The synthesis of organic molecules H and G are straightforward. Compound H was synthesized from B21C7-based derivative A (Lu et al., 2018) and cyanostilbene-derived compound 5 (Scheme 1). As shown in Scheme 1, starting from p-anisaldehyde and 4-methoxybenzyl cyanide, compound 4 was prepared in ethanol solution by condensation reaction. Demethylation of compound 4 with boron tribromide in dichloromethane (DCM) yields compound 5 (Gu et al., 2012). Compound G was synthesized according to literature report (Li et al., 2018). The compounds that have not been reported previously are carefully characterized by ¹H NMR, ¹³C NMR, and HR-MS (Supplementary Figures 1–4).

In order to examine whether the cyanostilbene motif bridged B21C7 is AIE active, the fluorescence spectra of H in mixed H₂O/Tetrahydrofuran (THF) solutions were investigated. As shown in Figure 2, H shows an obvious AIE behavior. There is no fluorescence emission when H was in pure THF (a good solvent for H). When water (a poor solvent for H) content was increased gradually to 80%, a moderate emission was observed. The absorption spectrum of H is shown in Supplementary Figure 5. The emission wavelength was at 480 nm when exited at 365 nm. Upon increasing water content to 95%, the fluorescence intensity of H exhibits a dramatic enhancement with a bright blue color. The dried powder of H was obtained as a light yellow solid, which exhibited intense blue luminescence under irradiation at 365 nm at room temperature (Figure 2B). Interestingly, exposing the sample to DCM vapor resulted in a distinct change of color from blue to green within only 30 s (Figure 2B). Notably, the blue color can be recovered by heating the sample to remove the DCM (Figure 2B).

Supramolecular polymerization of H and G was first investigated by concentration-dependent ¹H NMR. It was measured in mixed CDCl₃/CD₃CN (1:1, v/v) at concentrations in the range of 2–64 mM (Figure 3). The concentration-dependent ¹H NMR spectra showed a complex picture owing to the slow-exchange complexation of the B21C7 motif with the dialkylammonium salt on the NMR timescale. It should be noted that the peak splitting is relatively sharp at low concentrations (2–8 mM), suggesting that the cyclic oligomers are predominant species at this stage. As the concentration increases, these peaks became broad, indicating the formation of high-molecular-weight assemblies, such as supramolecular polymers. By contrast, the concentration-dependent ¹H NMR spectra of individual H shows no chemical shift change upon concentration increasing (Supplementary Figure 6).

To further study the supramolecular polymerization driven by crown ether-based host-guest interaction, viscosity measurements were performed by using a micro-Ubbelohde viscometer. A double logarithmic curve of specific viscosity toward monomer concentration is depicted in Figure 4. During the low concentration range, the slope value was tested to be 1.04, which is the characteristic of cyclic oligomers with constant size. When the concentration increased to 9 mM, a steeper curve with a slope 1.84 was obtained, suggesting that the cyclic oligomers are gradually transformed into supramolecular polymers. This phenomenon was in line with concentration-dependent ¹H NMR.

The formation of supramolecular polymers was further evidenced by its processibility. Fibers can be drawn from a concentrated solution of the host and guest with a molar ratio of H/G = 1/1 (Figure 5A). Such fibers can be only made from entanglements of large aggregates. By contrast, no fiber can be pulled out from the concentrated solution of individual H or individual G. The fiber is colorless under visible light (Figure 5A) and generates blue fluorescence under UV light (Figure 5B). This fiber still has fluorescent luminescence after preparation for several days, indicating that the supramolecular polymer has potential applications in the area of supramolecular luminescent materials. The photophysical property of the supramolecular polymer was further investigated by solid-state fluorescence spectroscopy. As shown in Figure 5C, the emission wavelength of H shows a hypochromic shift from 480 nm in solution to 415 nm in the solid state. Compared with individual H, the supramolecular polymer in the solid state exhibited a stronger emission and bathochromic shift to 430 nm, indicating that the incorporation of the guest affected the packing of the fluorophores in the solid state, resulting in modified luminescent properties.

All chemicals, reagents, and solvents were purchased from commercial suppliers and used, unless otherwise stated, without further purification. If needed, solvents were dried by literature-known procedures. All yields were given as isolated yields. The ¹H NMR and ¹³C NMR spectra were recorded with a Bruker AVANCE III (300 MHz) spectrometer and calibrated against the residual proton signal or natural abundance carbon resonance of the used deuterated solvent from tetramethylsilane as the internal standard. The chemical shifts δ are indicated in ppm and the coupling constants J in Hz. The multiplicities are given as s (singlet), d (doublet), dd (doublet of doublets), t (triplet), and m (multiplet). High-resolution electrospray ionization mass spectra (HR-ESI-MS) were recorded on an Agilent Technologies 6540 UHD Accurate-Mass. Fluorescence measurements were performed on an Agilent Cary Eclipse spectrofluorometer. Viscosity measurements were carried out with Ubbelohde microviscometers (Shanghai Liangjing Glass Instrument Factory, 0.40 mm inner diameter) at 298 K in chloroform and acetonitrile.

To a solution of compound 5 (237 mg, 1.0 mmol) in THF (15 mL) was added compound A (1.26 g, 3.0 mmol) and 4-dimethylaminopyridine (18 mg, 0.15 mmol) at room temperature under N₂ atmosphere. Then the Et₃N (303 mg, 3.0 mmol) was added with vigorous stirred over 15 min. The reaction mixture was heated at 70°C for 2 h and then poured into water (100 mL). The resulting mixture was extracted with DCM (50 mL × 3) and the combined extracts were washed with H₂O (100 mL × 3), brine (50 mL × 3), dried over anhydrous Na₂SO₄ and concentrated under reduced pressure. The resulting residue was chromatographed over silica gel (DCM:MeOH = 60:1, v/v) to afford compound H as a light yellow solid (460 mg, 0.46 mmol), yield: 46%. ¹H NMR (300 MHz, CDCl₃): δ (ppm) = 7.98 (d, J = 9.0 Hz, 2H, ArH), 7.85 (dd, J = 8.4, 2.1 Hz, 2H, ArH), 7.74 (d, J = 8.7 Hz, 2H, ArH), 7.69 (d, J = 1.8 Hz, 2H, ArH), 7.54 (s, 1H, alkene-H), 7.32 (m, 4H, ArH), 6.96 (d, J = 8.7 Hz, 2H, ArH), 4.33–4.19 (m, 8H, -OCH₂CH₂O-), 4.03–3.93 (m, 8H, -OCH₂CH₂O-), 3.82 (m, 8H, -OCH₂CH₂O-), 3.76 (m, 8H, -OCH₂CH₂O-), 3.69 (s, 16H, -OCH₂CH₂O-). ¹³C NMR (75 MHz, CDCl₃): δ (ppm) = 164.6, 164.5, 153.7, 153.7, 152.6, 151.8, 148.5, 141.2, 132.0, 131.2, 130.6, 127.2, 124.9, 124.8, 122.6, 122.5, 121.7, 121.6, 117.9, 114.9, 112.3, 110.8, 71.4, 71.3, 71.2, 71.1, 71.0, 71.0, 70.6, 69.6, 69.5, 69.4, 69.2. HR-ESI-MS: m/z calcd for [C₅₃H₆₄NO₁₈]⁺ = 1002.4118, found = 1002.4120.