Janus Graft Block Copolymers: Design of a Polymer Architecture for Independently Tuned Nanostructures and Polymer Properties

Article abstract of DOI:10.1002/anie.201802844

The graft-through synthesis of Janus graft block copolymers (GBCPs) from branched macromonomers composed of various combinations of homopolymers is presented. Self-assembly of GBCPs resulted in ordered nanostructures with ultra-small domain sizes down to 2.8 nm (half-pitch). The grafted architecture introduces an additional parameter, the backbone length, which enables control over the thermomechanical properties and processability of the GBCPs independently of their self-assembled nanostructures. The simple synthetic route to GBCPs and the possibility of using a variety of polymer combinations contribute to the universality of this technique.

Full text of DOI:10.1002/anie.201802844

Angewandte
Communications
Chemie
International Edition: DOI: 10.1002/anie.201802844
German Edition: DOI: 10.1002/ange.201802844
Nanostructures Very Important Paper
Janus Graft Block Copolymers: Design of a Polymer Architecture for
Independently Tuned Nanostructures and Polymer Properties
Zi-Hao Guo+, An N. Le+, Xunda Feng, Youngwoo Choo, Bingqian Liu, Danyu Wang,
Zhengyi Wan, Yuwei Gu, Julia Zhao, Vince Li, Chinedum O. Osuji, Jeremiah A. Johnson,* and
Mingjiang Zhong*
Abstract: The graft-through synthesis of Janus graft block
copolymers (GBCPs) from branched macromonomers com-
posed of various combinations of homopolymers is presented.
Self-assembly of GBCPs resulted in ordered nanostructures
with ultra-small domain sizes down to 2.8 nm (half-pitch). The
grafted architecture introduces an additional parameter, the
backbone length, which enables control over the thermome-
chanical properties and processability of the GBCPs inde-
pendently of their self-assembled nanostructures. The simple
synthetic route to GBCPs and the possibility of using a variety
of polymer combinations contribute to the universality of this
technique.
processability, mechanical strength, and thermal stability in
ways that are undesirable in a given application. The inability
to independently regulate nanostructure and material proper-
ties of BCPs limits their use in a variety of scenarios.
One such scenario is in the use of BCPs for nano-
templating, pattern transfer, and lithography, where there is
a concerted effort directed towards achieving ultra-small, for
example, sub-10 nm, nanodomain sizes.[5a] Such small nano-
domains are of particular interest to separation engineering
applications in demand of (macro)molecular-level selectivity
while maintaining high-flux mass transport and to the micro-
electronics industry in its continuous pursuit of increased chip
density.[6] In BCPs with moderate inter-segment repulsion,
typically reflected by a relatively low value of the Flory–
Huggins interaction parameter (c), a high N value that is
required to ensure a sufficiently large thermodynamic driving
force for the formation of well-ordered nanostructures
inevitably results in a large nanodomain size (Figure 1a). A
prevailing approach to scaling down nanodomains is based on
the design of high-c BCPs that allow for the creation of
ordered nanostructures with significantly reduced N (Fig-
ure 1b).[7] The introduction of high-c segments in low-N BCPs
to compensate for the loss in the driving force for self-
assembly may interfere with other properties, such as
thermomechanical behaviors and processability, that are
essential for a chosen application.
Herein, we demonstrate that appropriately designed
Janus graft block copolymers (GBCPs) that we[8] and other
groups[9] developed previously can be used to achieve nano-
structured polymers with ultra-small nanodomains and
diverse morphologies without sacrificing our command of
materials properties that are critical for processing and
functions. The bulk properties of GBCPs can conversely be
tuned either by selecting a variety of sidechains or through
adjusting the backbone length with minimal interference with
the nanostructures. This independent tunability between
polymer properties and nanostructures has not been realized
in conventional linear BCPs or other reported polymer
architectures and will significantly expand the scope of BCP
applications.
N
anophase-separated block copolymers (BCPs) are a class
of widely investigated nanostructured materials with applica-
tions ranging from microelectronics[1] and photonics[2] to
separation[3] and energy conversion.[4] The versatility of BCPs
in various applications draws on their highly tunable bulk
properties, and their high performance relies on the nano-
structures having precisely defined size, morphology, orien-
tation, and molecular functionality.
