Covalent capture of self-assembled rosette nanotubes

Article abstract of DOI:10.1021/ma3012976

Rosette nanotubes (RNTs) are self-assembled tubular architectures which have extensive chemical and physical tuning capabilities, owing to their ease of surface functionalization and flexible inner channel design. To marry these tunable features of the RN

Full text of DOI:10.1021/ma3012976

Article
pubs.acs.org/Macromolecules
Covalent Capture of Self-Assembled Rosette Nanotubes
Bo-Liang Deng, Rachel L. Beingessner, Ross S. Johnson, Navdeep K. Girdhar, Christophe Danumah,
Takeshi Yamazaki, and Hicham Fenniri*
National Institute for Nanotechnology, Departments of Chemistry and Biomedical Engineering, University of Alberta, 11421
Saskatchewan Drive, Edmonton, Alberta T6G 2M9, Canada
*
S Supporting Information
ABSTRACT: Rosette nanotubes (RNTs) are self-assembled tubular
architectures which have extensive chemical and physical tuning capabilities,
owing to their ease of surface functionalization and flexible inner channel
design. To marry these tunable features of the RNTs with the enhanced
stability of a covalent polymer, here we demonstrate the covalent capture of
the RNT supramolecular structure by polymerizing alkyldiamine functional
groups expressed on their outer periphery in the presence of adipoyl
chloride (nylon-6,6 process). The resulting polymeric materials were
characterized using proton nuclear magnetic resonance spectroscopy,
Fourier transform infrared spectroscopy, dynamic light scattering, and
differential scanning calorimetry. Transmission and scanning electron
microscopy revealed the formation of fibers and films composed of RNTs.
INTRODUCTION
be increased from 1.1 nm (bicyclic motif) to 1.4 nm (tricyclic
■
1
0,12
11
1
motif)
or 1.7 nm (tetracyclic motif). This results in
Supramolecular polymers combine the unique features of
covalent polymers with the elegant design principles of self-
enhanced electronic communication along the RNTs’ main axis
13
12
2
as evidenced by their J-type optoelectronic properties.
assembly. Because supramolecular polymers are built using
Because of the RNTs design flexibility, polymerization of
their supramolecular structure provides a strategy to synthesize
many novel covalent polymers. To this end, here we describe
the synthesis and self-assembly of 3a and 3b (Figure 1) into
RNTs expressing alkyl triamine groups on their outer surface
and utilize these as sites for polymerization based on the nylon-
reversible and highly directional secondary interactions
between monomeric units, they benefit over traditional
polymers from their tunability, recyclability, and self-healing
characteristics. While these properties are a significant
advantage, the caveat of their noncovalent design is their
comparatively weaker architectural and dynamic stability at
higher temperatures. By capturing a supramolecular structure
14
6
,6 process. Details pertaining to the structure, thermo-
3
stability, and morphology of the resulting RNT polymer
such as a tubular assembly using a polymerization process,
1
materials 4a and 4b are provided using H NMR spectroscopy,
however, the structural control and intricacy of the self-
assembled polymer can be harnessed and transformed into a
thermostable and processable material. Herein, we demonstrate
this principle with the first reported polymerization of self-
assembled rosette nanotubes (RNTs).
FTIR spectroscopy, dynamic light scattering (DLS), differential
scanning calorimetry (DSC), scanning electron microscopy
(
SEM), and transmission electron microscopy (TEM).
4
RNTs are discrete, biocompatible tubular architectures
RESULTS AND DISCUSSION
■
formed in solution from a heterobicyclic molecule (G∧C)
that has the Watson−Crick donor−donor−acceptor H-bonding
array of guanine (G) and acceptor−acceptor−donor H-
In applying the synthetic strategy previously developed for
5,9
functionalizing the G∧C motif,
the synthesis of RNT
5a
5
polymers 4a and 4b began by coupling aldehyde 1 to
amine 2a or 2b using a reductive amination reaction (Figure 1).
