Design, Synthesis, and Self-Assembly of Polymers with Tailored Graft Distributions

Article abstract of DOI:10.1021/jacs.7b10525

Grafting density and graft distribution impact the chain dimensions and physical properties of polymers. However, achieving precise control over these structural parameters presents long-standing synthetic challenges. In this report, we introduce a versatile strategy to synthesize polymers with tailored architectures via grafting-through ring-opening metathesis polymerization (ROMP). One-pot copolymerization of an ω-norbornenyl macromonomer and a discrete norbornenyl comonomer (diluent) provides opportunities to control the backbone sequence and therefore the side chain distribution. Toward sequence control, the homopolymerization kinetics of 23 diluents were studied, representing diverse variations in the stereochemistry, anchor groups, and substituents. These modifications tuned the homopolymerization rate constants over 2 orders of magnitude (0.36 M^-1 s^-1 < k_homo < 82 M^-1 s^-1). Rate trends were identified and elucidated by complementary mechanistic and density functional theory (DFT) studies. Building on this foundation, complex architectures were achieved through copolymerizations of selected diluents with a poly(d,l-lactide) (PLA), polydimethylsiloxane (PDMS), or polystyrene (PS) macromonomer. The cross-propagation rate constants were obtained by nonlinear least-squares fitting of the instantaneous comonomer concentrations according to the Mayo-Lewis terminal model. In-depth kinetic analyses indicate a wide range of accessible macromonomer/diluent reactivity ratios (0.08 < r₁/r₂ < 20), corresponding to blocky, gradient, or random backbone sequences. We further demonstrated the versatility of this copolymerization approach by synthesizing AB graft diblock polymers with tapered, uniform, and inverse-tapered molecular "shapes." Small-angle X-ray scattering analysis of the self-assembled structures illustrates effects of the graft distribution on the domain spacing and backbone conformation. Collectively, the insights provided herein into the ROMP mechanism, monomer design, and homo- and copolymerization rate trends offer a general strategy for the design and synthesis of graft polymers with arbitrary architectures. Controlled copolymerization therefore expands the parameter space for molecular and materials design.

Full text of DOI:10.1021/jacs.7b10525

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Article
Design, Synthesis, and Self-Assembly of
Polymers with Tailored Graft Distributions
Alice B. Chang, Tzu-Pin Lin, Niklas B. Thompson, Shao-Xiong Luo, Allegra
Lauren Liberman-Martin, Hsiang-Yun Chen, Byeongdu Lee, and Robert H. Grubbs
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.7b10525 • Publication Date (Web): 08 Nov 2017
Downloaded from http://pubs.acs.org on November 8, 2017
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Design, Synthesis, and Self-Assembly of Polymers with Tailored
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Alice B. Chang,†,‡ Tzu-Pin Lin,†,‡ Niklas B. Thompson,† Shao-Xiong Luo,† Allegra L. Liberman-Mar-
tin,† Hsiang-Yun Chen,† Byeongdu Lee,§ and Robert H. Grubbs*†
†Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United
States
§X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439
ABSTRACT: Grafting density and graft distribution impact the chain dimensions and physical properties of polymers. However,
achieving precise control over these structural parameters presents long-standing synthetic challenges. In this report, we introduce a
versatile strategy to synthesize polymers with tailored architectures via grafting-through ring-opening metathesis polymerization
(ROMP). One-pot copolymerization of an ω-norbornenyl macromonomer and a discrete norbornenyl co-monomer (diluent) provides
opportunities to control the backbone sequence and therefore the side chain distribution. Toward sequence control, the homopoly-
merization kinetics of 23 diluents were studied, representing diverse variations in the stereochemistry, anchor groups, and substitu-
ents. These modifications tuned the homopolymerization rate constants over two orders of magnitude (0.36 M−1 s−1 < khomo < 82 M−1
s−1). Rate trends were identified and elucidated by complementary mechanistic and density functional theory (DFT) studies. Building
on this foundation, complex architectures were achieved through copolymerizations of selected diluents with a poly(D,L-lactide)
(PLA), polydimethylsiloxane (PDMS), or polystyrene (PS) macromonomer. The cross-propagation rate constants were obtained by
non-linear least squares fitting of the instantaneous co-monomer concentrations according to the Mayo-Lewis terminal model. In-
depth kinetic analyses indicate a wide range of accessible macromonomer/diluent reactivity ratios (0.08 < r1/r2 < 20), corresponding
to blocky, gradient, or random backbone sequences. We further demonstrated the versatility of this copolymerization approach by
synthesizing AB graft diblock polymers with tapered, uniform, and inverse-tapered molecular “shapes.” Small-angle X-ray scattering
analysis of the self-assembled structures illustrates effects of the graft distribution on the domain spacing and backbone conformation.
Collectively, the insights provided herein into the ROMP mechanism, monomer design, and homo- and copolymerization rate trends
offer a general strategy for the design and synthesis of graft polymers with arbitrary architectures. Controlled copolymerization there-
fore expands the parameter space for molecular and materials design.
erties. Despite the importance of grafting density and graft dis-
tribution, synthetic strategies that permit precise control of
INTRODUCTION
these parameters are currently limited. Grafting-to27-30 and
grafting-from31-34 approaches require multiple steps in which
side chains are either attached to or grown from a pre-formed
backbone. Steric congestion along the backbone typically pre-
vents precise control over the molecular weight, grafting den-
sity, and side chain distribution. As a result, the synthesis of
well-defined architectural variants – let alone materials with
variable chemical compositions – is challenging. Grafting-
through ring-opening metathesis polymerization (ROMP)
closes this gap by affording wide functional group tolerance and
enabling simultaneous control over side chain and backbone
lengths.35-37 We recently introduced a ROMP strategy that pro-
vides access to polymers with uniform grafting densities span-
ning the linear to bottlebrush regimes.38 In this report, we fur-
ther expand the scope of architectural design by demonstrating
that ROMP can be exploited to further tune “molecular shapes.”