Control over BCP nanostructure and bulk properties can
be exercised through judicious control of various aspects of
molecular structures, principally chain length (that is, molec-
ular weight), chemical composition, stereochemistry, and
chain architecture or topology.[5] However, realizing inde-
pendent control of nanostructure and bulk properties in
a single polymer material remains an unmet challenge. This
challenge arises from the mutual dependences of nano-
structure and bulk properties on molecular structure, as
highlighted; for instance, the nanodomain size in self-
assembled linear diblock copolymers containing two seg-
ments A and B, referred to as AB-linear BCPs in this report,
is intimately related to the degree of polymerization (N),
which when changed may alter bulk properties such as
[*] Dr. Z.-H. Guo,[+] A. N. Le,[+] Dr. X. Feng, Y. Choo, B. Liu, D. Wang,
Z. Wan, V. Li, Prof. C. O. Osuji, Prof. M. Zhong
Department of Chemical and Environmental Engineering
Yale University, New Haven, CT 06511 (USA)
E-mail: mingjiang.zhong@yale.edu
Janus GBCPs developed in this work contain two types of
polymeric sidechains connected in a pseudo-alternating
sequence and can be viewed as AB-linear BCPs preorganized
covalently at the AB-junction (Figure 1c). A graft-through
strategy was employed to synthesize GBCPs by the third-
generation Grubbs catalyst (G3)-initiated ring opening meta-
thesis polymerization (ROMP)[10] of norbornene-based
branched macromonomers (BMMs) appended with homo-
Y. Gu, J. Zhao, Prof. J. A. Johnson
Department of Chemistry, Massachusetts Institute of Technology
Cambridge, MA 02139 (USA)
E-mail: jaj2109@mit.edu
[+] These authors contributed equally to this work.
Supporting information and the ORCID identification number(s) for
the author(s) of this article can be found under:
https://doi.org/10.1002/anie.201802844.
Angew. Chem. Int. Ed. 2018, 57, 1 – 6
ꢀ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1
These are not the final page numbers!

Angewandte
Communications
Chemie
Figure 1. Idealized illustrations of self-assembly of AB-linear BCPs with a) low c-high N and b) high c-low N; c) Covalent preorganization of
disordered AB-linear BCPs (low c-low N) results in Janus GBCPs with ordered nanostructures and small domain sizes. (cN)ODT: critical value of
cN at the order–disorder transition.
polymers A and B (Scheme 1; see details for the synthesis in
the Supporting Information). Verification of the essential role
of the pseudo-alternating sidechain sequence in decoupling
property control from nanostructure is discussed in the
Supporting Information, Scheme S1, Figure S3.
Scheme 1. Janus GBCP from PLA-branch-PDMS BMM.
Polydimethylsiloxane (PDMS) and atactic poly(lactic
acid) (PLA) were selected owing to their well-developed
synthetic routes to monodisperse low-N products,[11] the
commercial availability of monomers, as well as a high etch
contrast in their potential nanolithography application.[12] The
Figure 2. SAXS profiles of BMMs and GBCPs for a) PDMS15-branch-
corresponding BMMs are referred to as PDMSm-branch-
PLAn, where m and n are the N of the synthesized
monodisperse PDMS and PLA, respectively. ROMP of
PDMSm-branch-PLAn BMMs with varied monomer to ini-
tiator ratios, r= [BMM]0/[G3]0, yielded GBCPs (PDMSm-
branch-PLAn)r with well-controlled backbone length
(Table S1, Figures S50–S65). Morphologies of thermally
annealed samples (1008C in a vacuum oven for 12 h) of the
BMMs and their corresponding GBCPs were studied using
small-angle X-ray scattering (SAXS). For BMMs with
relatively large N, e.g., PDMS15-branch-PLA16, both BMMs
and corresponding GBCPs displayed SAXS patterns consis-
tent with the formation of long-range ordered lamellar SAXS
patterns (Figure 2a), corroborated by transmission electron
microscopy (TEM) studies, as shown by the representative
PLA16 and c) PDMS11-branch-PLA12; b) TEM image of (PDMS15-branch-
PLA16)200 (inset: 2D Fourier transform of the image); d) Diagram
showing order-disorder phase boundaries of (PDMSm-branch-PLAn)50
(solid line) and BMMs (dashed line). Numbers in the diagram stand
for the d-spacings of ordered GBCPs and corresponding BMMs (in
parentheses).
