Self-assembly of supra-amphiphile of azobenzene-galactopyranoside based on dynamic covalent bond and its dual responses

Article abstract of DOI:10.1016/j.cclet.2016.05.009

In this paper, dynamic covalent bond has been employed to construct supra-amphiphile of carbohydrate for the first time. In neutral environment, the molecule was fabricated by reacting a hydrophobic building block bearing benzoic aldehyde with a hydrophilic building block bearing hydrazine to form a sugar-containing supra-amphiphile based on acylhydrazone bond. The obtained azobenzene-galactopyranoside (Azo-Gal) supra-amphiphile self-assembled to fibrillar structure in water, which showed dual responses to UV light and pH.

Full text of DOI:10.1016/j.cclet.2016.05.009

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Contents lists available at ScienceDirect
Chinese Chemical Letters
journal homepage: www.elsevier.com/locate/cclet
Original article
Self-assembly of supra-amphiphile of azobenzene-galactopyranoside
based on dynamic covalent bond and its dual responses
*
Tian-Nan Wang, Guang Yang, Li-Bin Wu, Guo-Song Chen
The State Key Laboratory of Molecular Engineering of Polymers and Department of Macromolecular Science, Fudan University, Shanghai 200433, China
A R T I C L E I N F O
A B S T R A C T
Article history:
In this paper, dynamic covalent bond has been employed to construct supra-amphiphile of carbohydrate
for the first time. In neutral environment, the molecule was fabricated by reacting a hydrophobic
building block bearing benzoic aldehyde with a hydrophilic building block bearing hydrazine to form a
sugar-containing supra-amphiphile based on acylhydrazone bond. The obtained azobenzene-
galactopyranoside (Azo-Gal) supra-amphiphile self-assembled to fibrillar structure in water, which
showed dual responses to UV light and pH.
Received 7 April 2016
Received in revised form 3 May 2016
Accepted 5 May 2016
Available online xxx
Keywords:
ß 2016 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.
Published by Elsevier B.V. All rights reserved.
Supra-amphiphile
Self-assembly
Dynamic covalent bond
Carbohydrate
Dual responses
1. Introduction
of carbohydrate has not been achieved on the basis of dynamic
covalent bond.
Supra-amphiphiles [1] refer to amphiphiles that are con-
structed by dynamic covalent bonds [2,3] or non-covalent
Herein, for the first time, construction of azobenzene-galacto-
pyranoside (Azo-Gal) supra-amphiphile based on acylhydrazone
dynamic covalent bond formed by the aldehyde of the azobenzene-
containing hydrophobic domain (Azo-CHO) and the hydrazine of
the sugar moiety (Gal-N2H4) was reported (Fig. 1). Acylhydrazone
bond is stable in neutral or alkaline environment, but it can be
hydrolyzed under acidic condition. Besides, azobenzene is utilized
as a model hydrophobic moiety since it is a wildly used building
interactions such as hydrogen bonding,
p–p interaction, host–
guest interaction and charge transfer interaction [4–6]. Generally,
the hydrophilic part and the hydrophobic part can be easily linked
together via these dynamic connections, which avoids tedious
syntheses. Moreover, the supra-amphiphiles are easier to be
manipulated compared with amphiphiles fabricated by covalent
bonds due to the dynamic nature of the linkage. They undergo self-
assembly and disassembly processes in a controllable way with
stimuli-responsive properties [7,8].
block for self-assembly and forms reversible complex with
a-CD.
The Azo-Gal supra-amphiphile self-assembles into fiber in
scale, which is featured by light and pH responsiveness.
mm
Carbohydrates play an important role in a variety of biological
processes, such as cell adhesion, proliferation, differentiation,
recognition, inflammation and the immune response [9]. They are
able to form hydrogen bonds, which makes them become
important building blocks in supramolecular chemistry [10].