Molecular architecture impacts the chemical and physical
properties of all polymers. Achieving precise control over the
chain connectivity, sequence, and symmetry presents synthetic
challenges as well as rich opportunities for materials design.
Over the past several decades, advances in controlled polymer-
ization have enabled the synthesis of polymers with complex
architectures.1-4 Graft polymers are a class of such nonlinear ar-
chitectures featuring polymeric side chains attached to a poly-
meric backbone. The grafting density and distribution of grafts
along the backbone determine the steric interactions between
side chains and in turn influence the physical properties. Graft
polymers display many unique properties compared to their lin-
ear analogues, such as extended chain conformations,5-8 in-
creased entanglement molecular weights,9-12 and architecture-
dependent rheological behavior.13-16 Recent studies have har-
nessed these properties in a wide variety of applications in pho-
tonics,17-19 drug delivery,20-22 transport,23-24 and thermoplas-
tics.25-26 Continued progress in synthetic command over poly-
mer architecture enables further studies of structure-property
relationships and inspires new potential applications.
Our approach employs controlled copolymerization of a
macromonomer and a small-molecule diluent. The relative re-
activity of the two co-monomers directly dictates the spatial ar-
rangement of the side chains. For example, if the macromono-
mer and diluent copolymerize at approximately the same rate,
the side chains are therefore uniformly distributed along the pol-
ymer backbone (Figure 1A). Such polymers are widely termed
Graft polymers represent ideal platforms to study how chain
connectivity defines nanostructures and thereby physical prop-
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“cylindrical molecular brushes” due to their steric-induced stiff-
Page 2 of 25
ness and axes of symmetry.39-43 These cylindrical brushes can
be modeled as wormlike chains with the same average cross-
sectional radius (Rc) along the entire backbone.5,44-46 On the
other hand, if the macromonomer and diluent copolymerize at
different rates, the resulting gradient sequences are anticipated
to template different side chain conformations. Depending on
the extent of side chain stretching, Rc varies and tapered, non-
cylindrical molecular shapes result (Figure 1B). Control over
the co-monomer distribution therefore opens opportunities to
manipulate the chain dimensions and physical properties.
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In this report, we provide the first demonstration that vary-
ing the stereochemistry and steric profiles of discrete co-mono-
mers enables the synthesis of well-defined graft polymers with
tunable grafting density and graft distribution. We will first dis-
cuss the homopolymerization kinetics of a library of discrete
norbornenyl monomers, then build complexity through con-
trolled copolymerizations of these small molecules with ω-nor-
bornenyl macromonomers. Trends in the homo- and cross-prop-
agation rates will be outlined to provide guidance for future ra-
tional design of polymer architectures with arbitrary graft
chemistry and distribution. We will illustrate the versatility of
this copolymerization strategy through the synthesis of graft
polymers with different anticipated molecular shapes. The
physical consequences of varying the graft distribution will be
discussed in the context of block polymer self-assembly.
Figure 1. Grafting-through ROMP of a small-molecule diluent
(white) and a macromonomer (black). Since the side chains (red)
are connected to certain backbone units, control over the backbone
sequence directly determines the side chain distribution: (A) uni-
form, (B) gradient, etc. The anticipated average cross-sectional ra-
dius of gyration (Rc) is indicated. For ease of visualization, chains
are illustrated in the limit of fully extended backbones.
RESULTS AND DISCUSSION
Monomer Design. Previous work introduced endo,exo-nor-
bornenyl dialkylesters as appropriate discrete monomers (dilu-
ents) to control the grafting density of polymers with poly(D,L
-
Chart 1 highlights opportunities for monomer design. The
polymerizable strained olefin, anchor group, and substituents
can all be readily modified. Substituted norbornenes were se-
lected for our study due to (1) the ease of modifying the stereo-
chemistry and functional groups and (2) the high ring strain,
which disfavors unproductive [2+2] cycloreversion.52 The im-
portance of the anchor group in homopolymerization kinetics
has been demonstrated for both discrete norbornenes53-54 and
more recently, ω-norbornenyl macromonomers.55 In contrast,
anchor group effects on the copolymerization of discrete mon-
omers and macromonomers have not been studied. In order to
investigate these effects, discrete substituted norbornenes with
five different types of anchor groups were synthesized:
endo,exo-diester (dx-DE, 1), endo,endo-diester (dd-DE, 2),
exo,exo-diester (xx-DE, 3), endo-imide (d-I, 4), and exo-imide
(x-I, 5). For each anchor group, monomers with different sub-
stituents (R) were prepared, including for example homologous
alkyl groups or para-substituted phenyl rings. All monomers
can be prepared in high yields in one or two steps from com-
mercially available starting materials. (Further synthetic details
can be found in the Supporting Information.) These steric and
electronic variations provide a diverse library of co-monomers
for ROMP.