data for (PDMS15-branch-PLA16)200 (Figure 2b). An
increased d-spacing after polymerizing BMMs to GBCPs
(7.07 nm to 7.73 nm) can be ascribed to stretching of the
densely grafted sidechains in GBCPs.[8]
Disordered BMMs with reduced N, for example, PDMS11-
branch-PLA12, were converted into an ordered lamellar
structure upon ROMP (Figure 2c), a result of the back-
bone-stabilized interface and suppressed mixing entropy
2
www.angewandte.org
ꢀ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2018, 57, 1 – 6
These are not the final page numbers!

Angewandte
Communications
Chemie
originating from the GBCP architecture, as well as an
increase in the overall N of the polymer chain. An expanded
ordered phase region was observed in the phase diagram for
the series of (PDMSm-branch-PLAn)50 GBCPs compared to
corresponding BMMs (Figure 2d). Despite this reduced
critical N value for ordered GBCPs, a slight chain stretching
may increase such small d-spacings significantly, leading to
only a minor reduction in minimum d-spacing in ordered
GBCPs compared to BMMs (6.30 nm for GBCPs vs. 6.34 nm
for BMMs). The ordered phase region was further expanded
by introducing disperse sidechains, which have been demon-
strated to facilitate self-assembly.[13] A commercial disperse
PDMS (ꢀ = 1.2) with a multi-modal gel permeation chroma-
tography (GPC) trace (Figure 3a) was used to synthesize
Figure 4. SAXS patterns for BMMs (left) and corresponding GBCPs
(right) of PS-3.9k-branch-PtBA-3.7k, PDMS-1k-branch-PEG-750, and
PDMS-5k-branch-PtBA-3k. (d*: d-spacing).
and powerful strategy to extend the application of BCPs due
to a weaker dependency of the driving force in phase
separation on the type of monomer, that is, on c.
While other complex architectures such as star and
miktoarm BCPs have been theoretically predicted[16] and
experimentally demonstrated[17] to exhibit ordered self-
assembly with markedly smaller nanodomains than those
found in their linear counterparts, the GBCP architecture
allows for tuning of macroscopic properties through varying
the length of backbones and potentially the sidechain grafting
density and sequence while minimizing any interference with
the nanostructure,[18] which is primarily determined by the
length of the sidechains when the backbone length reaches
the threshold for an ordered phase.
Herein, we expect the backbone length to impact the
thermomechanical properties of GBCPs and to serve as
a handle for adjusting the processability, offering improve-
ment over linear BCPs of fixed N or extremely low N, which
can be difficult to process into application relevant macro-
scopic forms (for example, membranes, fibers, and thin films).
Data summarized from differential scanning calorimetry
(DSC) and rheology measurement (Figure 5a and Supporting
Information, Figure S1) indicated that the glass transition
Figure 3. a) GPC traces of disperse PDMS-1k and uniform PDMSm
(m=7, 11, 15); b) SAXS profiles of PDMS-1k-branch-PLA8 BMM and
its corresponding GBCPs.
BMMs of PDMS-1k-branch-PLAn, where “1k” stands for the
number-average molecular weight of the disperse PDMS. In
this series of samples, GBCPs containing PLA8 retained an
ordered lamellar phase when [BMM]0/[G3]0 was above 30
(Figure 3b). An ultra-small lamellar nanodomain size of
2.81 nm, calculated based on the half-pitch of d-spacing of
5.62 nm, was obtained in these samples.