Deprotection under acidic conditions (95:5, TFA:thioansiole,
v:v) then provided 3a and 3b as the TFA salts in excellent
yields of 82% and 95%, respectively. The structures of these
bonding array of cytosine (C). The tubular structure of the
RNT is comprised of stacked six-membered rosettes main-
tained in solution by a network of H-bonds, van der Waals, and
π−π stacking interactions. Detailed microscopy and spectros-
copy studies have shown that these architectures have an
exceptionally controlled organization that is based on these
cumulatively strong and directional noncovalent interactions.
As well, these materials have excellent chemical and physical
tuning capabilities, owing to their ease of surface functionaliza-
1
G∧C monomers were confirmed by H NMR, HRMS,
elemental analysis, and FTIR. Subsequent self-assembly of
5
motifs 3a and 3b (1 mg/mL) in water generated the respective
6
7
tion with bioactive molecules, inorganic complexes, nano-
Received: June 24, 2012
Revised: August 10, 2012
Published: August 22, 2012
8
9
particles, and other organic moieties. By extending the length
10−12
of the G∧C scaffold,
the RNT channel diameter can also
©
2012 American Chemical Society
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I and II bands and CH scissoring bands were supportive of at
2
least the partial polymerization of 3b.
Subsequent DLS studies of RNTs 3a and 3b in water (1 mg/
mL, 25 °C) resulted in well-equilibrated structures, which were
evident by the narrow unimodal size distributions (Figure
2
A,B). The average hydrodynamic diameters of these materials
Figure 1. Synthesis of polymers 4a and 4b (top) and negatively
stained TEM images of RNTs assembled in water from 3a (A) and 3b
(
B). White arrows point to individual RNTs; scale bars in nm.
RNTs having average diameters of 3.4 ± 0.2 nm as determined
by TEM (Figure 1).
Interfacial polycondensation based on the nylon-6,6 syn-
1
4
thesis was next carried out using the respective nanotube
solutions. Specifically, a solution of 3a (or 3b) (1 mg/mL) in
water was treated with Na CO , cooled to 0 °C, and then
2
3
added dropwise to an ice-cooled solution of adipoyl chloride in
dichloromethane. The polymerization occurred immediately at
the interface of the two solvents to yield polyamides 4a and 4b.
The films formed were recovered and washed with hot water,
acetone, and methanol to remove unreacted starting material.
1
H NMR spectroscopy, FTIR spectroscopy, and DLS were
Figure 2. DLS of (A) 3a and 3b in water and (B) 4a and 4b in MeCN
(1 mg/mL, 25 °C); DSC of 3b (C) and 4b (D) performed on the
solid materials at a heating rate of 10 °C/min.
1
used to establish the formation of polymers 4a and 4b. The H
NMR spectra of 4a obtained in deuterated trifluoroacetic acid
displayed the methylene protons of the adipoyl moiety on the
polymer backbone, the methylene protons connecting the G∧C
base to the polymer, and the methyl group on the G-face of the
motif (Figure S2). The relative integrations of these H NMR
peaks suggested that the polymerization was quantitative. FTIR
were determined to be 129 and 102 nm, respectively, which
indicates that 3a forms slightly larger aggregates. DLS
measurements of 4a and 4b (1 mg/mL, 25 °C, carried out in
acetonitrile for solubility reasons) gave larger average hydro-
dynamic diameters of 250 and 152 nm, respectively. Although
the hydrodynamic dimensions of polymerized and non-
polymerized RNT samples were obtained in different solvents,
and thus may not be directly comparable, the significantly larger
diameter and polydispersity of 4a and 4b are in agreement with
the polymerization of the RNTs.
Using DSC, the thermal behaviors of 3a and 3b were next
compared to the polymerized materials 4a and 4b, respectively.
In the case of 3a (functionalized with the ethylene triamine
moiety), the absence of a melting transition in the range of 50−
270 °C (data not shown) suggested an amorphous state for this
material. In contrast, the corresponding polymerized solid 4a
had two broad melting transitions around 108 and 185 °C
(Figure S10), suggesting the presence of two broad polymer
states or populations, possibly with intra- and inter-RNT
1
analysis further confirmed this polymerization since the
−
1
ammonium groups stretching bands (3600−2300 cm )
assigned to the ethylamines of 3a were replaced by CH
stretchings attributed to the polymer backbone of 4a.