However, few works have been done to incorporate carbohydrates
into supra-amphiphiles [11]. Zhang and co-workers constructed
the first example of sugar-containing supra-amphiphile, i.e.
supramolecular glycolipid based on host-enhanced charge transfer
interaction [12]. However, as far as we know, supra-amphiphile
2. Experimental
2.1. Materials and experiments
Ethyl 3-hydroxypropanoate was purchased from Maya Chemi-
cal and used as received. -Galactose was purchased from
D
Bangcheng Chemical and used as received. Trichloroacetonitrile,
dichloromethane (DCM) and N,N-dimethylformamide (DMF) were
distilled before use. Unless specially mentioned, all other
chemicals were purchased from J&K Chemical and used as
received. The reactions were monitored and the Rf values were
determined using analytical thin-layer chromatography (TLC). The
TLC plates were visualized by immersion into 5% sulfuric acid
solution in ethanol followed by heating using hot air heater.
*
Corresponding author.
E-mail address: guosong@fudan.edu.cn (G.-S. Chen).
http://dx.doi.org/10.1016/j.cclet.2016.05.009
1001-8417/ß 2016 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.
Please cite this article in press as: T.-N. Wang, et al., Self-assembly of supra-amphiphile of azobenzene-galactopyranoside based on
dynamic covalent bond and its dual responses, Chin. Chem. Lett. (2016), http://dx.doi.org/10.1016/j.cclet.2016.05.009

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temperature, it was concentrated under vacuum. The product
was purified by column chromatography using EtOAc/petroleum
ether (1:2) as eluent to yield 0.3 g (42.5%) of G4 as white solid. 1H
NMR (400 MHz, CDCl3): d 5.39 (dd, 1H, J = 3.4, 1.1 Hz), 5.18 (dd, 1H,
J = 10.5, 7.9 Hz), 5.01 (dd, 1H, J = 10.5, 3.4 Hz), 4.52 (d, 1H, J = 8.0 Hz),
4.19–4.10(m, 5H), 3.96–3.81(m, 2H), 2.65–2.56(m, 2H), 2.15(s, 3H),
2.05 (d, 6H, J = 0.8 Hz), 1.98 (s, 3H), 1.27 (t, 3H, J = 7.1 Hz). 13C NMR
(101 MHz, CDCl3): d 171.02, 170.39, 170.25, 170.15, 169.46, 101.53,
70.85, 70.65, 68.64, 67.00, 65.54, 61.24, 60.58, 34.83, 20.71, 20.66,
20.58, 14.17.
Synthesis of Gal-N2H4: A mixture of G4 (0.7 g, 1.56 mmol), 85%
hydrazine hydrate (0.59 g, 15.7 mmol) in ethanol was stirred at
ambient temperature for 1 d until the complete disappearance of
the raw material of G4 and appearance of the product (using the
TLC to monitor the reaction process). The mixture was concen-
trated under vacuum and was purified by column chromatography
using water/acetonitrile (1:2) as eluent to yield 0.2 g (48.8%) of
Gal-N2H4 as white solid. 1H NMR (400 MHz, D2O):
d 4.26 (d, 1H,
J = 7.9 Hz), 4.01 (dt, 1H, J = 10.8, 6.0 Hz), 3.85–3.77 (m, 2H), 3.64
(qd, 2H, J = 11.7, 6.1 Hz), 3.54 (ddd, 2H, J = 13.4, 8.9, 3.8 Hz), 3.37
(dd, 1H, J = 9.9, 7.9 Hz), 2.42 (t, 2H, J = 6.0 Hz). 13C NMR (101 MHz,
Fig. 1. An Azo-Gal supra-amphiphile based on a dynamic covalent bond.
D2O):
d 172.78, 102.83, 75.10, 72.64, 70.60, 68.57, 65.80, 60.95,
34.36. Maldi-TOF MS: calcd. for C9H18N2O7 266.11, found 266.29
(289.29-Na+23).
Column chromatography was carried out on silica gel (200–300
mesh).
