Branched Aggregates with Tunable Morphology via Hierarchical Self-Assembly of Azobenzene-Derived Molecular Double Brushes

Article abstract of DOI:10.1002/anie.202106321

Hierarchical self-assembly is one of the most effective approaches to fabricate nature-inspired materials with subtle nanostructures. We report a distinct hierarchical self-assembly process of molecular double brushes (MDBs) with each graft site carrying

Full text of DOI:10.1002/anie.202106321

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Accepted Article
Title: Branched Aggregates with Tunable Morphology via Hierarchical
Self-Assembly of Azobenzene-Derived Molecular Double-
Brushes
Authors: Binbin Xu, Hongyu Qian, Ling Zhang, and Shaoliang Lin
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RESEARCH ARTICLE
Branched Aggregates with Tunable Morphology via Hierarchical Self-
Assembly of Azobenzene-Derived Molecular Double-Brushes
Binbin Xu, Hongyu Qian, Ling Zhang, and Shaoliang Lin*
[*]
Dr. B. Xu, H. Qian, Prof. Dr. L. Zhang, Prof. Dr. S. Lin
Shanghai Key Laboratory of Advanced Polymeric Materials, Key Laboratory for Ultrafine Materials of Ministry of Education, Frontiers Science Center for
Materiobiology and Dynamic Chemistry, School of Materials Science and Engineering, East China University of Science and Technology
Shanghai 200237 (China)
E-mail: slin@ecust.edu.cn
Supporting information for this article is given via a link at the end of the document.
Abstract: Hierarchical self-assembly has been one of the most
effective approach to fabricate nature-inspired materials with subtle
nanostructures and variable functions. Herein, we report a distinct
hierarchical self-assembly process of azobenzene-derived Janus
molecular double-brushes (MDBs) with each graft site carrying a
poly(azobenzene-acrylate) (PAzo) chain and a poly(ethylene oxide)
(PEO) chain. Asymmetric tapered-worm (ATW) nanostructures with
chain-end reactivity assembling from the azobenzene-derived MDBs
serve as primary subunits to prepare branched supermicelles by
increasing water content (Cw) in THF/water, which is predominantly
facilitated by the distinctive molecular brush architecture and the
intermolecular interaction of PAzo brushes. Various natural antedon-
shaped multiarm worm-like aggregates (MWAs) can be created
depending on Cw via the particle-particle connection of ATWs.
Intriguingly, the azobenzene moieties undergo trans-cis isomerization
upon UV irradiation and further promote a morphology evolution of
MWAs, leading the formation of starfish-shaped aggregates.
Subsequently, multiscale luidia ciliaris and crossaster papposus-
shaped supermicelles with different features of central body and arms
are prepared by manipulating irradiation time.
workers realized various “cross” and multidimensional
superstructures based on living crystallization-driven self-
assembly (CDSA).[4] Du et al. created multipod polymersomes
with precisely defined spatial structures by utilizing fusion-induced
particle assembly strategy.[5] Zhou et al. prepared hierarchical
sea-urchin-like aggregates via emulsion-assisted polymerization-
induced self-assembly.[6] Despite of these great achievements, it
is still challenging to build branched supermicelles with abundant
hierarchical structures and stimuli-responsive morphology
deformability, which restricts their potential applications.
Molecular brushes (MBs),[7] or bottlebrush polymers, are
branched macromolecules[8] which graft polymeric chains onto a
linear polymeric backbone densely. The high concentration of
polymeric brushes, distinct worm-like features, and tunable
architecture of MBs provide a new avenue for creating novel and
distinct nanostructures that are difficult to achieve for linear
amphiphiles, which endow them with lots of applications, such as
sensors, supersoft elastomers, drug delivery, and photonic
crystals.[9] In particular, MBs-based nanostructures possess
active chain ends that are not fully shielded by the corona
chains.[10] The chain-end reactivity renders the nanostructures
more accessible and exposes their internal functionalities, which
can be utilized to direct the hierarchical assembly of primary
nanostructures into higher-order structures. Similar to CDSA, the
end-to-end self-assembly of MBs-based nanostructures as an
alternative route to form the multidimensional supramolecular
assemblies with great designability and tunability is particularly
appealing. On the other hand, azobenzene-containing
nanoparticles are fascinating due to their strong noncovalent π-π
interactions and the ability to exhibit morphology deformation
upon alternative UV/vis light irradiation driven by trans-cis
reversible isomerization process.[11] Therefore, combining the
feature of azobenzene molecules with the properties of MBs,
azobenzene-containing MBs-based hierarchical supermicelles
with morphology deformability could be achieved.
