M. Enke et al. / Polymer xxx (2015) 1e9
3
1H NMR (300 MHz, CDCl3):
d
¼ 1.97 (s, 3H, eCH3), 3.06 (dq,
EA: found: C: 75.52%; H: 11.20%; N: 1.18%.
DSC: no Tg observed; TGA: Td: 307 ꢀC.
P3
J ¼ 4.8 Hz, 12.6 Hz, 2H, eCH2ꢁ), 3.61 (s, 3H, eOCH3), 4.82 (m, 1H,
eCHe), 5.34 (s, 1H, ]CH2), 5.81 (s, 1H, ]CH2), 6.55 (s, 1H, He2Im),
7.08 ‒ 7.13 (m, 6H, H-aromatic), 7.31 ‒ 7.34 (m, 9H, H-aromatic), 7.37
(s, 1H, He5Im), 7.80 (d, J ¼ 7.6 Hz, 1H, eNHe) ppm.
1H NMR (300 MHz, CDCl3):
d
¼ 0.57 ‒ 2.02 (120H), 2.65 ‒ 2.85
(1H), 3.10 ‒ 3.27 (1H), 3.77 ‒ 4.06 (10H), 4.33 (1H), 6.54 ‒ 7.70 (17H)
13C NMR (75 MHz, CDCl3):
d
¼ 18.6 (eCH3), 29.8 (eCH2e), 52.2
ppm.
(eOCH3), 52.8 (eCHe), 75.4 (eCePh3), 119.8 (]CH2), 120.4
(Ce2Im),128.2 (Ce4Ph; Ce2Ph; Ce6Ph),129.9 (Ce3Ph; Ce5Ph),136.8
(Ce3Im), 138.9 (Ce5Im), 139.6 (Ce1Ph), 142.4 (C]CH2), 168,1
(eNHeC]O), 172.0 (C]O) ppm.
SEC (DMAc + 0.21% LiCl): Mn ¼ 14,800 g/mol; Mw ¼ 17,400 g/mol;
PDI ¼ 1.17.
EA: found: C: 66.81%; H: 8.63%; N: 2.26%.
DSC: Tg: 50 ꢀC; TGA: Td: 312 ꢀC.
ESI-TOF MS (HR MS): calc.: m/z ¼ 480.2282 [MþH]þ; found:
P4
m/z ¼ 480.2263 [MþH]þ; error: 3.9 ppm.
1H NMR (300 MHz, CDCl3):
d
¼ 0.75 ‒ 2.04 (345H), 2.85 (1H),
3.25 (1H), 3.84 ‒ 4.06 (15H), 4.14 (1H), 7.15 ‒ 7.56 (17H) ppm.
SEC (CHCl3/IPA/TEA): Mn ¼ 22,400 g/mol; Mw ¼ 34,200 g/mol;
PDI ¼ 1.53.
2.2.2. Na-Methacryloyl-Nt-tritylhistidine (4)
2 (1.50 g, 3.77 mmol) was dissolved in 50 mL dry dichloro-
methane under nitrogen atmosphere. Subsequently, triethylamine
(1.05 mL, 7.45 mmol) and DMAP (10 mol%) were added. After
15 min, methacrylic anhydride (0.56 mL, 3.77 mmol) was added
dropwise. After complete conversion, which was monitored by TLC,
the solvent and the triethylamine were evaporated in vacuo and the
residue was dissolved in 50 mL chloroform. The organic layer was
washed three times with deionized water and dried over Na2SO4.
Purification by silica gel chromatography (MeOH/CHCl3 1:10,
Rf ¼ 0.4) leads to the product.
EA: found: C: 75.35%; H: 11.55%; N: 0.63%.
DSC: no Tg observed; TGA: Td: 230 ꢀC.
2.3.2. Cleavage of the trityl-group of histidine containing polymers
(P5 to P8)
In a 100 mL one neck flask the desired amount of polymer was
dissolved in 30 mL chloroform. Afterwards the same volume of
trifluoroacetic acid (TFA) was added. Additionally, triethylsilane
was added as scavenger and the solution was stirred for 2 h at room
temperature. The reaction mixture was washed with 50 mL water
and 50 mL aqueous saturated NaHCO3 solution. The organic layer
was dried over Na2SO4 and concentrated. The resulting viscous
solution was precipitated in cold methanol. All reaction details are
summarized in Table 2.
Yield: 1.25 g of a white solid, 71%.
Melting point: 124 e 125 ꢀC.
1H NMR (300 MHz, CDCl3):
d
¼ 1.82 (s, 3H, eCH3), 3.22 (s, 2H,
eCH2ꢁ), 4.52 (s, 1H, eCHe), 5.21 (s, 1H, ]CH2), 5.53 (s, 1H, ]CH2),
6.57 (s, 1H, He2Im), 6.92 ‒ 7.41 (m, 15H, H-aromatic), 7.68 (s, 1H,
He5Im), 10.11 (bs, 1H, eOH) ppm.