lactide) (PLA, Mn = 3230 g mol−1), polydimethylsiloxane
(PDMS, Mn = 1280 g mol−1), or polystyrene (PS, Mn = 3990 g
mol−1) side chains.38 Across all macromonomer/diluent combi-
nations and feed ratios, kinetic analyses indicated approxi-
mately equal rates of co-monomer consumption and therefore
approximately uniform side chain distributions. Obtaining non-
uniform side chain distributions requires changing the relative
reactivity of the macromonomer and diluent. We propose that
designing new small-molecule co-monomers is the most con-
venient route. This strategy avoids potentially tedious end-
group modifications to the macromonomers and retains the syn-
thetic utility of one-pot batch copolymerization. While semi-
batch methods (involving continuous addition of one monomer
to another) can afford wide control over polymer sequences,47-
48
they require additional instrumentation and optimization of
factors such as feed ratio and feed rate.49-50 Similarly, while se-
quential addition of macromonomers with different molecular
weights can also provide access to tapered architectures,51 this
approach requires the preparation of multiple well-defined mac-
romonomers and fixes the grafting density at 100%.
The homopolymerization kinetics of all monomers were
studied under the same conditions. ROMP of each monomer in
dichloromethane ([M] = 50 mM) was catalyzed by the fast-ini-
tiating third-generation ruthenium metathesis catalyst,
(H2IMes)(pyr)2(Cl)2Ru=CHPh ([G3]0 = 0.5 mM). Over the
course of the polymerization, aliquots (<20 μL) were collected
and immediately quenched into separate vials containing excess
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ethyl vinyl ether and a silica-bound metal scavenger (SiliaM-
d[M]t
dt

 kobs[M]t  khomo[G3]0[M]t
(1)
etS).56 Removing the quenched ruthenium complex from solu-
tion prevents potential reactivation and undesired metathesis
that would affect the apparent rates. Analysis by size-exclusion
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For many monomers, the rate constants were determined at least
in triplicate. The calculated values typically varied by no more
than five percent (Figure S6).
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chromatography (SEC) and H NMR spectroscopy indicates
first-order rate dependence on monomer concentration. The
first- and second-order rate constants (kobs and khomo, respec-
tively) were determined according to Eq. 1:
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Chart 1. Monomer design for ring-opening metathesis copolymerization.
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Studying trends in khomo with variations in steric and elec-
tronic structure guides monomer design. The first class of mon-
omers studied herein features endo,exo-diester anchor groups
(dx-DE). The homopolymerization kinetics of ten dx-DE mon-
omers with different substituents were analyzed (1a–1j, Figure
2). The monomers were readily synthesized by esterification of
commercially available norbornene endo,exo-dicarboxylic acid
with the appropriate alcohol (1a–d, Scheme S1). (For the syn-
thesis of 1e–1j, the acyl chloride derivatives were required,
Scheme S2.) In a series of monomers with homologous alkyl
substituents (R = methyl, ethyl, n-propyl, n-butyl; 1a–d), khomo
decreases with increasing substituent size. Increasing the steric
bulk with isopropyl- and tert-butyl-substituted monomers (1e–
f) further decreases khomo. These results indicate that sterics
clearly impact the homopolymerization kinetics: for example,
the methyl-substituted monomer polymerizes over three times
faster than the tert-butyl-substituted analogue (khomo = 18.7 ver-
sus 5.36 M−1 s−1). The effects of electronic variations were also
studied. Monomers with ethyl (1b, 14.6 M−1 s−1) and trifluoro-
ethyl (1g, 10.5 M−1 s−1) substituents polymerize at approxi-
mately the same rate. Comparison of dx-DE monomers with dif-
ferent para-substituted phenyl rings further reveals that the
electronic effects are minor. dx-norbornenyl diphenylester (1h)
has a larger khomo (8.36 M−1 s−1) than monomers with either an
electron-withdrawing para-trifluoromethyl group (1i, 5.14 M−1
s−1) or an electron-donating para-methoxy group (1j, 7.76 M−1
s−1). These electronic variations may exist too far away from the
polymerizable olefin to affect khomo. Modifying norbornene it-
self rather than the distal substituents (for example, by substi-
tuting oxanorbornene or otherwise changing the bridge posi-
tion) may result in more apparent electronic effects.
Figure 2. Homopolymerization rate constants (khomo) for substi-
tuted endo,exo-norbornenyl diester monomers (left to right: 1a–j).
khomo decreases with increasing steric bulk (R = Me to tBu, 1a–f).
khomo does not change significantly with electronic changes via
fluorination (1g) or para-substitution of a phenyl ring (1h–j).
Changing the stereochemistry of the diester anchor groups
further demonstrates the effects of steric variations on polymer-
ization rates. (Synthetic details: Schemes S3–S4.) Comparing
series with the same substituents (Figure 3A) indicates that dx-
DE monomers (1a–d) all polymerize significantly faster than
the corresponding endo,endo isomers (dd-DE, 2a–d) and
slightly slower than the corresponding exo,exo isomers (xx-DE,
3a–d). For example, the measured khomo for dx-norbornenyl di-
methylester is 18.7 M−1 s−1, while khomo values for the dd-DE and
xx-DE analogues are 2.24 M−1 s−1 and 30.8 M−1 s−1, respectively.
The same anchor group trend occurs for ethyl-, n-propyl-, and
n-butyl-substituted norbornenyl diesters and is anticipated to be
independent of the substituent.
