Browsing by Subject "Polyrotaxanes"

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    Catalytic self-threading: a new route for the synthesis of polyrotaxanes
    (American Chemical Society, 2004) Tuncel, D.; Steinke, J. H. G.
    Main chain and branched polyrotaxanes have been synthesized in which polymerization and rotaxane formation occur simultaneously, due to the presence of the catalytically active self-threading macrocycle cucurbit[6]uril. Using monomers that contain stopper groups to prevent the catalytic macrocycle from noncatalytic threading, it was possible to prepare polyrotaxanes in high yields with molecular weights up to 39000. These polyrotaxanes are structurally perfect in the sense that exactly two macrocyles are threaded onto each structural repeat unit. Investigations into the polymerization mechanism have demonstrated that the catalyst cucurbit[6]uril is highly sensitive toward the structure of the monomers employed and a poorly designed monomer may result in complete inactivity. Features of the mechanism are discussed in some detail.
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    Highly luminescent CB[7]-based conjugated polyrotaxanes embedded into crystalline matrices
    (Wiley-VCH Verlag, 2017) Erdem, T.; Idris, M.; Demir, Hilmi Volkan; Tuncel, D.
    π-Conjugated polymers suffer from low quantum yields (QYs) due to chain–chain 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). Subsequently, the conjugated polyrotaxanes are incorporated into organic crystalline matrices to obtain highly efficient color-converting solids suitable for solid-state lighting. Upon threading the polymer backbone with CB7s, although the QY of the resulting polyrotaxane in solution state increases, the quenching problem in their solid state is not completely tackled. To solve this problem, these conjugated polyrotaxanes are embedded into various crystalline matrices and their remarkably high QYs (>50%) in the solution are successfully maintained in the solid state. To demonstrate the suitability of these aforementioned materials for solid-state lighting, a proof-of-concept light-emitting diode is constructed by employing their powders as color converters.
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    pH-responsive rotaxanes and polypseudorotaxanes
    (2007) Tiftik, Hasan Burak
    In this study, a series of mechanically interlocked molecules like polypseudorotaxanes, rotaxanes and pseudorotaxanes have been synthesized via CB6 catalyzed 1,3-dipolar cycloaddition using diazide and dialkyne monomers, which contain long dodecyl and short propyl aliphatic spacers. To reach these novel interlocked molecules, first appropriate monomeric units were designed and synthesized. These monomeric units were diazido and dialkyne functionalized, propyl and dodecyl spacers containing, diamine salts. These monomers were fully characterized by spectroscopic techniques like 1H, 13C-NMR and FT-IR and elemental analysis. After the preparation of the monomers, polypseudorotaxanes were synthesized via CB6 catalyzed 1,3-dipolar cycloaddition. The polymer formation proceeded through step-growth polymerization in the presence of CB6. The reaction was followed by 1H-NMR spectroscopy easily, because the appearance of a diagnostic peak at 6.5 ppm indicated the formation of triazole ring, which joins the monomers. The polypseudorotaxane was also characterized by spectroscopic techniques like 1H, 13C-NMR and FT-IR and matrix assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF MS). It produced a maximum mass at around 15600 Da which corresponds to about six repeating units that is basically 12 CB6s threaded triazoles. The experimental results reveal that this polypseudorotaxane behaves as a pH-driven polymeric switch. Thus, when amine groups are protonated at an appropriate pH, CB6s are located on the triazole rings due to ion–dipole interaction, whereas at high pH they move onto the hydrophobic aliphatic spacer rather than slipping off the polypseudorotaxane. After the synthesis of the polypseudorotaxanes, a series of rotaxanes and pseudorotaxanes have also been synthesized using the already prepared dialkyne and diazide monomers. Rotaxanation was also carried out via a 1, 3-dipolar cycloaddition reaction catalyzed by CB6. Among them, a bistable CB6-based [3]rotaxane synthesized through CB6 catalyzed 1,3-dipolar cycloaddition contains two recognition sites and behaves as a reversible molecular switch. It exhibits conformational changes caused by the movement of rings under base, acid and heat stimuli from one location to the other.
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