Introduction
Branched architectures are ubiquitous in nature, which have
received considerable attention owing to their unique geometries
and functionalities.[1] For example, sea urchins, antedon, starfish
and other echinoderms are well recognizable by their radial
symmetry. There is a great variability of branched features
between different classes of echinoderms, which is concomitant
with their individually distinctive biological processes. Antedon
consists of a tiny central body circled by 1-200 slender, feathery
arms, whereas in starfish the multiple fairly broad arms have been
incorporated into the relatively large body. The phenotypic
differences between closely related species may take thousands
of years during the evolution of species. Mimicking the naturally
occurring diverse structures and shape transformations/
evolutions would be a remarkably effective and feasible approach
to design nanomaterials with subtle nanostructures and variable
functions.[2]
Aiming at creating diverse branched nanostructures with
morphology deformability through hierarchical solution self-
assembly, herein, we design molecular double-brushes
(MDBs),[12] a Janus type of MBs, with two statistically distributed
side chains attached to each repeat unit of the backbone, wherein
photoresponsive hydrophobic azobenzene and hydrophilic PEO
brushes are simultaneously introduced into the backbone in order
to increase attractive forces between the reactive chain ends, as
In the past decade, tremendous efforts have been made to
create sophisticated branched supermicelles through the
hierarchical assembly of artificial molecules.[3] Manners and co-
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Scheme 1. Left: chemical structures of PA-g-PAzo/PEO MDBs. Right: the schematic representations and typical TEM images of ATWs and MWAs self-assembled
from Janus-type MDBs, and the evolution of MWAs from antedon to starfish-like branched architectures upon UV irradiation. Scale bars: 200 nm.
well as to trigger photo-induced changes of the molecular shape.
Primary asymmetric tapered-worms (ATWs) are formed by
amphiphilic Janus MDBs of polyacrylate-g-poly(6-(4-butyl-4′-
oxyazobenzene) hexyl acrylate)/poly(ethylene oxide) (PA-g-
PAzo/PEO) with each graft site carrying PAzo and PEO hetero
double-brushes, which was synthesized by simultaneous atom
transfer radical polymerization (ATRP) and click reaction in one
pot based on a bifunctional macro-agent of poly(Br-acrylate-
alkyne) (PBAA), as our previously reported.[13] The detailed
syntheses and characterizations of PBAA34 and PA34-g-
PAzo25/PEO17 MDBs are provided in Supporting Information
(Table S1 and Scheme S3). We demonstrate multiarm worm-like
aggregates (MWAs) with branched architectures could be
obtained via the hierarchical assembly of original ATWs with
active chain-end as the water content increased and the ATWs
were connected together (Scheme 1). More interestingly, the
evolution of artificial echinoderm-like MWAs from antedon to
starfish-shaped architectures was achieved (Scheme 1 and
Scheme S5) by taking advantage of the photo-responsive
morphology transformation of azobenzene-containing micelles
via trans-cis isomerization.
site, a tapered cylinder and a hemispherical end cap. We
hypothesize that the special tapering behavior of ATWs is a result
of PAzo brushes stretching to various extension levels along the
axis of the tapered assembly by considering the interfacial energy
of PAzo and PEO brushes and the interaction of intermolecular
PAzo brushes.[14] In other words, the intermolecular association
of pendant PAzo brushes within the tapered assembly varies
systematically along the tapered worms (Figure 2A).
Figure 1. (A) Simple models of ATWs consisting of an initiation site, a tapered
cylinder, and an end cap. TEM images of ATWs formed by PA-g-PAzo/PEO
MDBs at different conditions: (B) ATW 1, Cini = 0.05 mg mL-1 and Cw = 45%
(Inset scale bar: 100 nm); (C) ATW 2, Cini = 0.1 mg mL-1 and Cw = 45% (Inset
scale bar: 200 nm); (D) ATW 3, Cini = 0.2 mg mL-1 and Cw = 45% (Inset scale
bar: 500 nm).