Additional secondary amide I bands and CH2 scissoring
bands with increased intensity were also evident for 4a (Figure
S1).
1
In the case of polymer 4b, the presence of a H NMR peak
characteristic of a methylene α to an ammonium group
suggested that the polymerization occurred mainly on one of
the primary amines (Figure S3). Although ammonium group
−1
stretching bands (3700−2200 cm ) could not be conclusively
identified in the FTIR spectra of 4b to confirm this (because of
overlapping signals), the absorption between 3700 and 2800
−
1
cm was much stronger than that observed for 4a. Regardless,
the presence of CH stretchings and additional secondary amide
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connectivities. However, given the broadness of the peaks,
meaningful enthalpies could not be determined.
Interestingly, compound 3b (functionalized with the
propylene triamine moiety) displayed a single melting
transition at 87 °C (Figure 2C), which is reminiscent of the
solution melting temperature previously reported for RNTs
5a
functionalized with lysine amino acids and thus suggests that
b forms RNTs with similar thermal stability in the solid state
3
as well. In comparison, the melting profile of the corresponding
polymer 4b (Figure 2D) featured an intense endothermic
transition at a much higher temperature of 239 °C, which is
similar to nylon-6,6 (255−265 °C). The measured enthalpies
of endotherms (ΔH ) for compounds 3b and 4b are 4.59 and
15
m
5
0.1 J/g, respectively. While crystalline nylon-6,6 has a much
16
higher ΔH value (197 J/g), a lower degree of polymer-
m
1
7
18
ization or crystallinity decreases it to ca. of 53−61 J/g. As
this is the range where the ΔH of 4b is (50.1 J/g), this result is
m
in agreement with the NMR data suggesting incomplete
polymerization.
Thus, on the basis of DLS and DSC results, it was concluded
that the RNTs underwent surface-initiated polymerization
leading to the covalent capture and stabilization of the RNTs
with varying degrees of polymerization depending on their
surface functionalities.
SEM and TEM images of 4a (Figure 3 and Figures S6 and
S8) and 4b (Figure 4 and Figures S7 and S9) revealed the
Figure 4. TEM images of 4b (1 mg/mL in MeCN) showing the
formation of thin films (A, B) and fibrous materials (C, D). Black
arrows in image C point to RNT bundles; gray arrow points to a single
RNT. Scale bars in nm.
Na CO3 in the course of the polymerization reaction.
2
Polymerization thus likely occurs along the length of the
RNTs as well as between adjacent nanotubes. Overall, this
demonstrates that the self-assembled RNT architecture is
indeed maintained and captured during the polymerization
process and that, moreover, this strategy holds substantial
promise for the design of novel polymeric materials with unique
hierarchical architecture.
Using the minimized molecular model of RNTs 3a shown in
Figure 5, the accessible polymerization connections between
the nitrogen labeled N1 on a given G∧C motif and the
neighboring N1 or N2 atoms on a different motif within the
same nanotube were examined. Given that the measured
carbonyl-to-carbonyl length of adipoyl chloride in the all-trans
configuration is ca. 6.5 Å, and that upon polymerization the
bond length between the carbonyl carbon of the adipoyl moiety
and N1 would be ca. 1.4 Å, we can roughly predict that
neighboring N atoms at a distance of ca. 9.3 Å from N1 shown
in yellow could be bridged together. N-to-N1 (or N2) distances
represented in orange are not within a favorable range for cross-
linking with adipoyl chloride assuming these length restrictions.
On this basis, adjacent rosettes as well as alternating rosettes
can be covalently linked via the adipoyl tether in many different
combinations (Figure S13). Although the example in Figure 5C
is idealized, it provides insight into the bridging of N1−N1 and
N2−N2 atoms between adjacent rosettes.