1H NMR and 13C NMR spectra were recorded on an AVANCE III
HD 400 MHz spectrometer. The matrix-assisted laser desorption
ionization time-of-flight mass spectrometry (Maldi-TOF MS)
measurement was performed using a Perspective Biosystem
Voyager DE-STR MALDI-TOF MS (Applied Biosystems, Framing-
ham, MA). Transmission electron microscopy (TEM) images
were taken on Tecnai G2 operating at 200 kV. Atomic force
microscope (AFM) was carried out on a Bruker Multimode VIII
SPM equipped with a J scanner. Dynamic light scattering studies
(DLS) were conducted using Zetasizer Nano-ZS from Malvern
Instruments. UV–vis spectroscopy was recorded in a conven-
tional quartz cell (light path 10 mm) on a Perkin–Elmer Lambda
35 spectrophotometer.
2.3. Preparation of Azo-Gal supra-amphiphile
Mixing Azo-CHO and Gal-N2H4 together in the molar ratio of
1:1 in DMSO for 3 days until the complete formation of Azo-Gal
and then stored as original solution. Ultrasound or heating
accelerates the formation speed.
2.4. Self-assembly of Azo-Gal supra-amphiphile
Deionized water (8 mL) was added into the DMSO solution of
Azo-Gal (1 mL, 1 mg/mL) dropwise by using a syringe pump at the
rate of 20 mm/h under vigorous stirring. Then the solution was
dialyzed (MWCO 1000) against deionized water to remove the
extra DMSO. Concentration of the solution was fixed at 0.1 mg/mL
by adding extra deionized water.
2.2. Synthesis
The synthesis details of A1–A3 and G1–G3 are shown in
Supporting information.
3. Results and discussion
Synthesis of Azo-CHO: A2 (130 mg, 0.67 mmol), A3 (461 mg,
1 mmol) were added to acetonitrile and the mixture was refluxed
overnight. After cooling down to room temperature, the solvent
was evaporated under vacuum and the crude product was purified
by column chromatography using EtOH/DCM (1:20) as eluent to
yield 300 mg (70%) of Azo-CHO as yellow powder. 1H NMR
3.1. Preparation of the Azo-Gal supra-amphiphile
First, the two new precursors of Azo-Gal, Azo-CHO and Gal-
N2H4 were synthesized separately. As shown in Scheme 1, Azo-
CHO was prepared via four steps. First, 4-hydroxybenzaldehyde
reacted with 1,2-dibromoethane in the presence of K2CO3
affording compound A1. Then A1 was treated with dimethylamine
hydrochloride in the presence of K2CO3 to afford compound A2.
Meanwhile, compound A3 was synthesied by reacting 4-pheny-
lazophenol with 1,12-dibromododecane in the presence of K2CO3.
In the end, through the reaction between A2 and A3, the final
product Azo-CHO was formed. On the other hand, Gal-N2H4 was
synthesized via five steps following the classical glycosylation
strategy. First all of the hydroxy groups of galactose were protected
by acetyl groups. After selectively deprotecting the acetyl group on
the anomeric carbon followed by reacting with trichloroacetoni-
trile, galactosyl trichloroacetimidate was synthesized. Compound
G4 was prepared via glycosylation of ethyl 3-hydroxypropanoate
with the galactosyl trichloroacetimidate and was transformed to
the final product of Gal-N2H4 with hydrazine hydrate in ethanol.
After mixing the synthesized Azo-CHO and Gal-N2H4 in DMSO,
the dynamic covalent bond formed, which was confirmed by 1H
NMR. The spectrum of the mixture of Azo-CHO and Gal-N2H4 in
(400 MHz, CDCl3):
d 9.91 (s, 1H), 8.03–7.79 (m, 6H), 7.57–7.36 (m,
3H), 7.03 (dd, 4H, J = 25.8, 8.8 Hz), 4.65 (s, 2H), 4.35 (s, 2H), 4.04 (t,
2H, J = 6.5 Hz), 3.75–3.55 (m, 6H), 1.94–1.77 (m, 4H), 1.56–1.21 (m,
17H). 13C NMR (101 MHz, CDCl3):
d 190.62, 161.70, 152.74, 146.81,
132.16, 130.32, 129.03, 124.73, 122.51, 114.93, 114.71, 114.13,
68.34, 62.71, 62.56, 52.12, 43.95, 29.48, 29.45, 29.42, 29.38, 29.31,
29.22, 29.16, 26.29, 25.98, 22.96. Maldi-TOF MS: calcd. for
+
C
35H48N3O3 558.37, found 558.37.