Results and Discussion
In the first step, primary ATWs were prepared by using the
selective solvent addition method. Deionized water, a poor
solvent for PAzo brushes, was added slowly into the THF solution
of PA-g-PAzo/PEO MDBs under stirring. The volume percentage
of the added water relative to the whole volume (Cw) was 45%.
Then, nanoparticles in THF/H2O with various initial concentration
(Cini, in THF) were kinetically trapped by addition of excess water
(100 times) to retain the original morphological sizes and
geometries. Figure 1 and Figure S7 show a set of scanning
electron microscopy (SEM) and transmission electron microscopy
(TEM) images of the obtained tapered-worm structures as
functions of initial polymer concentration at 45% water content. At
a low Cini of 0.05 mg mL-1, the aggregates are asymmetric tapered
worm-like nanoparticles with unobvious end caps (defined as
ATW 1, Figure 1B). As Cini increased to 0.1 mg mL-1, asymmetric
worm-like nanoparticles developed and further evolved to
extended tapered-worm morphology (ATW 2, Figure 1C). At a Cini
of 0.2 mg mL-1, as shown in Figure 1D, the asymmetric tapered-
worm structures (ATW 3) can still be observed. However, the
length of the ATW 3 becomes increasingly long (several
micrometers) due to ordered packing of more MDBs in
aggregates with the increase of Cini. Figure 1A shows the
schematic models of ATWs, which typically consist of an initiation
In the current work, the most important factors affecting the
tapered-worm formation are the chain mobility and Janus-type
structure of MDBs. It is well known that changing the
environmental medium can change the conformational degrees of
freedom and mobility of individual molecules. In our case, the slow
addition of water caused the different mobility of PAzo brushes at
different stage. In the early assembly stage, the mobile PAzo
brushes of PA-g-PAzo/PEO with relative short backbone
promoted interactions among them under the condition of high
ratio of THF (good solvent for PAzo brushes) and the inter-
molecular PAzo brushes adopted a chain-interlaced structure,
which would result in a smaller core segment at the initial site of
assemblies (Figure 2A). Once sufficient water was added,
continuously increasing interfacial energy between dense PAzo
and PEO brushes would drive brushes to stretch away from the
interface so as to limit the interactions of the immiscible double-
brushes.[4a,15] Notably, the stretching of PEO and PAzo brushes is
a much faster process than intermolecular interactions of PAzo
brushes in relatively poor solvent. Thus, the internal extension of
PAzo brushes occurred at the end of assemblies and the
asymmetric tapered-worms were observed. Moreover, the inner
hydrophobic cores are fully surrounded by hydrophilic shells to
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minimize exposure to the selective solvent due to the existence of
hemispherical caps at the ends of ATWs (Figure 1A).
To further investigate the effect of the chain mobility of the
PAzo brushes in tapered-worm conformations, we examined the
self-assembly behaviors of MDBs by adding the selective solvent
quickly to generate kinetic morphologies. We started with a
system that had 0.1 mg mL-1 initial concentration of PA-g-
PAzo/PEO in THF. Then deionized water was added at a fast rate
of 5 mL h-1 to reach a water concentration of 45%. Interestingly,
the kinetically trapped morphology of homogeneous symmetric
worms was observed in the rapid manner (Figure 2 and Figure
S10). As estimated from the TEM images, the diameter of the
symmetric worms is approximately 16 nm (Figure 2A and Figure
S11), which is different from the dimensions of the corresponding
ATW 2 range from 22 nm at the large end and 11 nm at the small
initiation site. The fast addition of water had a combined effect of
quickly aggregating the hydrophobic PAzo brushes into
aggregate cores while concurrently stretching the hydrophilic
PEO brushes. Considering the poor mobility of PAzo brushes
during the fast water addition process, the formation of symmetric
worms is based on the relatively uniform chain stretching and
weak chain-interlaced structure of intermolecular PAzo brushes
along the axis (Figure 2A). Additionally, we carried out dialysis
experiments without quench process to monitor whether these
kinetically generated aggregates transform to the thermo-
dynamically stable morphology. Intriguing self-assembled
structures were expected to be created during dialysis because of
the active ends of the symmetric worms. As expected, the
obtained images show that vine-like nanostructures with many
branching sites were observed (Figure 2E, F and Figure S12),
which facilitated by more than two fusion sites between one
symmetric worm and its neighbors. The vine-like nanostructures
revealed that the primary aggregates formed by MDBs could be
readily used to access sophisticated branched supermicelles
through the hierarchical assembly process.