Figure 3. TEM images of 4a (1 mg/mL in MeCN) showing the
formation of thin films made up of RNTs. The parallel tape-like
formation of the RNTs is seen in image D. Scale bars in nm.
formation of thin films as well as fibrous materials and provided
insight into the organization of the polymer network. In
particular, the images in Figure 3D (and Figure S8D) show
polymer 4a in a parallel tape-like formation in which the RNTs
are aligned along their main axis. The average distance between
consecutive RNTs was measured to be 3.4 ± 0.2 nm, which is
in excellent agreement with the calculated average diameter for
the nonpolymerized RNT (3a). This alignment suggests that
the well-dispersed, protonated RNTs form bundles and tapes
prior to polymerization as a result of their neutralization with
CONCLUSION
■
In summary, we have demonstrated the covalent capture of self-
assembled RNTs using a polymerization strategy based on
nylon-6,6 methodology. Specifically, ethylene and propylene
diamine groups expressed on the outer RNT surface were
polymerized using adipoyl chloride under basic conditions. The
1
resulting materials were characterized by H NMR, FTIR, DSC,
DLS, and electron microscopy techniques. DSC established our
main aim, which is an enhanced thermostability of polymer 4b
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DLS experiments were performed using a Malvern Zetasizer Nano S
working at a 173° scattering angle at 25 °C. This instrument is
equipped with a 40 mW He−Ne laser (λ = 633 nm) and an Avalanche
photodiode detector. Solutions (1 mg/mL) were prepared and then
filtered through a Whatman 0.45 μm pore diameter PVFD membrane
filter prior to measurement.
DSC was performed on a DSC1000 differential calorimeter (TA
Instruments) fitted with a liquid nitrogen cooling system. The samples
were placed in hermetically sealed DSC pans and then heated and
cooled at rates of 10 and 5 °C, respectively. A first heating scan was
performed to erase the thermal history of the materials. DSC
measurements were then obtained in the second heating scan. In all
cases, the endotherms were reversible.
Synthesis of 2a. A solution of diethylenetriamine (0.43 g, 4.2
mmol) and triethylamine (1.8 mL, 13 mmol) in THF (10 mL) was
cooled to 0 °C and stirred under a nitrogen atmosphere. A solution of
2
-(tert-butoxycarbonyloxyimino)-2-phenylacetonitrile (2.1 g, 8.3
mmol) in THF (40 mL) was then added over a period of 1 h. The
mixture was stirred at 0 °C for 2.5 h, followed by 2 h at room
temperature. The solvent was removed under reduced pressure
(rotavap) to provide a light yellow oil, which was redissolved in
CH Cl (120 mL) and washed with an aqueous solution of 5% NaOH
2
2
(
2 × 40 mL). The organic layer was further washed with dH O (50
2
mL) and brine (35 mL), dried over anhydrous Na SO , and
2
4
Figure 5. Molecular models of RNT 3a illustrating one possible mode
of cross-linking within the nanotube. (A) Compound 3a with nitrogen
atoms labeled N1 and N2. (B) Distances (Å) from N1 on a motif to
neighboring N1 or N2 on a different motif. An atom-to-atom length of
ca. 9.3 Å (marked in yellow) is optimal for two amines (N1−N1 or
N2−N2) to be linked to adipoyl chloride given an all-trans
configuration. N-to-N distances represented in orange are not within
an appropriate range for polymerization with adipoyl chloride. (C)
Example of an N1−N1, N2−N2 connectivity of 3a through the
adipoyl tether.
concentrated under reduced pressure (rotavap). Purification by silica
gel chromatography (10% MeOH/CH Cl ) provided 1.22 g of
2
2
1
compound 2a (C H N O , 97%) as a colorless solid. H NMR
14
29
3
4
(
300 MHz, CDCl ) δ (ppm): 4.85 (brs, 2H), 3.15−3.25 (m, 4H), 2.71
3
3
(
t, J = 6.0 Hz, 4H), 1.65 (brs, 1H), 1.43 (m, 18H). CI-MS: expected
for (M + H )/z: 304; observed: 304 ((M + H) /z, 100%).