The Janus GBCP architectural approach to the creation of
ultra-small domains affords distinct advantages over the
strategy involving BCPs with high c and low N. In particular,
the use of high c chemistries can confound the generation of
long-range order owing to the high activation barriers for
defect removal in such systems.[14] This issue is avoided in the
Janus GBCP system, as the length scale for self-assembly is
effectively decoupled from the overall molecular weight of
the macromolecule, and the absence of entanglements[15] aids
rapid ordering of the nanostructure. Importantly, sub-10 nm
or even smaller nanodomains can be realized from GBCPs
containing polymer combinations that are not in the high-c
category but are of industrial significance. This was confirmed
by synthesizing BMMs tethered with various combinations of
low-c polymers that can be readily prepared, for example,
polystyrene (PS), poly(tert-butyl acrylate) (PtBA), and poly-
(ethylene oxide) (PEO). GBCPs synthesized from three
disordered low-c BMMs (PS-3.9k-branch-PtBA-3.7k, PDMS-
1k-branch-PEO-750, and PDMS-5k-branch-PtBA-3k) all dis-
played ordered lamellar, gyroidal, and cylindrical morpholo-
gies, respectively, with nanodomain sizes in the range of 3–
7 nm (Figure 4). This realization of unusually small nano-
domains enabled by GBCP architecture can be a universal
Figure 5. Bulk properties of GBCPs polymerized from PDMS-1k-branch-
PLA16 BMM. a) [BMM]0/[G3]0-dependent Tg (black square), TODT (black
circle), and G’ (red square) curves; b) Photographs for the macro-
scopic appearance of BMM (viscous liquid, left), (PDMS-1k-branch-
PLA16)10 (tacky solid, middle), and (PDMS-1k-branch-PLA16)50 (glassy
solid, right).
Angew. Chem. Int. Ed. 2018, 57, 1 – 6
ꢀ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
3
These are not the final page numbers!

Angewandte
Communications
Chemie
temperature (Tg) and shear storage modulus (G’) both
increase when the backbone becomes longer. Figure 5b
shows that while the BMMs were viscous oils (Figure 5b,
left) with Tg of 08C and G’ of 0.11 MPa, the GBCPs with
[BMM]0/[G3]0 = 10 were sticky solid-like materials (Fig-
ure 5b, middle) with Tg of 228C and a modulus one order of
magnitude higher (G’ = 6.84 MPa). With sufficiently long
backbones, the GBCP materials became capable of forming
free-standing glassy films while maintaining the same nano-
structure (lamellar morphology with d-spacing of 7.68 nm for
all GBCPs), as demonstrated by PDMS-1k-branch-PLA16
with [BMM]0/[G3]0 = 50 (Figure 5b, right). This nanostruc-
tured film with Tg of 268C and G’ of 13.1 MPa was produced
by simply evaporating a solution of the GBCP or by thermal
molding, demonstrating that the GBCPs are both solution
and melt processable, making them highly amenable to a wide
range of applications, potentially on a large processing scale.
The preservation of nanostructure upon varied backbone
lengths in GBCPs (Figure 2a,c; Supporting Information,
Figures S67–S79) is of particular significance to nanolithog-
raphy applications in which resist-like materials must have
sufficient viscosity to form robust films.
Fellowships. Y.C. and C.O. acknowledge NSF support through
DMR-1410568. The research used resources of Advanced
Photon Source, a U.S. DOE Office of Science User Facility
operated for the DOE Office of Science by Argonne National
Laboratory (Contract No. DE-AC02-06CH11357), and the
CMS beamline (11-BM) of the National Synchrotron Light
Source II, a U.S. Department of Energy (DOE) Office of
Science User Facility operated for the DOE Office of Science
by Brookhaven National Laboratory (Contract No. DE-
SC0012704).
Conflict of interest
The authors declare no conflict of interest.
Keywords: graft block copolymers · monomer sequences ·
nanostructures · polymer architectures ·
thermomechanical properties
Furthermore, the stability of the nanostructure, evaluated
by the order–disorder transition temperature (TODT), was also
improved with increased [BMM]0/[G3]0. A TODT of 628C was
observed in PDMS-1k-branch-PLA16 BMM. Although all
GBCPs polymerized from PDMS-1k-branch-PLA16 BMM
displayed similar ordered morphology at room temperature,
TODT increased to 978C for [BMM]0/[G3]0 = 10 and up to
1058C for [BMM]0/[G3]0 = 50, which was further confirmed
by the SAXS experiments (Supporting Information, Fig-
ure S2). The increase in TODT can be rationalized by the
increased stability of phase separation when more BMMs are
polymerized, as discussed previously.
