudorotaxanes could also be prepared by threading the macrocycles onto the pre-synthesized polymers. [43] Based on this idea, recently conjugated polypseudorotaxanes have been synthesized through the threading of cucurbiturils onto the cationic poly(pyridyl vinylene), PPyV.…”

“…[42] To achieve this, we have embedded them in organic crystalline matrices such as trehalose and sucrose by co-crystallization. [42] To achieve this, we have embedded them in organic crystalline matrices such as trehalose and sucrose by co-crystallization.…”

“…We observed that although isolating some part of the conjugated backbone could increase the solid state fluorescence quantum yield of the conjugated polymer and the emission quenching could be minimized compared to its polymer counterpart but still it requires some improvements. [42] To achieve this, we have embedded them in organic crystalline matrices such as trehalose and sucrose by co-crystallization. As a result, we obtained a highly efficient color-converting solids suitable for solid-state lighting with high fluorescence quantum efficiency (> 50 %).…”