Supplementary Material

Cucurbit[7]uril based fluorene polyrotaxanes

Aurica Farcas a*, Khaleel I. Assaf b, Ana-Maria Resmerita a, Sophie Cantin c, Mihaela Balan a, Pierre-Henri Aubert c, Werner M. Nau b*

a‘‘Petru Poni’’ Institute of Macromolecular Chemistry, 700487 Iasi, Romania

b Department of Life Sciences and Chemistry, Jacobs University Bremen, 28759 Bremen, Germany

c Laboratoire de Physicochimie des Polymères et des Interfaces (EA 2528), Institut des Matériaux, Université de Cergy-Pontoise, F-95031 Cergy-Pontoise Cedex, France

* Corresponding authors: Email: Aurica Farcas, ;

Werner M. Nau,

1. Experimental section

1.1. Materials

2,7-dibromofluorene (97%) (1), 9,9-dioctylfluorene-2,7-diboronic acid bis(1,3-propanediol) ester (97%) (2), tetrakis(triphenylphosphine) palladium (99%) (Ph3P)4Pd(0), bromobenzene (99%) (Br-Ph), dimethylsulphoxide (DMSO) and ferrocene (Fc) were purchased from Sigma-Aldrich and used as received. CB7 was synthesized according to a previously reported procedure [1]. Tetrabutylammonium perchlorate (TBAClO4) for electrochemical analysis (99.0%) (Fluka) was used without further purification. Acetonitrile (ACN) (Fischer), chloroform (CHCl3), toluene and all other solvents were purchased from commercial sources (Sigma-Aldrich, Fisher) and used without further purification.

1.2. Characterization

1H-NMR spectra have been recorded on a Bruker Avance DRX 400 MHz instrument equipped with a 5 mm QNP direct detection probe and z-gradients. Spectra have been recorded in DMSO-d6, at room temperature. The chemical shifts are reported as δ values (ppm) relative to the residual peak of the solvent. The FTIR (KBr pellets) spectra were obtained on a Bruker Vertex 70 spectrophotometer. The molecular weights of copolymers were determined by gel permeation chromatography (GPC) using Water Associates 440 instrument, polystyrene (Pst) calibrating standards and THF as eluent. The thermal properties of 3·CB7 and 3 were evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC was performed with a Mettler Toledo DSC-12E calorimeter with two repeated heating-cooling cycles at a heating rate of 5o×min-1 under N2 atmosphere. TGA analysis was performed under constant nitrogen flow (20 ml×min-1) with a heating rate of 10 oC×min−1 using a Mettler Toledo TGA/SDTA 851e balance. UV–vis and fluorescence spectra were performed using Varian Cary 4000 UV–vis spectrophotometer and Varian Cary Eclipse fluorometer. Fluorescence lifetime decay traces were recorded on a time-correlated single photon counting (TCSPC) fluorometer (FLS920, Edinburgh Instruments, Edinburgh, Scotland) by using a picosecond pulsed excitation. The fluorescence decays could be satisfactorily fitted (c2 <1.2) by using monoexponential decay functions. CVs were carried out in a three-electrode cell in which Pt (1 mm diameter) was used as a working electrode, a Pt-wire as counter-electrode and Ag wire as pseudo-reference electrode. 0.1 M TBAClO4 solution in anhydrous ACN was used as the supporting electrolyte. The set-up was introduced into a glove box and controlled by AUTOLAB PGSTAT 101 (Ecochemie) using NOVA software. The pseudo-reference was calibrated with a 10−3 M of ferrocene solution in ACN. The polymer samples were drop-casted onto the working electrode from a concentrated DMSO/(THF1/9 v/v solvent mixtures and studied in the interval −2.5 and +2.0 V vs. Ag wire. Cathodic and anodic scans were performed independently. Advancing and receding contact angle measurements were performed by using the drop shape analysis profile device equipped with a tiltable plane (DSA-P, Kruss, Germany). Ultrapure water (Millipore, resistivity=18 MΩ×cm) or a diiodomethane drop was first deposited on the sample using a variable volume micropipette. The drop volume was set to 15 µL for water and 10 µL for diiodomethane. In order to perform dynamic contact angle measurements, the sample surface sustaining the drop was tilted at a constant speed (1 deg×s−1) and the images of the drop simultaneously recorded. The advancing contact angle was measured at the front edge of the drop, just before the triple line starts moving. The angle was obtained using the tangent of the drop profile at the triple line. For each sample, contact angles were measured on four samples and three drops per sample. The reported contact angle values correspond to the average of all measurements with an error bar corresponding to the standard deviation. The morphological aspects of 3 and 3·CB7 films were highlighted using a Scanning Probe Microscope (Solver PRO-M, NTMDT, Russia) with a commercially available NSG10 cantilever (Solver PRO-M, NTMDT, Russia) having the resonant frequency of 293 kHz. Squares of 10 µm side were scanned in the semi-contact mode, in air, at room temperature. The resulted topographical bi- (2D) and three-dimensional (3D) atomic force microscopy (AFM) images were analyzed using the software Nova v.1.26.0.1443 for Solver.

1.3. Binding of 1 with CB7 in DMSO

Fig. S1. The changes in the UV-vis absorption of an aqueous solution of 1 upon increasing the CB7 concentration in DMSO. The changes clearly indicate the complexation of 1 with CB7.