In summary, we demonstrated that a graft-through syn-
thesis of Janus GBCPs can be applied as an efficient strategy
for decoupling polymer properties from nanostructure char-
acteristics. Owing to the interfacial organization of the two
blocks by the graft-through synthesis, the GBCPs form stable
self-assembled nanostructures capable of creating ultra-small
nanodomains, the size of which are dependent primarily on
the length of the sidechains. Simultaneously, the length of the
backbone can be varied to achieve the desired thermome-
chanical properties, providing independent tunability in the
processability of the GBCP materials, which is advantageous
in a number of materials applications. As the ability of the
GBCPs to self-assemble is less dependent on c, compared to
in AB-linear BCPs, this architectural strategy is a promising
method of incorporating diverse functionalities into nano-
structured polymeric materials, further expanding their
versatility.
[1] a) R. Ruiz, H. Kang, F. A. Detcheverry, E. Dobisz, D. S.
Kercher, T. R. Albrecht, J. J. de Pablo, P. F. Nealey, Science
2008, 321, 936 – 939; b) H.-C. Kim, S.-M. Park, W. D. Hinsberg,
Chem. Rev. 2010, 110, 146 – 177; c) H. S. Suh, D. H. Kim, P. Moni,
S. Xiong, L. E. Ocola, N. J. Zaluzec, K. K. Gleason, P. F. Nealey,
Nat. Nanotechnol. 2017, 12, 575 – 581.
[2] a) B. R. Sveinbjçrnsson, R. A. Weitekamp, G. M. Miyake, Y.
Xia, H. A. Atwater, R. H. Grubbs, Proc. Natl. Acad. Sci. USA
2012, 109, 14332 – 14336; b) M. Stefik, S. Guldin, S. Vignolini, U.
Wiesner, U. Steiner, Chem. Soc. Rev. 2015, 44, 5076 – 5091;
c) G. M. Miyake, V. A. Piunova, R. A. Weitekamp, R. H.
Grubbs, Angew. Chem. Int. Ed. 2012, 51, 11246 – 11248;
Angew. Chem. 2012, 124, 11408 – 11410.
[3] a) J. R. Werber, C. O. Osuji, M. Elimelech, Nat. Rev. Mater. 2016,
1, 16018; b) S. P. Nunes, Macromolecules 2016, 49, 2905 – 2916.
[4] a) S. B. Darling, Energy Environ. Sci. 2009, 2, 1266 – 1273;
b) M. C. Orilall, U. Wiesner, Chem. Soc. Rev. 2011, 40, 520 – 535.
[5] a) F. S. Bates, G. H. Fredrickson, Phys. Today 1999, 52, 32 – 38;
b) G. Polymeropoulos, G. Zapsas, K. Ntetsikas, P. Bilalis, Y.
Gnanou, N. Hadjichristidis, Macromolecules 2017, 50, 1253 –
1290; c) M. R. Golder, Y. Jiang, P. E. Teichen, H. V. T. Nguyen,
W. Wang, N. Milos, S. A. Freedman, A. P. Willard, J. A. Johnson,
J. Am. Chem. Soc. 2018, 140, 1596 – 1599.
[6] a) H. Ahn, S. Park, S.-W. Kim, P. J. Yoo, D. Y. Ryu, T. P. Russell,
ACS Nano 2014, 8, 11745 – 11752; b) H. B. Park, J. Kamcev,
L. M. Robeson, M. Elimelech, B. D. Freeman, Science 2017, 356,
eaab0530.
[7] a) J. G. Kennemur, M. A. Hillmyer, F. S. Bates, Macromolecules
2012, 45, 7228 – 7236; b) C. Sinturel, F. S. Bates, M. A. Hillmyer,
ACS Macro Lett. 2015, 4, 1044 – 1050; c) G. Jeong, D. M. Yu,
J. K. D. Mapas, Z. Sun, J. Rzayev, T. P. Russell, Macromolecules
2017, 50, 7148 – 7154; d) S. R. Nowak, W. Hwang, L. R. Sita, J.