+
+
19
Synthesis of 3a. Amine 2a (0.5 g, 0.78 mmol) was added to a
5a
solution of aldehyde 1 (237 mg, 0.78 mmol in 1,2-dichloroethane
(
(
20 mL) under a N atmosphere. After stirring for 6 h, Na(OAc) BH
196 mg, 0.93 mmol) was added. The reaction mixture was then
2
3
stirred at rt under N for 36 h before being quenched with H O and
2
2
extracted with CHCl (200 mL). The organic layer was subsequently
3
washed with 10% citric acid solution (50 mL), dH O (50 mL), 5%
2
compared to the corresponding supramolecular system 3b.
TEM imaging confirmed that the RNT architecture is
preserved to some extent during the polymerization process
and that the polymer network has substantial organization,
which is based on the alignment and cross-linking of adjacent
RNTs. With our ability to tailor the physical and chemical
properties of the RNTs including their inner channels and
surface functional groups, we envision that a variety of new
RNT covalent polymers with unique physical and chemical
properties could be generated.
NaHCO (50 mL), and brine (50 mL), dried over anhydrous Na SO ,
3
2
4
filtered, and concentrated under reduced pressure (rotavap).
Purification by flash chromatography over silica gel (20% EtOAc/
hexane) provided the protected coupled G∧C base as a white foam
1
(
0.61 g, C H N O , 84% yield). H NMR (CDCl , 400 MHz) δ
45 69
9
12
3
(
ppm): 7.45−7.32 (m, 5H), 5.56 (s, 2H), 5.14 (brs, 2H), 4.37 (t, J =
7
2
1
1
7
.6 Hz, 2H), 3.46 (s, 3H), 3.18 (d, J = 5.6 Hz, 4H), 2.81 (t, J = 7.6 Hz,
H), 2.68 (t, J = 5.6 Hz, 4H), 1.57 (s, 9H), 1.43 (s, 18H), 1.32 (s,
13
8H). C NMR (CDCl , 100 MHz) δ (ppm): 165.9, 161.4, 161.2,
3
60.6, 156.4, 155.9, 152.5, 149.5, 135.1, 128.8−128.6, 93.2, 84.0, 83.2,
9.2, 70.3, 54.3, 51.2, 41.4, 39.0, 35.2, 28.7, 28.3, 28.1. Positive ESI-
+
+
MS: expected for (M + H) /z: 928.5; observed: 928.8 ((M + H) /z,
EXPERIMENTAL SECTION
All commercial chemicals were used as purchased without further
purification. NMR characterizations were performed on a 300−600
MHz spectrometers in the specified deuterated solvents (D O,
+
1
00%). Positive high-resolution ESI-MS: expected for (M + Na) /z:
■
950.4958; observed: 950.4958.
Trifluoroacetic acid and thioanisole (95:5 v/v, 10 mL) were added
to the protected coupled G∧C base (0.61 g, 0.657 mmol) and stirred
2
trifluoracetic acid-d, CDCl ). The NMR data are presented as follows:
at rt under a N atmosphere for 72 h. Diethyl ether (20 mL) was then
2
3
chemical shift, assignment, coupling, integration.
FTIR was performed on a Nicolet Nic-Plan IR microscope
equipped with a MCT-A detector attached to a Nicolet Magna 750
added to precipitate the product, which was collected by
centrifugation, washed with diethyl ether (10 mL), and dried under
reduced pressure (rotavap) to provide 3a as a white solid (444 mg,
−1
1
FTIR. The spectra were acquired from 4000 to 650 cm using 128
C
13
H
23
N
9
O
2
+ 3(CF
3
COOH) + H
2
O, 97%). H NMR (400 MHz,
−1
scans at 4 cm resolution and Nicolet Omnic software.
