Supporting Information

S1

Supporting Information

Alginate-Phenylboronic Acid Based Hydrogels

S2

Table of Contents

page

1. Self-healing and stretchable hydrogels in literature……….. S3

2. NMR spectra………... S6

3. FT-IR spectroscopy……...………... S7

4. Additional SEM images...………... S8

5. Additional stimuli-responsive behavior of 7-35………... S9

6. Additional stretching experiments……… S10

7. Additional rheological measurements………. S13

8. Additional cell release images……….. S16

9. References……….……….. S17

S3

1. Self-healing and stretchable hydrogels in literature

Table S1: Comparison of maximum stretchability of our material with already reported super stretchable gels.

System Max. strain (ε) or stretch ratio (λ)

Reference

Host-guest polymer λ > 100 Adv. Mater., 2017, 29, 1605325 Nanocomposite

spherulite NP

λ = 121 Nat. Comm., 2016, 7, 12095

PAAm + hydrophobic spacer (hydrophobic,

micellar)

λ > 100 Adv. Mater., 2016, 28, 4678

Ionic interaction ε = 1500% Nat. Comm., 2014, 5, 5124 Ionic interaction,

nanocomposite

λ = 21, ε = 2300% Macromolecules, 2016, 49, 5660

Nanocomposite, C-dot ε = 5000% Macromolecules, 2016, 49, 3174 Dynamic covalent, ionic

interaction

ε = 2000% Chem. Sci., 2016, 7, 6715

Dynamic covalent λ = 30 Adv. Mater. 2017, 29, 1702181

Ionic interaction ε = 10000% Nat. Chem. 2016, 8, 618 Ionic interaction ε = 3400% Macromol. Rapid Commun. 2016,

37, 952

Hydrogen bonds ε = 2705% J. Mater. Chem. B, 2017, 5, 7021 Dynamic covalent ε = 500% ACS Macro. Lett. 2017, 6, 1129 Carboxymethylagarose

+ PVA + boric acid (Dynamic covalent)

λ = 100 Arab. J. Chem., 2018,

doi.org/10.1016/j.arabjc.2017.12.034

Agar + HPAAm (hydrophobic, micellar)

λ = 10 Adv. Funct. Mater. 2015, 25, 1598

Olefin-containing polymer (metathesis

covalent bond)

ε = 950% J. Am. Chem. Soc. 2015, 137, 4846

AACA + F127DA (micellar)

ε = 2500% RSC. Adv., 2017, 7, 29489

PAAm + CD + adamantine (host-

guest)

ε = 2442% Macromolecules 2013, 46, 5317

S4

PAA + POSS (micellar) ε > 4200% Chin. J. Pol. Sci., 2016, 34, 185 PAAm + alginate (ionic) λ > 20 Nature 2012, 489, 133

PDMA + stearyl methacrylate (micellar)

λ =43 Eur. Polym. J. 2014, 59, 113

PNIPAm-PAM-clay (nanocomposite)

ε = 2000% Soft Matter, 2014, 10, 3506

Polyelectrolytes (ionic interaction)

ε = 800% Adv. Mater. 2015, 27, 2722

A6ACA with flexible side chains (hydrogen

bonds)

ε = 66% PNAS 2012, 109, 4383

PNAGA-PAMPS + PEDOT/PSS (hydrogen

bonds)

ε = 1710% Sci. Rep., 2017, 7, 41566

Alginate-catechol + borax (dynamic covalent chemistry)

ε = 400% ACS Appl. Mater. Interfaces 2017, 9, 15541

PAA + vinyl hybrid silica NPs (hydrogen bonds)

ε > 3700% Nat. Commun., 2015, 6, 10310

GO PAA

nanocomposite + Fe3+

(ionic interaction)

ε = 2980% J. Mater. Chem. B, 2015, 3, 4001

VSNP-PAA nano brush hydrogels + Fe3+ (ionic

interaction)

ε = 2300% Soft Matter, 2015, 11, 4235

Polyelectrolyte NaSS + MPTC (ionic

interaction)

λ = 25 Soft Matter, 2015, 11, 9355

PAA + Fe3+ (ionic interaction)

ε = 1500% Adv. Mater. 2017, 29, 1700533

GO-PAACA composite (ionic interaction, hydrogen bonds)

ε = 1190 % Chem. Mater. 2013, 25, 3357

Poly(N- acryloylgycinamide)

PNAGA (hydrogen bonds)

ε = 1400% Adv. Mater. 2015, 3566

S5 Polyelectrolyte MPTC +

NaSS (ionic interaction)

ε = 700% ACS Macro Lett. 2015, 4, 961

Polydopamine- polyacrylamide (PDA- PAM) (hydrogen bonds

+ pi-pi stacking)

λ = 31, ε = 3300% NPG Asia Materials, 2017, 9, 372 (adhesion property)

GO-P(AM-co-DAC) (ionic interaction, hydrogen bonds)

ε = 1700% ACS Appl. Mater. Interfaces 2017, 9, 38052

K-carrageenan/PAAm (sol-gel transition)

ε = 2000% ACS Appl. Mater. Interfaces 2017, 9, 26429

PEO with aldehyde or acylhydrazine (dynamic

covalent chemistry, hydrophobic/micellar

interaction)

λ = 117 ACS Macro Lett. 2017, 6, 881

Alginate with phenyl boronic acid derivative

ε >16000% Material reported in this thesis

S6 2. NMR spectra

Figure S1. ¹H NMR spectrum of Alg-PBA at different pH, blue: pH 7, red: pH 3, green: pH 10.