Am. Chem. Soc. 2017, 139, 5281 – 5284; e) A. P. Lane, X. Yang,
M. J. Maher, G. Blachut, Y. Asano, Y. Someya, A. Mallavarapu,
S. M. Sirard, C. J. Ellison, C. G. Willson, ACS Nano 2017, 11,
7656 – 7665; f) B. van Genabeek, B. A. G. Lamers, B. F. M.
de Waal, M. H. C. van Son, A. R. A. Palmans, E. W. Meijer, J.
Am. Chem. Soc. 2017, 139, 14869 – 14872; g) D. M. Yu, J. K. D.
Mapas, H. Kim, J. Choi, A. E. Ribbe, J. Rzayev, T. P. Russell,
Macromolecules 2018, 51, 1031 – 1040.
Acknowledgements
Financial support was provided by Yale University. J.A.J.,
Y.G., and J.Z. acknowledge support of U.S. Air Force Office
of Scientific Research (FA9550-14-1-0292). A.N.L. and J.Z.
thank the National Science Foundation Graduate Research
4
www.angewandte.org
ꢀ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2018, 57, 1 – 6
These are not the final page numbers!

Angewandte
Communications
Chemie
[8] a) K. Kawamoto, M. Zhong, K. R. Gadelrab, L. C. Cheng, C. A.
Listak, W. Jakubowski, L. Mueller, A. Plichta, K. Matyjaszewski,
Ross, A. Alexander-Katz, J. A. Johnson, J. Am. Chem. Soc. 2016,
138, 11501 – 11504; b) Y. Rokhlenko, K. Kawamoto, J. A.
Johnson, C. O. Osuji, Macromolecules 2018, https://doi.org/10.
1021/acs.macromol.8b00261.
M. R. Bockstaller, Macromolecules 2008, 41, 5919 – 5927; f) B.
van Genabeek, B. F. M. de Waal, B. Ligt, A. R. A. Palmans,
E. W. Meijer, ACS Macro Lett. 2017, 6, 674 – 678; g) B.
Oschmann, J. Lawrence, M. W. Schulze, J. M. Ren, A. Anasta-
saki, Y. Luo, M. D. Nothling, C. W. Pester, K. T. Delaney, L. A.
Connal, A. J. McGrath, P. G. Clark, C. M. Bates, C. J. Hawker,
ACS Macro Lett. 2017, 6, 668 – 673.
[9] a) Y. Zhang, X. Li, G. Deng, Y. Chen, Macromol. Chem. Phys.
2006, 207, 1394 – 1403; b) H. Zhu, G. Deng, Y. Chen, Polymer
2008, 49, 405 – 411; c) N. Xia, G. Zhang, T. Li, W. Wang, H. Zhu,
Y. Chen, G. Deng, Polymer 2011, 52, 4581 – 4589; d) Y. Li, E.
Themistou, J. Zou, B. P. Das, M. Tsianou, C. Cheng, ACS Macro
Lett. 2012, 1, 52 – 56; e) B. Xu, C. Feng, X. Huang, Nat. Commun.
2017, 8, 333; f) S. Chakraborty, S. G. Ramkumar, S. Ramak-
rishnan, Macromolecules 2017, 50, 5004 – 5013; g) H. Luo, M.
Szymusiak, E. A. Garcia, L. L. Lock, H. Cui, Y. Liu, M. Herrera-
Alonso, Macromolecules 2017, 50, 2201 – 2206; h) S. E. Sherman,
Q. Xiao, V. Percec, Chem. Rev. 2017, 117, 6538 – 6631; i) T.
Pelras, C. S. Mahon, M. Muellner, Angew. Chem. Int. Ed. 2018,
https://doi.org/10.1002/anie.201711878; Angew. Chem. 2018,
https://doi.org/10.1002/ange.201711878.
[10] a) T.-P. Lin, A. B. Chang, H.-Y. Chen, A. L. Liberman-Martin,
C. M. Bates, M. J. Voegtle, C. A. Bauer, R. H. Grubbs, J. Am.
Chem. Soc. 2017, 139, 3896 – 3903; b) Y. Xia, J. A. Kornfield,
R. H. Grubbs, Macromolecules 2009, 42, 3761 – 3766; c) Y. Xia,
B. D. Olsen, J. A. Kornfield, R. H. Grubbs, J. Am. Chem. Soc.
2009, 131, 18525 – 18532.
[14] a) C. M. Bates, M. J. Maher, D. W. Janes, C. J. Ellison, C. G.