In order to further examine the relationship between anchor
groups and homopolymerization kinetics, norbornenyl mono-
mers with endo-imide (d-I) and exo-imide (x-I) linkages were
also synthesized (Schemes S5–S6). The x-I anchor group has
been widely incorporated in macromonomers toward the syn-
thesis of bottlebrush polymers by grafting-through
ROMP,21,55,57-59 motivating our interest in imide-based diluents.
Compared to diester anchor groups, imides are more rigid due
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Page 4 of 25
to their fused rings and thereby change the monomer steric pro- for tuning the polymerization rates. Understanding the origin of
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file. The electronic character differs as well, since the electron
density of an imide oxygen is typically greater than the electron
density of an ester oxygen. The interplay of steric and electronic
influences will be discussed further in the following section.
trends in khomo provides insight into the ROMP mechanism.
While developing a complete mechanistic understanding is out-
side the scope of this study, we aim to identify key components
of khomo in order to facilitate applications of this method as well
as future monomer design.
Figure 3B compares khomo for monomers with each of the
five anchor groups. The endo/exo rate difference between d-I
and x-I is magnified compared to the endo/exo rate differences
observed among the diester-substituted monomers. The khomo
values for methyl-substituted dd-DE and xx-DE are 2.24 and
30.8 M−1 s−1 respectively, representing a tenfold rate difference;
in comparison, the khomo values for methyl-substituted d-I and x-
I are 0.814 and 82.4 M−1 s−1 respectively, representing a
hundredfold rate difference. Figure 3B also shows that the steric
effects of the R group are smaller for x-I and d-I compared to
the diester series. For monomers containing the same substitu-
ents, the following trend in khomo is observed: d-I < dd-DE < dx-
DE < xx-DE < x-I.
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Figure 3. (A) Homopolymerization rate constants (khomo) for mon-
omers with exo,exo-diester (xx, green), endo,exo-diester (dx, red),
and endo,endo-diester (dd, yellow) anchor groups. Comparison of
Figure 4 and Table S1 summarize the homopolymerization
kinetics for all monomers studied herein. Variations in the an-
chor groups and substituents afford a wide range of khomo over
two orders of magnitude, spanning 0.362 M−1 s−1 (2d) to 82.4
M−1 s−1 (5a). This library of monomers can be readily diversified
by simple esterification reactions, providing a versatile platform
k
homo for monomers with R = Me, Et, nPr, and nBu supports the ste-
ric influences of stereochemistry and substituent size. (B) khomo for
n
Me- and Bu-substituted monomers with each of the five anchor
groups; endo-imide (d-I, blue) and exo-imide (x-I, purple).
Figure 4. Plot of khomo values for all monomers studied herein. The monomers are sorted according to their anchor groups: left to right:
endo,exo-diester (red, 1a–j), endo,endo-diester (yellow, 2a–d), exo,exo-diester (green, 3a–d), endo-imide (blue, 4a–c), and exo-imide (pur-
ple, 5a–c and macromonomers). khomo values for methyl-substituted monomers are provided for comparison.
Origin of Rate Trends. Polymerization rates are deter-
mined by a combination of steric and electronic factors. Our re-
sults suggest that steric effects dominate: (1) In a series of mon-
omers with homologous alkyl R groups, the electronic character
is similar but khomo decreases as the steric bulk increases (Figure
2). (2) khomo is relatively insensitive to distal electronic varia-
tions (for example, via para-substitution of phenyl R groups,
Figure 2). (3) khomo decreases for endo-substituted monomers
compared to the corresponding exo isomers (Figure 3). In agree-
ment with this work, previous studies of the ROMP of nor-
bornene derivatives have also observed that endo isomers poly-
merize more slowly than their exo counterparts.54,60-63
The observed rate trends could be motivated by a combina-
tion of factors, including but not limited to pyridine coordina-
tion, olefin coordination, cycloaddition, and formation of a six-
membered chelate involving the ruthenium center and the ester-
or imide-functionalized chain end.64 In order to deconvolute
these potential contributions to khomo, we examined the mecha-
nism of ROMP. Based on previously reported results for related
phosphine-based catalysts,65-67 we proposed a dissociative path-
way (Figure 5A) in which pyridine dissociation (Keq,1 = k1/k-1,
Keq,2 = k2/k-2) generates a 14-electron intermediate (b) that can
coordinate with a free olefin (c, Keq,3 = k3/k-3). The olefin adduct
then undergoes cycloaddition (k4) to form a metallacyclobutane
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intermediate. Subsequent cycloreversion yields a Pn+1 alkyli- ground-state potential energy surfaces corresponding to one
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dene and regenerates the 14-electron species. From a Van’t
Hoff analysis, Guironnet and coworkers recently reported an
equilibrium constant Keq,1 = k1/k−1 = 0.5 M in CD2Cl2 at 298 K.68
In agreement with this work, we observed a similar Keq,1 value
productive ROMP cycle were computed (Figures 5B and S9).