Synthesis of G4: A mixture of G3 (1 g, 2 mmol), ethyl 3-
hydroxypropanoate (0.186 g, 1.6 mmol) in dry DCM (15 mL) was
stirred at À35 8C for 30 min under Ar atmosphere. Trimethylsilyl
trifluoromethanesulfonate (TMSOTf, 140
mL, 0.77 mmol) was
added dropwise to the mixture while stirring. Then the mixture
was stirred at À35 8C until the complete disappearance of the
starting material G3 (using the TLC to monitor the reaction
process). Then the reaction was quenched by adding triethylamine.
After the reaction mixture was recovered to the ambient
Please cite this article in press as: T.-N. Wang, et al., Self-assembly of supra-amphiphile of azobenzene-galactopyranoside based on
dynamic covalent bond and its dual responses, Chin. Chem. Lett. (2016), http://dx.doi.org/10.1016/j.cclet.2016.05.009

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3
OH
(a)
CHO
CHO
CHO
O
HCl
HN
Br
Br
K2CO3
Acetone
Br(CH2)12Br
N
(CH2)12 Br
O
N
K2CO3
DMF
K2CO3
N
OH
O
N
Acetone
A3
Br
N
A2
A1
N
N
O
CH3CN
Relux
+
N
A2
A3
O
Br
CHO
Azo-CHO
(b)
OH
OH
OAc
OAc
OAc
OAc
Ac2O
CCl3CN Cs2CO3
DCM
AcOH·N2H4
OAc
OAc
O
O
O
O
DMF
OH
HO
I2
OAc
AcO
O
AcO
OH
AcO
OH
CCl3
OAc
OAc
OAc
HN
G1
G3
G2
O
HO
O
OH
OAc
OAc
TMSOTf
NH2NH2·H2O
OH
O
O
DCM -30 °C
O
O
EtOH
O
HO
AcO
OH
OAc
NHNH2
O
O
G4
Gal-N2H4
Scheme 1. Synthetic routes of (a) Azo-CHO and (b) Gal-N2H4.
equimolar amount showed obvious differences from those of the
two compounds themselves (Fig. 2). When the mixing time was
increased, intensity of the signal at 9.91 ppm corresponding to the
aldehyde group in Azo-CHO decreased gradually. Concomitantly a
new peak at 11.2 ppm gradually became stronger, indicating
acylhydrazone bond and its response to pH. In addition, the
acylhydrazone bond formation was also supported by Maldi-TOF
MS result (Fig. S1 in Supporting information).
3.2. Self-assembly of the Azo-Gal supra-amphiphile
formation of the acylhydrazone bond [13]. After addition of 5.0
mL
DCl solution (20 wt% in D2O), the signal of the aldehyde group at
9.91 ppm appeared again with disappearance of the peak at
11.2 ppm, indicating hydrolyzation of the acylhydrazone bond.
The amphiphilic Azo-Gal was assembled by selective solvent
method. The obtained assemblies were first characterized by TEM
and AFM. One dimentional fibrillar structure was observed with
their length in micrometer scale and their width in nanometer
scale under TEM (Fig. 3a). As shown in the AFM image in Fig. 3b,
height of the fibers was found around 150 nm. This result indicates
that the fiber was formed by multilayers of the Azo-Gal molecules.
Under TEM and AFM, the fibers were found in similar size and
morphology with relatively sharp endings, indicating the mor-
phology was quite stable and reproducible. Finally, DLS was
performed proving existence of the fibers in aqueous solution
(Fig. S2 in Supporting information).