Willson, Macromolecules 2014, 47, 2 – 12; b) S.-M. Hur, V.
Thapar, A. Ramꢀrez-Hernꢁndez, G. Khaira, T. Segal-Peretz,
P. A. Rincon-Delgadillo, W. Li, M. Mꢂller, P. F. Nealey, J. J.
de Pablo, Proc. Natl. Acad. Sci. USA 2015, 112, 14144 – 14149.
[15] a) S. S. Sheiko, B. S. Sumerlin, K. Matyjaszewski, Prog. Polym.
Sci. 2008, 33, 759 – 785; b) J. Paturej, S. S. Sheiko, S. Panyukov,
M. Rubinstein, Sci. Adv. 2016, 2, e1601478.
[16] a) M. W. Matsen, M. Schick, Macromolecules 1994, 27, 6761 –
6767; b) M. W. Matsen, Macromolecules 2012, 45, 2161 – 2165.
[17] a) W. Shi, Y. Tateishi, W. Li, C. J. Hawker, G. H. Fredrickson,
E. J. Kramer, ACS Macro Lett. 2015, 4, 1287 – 1292; b) Z. Sun, W.
Zhang, S. Hong, Z. Chen, X. Liu, S. Xiao, E. B. Coughlin, T. P.
Russell, Polymer 2017, 121, 297 – 303; c) K. Yue, C. Liu, M.
Huang, J. Huang, Z. Zhou, K. Wu, H. Liu, Z. Lin, A.-C. Shi, W.-
B. Zhang, S. Z. D. Cheng, Macromolecules 2017, 50, 303 – 314;
d) P.-F. Jin, Y. Shao, G.-Z. Yin, S. Yang, J. He, P. Ni, W.-B. Zhang,
Macromolecules 2018, 51, 419 – 427.
[11] B. van Genabeek, B. F. de Waal, M. M. Gosens, L. M. Pitet,
A. R. Palmans, E. W. Meijer, J. Am. Chem. Soc. 2016, 138, 4210 –
4218.
[12] a) M. D. Rodwogin, C. S. Spanjers, C. Leighton, M. A. Hillmyer,
ACS Nano 2010, 4, 725 – 732; b) T.-Y. Lo, M. R. Krishnan, K.-Y.
Lu, R.-M. Ho, Prog. Polym. Sci. 2018, 77, 19 – 68.
[18] M. Vatankhah-Varnosfaderani, W. F. M. Daniel, M. H. Everhart,
A. A. Pandya, H. Liang, K. Matyjaszewski, A. V. Dobrynin, S. S.
Sheiko, Nature 2017, 549, 497 – 510.
[13] a) L. Leibler, H. Benoit, Polymer 1981, 22, 195 – 201; b) S. W.
Sides, G. H. Fredrickson, J. Chem. Phys. 2004, 121, 4974 – 4986;
c) N. A. Lynd, M. A. Hillmyer, Macromolecules 2005, 38, 8803 –
8810; d) M. W. Matsen, Phys. Rev. Lett. 2007, 99, 148304; e) J.
Manuscript received: March 7, 2018
Accepted manuscript online: April 26, 2018
Version of record online: && &&, &&&&
Angew. Chem. Int. Ed. 2018, 57, 1 – 6
ꢀ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
5
These are not the final page numbers!

Angewandte
Communications
Chemie
Communications
Nanostructures
Z.-H. Guo, A. N. Le, X. Feng, Y. Choo,
B. Liu, D. Wang, Z. Wan, Y. Gu, J. Zhao,
V. Li, C. O. Osuji, J. A. Johnson,*
M. Zhong*
&&&& — &&&&
Janus Graft Block Copolymers: Design of
a Polymer Architecture for Independently
Tuned Nanostructures and Polymer
Properties
Independently tunable polymer proper-
ties: Janus graft block copolymers are
synthesized with different backbone
length, which serves as a handle for
tuning of the thermomechanical proper-
ties of the polymer. Simultaneously, the
size of the ultra-small nanodomains is
controlled by the side chain length. A
broad range of monomers can be used.
6
www.angewandte.org
ꢀ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2018, 57, 1 – 6
These are not the final page numbers!