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Supporting Information for

Self-healing and shape-memory properties of polymeric materials cross-linked by

hydrogen bonding and metal-ligand interactions.

Yuichiro Kobayashi, Tomohiro Hirase, Yoshinori Takashima, Akira Harada* and

Hiroyasu Yamaguchi*

* To whom corresponding should be addressed

E-mail: harada@chem.sci.osaka-u.ac.jphiroyasu@chem.sci.osaka-u.ac.jp

Electronic Supplementary Material (ESI) for Polymer Chemistry.This journal is © The Royal Society of Chemistry 2019

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Materials All the reagents and solvents were commercially available and used as received without further purification. 4,4’-Bis(hydroxymethyl)-2,2’-bipyridine (bpy) and 2-(6-isocyanatohexylaminocarbonylamino)-6-methyl-4(1H)-pyrimidinone (UPy-NCO) were prepared according to previously described methods.1,2

MeasurementsThe 1H NMR spectra were obtained using a JEOL JNM-ECS 500 NMR spectrometer.

The concentration of each sample was adjusted to 1.4 wt%. Chemical shifts were referenced to the tetramethylsilane (TMS) (δ = 0.00 ppm) and solvent value (δ = 2.49 or 7.26 ppm for DMSO-d6, or CDCl3, respectively). Fourier transform infrared (FT-IR) spectra were obtained with a JASCO FT/IR 6100 spectrometer. UV-Vis measurements were performed using a JASCO V-650 spectrometer at room temperature. Mechanical properties of materials were measured by the mechanical tension testing system (Rheoner, RE–33005 (Yamaden Ltd.) and Autograph AG-X plus (Shimadzu Co.). Differential scanning calorimetry (DSC) was carried out with a Seiko Instruments EXSTAE6000 under a N2 atmosphere and 10 K min–1 heating rate. 3D laser micrographs were measured using a laser microscope (VK-X250, Keyence Co.).

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Preparation of bpy-PVL-PLA-UPy

OHHO

N

N

N

NO

OO

O

OHHO

n n

tolueneNH

NH

O HN

N

O

NO

SnOct2 O

O

N

NO

OO

O

OO

n n

OO

OOHmmO

O

OHO

N

NO

OO

O

OO

n n

OO

OOmmO

O

OO

NH

O HN

HN

O HN

N OHN

ONH

NH

ONH

NO

SnOct2

OO

O

O

-VL

DL-LA

UPy-NCO

bpy

bpy-PVL

bpy-PVL-PLA

bpy-PVL-PLA-UPy

SnOct2

Scheme S1. Preparation of the bpy-PVL-PLA-UPy copolymer

Preparation of the bpy-PVL polymer𝛿-Valerolactone (𝛿-VL) (11 g, 0.11 mol) and bpy (0.29 g, 1.4 mmol) were dried under

reduced pressure at room temperature for 1 h in Schlenk flask and then tin(II) 2-ethylhexanoate [Sn(Oct)2]/toluene solution (0.56 mL, 0.14 mmol) was injected. The polymerization was carried out at 110 °C for 24 h under N2. The mixture was dissolved into CH2Cl2 and the solution was added to cold MeOH to give a precipitate. The precipitate was washed several times with MeOH and dried under reduced pressure at room temperature, providing bpy-PVL polymer (8.9 g, yield = 79%). Molecular weight (MW) was calculated from integration values (S) in 1H NMR spectrum of the bpy-PVL polymer as follows (Figs. S1a and S1b);

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𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑎𝑟𝑚 𝑛𝑢𝑚𝑏𝑒𝑟 (𝑁) = 2 ×𝑆𝑑

(𝑆𝑑 + 𝑆𝑑')

𝐷𝑒𝑔𝑟𝑒𝑒 𝑜𝑓 𝑝𝑜𝑙𝑦𝑚𝑒𝑟𝑧𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑃𝑉𝐿 𝑝𝑎𝑟𝑡 (𝐷𝑃𝑃𝑉𝐿) =(𝑆𝑒 + 𝑆𝑓)

𝑆𝑓

𝑀𝑊𝑏𝑝𝑦 ‒ 𝑃𝑉𝐿 = 𝑁 × 𝐷𝑃𝑃𝑉𝐿 × 110.12 + 216.24

110.12 : MW of the VL unit216.24 : MW of the bpy unit

From these equations, the MW of the bpy-PVL polymer was estimated about 8,000.