Similar to symmetric worms, the initiation sites of ATWs are not
fully shielded by the corona PEO brushes (Figure 1A), which
endows the initiation sites with sufficient activity to induce second
self-assembly of the ATWs through the strong noncovalent
aromatic-aromatic interactions of PAzo brushes. It should be
noted that the hemispherical end-caps with a dense corona of
hydrophilic PEO brushes render the core face inaccessible and
efficiently inhibit hierarchical assembly at the chain ends (Figure
1A). To explore the possibility of this second self-assembly
approach of ATWs, we first attempted to disassemble the ATWs
by strong sonication of their solutions. It was found that the ATWs
were replaced by “seed” entities (Figure S13A), indicating that
disassembly of the worm nanostructures had occurred. As shown
in Figure S13B-C, end-to-end fusion of “seed” entities occurred
and the length of seed continuously increased as a function of the
aging time, demonstrating a relatively greater accessibility of the
seed terminus. Interestingly, we found that a part of seed clusters
appeared to be branched and interconnected with each other
(Figure S13D), which may reflect that the interactions between
seed entities were not necessarily unidirectional. Therefore, the
hierarchical self-assembly of the ATWs is expected to self-
assemble into higher-order aggregates with branched
architectures.
Figure 2. (A) Schematic illustration for the preparation of ATW 2 and symmetric
worms: different association of intermolecular PAzo brushes in cores. (B, C)
TEM images of symmetric worms formed by fast addition of water to a 0.1 mg
mL-1 initial MDBs solution in THF (Cw = 45% after addition). (D) Schematic
representation for the fusion of symmetric worms. (E, F) TEM images of vine-
like aggregates (inset: a photograph of vine) formed by the symmetric worms
after dialysis (Cw = 100%) without a quench process.
To better understand the role of Janus double-brushes in such
ATWs, we investigated the self-assembly behaviors of
amphiphilic poly(acrylic acid)-g-poly(6-(4-butyl-4-oxyazobenzene)
hexyl acrylate) (PAA-g-PAzo) MBs consisting of PAA backbone
and PAzo brushes at the same condition, which is chemically
similar to PA-g-PAzo/PEO apart from the absence of PEO
brushes (Scheme S4). As shown in Figure S9, PAA-g-PAzo
exhibited the self-assembly into symmetric worms, suggesting
that PAzo brushes stretching to the same level in the hydrophobic
cores. Thus, the stretching of PAzo brushes at the large end of
ATWs is caused by strong stretching of PEO brushes because of
the immiscibility of Janus double-brushes. These results indicate
that the slow rate of adding selective solvents and unique Janus-
type conformation are essential for the tapered-worm structures.
As shown in Figure 3, the second assembly/connection of
ATWs can be induced by increasing Cw.[3a,5,16] ATW 1 was fused
to form di- or tri-arm worm-like aggregates (defined as MWA 1,
Figure 3A and Figure S14A-C) when the Cw increases from 45%
to 50%. Then more ATW 1 were interconnected with each other
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to form multiarm worm-like aggregates (MWA 2, Figure 3B and
Figure S14D-G) at a Cw of 55%. Finally, worm clusters appeared
by usage of a Cw of 60% (MWA 3, Figure 3C and Figure S14H-I).
each tapered-worm cluster reach to 10 μm, the clusters were
characterized by optical microscopy (OM) (MWA 5, Figure 3G),
which further confirmed the branched multiarm worm-like
Interestingly, MWAs have both tiny central body and slender arms, morphology.
and such a branched structure is similar to the natural antedon
(Scheme S5, inset of Figure 3D). In order to clarify the Cw of the
mixture solvent driving the assembly, UV-Vis spectroscopy was
performed to monitor the changes of the turbidity of the solution
during the self-assembly. As shown in Figure S6, a sharp increase
in turbidity was observed at Cw of 40%, indicating the primary self-
assembly process. The turbidity kept steady changing until the Cw
reached 50% where the reactive initiation sites of ATWs were
activated. To reduce the unfavorable ends and high-energy
defects, the ATWs tend to fuse together by physical connecting
PAzo brushes on the initiation sites of ATWs at Cw > 50%.
Together with the TEM results, these data demonstrate the
successful preparation of the MWAs with branched structures
which evolved from particle-particle connection of individual ATW
1 via hierarchical self-assembly.