S7 3. FT-IR spectroscopy

4000 3500 3000 2500 2000 1500 1000 30

40 50 60 70 80 90 100

Tr an smitta nce

Wavenumber (cm-1) AlgPBAhydrogel7 AlgPBAsolid Algsolid 7Xerogel 3Xerogel PBA

1500 1000

70 80 90 100

Transmittance (%)

Wavenumber (cm

)

Alg-PBA alginate

Figure S2. FTIR spectra of a) Alg-PBA hydrogel, solid and xerogel (3-75 and 7-35), unmodified alginate and 3-phenylboronic acid.

S8 4. Additional SEM images

Figure S3. SEM images of the xerogel prepared by freeze-drying of the 3-75 hydrogel.

Figure S4. SEM images of the xerogel prepared by freeze-drying of the 7-35 hydrogel.

S9 5. Additional stimuli-responsive behavior of 7-35

Figure S5. Stimuli-responsiveness of 7-35, a) response to pH, b) response to glucose.

S10 6. Additional stretching experiments

Figure S6. Stretchability of 7-35 visualized after dye-doping with rhodamine B, a) under UV, b) under visible light.

Figure S7. Photographs of stretching the 7-35 gel. The centre portion of the gel shows a significant reduction in the area due to necking.

S11

Figure S8. Plot of true stress as a function of stretch ratio (λ) scaled with a stretching rate dependent scale factor, 𝑎_𝑅. 𝑎_𝑅 values of 0.1, 1 and 10 mm s^-1 strain rate curves are 1, 0.69 and 0.44 respectively.

Figure S9. Photographs of the self-healing experiment and stretching of the healed gel.

1 10 100

10

10

10

10

10

 t (Pa )

 a

10 mm/s 1 mm/s 0.1 mm/s

9 mm

S12

Figure S10. Self-healing of 7-35 gel. Tensile study on self-healed sample: the fresh gel and the gel self-healed for a minute showed almost similar extensional behavior.

Figure S11. Cyclic study on self-healed gel. Material did not show any failure even after 20 cycles of stretching to λ ~100.

1 10 100

10

10

10

10

10



t (P a)

 Original

1 minute self healing

1 10 100 1000 10000 100000

1 10 100

A p p .S tr es s (P a )



S13 7. Additional rheological measurements

Figure S12. Strain sweep experiments on a) 3-75 gel and b) 7-35 gel. The experiments were performed at 1 rad s^-1.

Figure S13. Linear viscoelastic response of the gels, a) frequency dependent G' and G" for different gel compositions. Solid moduli are plotted as filled symbols while loss moduli are plotted as open symbols, b) master curve obtained after normalizing the moduli using Gc and frequency using ωc.

The LVE data for all the gels are qualitatively similar and can be collapsed onto a single master curve by shifting along the modulus and frequency axes (Figure S12b). The horizontal and vertical shift factors, relative to the reference sample (3-75) are given Table S2. Excellent overlap is obtained, with vertical and horizontal shift factors varying by factors of 6.6 and 60, respectively, between 3-75 and 7-35 gels (Table S2). The master curve was fitted in Gʹ and Gʺ, spanning over four decades of frequency with a multiple mode Maxwell model:

𝐺

= ∑ (

1+𝜔²𝜏_𝑘²

) and 𝐺

= ∑ (

1+𝜔²𝜏_𝑘²

), (eq. S1) (𝐺

and 𝜏

are fitting parameters)

We observe that the master curve is fitted well with 4 modes (SI Table S3, Figure S14).

1 10 100

10

10

10

Sh ear M odu lus (Pa)

Strain (%)

G' G''

0.1 1 10

10

10

10

Sh ear M odu lus (Pa)

Strain (%)

G' G''

(a) (b)

S14

Table S2: Crossover frequency, frequency shift and modulus shift factors calculated for different gel formulations.

Sample name:

(Alg-PBA wt.%- NaOH amount in µl)

Crossover frequency,

ω

(rad/s)

Crossover modulus,

𝐺

(Pa)

Shift parameters

Frequency shift Modulus shift

3-75 0.25 360 1 1

3-35 1 425 0.25 1.14

5-75 6 1100 0.0417 0.4

7-35 15 2550 0.0167 0.15

Figure S14. Maxwell fit on the master curve. The solid line represents the fit.

Table S3. Parameters obtained by fitting discrete relaxation spectrum function to the shear rheology data.

G

(Pa) 𝝉

(s)

5162 0.02

2603 0.08

775 0.36

598 3.1

10

10

10

10

10

10

10

10

10

G', G' ' (Pa)

Frequency (rad/s)

G'

G''

S15

Note: Although the materials are termed “gel”, they can be classified as Maxwell fluids.

S16 8. Additional cell release images

Figure S15. Release of encapsulated HeLa cells after a) 24 h and b) 48 h of incubation.

S17 9. References

[1] M. Rubinstein, A. V. Dobrynin, Trends Polym. Sci. 1997, 5, 181-186.