Preparation of the bpy-PVL-PLA copolymerThe bpy-PVL polymer (4.5 g, 0.55 mmol) and DL-lactide (DL-LA) (6.5 g, 45 mmol)

were dried under reduced pressure at 60 °C for 1 h in Schlenk flask. After purging the flask with N2, the mixture was heated to 130 °C, and then Sn(Oct)2/toluene solution (0.18 mL, 45 μmol) was injected. The mixture was dissolved into CH2Cl2 and the solution was added to cold MeOH to give a precipitate. The precipitate was washed several times with MeOH and dried under reduced pressure at room temperature, providing bpy-PVL-PLA copolymer (9.4 g, yield = 85%). MW was calculated from integration values (S) in 1H NMR spectrum of the bpy-PVL-PLA copolymer as follows (Figs. S1b and S1c);

𝐷𝑒𝑔𝑟𝑒𝑒 𝑜𝑓 𝑝𝑜𝑙𝑦𝑚𝑒𝑟𝑧𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑃𝐿𝐴 𝑝𝑎𝑟𝑡 (𝐷𝑃𝑃𝐿𝐴) =(𝑆𝑚 + 𝑆𝑛)

𝑆𝑛

𝑀𝑊𝑏𝑝𝑦 ‒ 𝑃𝑉𝐿 ‒ 𝑃𝐿𝐴 = 𝑀𝑊𝑏𝑝𝑦 ‒ 𝑃𝑉𝐿 + 𝐷𝑃𝑃𝐿𝐴 × 114.13

114.13 : MW of the LA unit.

From these equations, the MW of the bpy-PVL-PLA copolymer was estimated about 20,000.

Preparation of the bpy-PVL-PLA-UPy copolymerThe bpy-PVL-PLA copolymer (4.0 g, 0.21 μmol) and UPy-NCO (0.49 g, 1.7 mmol)

were dried under reduced pressure at 60 °C for 1 h. After purging the flask with N2, dry toluene (0.50 L) was added, and then the solution was heated to 110℃. Sn(Oct)2/toluene

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solution (0.12 mL, 30 μmol) was injected into the mixed solution. The reaction was carried out at 110 °C for 20 h under N2. The non-reacted UPy-NCO was filtered off, and the filtrate was evaporated under reduced pressure. The product was dissolved into CHCl3 (0.20 L), and silica (5.0 g) and 5 drops of dibutyltin dilaurate were added. The mixed solution was stirred at 60℃ for 2 h under N2. The silica-bound UPy was filtered off and the CHCl3 was removed under reduced pressure. The product was dissolved into CH2Cl2 and the solution was added to cold MeOH to give a precipitate. The precipitate was washed several times with MeOH and dried under reduced pressure at room temperature, providing bpy-PVL-PLA-UPy copolymer (3.3 g, yield = 80%). MW of the bpy-PVL-PVL-UPy copolymer was calculated as follows,

𝑀𝑊𝑏𝑝𝑦 ‒ 𝑃𝑉𝐿 ‒ 𝑃𝐿𝐴 ‒ 𝑈𝑃𝑦 = 𝑀𝑊𝑏𝑝𝑦 ‒ 𝑃𝑉𝐿 ‒ 𝑃𝐿𝐴 + 293.33 × 𝑁

293.33 : MW of UPy unit.

From this equation, the MW of the bpy-PVL-PLA-UPy copolymer was calculated to be 21,000.

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Figure S1. 1H NMR spectra of (a) bpy, (b) bpy-PVL polymer, (c) bpy-PVL-PLA copolymer, and (d) bpy-PVL-PLV-UPy copolymer in CDCl3 at 25 °C.

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Preparation of filmsFilms were prepared by solution casting method as follows (Fig. S2).

bpy-UPy film and bpy film : bpy-PVL-PLA copolymer or bpy-PVL polymer were dissolved in CH2Cl2 (10 w/v%). The CH2Cl2 polymer solution was poured into a polytetrafluoroethylene dish, followed by evaporation of solvent under ambient condition for 24 h. The film was further dried at 50 °C for 24 h under reduced pressure. The thicknesses of these films were 100-150 μm.

[M(bpy)n]2+-UPy film: MeOH solution of a metal ion (ab. 8-10 mM) was added to a CH2Cl2 solution of bpy-PVL-PLA-UPy copolymer (1 w/v%) and the mixture was stirred for 30 min. The mixture was poured into a polytetrafluoroethylene dish, followed by evaporation of solvent under ambient condition for 24 h. The film was further dried at 50 °C for 24 h under reduced pressure. The thicknesses of these films were 100-150 μm. In this experiment, we used Fe(BF4)2·6H2O, Zn(NO3)2·6H2O, Co(NO3)2·6H2O, or Cu(NO3)2·3H2O to prepare the MeOH solution of the metal ion.