The relative free energies at 298 K (ΔG) indicate that formation
of the six-membered chelate is more favorable for the endo iso-
mer (ΔΔGchelate = 9.64 kcal mol−1) than for the exo isomer (ΔΔG-
1
= 5.87 kcal mol−1). The calculated free energies corre-
from H NMR pyridine titration experiments (0.25 M, Figure
5
chelate
S7). The large Keq,1 value indicates that >99.8% of the precata-
lyst G3 exists as the monopyridine adduct in solution under the
conditions employed in our homo- and copolymerization stud-
ies ([G3]0 = 0.5 mM). As a result, the concentration of free pyr-
idine is approximately equal to the initial concentration of G3
(i.e., [pyr] ≈ [G3]0). We derived a simplified rate expression
corresponding to a proposed dissociative ROMP pathway in
which olefin coordination is the rate-limiting step:69
sponding to olefin coordination to the vacant species, ΔΔGbind-
ing, are similar for the endo and exo isomers (8.86 and 8.91 kcal
mol−1, respectively). These results indicate that disruption of
chelation by olefin binding should be more favorable for exo
isomers than endo isomers (by 3.72 kcal mol−1). This disparity
provides a plausible motive for the observed endo/exo rate dif-
ferences (khomo = 30.8 M−1 s−1 for 3a, 2.24 M−1 s−1 for 2a). These
results are consistent with previous reports on the ROMP of dis-
crete norbornenyl monomers with similar ruthenium cata-
lysts64,66,72 and are anticipated to be valid whether olefin coor-
dination (k3 << k4) or cycloaddition (k3 >> k4) is the rate-limiting
step.73 Insights into the rate trends from mechanistic studies
help identify important elements of monomer design and, there-
fore, opportunities for controlled copolymerization.
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Keq,2k3
d[M]t
dt

 khomo[G3]0[M]t 
[G3]0[M]t
(2)
Keq,2  [pyr]
In this rate expression, Keq,2 corresponds to dissociation of
the second pyridine and is affected by the identity of the alkyli-
dene ligand. At high catalyst concentrations ([pyr] >> Keq,2), a
pseudo-zeroth-order dependence on [G3]0 is observed.68 At low
catalyst concentrations however, we observed a rate depend-
ence on [G3]0 for monomers 5a and 5b (Figure S8). Collec-
tively, these kinetic analyses are consistent with a dissociative
pathway.70
Copolymerization Kinetics. In order to analyze the copol-
ymerization kinetics of a macromonomer and a discrete co-
monomer, the Mayo-Lewis terminal model was adapted for G3-
catalyzed ROMP.38 The terminal model assumes that, for a mix-
ture of two monomers M1 and M2, there are two propagating
species (M1* and M2*) whose reactivities solely depend on the
last-incorporated monomer.74 The copolymerization kinetics
can be captured by four propagation reactions involving M1*
and M2*, each described by a unique rate constant k. Figure 6
shows the relevant reactions for a mixture of a discrete diluent
(M2) and a macromonomer (M1): (A) diluent self-propagation
(M2* → M2*, k22), (B) cross-propagation via addition of M1 to
M2* (M2* → M1*, k21), (C) macromonomer self-propagation
(M1* → M1*, k11), and (D) cross-propagation via addition of M2
to M1* (M1* → M2*, k12). The conversion over time of all spe-
cies can be described by a system of four ordinary differential
equations. Non-linear least squares regression, described in a
previous report,38 was used to fit the instantaneous monomer
concentrations over the entire course of the copolymerization.
Finding the best numerical solutions for the cross-propagation
rates k12 and k21 enables determination of the reactivity ratios, r1
= k11/k12 and r2 = k22/k21.
Figure 5. (A) Proposed dissociative ROMP pathway for G3. (B)
DFT-calculated free energy diagram corresponding to one ROMP
cycle for endo- (2a, blue) and exo-substituted (3a, red) norbornenyl
monomers. The following intermediates were calculated: (a) six-
membered Ru–O chelate, (b) 14-electron vacant species, (c) olefin
adduct, and (d) metallacyclobutane.
Density functional theory (DFT) methods were employed to
address potential chelation effects. Chelation sequesters the cat-
alyst in an unproductive form (Figure 5A, a) and therefore slows
the polymerization rate.71 For methyl-substituted endo,endo-
and exo,exo-norbornenyl diesters (2a and 3a, respectively), the
Figure 6. Propagation reactions for the copolymerization of a dis-
crete diluent (M2, dx-DE shown for example) and a macromonomer
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(M1) according to a terminal model. M2* and M1* are the corre-
suggest that both M1* and M2* (1) favor incorporating M2 when
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sponding propagating alkylidene species. (A) Diluent self-propa-
gation (k22), (B) cross-propagation (k21), (C) macromonomer self-
propagation (k11), (D) cross-propagation (k12).
k22 ≳ k11 and (2) favor incorporating M1 when k22 < k11. In other
words, both cross-propagation terms (k12 and k21) are functions
of the incoming olefin (to first order) and appear relatively in-
sensitive to the nature of the pendant chain.
The relative reactivity, captured by r1 and r2, determines the
polymer sequence. r1 and r2 can be tuned by building on insights
into homopolymerization rate trends. Monomer design ulti-
mately enables architecture design: for a polymerizable macro-
monomer with any side chain chemistry, a discrete co-monomer
can be selected among those in Figure 4 or otherwise designed
to target desired backbone sequences. In turn, control over the
backbone sequence directly controls side chain distribution. We
will first discuss general trends and opportunities for copoly-
merization, then outline potential implications for polymer ar-
chitectures by design.
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In order to study the impact of monomer structure on the
copolymerization kinetics, we selected 13 diluents and copoly-
merized each with the same ω-norbornenyl macromonomer
(PLA, Mn = 3230 g mol−1) (Figure 7A). Figure 7B arranges
these discrete co-monomers in order of increasing k22. For all
copolymerization experiments, the total backbone degree of
polymerization (Nbb) and monomer feed ratio (f) were fixed:
given x equivalents of the diluent and y equivalents of PLA rel-
ative to 1 equivalent of G3, Nbb = x + y ≈ 200 and f = x/y ≈ 1.