Owing to the advantage of photoresponsive behavior of PAzo
brushes (Figure S4), the morphology evolution of as-prepared
ATWs and MWAs can be achieved through trans-cis
photoisomerization. To test this hypothesis, we first examined the
morphology deformation of ATWs under the irradiation of 365 nm
light (70% light density, see experimental details in Supporting
Information). As shown in Figure 4 and Figure S17, ATWs
expanded resulting from trans-cis transformation upon UV
irradiation.[17] We propose that the photo-induced trans-cis
isomerization generates a change in azobenzene molecular
geometry and destroys the original ordered arrangement resulting
in a distinctive hydrophilicity and random configuration for the cis-
azobenzene. Therefore, azobenzene-containing ATWs expanded
when they converted to cis state upon UV irradiation. Conversely,
the diameter and hydrophilicity of PAzo core decreased upon
visible light irradiation, leading to the shrinkage of the ATWs
(Figure S21A). Once the photoresponsive properties of the ATWs
were investigated, the possibility of encapsulation and controlled
release of Nile Red was assessed.[18] As shown in Figure 4B, a
gradual decrease of the fluorescence intensity of Nile Red-
encapsulated ATWs was observed upon irradiation, suggesting
that controlled release of Nile Red from the aggregates to the
aqueous media.
Figure 3. TEM images of MWAs hierarchical assembled from original ATWs:
(A) MWA 1, Cini = 0.05 mg mL-1 and Cw = 50%, (B) MWA 2, Cini = 0.05 mg mL-1
and Cw = 55%, (C) MWA 3, Cini = 0.05 mg mL-1 and Cw = 60%, inset scale bar:
200 nm. (D) Schematic illustration of the connection process of ATWs by
increase of Cw (inset: simple model of natural antedon). (E) TEM image of MWA
4, Cini = 0.2 mg mL-1 and Cw = 60%. (F) CLSM image of MWA 4 encapsulated
with Nile Red. (G) OM image of MWA 5, Cini = 0.2 mg mL-1 and Cw = 67%.
Figure 4. (A) Schematic illustration of the expansion of ATWs upon UV light
irradiation. (B) Emission spectra of the Nile Red encapsulated ATW 2 recorded
at different UV light irradiation times. TEM images of the expanding worms
formed by (C) ATW 1 and (D) ATW 2 after UV light irradiation.
Afterwards, the connection of ATW 2 and ATW 3 was also
studied by TEM measurements upon addition of various amounts
of water. Figure S15 shows the increase of water content causes
ATW 2 and ATW 3 to fuse to longer-branched structures of MWAs.
Interestingly, when the Cw increases to 60%, asymmetric tapered-
worm clusters (MWA 4, Figure 3E), which can be defined as
multiple tapered-arm branched supermicelles, were obtained via
the fusion of multiple ATW 3. To enable direct characterization of
the tapered-worm clusters in solution, Nile Red was blended with
tapered-worm clusters to form fluorescent-containing aggregates.
The resulting aggregates were readily visualized in solution by
means of confocal laser scanning microscopy (CLSM). CLSM
images (Figure 3F and Figure S16) show that tapered-worm
clusters consisting of many radiating arms stretching out from the
central site indicates the antedon-shaped architectures. Upon
further increasing the water content, given that the diameter of
Subsequently the photo-induced evolution of MWAs was
assessed to study the effect of trans-cis isomerization on the
branched nanoparticle morphology. SEM and TEM analysis show
that expanding and merged MWAs (Figure 5 and Figure S19)
were obtained after UV light irradiation. For example, after
irradiation, MWA 1 were transformed to the expanding and
merged tri-arm worm-like aggregates (Figure 5B). Expanding and
merged multiarm worms (Figure 5C and Figure S18A) and worm
clusters (Figure 5D and Figure S18D) were observed which
evolved from MWA 2 and MWA 3, respectively. By analogy with
the expanding behaviors of ATWs under the irradiation of UV light,
the morphology evolution of branched MWAs can be explained by
the same rationale. The isomerization of PAzo brushes generates
an increase of the hydrophilicity and destroys the ordered align-
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Figure 5. (A) Schematic illustration of the evolution of MWAs from natural antedon to starfish-like branched architectures over different irradiation periods. Simple
models and photographs of luidia ciliaris and crossaster papposus, two types of starfish. TEM images of expanding and merged (B) MWA 1, (C) MWA 2, and (D)
MWA 3 after UV light irradiation (luidia ciliaris shape). TEM images of expanding and merged (E) MWA 2 and (F) MWA 3 after a longer period of UV light irradiation
(crossaster papposus shape).
ment, leading to a certain expansion and fusion of the multiarms.