Figure S2. Preparation of (a) [M(bpy)n]2+-UPy film and (b) bpy-UPy and bpy films.

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Swelling ratio of the [Fe(bpy)3]2+-UPy film10 mM Fe(BF4)2·6H2O MeOH solution (0.25 mL, 2.5 μmol; 0.51 mL, 5.1 μmol; 0.76

mL, 7.7 μmol) was added to a CH2Cl2 solution (50 mL) of bpy-PVL-PLA-UPy copolymer (0.50 g, 23 μmol) and the mixture was stirred for 30 min. The films were prepared by solution casting method as described above. The weight of the film before (Winitial) and after (Wswollen) immersion in CH2Cl2 was measured and swelling ratio was determined as

𝑆𝑤𝑒𝑙𝑖𝑛𝑔 𝑟𝑎𝑡𝑖𝑜 𝑜𝑓 𝑓𝑖𝑙𝑚 (%) =(𝑊𝑠𝑜𝑤𝑙𝑙𝑒𝑛 ‒ 𝑊𝑖𝑛𝑖𝑡𝑖𝑎𝑙)

𝑊𝑖𝑛𝑖𝑡𝑖𝑎𝑙× 100

Figure S3. Relationship between swelling ratio of [Fe(bpy)3]2+-UPy film and molar ratio of bpy and Fe.

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UV-Vis measurements.

Figure S4a shows experimental procedure. 80 μM Fe(BH4)2 MeOH/CH2Cl2 (1 : 3) solution was prepared in a UV cuvette (1 cm path length). Aliquots (25 μL) of 1.9 mM bpy-PVL-PLA-Upy copolymer MeOH/CH2Cl2 (1 : 3) solution were added to the 80 μM Fe(BH4)2 MeOH/CH2Cl2 (1 : 3) solution in the UV cuvette. After each aliquot addition, the solution was stirred until the absorbance reached a constant value. The absorbance was then corrected for dilution and plotted versus the equivalents of addition of the bpy-PVL-PLA-UPy copolymer (Fig. S4b). The end point of the titration was determined from the intersection of the linear segments of the curve, which was bpy-PVL-PLS-UPy/Fe2+ = 3 (Fig. S4c). These results indicate that bpy-PVL-PLS-UPy and Fe2+ ion form 3:1 metal ligand complex.

Figure S4. (a) Schematic illustration of experimental procedure. (b) UV-Vis absorption spectra of addition of aliquots (25 μL) of 1.9 mM bpy-PVL-PLA-Upy MeOH/CH2Cl2 (1 : 3) solution to the 80 μM Fe(BH4)2 MeOH/CH2Cl2 (1 : 3) solution. (c) Titration plot of bpy-PVL-PLA-UPy copolymer with Fe2+ ion.

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Self-healing experiment

Figure S5. (a) Schematic illustration of experimental procedure of self-healing test. Optical microscope images and depth profiles of the damaged (a) bpy, (b) bpy-UPy, and (c) [Fe(bpy)3]2+-UPy film measured with a laser microscope before and after heating at

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50 °C for 30 min.DSC measurement

Figure S6. DSC profiles of the bpy (gray), bpy-UPy (blue), and [Fe(bpy)3]2+-UPy film (red). Tg and Tm of the [Fe(bpy)3]2+-UPy film were lower than that of bpy-UPy film, because the crystallinity of the polymer was reduced due to steric hindrance by complex formation of [Fe(bpy)3]2+.

Table S1. Tg and Tm of bpy, bpy-UPy, and [Fe(bpy)3]2+-UPy film.Tg (°C) Tm (°C)

bpy film 9.3 47bpy-UPy film 12 46

[Fe(bpy)3]2+-UPy film 2.3 41

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Shape memory experiment

Figure S7. Photograph of 1st and 2nd cycle of shape memory experiment.

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References1. D. Miyoshi, H. Karimata, Z. M. Wang, K. Koumoto and N. Sugimoto, J. Am.

Chem. Soc., 2007, 129, 5919.2. P. Y. W. Dankers, P. J. H. M. Adams, D. W. P. M. Lowik, J. C. M. van Hest and E.

W. Meijer, Eur. J. Org. Chem., 2007, 3622.