P5
13C NMR (75 MHz, CDCl3):
d
¼ 18.7 (eCH3), 28.8 (eCH2e), 54.1
1H NMR (300 MHz, CDCl3):
3.68 (3H), 3.85 ‒ 4.12 (10H), 4.65 (1H), 6.84 (1H), 7.80 (1H) ppm.
d
¼ 0.87 ‒ 1.90 (120H), 3.12 (2H),
(eCHe), 75.8(eCePh3), 119.7 (]CH2), 120.4 (Ce2Im), 128.3
(Ce4Ph), 128.9 (Ce2Ph; Ce6Ph), 129.8 (Ce3Ph; Ce5Ph), 139.9
(Ce3Im), 140.7 (Ce5Im), 142.0 (Ce1Ph), 144.1 (C]CH2), 167,7
(eNHeC]O), 177.4 (C]O) ppm.
SEC (DMAc + LiCl): Mn ¼ 18,000 g/mol; Mw ¼ 19,500 g/mol;
PDI ¼ 1.08.
EA: found: C: 66.89%; H: 9.51%; N: 1.67%.
ESI-TOF MS (HR MS): calc.: m/z ¼ 466.2125 [MþH]þ; found:
DSC: Tg: 38 ꢀC; TGA: Td: 346 ꢀC.
m/z ¼ 466.2105 [MþH]þ; error: 4.3 ppm.
P6
1H NMR (300 MHz, CDCl3):
3.70 (3H), 3.85 ‒ 4.05 (11H), 4.61 (1H), 6.91 (1H), 7.73 (1H), 7.87
d
¼ 0.86 ‒ 1.89 (253H), 3.17 (2H),
2.3. Synthesis of histidine containing copolymers
(1H) ppm.
2.3.1. RAFT polymerization of P1 to P4
SEC (CHCl3/IPA/TEA): Mn ¼ 31,800 g/mol; Mw ¼ 35,100 g/mol;
In a 20 mL microwave vial the desired amounts of the two
monomers were dissolved in dry DMF. Afterwards, the exact vol-
umes of the stock solutions of the RAFT agent (CTA) and AIBN in
DMF were added. The [M] to [CTA] ratio was always 150/1 and the
ratio of [CTA] to [AIBN] 4/1. The ratio between BMA/LMA and his-
tidine monomer was held constant at 10:1. The reaction mixture
was degassed with nitrogen for 30 min. The reaction was per-
formed at 70 ꢀC overnight. All reaction details are summarized in
Table 1. Subsequently, the resulting polymers were precipitated
twice in ice-cold methanol.
PDI ¼ 1.10.
EA: found: C: 74.42%; H: 11.50%; N: 1.16%.
DSC: Tg: 45 ꢀC; TGA: Td: 241 ꢀC.
P7
1H NMR (300 MHz, CDCl3):
d
¼ 0.57 ‒ 1.89 (132H), 2.92 (2H),
3.73 ‒ 4.15 (11H), 4.45 (1H), 6.95 (1H), 7.61 (1H) ppm.
SEC (DMAc + LiCl): Mn ¼ 16,600 g/mol; Mw ¼ 19,400 g/mol;
PDI ¼ 1.16.
EA: found: C: 65.22%; H: 9.32%; N: 2.27%.
DSC: no Tg observed; TGA: Td: 302 ꢀC.
P8
P1
1H NMR (300 MHz, CDCl3):
(2H), 3.45 ‒ 3.65 (3H), 3.84 ‒ 4.10 (11H), 4.65 (1H), 6.57 (1H), 7.04 ‒
7.47 (16H), 7.84 ‒ 8.10 (1H) ppm.
d
¼ 0.78 ‒ 2.17 (132H), 2.79 ‒ 3.10
1H NMR (300 MHz, CDCl3):
d
¼ 0.85 ‒ 1.90 (345H), 2.94 (2H),
3.76 ‒ 4.14 (15H), 4.49 (1H), 6.86 (1H), 7.68 (1H) ppm.
SEC (CHCl3/IPA/TEA): Mn ¼ 22,100 g/mol; Mw ¼ 29,300 g/mol;
PDI ¼ 1.33.
SEC (DMAc + 0.21% LiCl): Mn ¼ 15,500 g/mol; Mw ¼ 16,800 g/
mol; PDI ¼ 1.08.
EA: found: C: 75.12%; H: 11.73%; N: 0.52%.
DSC: no Tg observed; TGA: Td: 218 ꢀC.
EA: found: C: 69.30%; H: 9.26%; N: 1.70%.
DSC: Tg: 45 ꢀC; TGA: Td: 288 ꢀC.
P2
2.3.3. General procedure for the crosslinking of the polymers (MP1
to MP24)
In a 5 mL vial the desired amount of polymer was dissolved in
1 mL chloroform. A solution of the metal salt in 1 mL methanol was
added. The ratio between the histidine unit of the polymers and the
metal salt was always 3:1. The used amounts of polymer and of the
1H NMR (300 MHz, CDCl3):
d
¼ 0.58 ‒ 2.13 (230H), 2.80 ‒ 3.08
(2H), 3.43 ‒ 3.61 (3H), 3.79 ‒ 4.06 (10H), 4.62 (1H), 6.56 (1H),
7.05 ‒ 7.38 (16H), 7.87 (1H) ppm.
SEC (CHCl3/IPA/TEA): Mn ¼ 29,900 g/mol; Mw ¼ 34,800 g/mol;
PDI ¼ 1.16.
Please cite this article in press as: Enke M, et al., Self-healing response in supramolecular polymers based on reversible zincehistidine