The copolymerization conditions, including monomer and cat-
alyst concentrations, were identical to those for the homopoly-
merization experiments described above: [M1]0 = [M2]0 = 50
mM, [G3]0 = 0.5 mM.75 The kinetics were monitored in the
same way as the homopolymerization kinetics, i.e., by quench-
ing aliquots of the polymerization mixture. The instantaneous
concentrations of the macromonomer and diluent were deter-
mined by integrating the olefin resonances in 1H NMR spectra,
and k12 and k21 were obtained by non-linear least squares regres-
sion. SEC data for all copolymers indicate low dispersities (Ð
< 1.1) and similar molecular weights (Figure S10, Table S2).
Figure 7C shows the self-propagation rate constants (k11,
k22) and reactivity ratios (r1, r2) for the copolymerization of
PLA (M1) with different diluents (M2). (All data, including the
cross-propagation rate constants k12 and k21, are compiled in Ta-
ble S3.) k11 is constant throughout the series (= 17.2 M−1 s−1)
since M1 is the same in each co-monomer pair, while k22 varies
over a wide range due to anchor group and substituent effects
(2d: 0.362 M−1 s−1 to 5a: 82.4 M−1 s−1). As k22 increases, r2 also
increases. The magnitude of r2 reflects the reactivity of the
propagating alkylidene M2* toward free M1 and M2.76 In the
case that r2 < 1, for example when PLA is copolymerized with
dd-DE or d-I diluents (2d to 2a, 0.4 < r2 < 0.9), M2* preferen-
tially adds M1. In the opposite case r2 > 1, for example when
PLA is copolymerized with dx-DE, xx-DE, or x-I diluents (3d
to 5a, 1.2 < r2 < 3.1), M2* preferentially adds M2 instead. In
other words, if a diluent is the terminal unit of the propagating
species, the probability of incorporating either a macromono-
mer or another diluent reflects the difference between the ho-
mopolymerization rate constants: when k22 < k11, r2 < 1 and M2*
Figure 7. (A) Copolymerization scheme: the same macromonomer
(PLA, M1) was copolymerized with 13 different diluents (M2). The
feed ratio (x/y = 1) and total backbone length (x + y = 200) were
fixed. (B) M2 arranged in order of increasing k22. (C) PLA/diluent
copolymerization data. Left axis, black: self-propagation rate con-
stants (k22: filled circles, k11: open circles). Right axis, red: reactiv-
ity ratios (r2: solid line, r1: dotted line).
We note that, while r1 generally decreases with increasing
k22, the trend is not monotonic. These results highlight the addi-
tional complexity that copolymerization introduces. While in-
formative, the difference between the homopolymerization rate
constants (k11−k22) is not a universal predictor for the values of
r1 and r2 (nor therefore the copolymer sequence). For example,
when PLA is copolymerized with a xx-DE diluent, r2 varies but
r1 remains the same (= 0.36 ± 0.02), regardless of whether k22
<
k11 (3d, 3c, and 3b) or k22 > k11 (3a). Meanwhile, when PLA is
copolymerized with the dx-DE analogue of 3a (i.e., 1a), the
self-propagation rates are equal (k22 = k11) and both r1 and r2 are
approximately equal to 1. These observations suggest that the
key interactions identified in our study of diluent homopoly-
merization rate trends do not fully capture the relative reactivity
upon copolymerization. The individual second-order rate con-
stants (k11, k12, k21, k22) are affected by both (1) pyridine binding
(Keq,2) and (2) chelation and olefin binding (k3). Both those
favors macromonomer addition; on the other hand, when k22
>
k11, r2 > 1 and M2* favors diluent addition.77 Translating these
trends to the copolymer sequence also requires examination of
r1, which reflects consumption of the other propagating species
M1*. Figure 7C shows that, as k22 increases, r1 generally de-
creases, opposite the trend observed for r2. These observations
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terms are inherently dictated by the identities of the approach- are compiled in Tables S4–S5, and SEC data are provided in
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ing olefin monomer and the propagating alkylidene. While elu-
cidating the origin of copolymerization rate trends is outside the
scope of this report, we note that the large disparity between the
molecular weights of the PLA macromonomer and diluents (10-
to 20-fold) likely plays a significant role in the departure from
simple chain-end control. Under the copolymerization condi-
tions (rapid stirring in dilute solution), simple diffusion of free
monomers to the catalyst active site is not expected to limit
propagation. However, beyond the anchor group and substitu-
ent effects outlined for discrete diluents, the presence of poly-
meric side chains in proximity to the metal center should am-
plify steric congestion. Excluded volume interactions and sol-
vent quality may further affect the steric and electronic environ-
ment around the propagating metal center.
Figures S11–S12 and Tables S6–S7.
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Graft Polymer Architecture. Monitoring the copolymeri-
zation kinetics enables determination of the instantaneous com-
position and therefore the graft polymer architecture. Using the
experimentally determined rate constants, the probability of in-
corporating either a diluent or a macromonomer at any point in
the growing chain can be simulated.38 Figure 8 plots these prob-
abilities as a function of the total conversion for several
PLA/diluent pairs. If r1 > r2, gradient sequences are obtained.
The copolymers are rich in M1 at early conversions and rich in
M2 at later conversions, producing tapered side chain distribu-
tions (e.g., PLA + 4a, Figure 8A). If r1 ≈ r2 ≈ 1, the copolymer
backbone sequence is approximately random and therefore the
side chains are uniformly distributed (e.g. PLA + 1a, Figure
8B). Lastly, if r1 < r2, the inverse-tapered graft polymers are
obtained, which are rich in M2 at early conversions and rich in
M1 at later conversions (e.g., PLA + 5a, Figure 8C).