Particularly, it is noteworthy to emphasize that expanding and
merged MWAs exhibit a unique shape of central site and arms,
which multiple fairly broad arms fuse in the central bodies. In
contrast to the antedon-shaped MWAs as described in Figure 3,
such high-branched structure (Figure 5C, D) agrees well with the
natural luidia ciliaris, one type of starfish (Figure 5A and Scheme
S5C).
prepared by the particle-particle connection of primary
azobenzene-containing PA-g-PAzo/PEO MDB aggregates via
hierarchical self-assembly, which further enables the morphology
evolution from antedon to starfish-shaped architectures upon UV
irradiation.
Conclusion
Given the observation that antedon-shaped MWAs evolved to
luidia ciliaris-shaped multiarm worms after UV irradiation, we
further evaluated the effect of irradiation time on the branched
morphology evolution. Considering the weak and unordered loose
structures of cis-state azobenzene-containing aggregates, the
typical intermediate morphologies were captured at low light
density (50%) over different irradiation periods. The TEM image
of MWA 2 taken at 1.5 h (Figure 5E and Figure S18B, C) was
featured by another type of starfish-shaped aggregates. It can be
clearly seen that multiple arms stretched out from the obvious
central body radially like rays shining out from the sun, which is
very similar to the structures of natural crossaster papposus
(Figure 5A and Scheme S5D). Meanwhile, a similar crossaster
papposus-shaped structure (Figure S18E, F) evolving from worm
clusters was also observed in the MWA 3 system after irradiation
for 1.5 h, in which the central body was fully covered by multiple
broad arms. When the irradiation time was increased to 2 h
(Figure 5F and Figure S20B, C), more crossaster papposus-
shaped aggregates were found in both MWA 2 and MWA 3
system. However, nano-fragments appeared around the
aggregates at this stage, indicating the dissociation of polymer
aggregates upon long time UV irradiation. Therefore, all of these
observations suggest that diverse branched supermicelles can be
In summary, we describe the effective formation of multiarm
branched supermicelles by utilizing the hierarchical self-assembly
of PA-g-PAzo/PEO MDBs. The topological polymer chemistry of
MDBs, π-π interaction and photoisomerization of PAzo brushes
guarantee the reactive sites of hierarchical self-assembly process,
enhanced noncovalent association and photo-induced
morphology deformability of PA-g-PAzo/PEO aggregates. We
found that PA-g-PAzo/PEO first self-assembled into ATWs that
can serve as the basic building block by taking advantage of
active initiation site. The primary ATWs were connected with each
other to form di- or tri-arm worms, multiarm worms, and worm
clusters upon increasing Cw. Interestingly, the obtained MWAs
could be expanded and fused gradually upon UV light irradiation,
leading to the morphological evolution of MWAs from antedon to
starfish-shaped architectures. Additionally, by manipulating the
irradiation time, the starfish-shaped aggregates displayed
accordingly variable branched features in their central body and
arms. The hierarchical assembly and morphology evolution of
MDBs-based nanostructures provide a new avenue for fabricating
extremely complex and deformable assemblies with diverse
geometries.
5
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Acknowledgements
This work is supported by National Natural Science Foundation of
China (Grant Nos. 52073092, 51873061, and 22001072). Support
by Shanghai Scientific and Technological Innovation Projects
(19JC1411700, 18JC1410802), Program of Shanghai Academic
Research Leader (19XD1401400), and Sailing Program
(19YF1410300) are also appreciated.
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Keywords: Azo compounds
• Branched supermicelles •
Hierarchical assembly • Molecular double-brushes • Photo-
responsiveness
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10.1002/anie.202106321
Angewandte Chemie International Edition
RESEARCH ARTICLE
Entry for the Table of Contents
Diverse branched supermicelles can be prepared by particle-particle connection of primary tapered worm-like aggregates from
azobenzene-containing Janus molecular double-brushes (MDBs), which further enables biomimetic morphology evolution from antedon
to starfish-shaped architectures upon UV irradiation.
7
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