Then, upon changing the condition back to basic by adding 2.75
mL
NaOD solution (40 wt% in D2O), the dynamic covalent bond
was regenerated with the reappearance of the acylhydrazone
peak at 11.2 ppm as well as the disappearance of the aldehyde
peak at 9.91 ppm. This result fully supported the formation of
Fig. 2. 1H NMR spectra (400 MHz, DMSO-d6) of (a) Azo-CHO, (b) Gal-N2H4, (c)–(g)
mixtures of (a) and (b) in the molar ratio of 1:1 with an increasing ultrasound time,
(h) after addition of DCl to (g), (i) after addtion of NaOD to (h).
Fig. 3. (a) TEM and (b) AFM images of the self-assembled Azo-Gal supra-
amphiphile.
Please cite this article in press as: T.-N. Wang, et al., Self-assembly of supra-amphiphile of azobenzene-galactopyranoside based on
dynamic covalent bond and its dual responses, Chin. Chem. Lett. (2016), http://dx.doi.org/10.1016/j.cclet.2016.05.009

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3.3. Dual-stimuli responsiveness of the self-assembly
of Azo-Gal, TEM experiment was performed. After addition of a-
CD in a molar ratio of 1:1 to Azo-Gal, the fibrillar aggregates
disassembled (Fig. 4c). As shown in Fig. S3 in Supporting
information, the 1H NMR clearly showed the formation of
It is known that the trans and cis conformations of azobenzene
can be transformed to each other by UV or visible light [14].
Previous works by us and other research groups suggested that the
assembly of the azobenzene-containing molecules into nano-
objects can be regulated by photo irradiation and vice versa
[15–18]. So at first we expected possible morphology transforma-
tion of the fiber upon irradiation of UV light. UV–vis spectroscopy
was first applied to investigate the photo responsiveness of the
Azo-Gal supra-amphiphile (Fig. 4a). Upon UV irradiation at 365 nm
for 0.5 h, the absorption band at around 325 nm of Azo-Gal in
water decreased remarkably compared to that before irradiation,
and concomitantly the band at around 430 nm increased slightly.
inclusion complex between
-CD, the hydrophobic azobenzene group was in the core of the
Azo-Gal assemblies, thus the signals of azobenzene group could
hardly been observed. However, after the addition of -CD in
equal amount, signals of azobenzene group appeared as a result of
the inclusion between -CD and azobenzene and the disassembly
a-CD and azobenzene. Before adding
a
a
a
of the self-assembled aggregates, which was consistent with
literature [20]. Thus the decrease of hydrophobicity of the
amphiphilic Azo-Gal supra-amphiphile after addition of
a-CD
induced the dissociation of the fiber. Moreover, when the
above system was irradiated by UV light, it was found that the
fibrillar structures formed again due to the dissociation of the
The absorption band at 325 nm is ascribed to
trans-azobenzene while the 430 nm absorption band is attributed
to n– * transition of the cis one [19]. This result clearly shows the
p–p* transition of
p
a
-CD/azobenzene complex (Fig. 4d).
transformation of trans-isomer of the Azo-Gal supra-amphiphile to
cis. After exposing the sample to ambient light, gradual increase of
the absorption peak at 325 nm as well as decrease of peak at
430 nm were observed, suggesting the transformation of cis-
isomer to trans. The above results proved that the reversible photo
isomerization ability of azobenzene was remained in Azo-Gal.
However, UV irradiation (365 nm, 600 s) did not induce any
significant change of the fiber morphology, as shown in Fig. 4b. We
suppose that after the assembly formed, the Azo-Gal supra-
amphiphile packed quite compactly, thus the photo isomerization
of azobenzene group had no obvious effect on the shape of self-
assembled aggregates.