D O) δ (ppm): 4.32−4.28 (t, J = 8.0 Hz, 2H), 3.15−3.12 (t, J = 6.4
2
SEM and TEM samples were prepared by floating a carbon-coated
00-mesh copper grid on a droplet of a 1 mg/mL solution of 3a or 3b
Hz, 4H), 3.05 (s, 3H), 2.98−2.90 (m, 6H). ESI-MS: expected for (M
+ +
4
+ H) /z: 338.2; observed: 338.2 ((M + H) /z, 100%). Positive high-
+
(
in water) or 4a or 4b (in MeCN) for 10 s. Excess material was blotted
resolution ESI-MS: expected for (M + H) /z: 338.2048; observed:
with filter paper at the edge of the grid. Negative staining (for TEM)
was performed by floating the grids on a drop of 1% uranyl acetate in
water for 10 s and blotting excess staining agent. The samples were
dried overnight at room temperature prior to imaging. SEM images
were obtained at 1.0 kV accelerating voltage and a working distance of
338.2049. Elemental analysis: calculated for [C H N O + 3-
1
3
23
9
2
(CF COOH) + H O]: C: 32.72; H: 4.05; N: 18.07; found: C:
3
2
32.98; H: 4.19; N: 18.02.
Synthesis of 4a. A solution of adipoyl chloride (27 μL, 0.19
mmol) in CH Cl (10 mL) was treated with an ice-cold solution of 3a
2
2
1
.0−2.0 mm on a high-resolution Hitachi S4800 cold field emission
(50 mg, 0.15 mmol) and Na CO (16 mg, 0.15 mmol) in dH O (5
mL) using a syringe. The polymerization occurred immediately
(without stirring) at the interface of the two solvents. The resulting 4a
2
3
2
SEM. TEM imaging was performed on a JEOL 2010 microscope
operated at 200 kV.
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was then removed from solution and washed with hot dH O (10 mL),
acetone (10 mL), and methanol (10 mL). H NMR (trifluoroacetic
acid-d, 400 MHz): δ (ppm) 3.34−3.22 (Me, brs, 3H), 2.72−2.54
2
ASSOCIATED CONTENT
■
* Supporting Information
1
S
FTIR, NMR, additional microscopy images, DSC, and
molecular modeling. This material is available free of charge
via the Internet at http://pubs.acs.org.
(
C
H, brs, 6H), 2.00−1.78 (C H, brs, 6H), 1.58−1.30 (C H,
b+c+d
a+e+f
g+i
m, 4H), 0.98−0.80 (C H, m, 4H).
h+j
Synthesis of 2b. A solution of bis(3-aminopropyl)amine (0.28 g,
2
.1 mmol) and triethylamine (0.88 mL, 6.3 mmol) in THF (10 mL)
was cooled to 0 °C and stirred under a N atmosphere. A solution of
AUTHOR INFORMATION
Corresponding Author
Tel 780-641-1750; Fax 780-641-1601; e-mail hicham.fenniri@
ualberta.ca.
2
■
*
2-(tert-butoxycarbonyloxyimino)-2-phentylacetonitrile (1.04 g, 4.19
mmol) in THF (20 mL) was then added over 30 min. The mixture
was stirred at 0 °C for 3 h then 1 h at rt. The solvent was then
removed under reduced pressure (rotavap) to yield a yellow oil which
was dissolved in CH Cl (100 mL) and washed with an aqueous
Notes
2
2
solution of 5% NaOH (2 × 40 mL). The organic layer was
The authors declare no competing financial interest.
subsequently washed with dH O (50 mL) and brine (50 mL), dried
2
over anhydrous Na SO and then concentrated in vacuo to provide 2b
ACKNOWLEDGMENTS
2
4
■
1
as a white solid (0.71 g, C H N O , quant) as a white solid. H NMR
1
6
33
3
4
We thank Canada’s National Research Council and Natural
Science and Engineering Research Council, Canada Foundation
for Innovation, the National Institute for Nanotechnology, and
the University of Alberta for supporting this work.
