Dynamic Polymers
FULL PAPER
tering length per unit volume, bi is the neutron scattering length of spe-
cies i, mi is the mass of species i and v is the specific volume of the mono-
mer (which has been taken to be equal to 0.89 cm3 gꢀ1) or the solvent
(e.g., 1.1494 cm3 gꢀ1 for deuterated acetone). P(q) is the form factor,
chains in solution, as observed by small-angle neutron scat-
tering. In the condensed phase, these chains could be dy-
namically cross-linked by adding a suitable cross-linking
agent to generate a dynamic elastomer. The fact that the
DA adducts linking the monomers can easily revert at room
temperature even in the condensed phase accounts for the
ability of the network to adapt in response to mechanical
elongation stress or to self-repair, even after the system has
reached its equilibrium. These findings extend to the molec-
ular/covalent domain those properties displayed by supra-
molecular/non-covalent entities.[1,2,12] Fine-tuning the equi-
librium constant of the connections used to form the dynam-
ers should permit us to control the self-healing properties or
to adapt the temperature range of the self-healing process.
V
chain =Nvmꢆ1.66ꢆ10ꢀ24 is the volume of N monomers (of mass m) in a
chain and fvol is the volume fraction of monomer. At high q ranges, the
scattering is assumed to arise from isolated chains, that is, S2(q)=0, and
thus I(q)/P(q).
2,3-Dicyano-but-2-enedioic acid 2-(2,3-dicyano-3-methoxycarbonyl-acryl-
oyloxy)-ethyl ester methyl ester (2): Ethylene glycol dicyanoacetate
(2.0 g, 10.2 mmol) and methylcyanoacetate (4.5 mL, 5 equiv) were dis-
solved in dry tetrahydrofuran (20 mL). Thionyl chloride (6.0 mL, 9.7 g,
8 equiv) was added, and the mixture was heated at reflux overnight
under an inert atmosphere. The reaction mixture was then cooled to RT,
and the precipitate that formed was filtered. This solid was suspended in
chloroform, filtered again, washed with ethyl acetate/chloroform (2:1)
and dried under reduced pressure to give the product as a white solid
(1.83 g, 46%). M.p. >1808C decomp; 1H NMR ([D6]DMSO, 400 MHz):
d=4.67 (s, 4H), 3.93 ppm (s, 6H); 13C NMR ([D6]DMSO, 100 MHz): d=
ꢀ
ꢀ
ꢀ ꢄ
158.7, 158.1 ( C(=O)O ), 125.7, 125.0 (C=C), 112.6, 112.4 ( C N), 65.2
Experimental Section
ꢀ ꢀ ꢀ
ꢀ
(O C C O), 55.0 ppm (O C); ESI-TOF-MS: m/z (%): calcd for
C16H10N4O8Na+: 409.0391 [M+Na]+; found: 409.0447 (100); elemental
analysis calcd (%) for C16H10N4O8: C 49.75, H 2.61, N 14.50; found: C
48.46, H 2.97, N 16.99.
General: All reagents were purchased from commercial suppliers (Acros,
Aldrich and Flucka) and used without further purification. Tetrahydro-
furan (THF) was dried over sodium·benzophenone. Preparative adsorp-
tion flash column chromatography was performed by using silica gel (Ge-
duran, silica gel 60 (230–400 mesh, 40–63 mm, Merck). 1H NMR
(400 MHz) and 13C NMR (100 MHz) spectra were recorded by using a
Bruker Advance 400 spectrometer. The spectra were internally refer-
enced to the residual solvent signal. In the assignments, the chemical
shifts are given in ppm. The coupling constants J are listed in Hz. The fol-
lowing notation is used for the splitting patterns: singlet (s), doublet (d),
triplet (t), q (quadruplet), multiplet (m). Electron impact (EI) mass spec-
tra were performed by the Service de Spectromꢀtrie de Masse, Institut
de Chimie, Universitꢀ Louis Pasteur. Electrospray (ESI and ESI-TOF)
studies were performed by using a Bruker Micro TOF mass spectrome-
ter. Sample solutions were introduced into the mass spectrometer source
by using a syringe pump with a flow rate of 40 mLminꢀ1. Melting points
were recorded by using a Bꢅchi Melting Point B-540 apparatus and are
uncorrected. Microanalyses were performed by the Service de Microana-
lyse, Institut de Chimie, Universitꢀ Louis Pasteur. SANS experiments
were carried out by using the Pace spectrometer in the Lꢀon Brillouin
Laboratory at Saclay (LLB, France). The chosen incident wavelength, l,
depends on the set of experiments, as follows. For a given wavelength,
the range of the amplitude of the transfer wave vector q was selected by
changing the detector distance, D. Three sets of sample-to-detector dis-
tances and wavelengths were chosen (D=1 m, l=4.5ꢂ0.5 ꢄ; D=
1.86 m, l=6ꢂ0.5 ꢄ; and D=4.7 m, l=12ꢂ1 ꢄ) so that the following q
General procedure for the synthesis of solid tricyanoethylenecarboxy-
lates: TCNE (6.0 g, 5.5 equiv) was dissolved in dry tetrahydrofuran
(30 mL) at 708C. Cyanoacetate (8.5 mmol) was added, followed by pyri-
dine (100 mL), which caused the reaction mixture to become dark. The
mixture was refluxed for 40 h, then allowed to cool down to RT and then
diluted with chloroform (50 mL) and pentane (100 mL). The mixture was
allowed to stand for 1 h, during which a black tarry phase settled out and
some of the excess TCNE precipitated. The precipitate was filtered off
and the filtrate was washed repeatedly with water until the organic layer
became a light red/purple colour. It was then dried over magnesium sul-
phate and concentrated under reduced pressure until a precipitate started
to form. The mixture was filtered, then heptane (50 mL) was added to
the filtrate and the solution concentrated again. When a precipitate start-
ed to form, the solution was cooled to 08C and the white solid that
formed was filtered off. If necessary, this solid was recrystallised from a
mixture of chloroform (10%) in pentane. This operation was repeated
until the 13C NMR spectrum showed no trace of TCNE.