As above described, the dynamic covalent bond used here is
pH-responsive, which can be fabricated under neutral or alkaline
conditions and hydrolyzed in acidic environment. To explore the
pH responsiveness of the Azo-Gal assemblies, TEM and DLS
experiments were carried out. When changing the self-assem-
bled Azo-Gal solution to acidic condition (2 mL Azo-Gal solution,
20
mL 20 wt% HCl solution), the fibers transformed into nano-
spheres as a result of the hydrolysis of the acylhydrazone bond
(Fig. 5a). Since the Gal-N2H4 has very good water solubility and
cannot form aggregates in water itself, the corresponding
spherical aggregates was formed by Azo-CHO. When adjusting
the solution back to slightly alkaline (2 mL Azo-Gal solution,
a
-CD and azobenzene is a well-known host-guest pair in
supramolecularchemistry. Only trans-azobenzene can berecognized
by -CD to form a stable complex, while the cis one could not [20,21].
In order to further explore the effect of -CD on the self-assembly
10.92 mL 40 wt% NaOH solution), the morphology returned to
fiber again because of the formation of the dynamic covalent
bond (Fig. 5b). DLS results were in consistent with the
observations under TEM (Fig. 5c).
a
a
Fig. 4. (a) UV–vis spectra of Azo-Gal before and after 0.5 h irradiation with UV light (365 nm) as well as the time-dependent interconversion of cis- to trans-Azo-Gal under
ambient light. The concentration of Azo-Gal is 0.05 mg/mL. TEM images of Azo-Gal: (b) (c) after UV irradiation with UV light (365 nm); (c) mixed with
(d) after irradiation with UV light (365 nm).
a-CD (1:1 molar ratio);
Fig. 5. TEM images of Azo-Gal aggregates (a) in acidic environment and (b) then changing back to slightly alkaline environment; (c) DLS of Azo-Gal supra-amphiphile
assemblies (blue), after adding HCl (red) and then after adding NaOH (black).
Please cite this article in press as: T.-N. Wang, et al., Self-assembly of supra-amphiphile of azobenzene-galactopyranoside based on
dynamic covalent bond and its dual responses, Chin. Chem. Lett. (2016), http://dx.doi.org/10.1016/j.cclet.2016.05.009

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References
[1] C. Wang, Z.Q. Wang, X. Zhang, Amphiphilic building blocks for self-assembly:
from amphiphiles to supra-amphiphiles, Acc. Chem. Res. 45 (2012) 608–618.
[2] C.B. Minkenberg, L. Florusse, R. Eelkema, G.J.M. Koper, J.H. van Esch, Triggered self-
assembly of simple dynamic covalent Surfactants, J. Am. Chem. Soc. 131 (2009)
11274–11275.
[3] G.T. Wang, C. Wang, Z.Q. Wang, X. Zhang, Bolaform superamphiphile based on a
dynamic covalent bond and its self-assembly in water, Langmuir 27 (2011)
12375–12380.
[4] P.Y. Xing, T. Sun, A.Y. Hao, Vesicles from supramolecular amphiphiles, RSC Adv. 3
(2013) 24776–24793.
[5] F. Versluis, I. Tomatsu, S. Kehr, et al., Shape and release control of a peptide
decorated vesicle through pH sensitive orthogonal supramolecular interactions, J.
Am. Chem. Soc. 131 (2009) 13186–13187.
[6] Y.J. Jeon, P.K. Bharadwaj, S.W. Choi, J.W. Lee, K. Kim, Supramolecular amphiphiles:
spontaneous formation of vesicles triggered by formation of a charge-transfer
complex in a host, Angew. Chem. Int. Ed. 41 (2002) 4807.
[7] Q.Z. Zhou, H.J. Jiang, R. Chen, et al., A triply-responsive pillar[6]arene-based
supramolecular amphiphile for tunable formation of vesicles and controlled
release, Chem. Commun. 50 (2014) 10658–10660.
[8] L. Shao, J. Zhou, B. Hua, G.C. Yu, A dual-responsive supra-amphiphile based on a
water-soluble pillar[7]arene and a naphthalene diimide-containing guest, Chem.
Commun. 51 (2015) 7215–7218.
Scheme 2. The cartoon illustration of the dual-responsive self-assembly and
disassembly of the Azo-Gal supra-amphiphile.