3
(
300 MHz, CDCl ) δ (ppm): 5.14 (brs, 2H), 3.18 (m, 4H), 2.63 (t, J
3
=
6.6 Hz, 4H), 1.65 (brs, 1H), 1.62 (m, 4H), 1.42 (s, 18H). EI-MS:
+
+
expected for (M + H) /z: 332.3; observed: 332.3 ((M + H) /z, 1.2%),
+
+
5
7.10 (C H /z, 100%). CI-MS: expected for (M + H )/z: 332.3;
4 9
20
+
observed: 331.9 ([M + H] /z, 100%).
Synthesis of 3b. Amine 2b (0.52 g, 1.56 mmol) was added to a
REFERENCES
■
5a
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3) (a) Perino, A.; Schmutz, M.; Meunier, S.; Mesini, P. J.; Wagner,
mmol) in 1,2-dichloroethane (25 mL) under a N atmosphere. After
2
stirring for 10 min, Na(OAc) BH (393 mg, 1.86 mmol) was added.
3
The reaction mixture was then stirred at rt for 36 h under N2
atmosphere before being quenched with H O and extracted with
2
CHCl (200 mL). The organic layer was subsequently washed with
3
1
0% citric acid solution (50 mL), dH O, 5% NaHCO (50 mL), and
2 3
brine (50 mL), dried over anhydrous Na SO , filtered, and then
2
4
concentrated under reduced pressure (rotavap). Purification by flash
chromatography over silica gel (20% EtOAc/hexane) provided the
protected coupled G∧C base 3b as a white solid (1.42 g, C H N O ,
4
7
73
9
12
1
6
(
1
1
9
5
3
4
5% yield). H NMR (CDCl , 500 MHz) δ (ppm): 7.45−7.36 (m,
3
H), 5.59 (s, 2H), 5.23 (brs, 2H), 4.42 (t, J = 6.5 Hz, 2H), 3.47 (s,
H), 3.18−3.08 (m, 4H), 2.77 (t, J = 6.5 Hz, 2H), 2.56 (t, J = 6.5 Hz,
H), 1.65−1.60 (m, 4H), 1.60 (s, 9H), 1.44 (s, 18H), 1.35 (s, 18H).
1
3
C NMR (CDCl , 125 MHz) δ (ppm): 165.7, 161.1, 161.0, 160.3,
3
(
1
7
56.1, 155.7, 152.4, 149.4, 134.9, 128.6−127.8, 92.9, 83.8, 83.0, 78.8,
A. Langmuir 2011, 27, 12149−12155. (b) Kim, Y.; Mayer, M. F.;
Zimmerman, S. C. Angew. Chem. 2003, 115, 1153−1158. (c) Ouhib,
F.; Bugnet, E.; Nossov, A.; Bonardet, J.-L.; Bouteiller, L. Polymer 2010,
0.1, 52.0, 50.7, 40.8, 39.0, 34.9, 28.5, 28.2, 27.8, 27.6. Positive ESI-
+
+
MS: expected for (M + H) /z: 956.5; observed: 956.5 ((M + H) /z,
+
100%). Positive high-resolution ESI-MS: expected for (M + H) /z:
3
6
360−3364. (d) Huang, K.; Rzayev, J. J. Am. Chem. Soc. 2009, 131,
956.5452; observed: 956.5447.
880−6885. (e) Barboiu, M.; Cerneaux, S.; van der Lee, A.; Vaughan,
Trifluoroacetic acid and thioanisole (95:5 v/v, 10 mL) were added
G. J. Am. Chem. Soc. 2004, 126, 3545−3550. (f) Kim, Y.; Mayer, M. F.;
the protected coupled G∧C base (1.20 g, 1.25 mmol) and stirred at rt
under a nitrogen atmosphere for 72 h. Diethyl ether (20 mL) was then
added to precipitate the product, which was collected by
centrifugation, washed with diethyl ether, and dried under reduced
pressure to provide 1.04 g of 3b (C H N O + 4(CF COOH) +
Zimmerman, S. C. Angew. Chem., Int. Ed. 2003, 42, 1121−1126.
(
(
(
1
(
g) Stewart, S.; Liu, G. Angew. Chem., Int. Ed. 2000, 39, 340−344.
h) Beginn, U.; Zipp, G.; Mo
i) Zhou, M.; Kidd, T. J.; Noble, R. D.; Gin, D. L. Adv. Mater. 2005,
7, 1850−1853.