Figure 9. Data for the copolymerization of M1 = PDMS (left) or
PS (right) with different diluents. Left axis, black: self-propagation
rate constants (k22: filled circles, k11: open circles). Right axis, red:
reactivity ratios (r2: solid line, r1: dotted line).
Copolymerizations of PDMS with each of the selected dil-
uents generally follow the same trends outlined for PLA/diluent
copolymerizations. As k22 increases while k11 remains constant,
r2 increases and r1 decreases. In other words, as k22 increases,
both M1* and M2* increasingly favor incorporating M2 instead
of M1. The xx-DE diluents (3a, 3d) are again outliers, leading
to smaller values of r1 than diluents with any other anchor
group. As a result, at least for copolymerizations with PDMS
or PLA macromonomers, the xx-DE anchor group inherently
favors gradient sequences that are M2-rich at early conversions
and M1-rich at later conversions. Copolymerizations of PS with
any of the selected diluents reveal a similar kinetic preference
for gradient sequences. Unlike copolymerizations with either
PLA or PDMS, regardless of the relative magnitude of k22 (2.7
< k22−k11 < 78 M−1 s−1), r2 remains constant (≈ 1). The constant
magnitude of r2 suggests that M2* displays similar reactivity to-
ward PS and any diluent. Meanwhile, since M1* favors incor-
porating M2 (r1 < 1), gradient sequences result.
The copolymerization kinetics for PLA, PDMS, and PS
collectively illustrate how different diluents can be used to con-
trol the graft polymer architecture. The magnitudes of r1 and r2
determine the backbone sequence, which can be alternating (r1
≈ r2 ≈ 0), blocky (r1, r2 >> 1), gradient (r1 >> r2 or r1 << r2), or
random (r1 ≈ r2 ≈ 1).76 The backbone sequence in turn directly
determines the side chain distribution (Figure 1). Figure 10 il-
lustrates the wide range of distributions obtained by copolymer-
izing PLA, PDMS, or PS with selected diluents. The relative
reactivities of the macromonomers and diluents are interpreted
in terms of the quotient r1/r2, which reflects the kinetic prefer-
ence for the chain end (either M1* or M2*) to incorporate M1
over M2.
Figure 8. Simulated sequences and (inset) graft polymer architec-
tures for the copolymerization of PLA with different diluents: (A)
4a, (B) 1a, or (C) 5a. For ease of visualization, the simulated struc-
tures show fully extended side chains and backbones.
The ROMP copolymerization strategy outlined herein pro-
vides a general approach to architecture design for any side
chain chemistry. In principle, given any polymerizable macro-
monomer, a diluent can be designed to access any desired se-
quence. Although the magnitudes of r1 and r2 cannot presently
be predicted de novo, insights into the relationships among r1,
r2, and diluent structure should guide the selection of appropri-
ate macromonomer/diluent pairs. In order to further illustrate
these design principles, the copolymerization kinetics of vari-
ous diluents with either a PDMS (Mn = 1280 g mol−1) or PS (Mn
= 3990 g mol−1) macromonomer were also studied. PDMS and
PS polymerize faster (k11 = 21.6 M−1 s−1) and slower (k11 = 4.18
M−1 s−1)than PLA, respectively. The selected diluents all homo-
polymerize slower than PDMS (k22 < k11, with the exception of
3a) and faster than PS (k22 > k11). The self-propagation rate con-
stants and reactivity ratios are provided in Figure 9. All values
PLA/diluent copolymerizations obtain r1/r2 ranging from
0.20 (PLA + 5a) to 5.8 (PLA + 4a). Copolymerizing PDMS
with 4a, one of the slowest-polymerizing diluents studied
herein, produces a remarkably large difference between r1 and
r2: r1/r2 = 19. This large disparity in reactivity results in a highly
gradient – potentially even blocky – distribution of side chains.
Since r1 >> r2, the graft polymers are densely grafted (i.e., rich
in M1) at early conversions and loosely grafted (i.e., rich in M2)
at later conversions. Copolymerizing PS with 5b, one of the
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fastest-polymerizing diluents introduced in this report, also af- tures with uniform (BP-1) or gradient (BP-2, BP-3) graft distri-
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fords a wide gap in reactivity: r1/r2 = 0.084. Compared to
PDMS + 4a, the inverse-tapered sequence is obtained. The abil-
ity to invert the gradient direction may not affect the properties
of homopolymers, but it is valuable in the design of block pol-
ymers and other multicomponent materials. In the final section,
we will demonstrate the physical consequences of varying the
sequence distribution in the context of block polymer self-as-
sembly.