Methyl tricyanoethylenecarboxylate (3): The product was obtained as a
white powder (4%). M.p. 89–918C; 1H NMR (CDCl3, 400 MHz): d=
13
ꢀ
ꢀ
4.11 ppm (s, 3H); C NMR (CDCl3, 100 MHz): d=156.4. ( C(=O)O ),
ꢀ
ꢀ
ꢀ
ꢀ ꢄ
131.3 (C=CACTHUNGTRENNUNG
( CN) C(=O) ), 110.6, 109.4, 108.3 (3ꢆ C N), 106.6 (C=C-
ꢀ
ꢀ
( CN)2), 55.6 ppm (O C); elemental analysis calcd (%)for C7H3N3O2: C
52.18, H 1.88, N 26.08; found: C 52.48, H 1.73, N 25.94.
ranges were available
:
4.2ꢆ10ꢀ2 ꢃq [ꢄꢀ1]ꢃ4.3ꢆ10ꢀ1
,
1.7ꢆ10ꢀ2 ꢃq
Ethyl tricyanoethylenecarboxylate (4): The product was obtained as a
white powder (14%). M.p. 65–668C; 1H NMR (CDCl3, 400 MHz): d=
[ꢄꢀ1]ꢃ1.8ꢆ10ꢀ1 and 3.4ꢆ10ꢀ3 ꢃq [ꢄꢀ1]ꢃ3.4ꢆ10ꢀ2, respectively. Mea-
sured intensities were calibrated to absolute values (cmꢀ1) by normalisa-
tion using the attenuated direct beam classical method. Standard proce-
dures to correct the data for the transmission, detector efficiency and
backgrounds (solvent, empty cell, electronic and neutronic background)
were carried out. The scattered wave vector, q, is defined by Equa-
tion (5), in which q is the scattering angle:
4.55 (q, 3J(H,H)=7.1 Hz, 2H), 1.49ppm (t, 3J
ACTHUNTGRNENUG ACHTUNTGERN(NUGN H,H)=7.1 Hz, 3H);
13C NMR (CDCl3, 100 MHz): d=155.8. ( C(=O)O ), 131.9 (C=C
ACHTUNGTRENNUNG(
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ ꢄ
ꢀ
CN) C(=O) ), 110.7, 109.4, 108.4 (3ꢆ C N), 106.4 (C=CACTHUNGTERN(UNNG CN)2), 66.0
+
ꢀ ꢀ
ꢀ ꢀ
(O C C), 13.8 ppm (O C C); EI-MS: m/z: calcd for C16H4N6O4Na :
175.04 [M]+; found: 175.0; elemental analysis calcd (%) for C8H5N3O2: C
54.86, H 2.88, N 23.99; found: C 54.59, H 2.97, N 24.72.
Allyl tricyanoethylenecarboxylate (5): The product was obtained as a
white powder that must be stored at ꢀ308C (26%). M.p. >1178C
4p
l
q
ð5Þ
q ¼
sin
decomp; 1H NMR (CDCl3, 400 MHz): d=6.01 (ddt, 3J
ACTHNUTRGNE(NUG H,H)=17.2, 10.2,
2
3
4
3
6.4 Hz, 1H), 5.58 (dd, J
ACHUTGTNREN(NUG H,H)=17.2, JACHTNUGTRENNUNG
(H,H)=0.6 Hz, 1H), 4.98 ppm (ddd, 3J
(H,H)=1.2, 0.6 Hz, 2H); C NMR (CDCl3, 100 MHz): d=155.7 ( C(=
G
The usual equation for absolute neutron scattering combines the intra-
particle scattering S1(q)=Vchain
scattering S2(q) factor:
A
13
fvolP(q) form factor with the inter-particle
ꢀ
N
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
O)O ), 131.7 (C=C
( CN) C(=O) ), 128.9 (C C=C), 122.3 (C C=C),
ꢀ ꢄ
ꢀ
ꢀ ꢀ
110.7, 109.5, 108.4 (3ꢆ C N), 105.5 (C=C
( CN)2), 90.1 (O C( C)3),
IðqÞðcmꢀ1Þ ¼ ðD1Þ ðS1ðqÞ þ S2ðqÞÞ ¼ ðD1Þ ðVchainꢀvolPðqÞ þ S2ðqÞÞ
2
2
ꢀ ꢀ
27.6 ppm (O C C); elemental analysis calcd (%) for C9H5N3O2: C 57.76,
ð6Þ
H 2.69; found: C 57.71, H 2.96 (N was not determined).
2
in which (D1)2 =(1monomerꢀ1solvent
)
is the difference per unit volume be-
tert-Butyl tricyanoethylenecarboxylate (6): The product was obtained as a
white powder that must be stored at ꢀ308C (41%). M.p. 102–1038C;
1H NMR (CDCl3, 400 MHz): d=1.65 ppm (s, 9H); 13C NMR (CDCl3,
tween the polymer and the solvent and was determined from the known
chemical composition. 1=ꢀnibi/(ꢀnimivꢆ1.66ꢆ10ꢀ24) represents the scat-
Chem. Eur. J. 2009, 15, 1893 – 1900
ꢃ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1899