4) (a) Journeay, W. S.; Suri, S. S.; Moralez, J. G.; Fenniri, H.; Singh,
̈
ller. Adv. Mater. 2000, 12, 510−513.
1
5
27
9
2
3
1
H O, 99%). H NMR (400 MHz, D O) δ (ppm): 4.49−4.46 (t, J = 6.4
2
2
Hz, 2H), 3.49−3.46 (t, J = 6.4 Hz, 2H), 3.32−3.28 (m, 4H), 3.00−
.96 (m, 4H), 2.91 (s, 3H), 2.07−1.98 (m, 4H). Positive ESI-MS:
B. Small 2008, 4, 817−823. (b) Journeay, W. S.; Suri, S. S.; Moralez, J.
G.; Fenniri, H.; Singh, B. Small 2009, 5, 1446−1452. (c) Journey, W.
S.; Suri, S. S.; Moralez, J. G.; Fenniri, H.; Singh, B. Int. J. Nanomed.
008, 3, 373−383.
5) (a) Fenniri, H.; Deng, B. L.; Ribbe, A. E. J. Am. Chem. Soc. 2002,
2
+
+
expected for (M + H) /z: 366.2; observed: 366.3 ((M + H) /z,
+
1
3
00%). Positive high-resolution ESI-MS: expected for (M + H) /z:
66.2366; observed: 366.2368. Elemental analysis: calculated for
2
(
[
C H N O + 4(CF COOH) + H O]: C: 32.90; H: 3.96; N: 15.02;
15 27 9 2 3 2
124, 11064−11072. (b) Moralez, J. G.; Raez, J.; Yamazaki, T.; Motkuri,
found: C: 32.77; H: 4.07; N: 14.64.
R. K.; Kovalenko, A.; Fenniri, H. J. Am. Chem. Soc. 2005, 127, 8307−
Synthesis of 4b. A solution of adipoyl chloride (0.02 mL, 0.14
mmol) in CH Cl (10 mL) was treated with an ice-cold solution of 3b
8
309. (c) Fenniri, H.; Deng, B. L.; Ribbe, A. E.; Hallenga, K.; Jacob, J.;
2
2
Thiyagarajan, P. Proc. Natl. Acad. Sci. U. S. A. 2002, 99, 6487−6492.
(d) Raez, J.; Moralez, J. G.; Fenniri, H. J. Am. Chem. Soc. 2004, 126,
16298−16299. (e) Fenniri, H.; Mathivanan, P.; Vidale, K. L.; Sherman,
D. M.; Hallenga, K.; Wood, K. V.; Stowell, J. G. J. Am. Chem. Soc.
2001, 123, 3854−3855. (f) Yamazaki, T.; Fenniri, H.; Kovalenko, A.
ChemPhysChem 2010, 11, 361−367. (g) Marsh, A.; Silvestri, M.; Lehn,
J.-M. Chem. Commun. 1996, 1527−1528. (h) Mascal, M.; Hext, N. M.;
Warmuth, R.; Moore, A. H.; Turkenburg, J. P. Angew. Chem., Int. Ed.
1996, 108, 2203−2206.
(
50 mg, 0.14 mmol) and Na CO (19 mg, 0.14 mmol) in dH O (5
2
3
2
mL) using a syringe. The polymerization occurred immediately
without stirring) at the interface of the two solvents. The resulting 4b
(
was then removed from solution and washed with hot dH O (10 mL),
2
1
acetone (10 mL), and methanol (10 mL). H NMR (trifluoroacetic
acid-d, 400 MHz) δ (ppm): 3.56−3.48 (C H, brs, 2H), 3.37−3.20
g
(
6
Me, brs, 3H), 2.80−2.43 (C
H, m, 6H), 2.16−1.70 (C
H, m,
a+h+e
b+c+d
H), 1.65−1.25 (C H, m, 4H), 1.05−0.83 (C H, m, 2H).
f+i
j
7
161
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