[9] C.R. Bertozzi, L.L. Kiessling, Chemical glycobiology, Science 291 (2001) 2357–2364.
[10] M. Delbianco, P. Bharate, S. Varela-Aramburu, P.H. Seeberger, Carbohydrates in
supramolecular chemistry, Chem. Rev. 116 (2015) 1693–1752.
[11] Y.T. Kang, K. Liu, X. Zhang, Supra-amphiphiles: a new bridge between colloidal
science and supramolecular chemistry, Langmuir 30 (2014) 5989–6001.
[12] L.L. Yang, H. Yang, F. Li, X. Zhang, Supramolecular glycolipid based on host-
enhanced charge transfer interaction, Langmuir 29 (2013) 12375–12379.
[13] J.M. Lehn, Dynamers: dynamic molecular and supramolecular polymers, Prog.
Polym. Sci. 30 (2005) 814–831.
[14] G.S. Kumar, D.C. Neckers, Photochemistry of azobenzene-containing polymers,
Chem. Rev. 89 (1989) 1915–1925.
[15] M.L. Rahman, G. Hegde, S.M. Sarkar, M.M. Yusoff, Synthesis and photoswitching
properties of azobenzene liquid crystals with a pentafluorobenzene terminal,
Chin. Chem. Lett. 25 (2014) 1611–1614.
4. Conclusion
In summary, we have successfully constructed a dual-respon-
sive Azo-Gal supra-amphiphile on the basis of acylhydrazone
dynamic covalent bond in water. The amphiphilic Azo-Gal self-
assembled into fibers that can be regulated by addition of a-CD and
pH (Scheme 2). This dual-responsive Azo-Gal supra-amphiphile
will enrich the family of supra-amphiphiles and have potential
applications in biomedical fields, such as drug delivery and
controlled release.
[16] J. Wu, X.M. Lu, F. Shan, J.F. Guan, Q.H. Lu, Photoresponding ionic complex
containing azobenzene chromophore for use in birefringent film, Chin. Chem.
Lett. 25 (2014) 15–18.
Acknowledgments
[17] K.C. Wei, J. Li, J.H. Liu, G.S. Chen, M. Jiang, Reversible vesicles of supramolecular
hybrid nanoparticles, Soft Matter. 8 (2012) 3300–3303.
[18] Z.Q. Li, Y.M. Zhang, H.Z. Chen, J. Zhao, Y. Liu, Hierarchical organization of spherical
assembly with reversibly photocontrollable cross-links, J. Org. Chem. 78 (2013)
5110–5114.
[19] J. Zhao, Y.M. Zhang, H.L. Sun, X.Y. Chang, Y. Liu, Multistimuli-responsive supra-
molecular assembly of cucurbituril/cyclodextrin pairs with an azobenzene-con-
taining bispyridinium guest, Chem. Eur. J. 20 (2014) 15108–15115.
[20] Y. Wang, N. Ma, Z. Wang, X. Zhang, Photocontrolled reversible supramolecular
assemblies of an azobenzene-containing surfactant with alpha-cyclodextrin,
Angew. Chem. Int. Ed. 46 (2007) 2823–2826.
National Natural Science Foundation of China (Nos. 91527305,
21474020, 91227203 and 51322306) and the Innovation Program
of the Shanghai Municipal Education Commission are acknowl-
edged for their financial support.
Appendix A. Supplementary data
[21] X.J. Liao, G.S. Chen, X.X. Liu, et al., Photoresponsive pseudopolyrotaxane hydrogels
based on competition of host–guest interactions, Angew. Chem. Int. Ed. 49 (2010)
4409–4413.
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.cclet.2016.05.009.
Please cite this article in press as: T.-N. Wang, et al., Self-assembly of supra-amphiphile of azobenzene-galactopyranoside based on
dynamic covalent bond and its dual responses, Chin. Chem. Lett. (2016), http://dx.doi.org/10.1016/j.cclet.2016.05.009