1.4. Synthesis

1.4.1. Synthesis of 3·CB7 polyrotaxane

(0.243 g, 0.21 mmol) of CB7 was dissolved in 4.0 ml of water by sonication for 15 min at 30 oC. Then 0.067 g (0.21 mmol) of the monomer 1 was added and the mixture was sonicated for 15 min followed by vigorously stirred at room temperature for 48 hr. The water was removed by liophilization and to the mixture (0.116 g, 0.21 mmol) of the monomer 2, 4.0 ml of degassed DMSO, 2 ml of Na2CO3 (3M) solution and subsequently 8.6 mg (7.5 ´ 10−3 mmol) of (Ph3P)4Pd(0) catalyst dissolved in degassed DMSO (2 ml) were added. The flask was then equipped with a condenser, evacuated and filled with nitrogen several times to remove traces of air. The mixture was vigorously stirred in the dark under argon atmosphere for 96 hr at 95 oC. A small excess of 2 (0.0013 g, 0.002 mmol) and 2 ml of DMSO was then added and the reaction was continued for 24 hr in order to obtain the macromolecular chain terminated with borate units. Finally, 0.1 ml of bromobenzene was added as end-capping reagent and the reaction was continued for 12 hr. After cooling, the mixture was poured into 50 ml methanol and the precipitate was filtered, washed with methanol, water and acetone. The solid was dried and purified by Soxhlet extraction for 48 hr with methanol, acetone and water in succession to remove the oligomers and the unthreaded CB7. The solid was then dissolved in DMSO under heating, and then precipitated in methanol and collected by centrifugation, filtered, washed with water, acetone and dried under vacuum at 70 oC for 48 hr. 0.1654 g (46.5 % yields) as yellow-brownish solid was obtained.

1H-NMR (400 MHz, DMSO-d6, ppm): δ = 8.01-7.38 (m, 12H, fluorene), 5.66 (m, 14H, CB7), 5.42 (s, 14H, CB7), the third characteristic peak of CB7 from 4.20-4.15 interval is overlapped with the water peak from the solvent, 2.09-0.75 (m, aliphatic H of fluorene dioctyl units).

FTIR (KBr, cm−1): 3418 (N-H), 2924 (C-H), 1728 (C=O), 1620 (C=C), 1476 (C-N), 1323, 1234, 1192, 1155, 968, 808.

GPC (THF, Pst standard): Mn = 13000, Mw/Mn = 2.6.

1.4.2. Synthesis of the neat 3 copolymer

The neat 3 was synthesized by similar experimental conditions as those described above for 3·CB7 polyrotaxane, except that free monomer 1 was used instead of 1·CB7. The DMSO suspension of the neat 3 was poured into methanol and the precipitate was filtered, washed with methanol and acetone. The solid was then extracted with a Soxhlet using methanol and acetone. Further the solid was dissolved in CHCl3, precipitated with methanol, collected by filtration and then vacuum dried at 60 oC. The copolymer was obtained as an orange solid in yield of 54.8 %.

1H-NMR (400 MHz, CDCl3, ppm): 7.91-7.21 (m, 12H, fluorene), 2.12 -0.86 (m, aliphatic H of dioctyl units).

FTIR (KBr, cm–1): 3438, 2851, 1615, 1378, 1261, 1196, 1092, 1023, 810.

GPC (THF, Pst standard): Mn = 4900, Mw/Mn = 1.7.

2. The structural characterization of 3·CB7 polyrotaxane

The chemical structure of the polyrotaxane 3·CB7 was confirmed by FTIR and 1H-NMR spectroscopies.

2.1. The FTIR spectrum of the polyrotaxane 3·CB7

FFig. S2. The FTIR spectrum of 3·CB7 polyrotaxane

The FTIR spectrum of 3·CB7 shows all characteristic bands of the neat 3 copolymer and additional bands located at 3418 (N-H), 2924 (C-H), 1728 (C=O), 1620 (C=C), 1476 (C-N), corresponding to CB7, consistent with those previously reported [2-4].

2.2. 1H-NMR spectrum of the polyrotaxane 3·CB7

The 1H-NMR spectrum of 3·CB7 polyrotaxane with assignments of the resonance peaks is presented in Fig. S3. By using the ratio of the integrated area of fluorene proton peaks (8.01-7.38 ppm, IH) and those of CB7 (5.66 - 5.42 ppm) the coverage ratio was found to be of about 27.4%. As expected, due to the large difference in the solubility of PFs chains and CB7, it was quite difficult to perform the solubilization of 3·CB7 polyrotaxane in DMSO-d6. The mixture of 3·CB7 and DMSO-d6 was maintained at room temperature in the NMR tube for 24 hr, but complete solubilization of the sample was not achieved.

Fig. S3. 1H-NMR spectrum of 3·CB7 polyrotaxane in DMSO-d6

3. The differential scanning calorimetry (DSC)

The DSC curves of 3·CB7 and 3 samples showed only glass-transitions temperature (Tg), Fig. S4. The non-rotaxane 3 copolymer exhibits a Tg at 89 oC, while the Tg value for 3·CB7 increases to 113 oC. Moreover, DSC results are in good accordance with our previously findings [5-9], and the increased Tg of the investigated 3·CB7 polyrotaxane supports the incorporation of the monomer 1 into CB7 cavities.

Fig. S4. DSC traces on second heating scan of 3 and 3·CB7 samples

4. The fluorescence lifetimes

The fluorescence lifetimes in DMSO solution follow a single exponential kinetics with a valuet = 0.6 ns for the neat 3. The lifetime upon encapsulation into CB7 cavity is about the same (0.7 ns) as also been observed for other conjugated polyrotaxanes [6,10].

Fig. S5. Fluorescence lifetime decay traces (λex = 373 nm, λem 416 nm) of 3 and the rotaxane 3·CB7 in DMSO solutions.

5. Computational methods

Density functional theory (DFT) calculations were performed within Gaussian 09 [11]. The full optimization was performed using dispersion corrected density function theory method (wB97XD/6-31G*).

References

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