butions. The backbones are drawn in the fully extended limit for
ease of visualization, and the side chain conformations and
cross-sectional radii are depicted as anticipated by existing the-
ory.5,44-46
BP-1 was synthesized by first copolymerizing PDMS and
endo,exo-norbornenyl dimethylester (dx-DMeE, 1a) in a 1:1
feed ratio. Since r1 = 1.1 and r2 = 0.94, the first block has an
ideal random backbone sequence and therefore uniform side
chain distribution. After complete consumption of PDMS and
dx-DMeE, the chain ends were still living, and the second block
(B) was added via a 1:1 mixture of PS and endo,exo-nor-
bornenyl di-n-butylester (dx-DnBuE, 1d). Since r1 = 0.80 and r2
= 1.2, the side chain distribution in the second block is also ef-
fectively uniform. A graft polymer with a gradient side chain
distribution (BP-2) was synthesized by keeping all conditions
exactly the same but simply switching the diluents. The first
block (A) was synthesized by copolymerizing PDMS with dx-
DnBuE instead of dx-DMeE; since r1 = 1.1 and r2 = 0.43, the
block is rich in the macromonomer at early conversions and rich
in the diluent at late conversions. Addition of PS + dx-DMeE as
the second block (B; r1 = 0.54, r2 = 1.4) therefore produces a
block polymer with low grafting density at the block-block
junction and increasing grafting density moving toward the free
chain ends. A third distinct graft block polymer (BP-3) was syn-
thesized by keeping all conditions exactly the same as those for
BP-2 but simply switching the order in which the blocks were
added. By polymerizing block B (PS + dx-DMeE) first and
block A (PDMS + dx-DnBuE) second, the product features the
inverse-tapered architecture compared to BP-2. Figure S13 pro-
vides the chemical structures of BP-1, -2, and -3. Analysis by
SEC (Figure S14) and 1H NMR (Figure S15) confirms that their
overall molecular weights and chemical compositions are iden-
tical.
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Figure 10. Reactivity ratio map. The copolymerization kinetics
studied for PLA, PDMS, and PS are interpreted in terms of the
quotient r1/r2, plotted on the x-axis. For ease of visualization, the
simulated structures show fully extended side chains and back-
bones.
Physical Consequences. Grafting density and graft distri-
bution are important parameters that govern polymer architec-
tures and physical properties. Grafting-through ring-opening
metathesis copolymerization has recently been exploited to
study how grafting density affects the scaling of the block pol-
ymer lamellar period.78 In the final section of this report, we will
further demonstrate the utility of the ROMP method by describ-
ing the synthesis of AB diblock polymers with variable side
chain distributions, then examine how differences in chain con-
nectivity affect self-assembly.
Three different AB graft diblock polymers were synthesized
by controlled ROMP. Simple substitutions of the discrete co-
monomers ensure that the block polymers differ only in the dis-
tribution of the grafts. All other aspects of the structure and
chemistry are identical:

All block polymers feature PDMS and PS side chains. The
grafting-through approach guarantees that the side chain
molecular weights are the same within each block (PDMS:
1280 g mol−1, PS: 3990 g mol−1).


The grafting density in each block is 50%.
The backbone degree of polymerization in each block is
the same. For the A block (PDMS + diluent), Nbb,A = 150;
for the B block (PS + diluent), Nbb,B = 50.
Figure 11. (A) Illustrations of three AB graft diblock polymers,
differing only in the side chain distribution: uniform (BP-1), gradi-
ent (BP-2), and inverse-gradient (BP-3). The horizontal dotted line
indicates the junction between blocks. (B) SAXS patterns corre-
sponding to the annealed block polymers: (i) BP-1, (ii) BP-2, (iii)
BP-3. The white “x” indicates the first-order diffraction peak, q*.

The above constraints enforce equal block volume frac-
tions for all three block polymers: f = 0.50.
The side chain distributions can be varied while fixing all of
the preceding parameters by switching the identity of the dilu-
ents in each block. Figure 11A illustrates the resulting architec-
The three graft block polymers were annealed for 24 hours
at 140 °C under vacuum and modest applied pressure. The re-
sulting microphase-separated structures were characterized by
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synchrotron-source small-angle X-ray scattering (SAXS). important design parameter, allowing materials to possess non-
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Comparison of the SAXS patterns (Figure 11B) indicates that
all three samples form long-range-ordered lamellar morpholo-
gies but also reveals two crucial differences. First, the lamellar
periods (d* = 2π/q*) differ. Equal values of d* are perhaps ex-
pected since the chemical compositions and backbone and side
chain lengths are all identical; on the contrary, BP-1 exhibits d*
= 51.0 nm (Figure 11B.i), while BP-2 (11B.ii) and BP-3
(11B.iii) exhibit d* = 49.5 and 46.5 nm, respectively. Second,
the relative thicknesses of the A and B domains (dA and dB) also
differ. Compared to BP-1, BP-2 forms more symmetric lamel-
lae, as evidenced by the weak intensities of the even-order dif-
fraction peaks (q2, q4, …). The inverse-gradient BP-3 forms la-
mellae that are the most symmetric of all; in fact, the complete
extinction of even-order peaks suggests that dA and dB are equal.
equilibrium density distributions.
CONCLUSION
Grafting-through ring-opening metathesis polymerization
(ROMP) provides a versatile strategy for the design and synthe-
sis of polymers with tailored side chain distributions. Con-
trolled copolymerization of an ω-norbornenyl macromonomer
and a discrete norbornenyl diluent constructs graft architectures
through the backbone; as a result, the backbone sequence di-
rectly dictates the side chain distribution. Since tuning the back-
bone sequence requires changing the relative reactivity of the
co-monomers, we first investigated steric and electronic effects
on the homopolymerization kinetics of 23 diluents. Varying the
stereochemistry, anchor groups, and substituents varies the ho-
mopolymerization rate constants over two orders of magnitude
(0.36 M−1 s−1 ≤ khomo ≤ 82 M−1 s−1), reflecting a wide scope of
monomer reactivity. These small-molecule monomers can be
readily prepared and diversified, providing a convenient library
for future development. In order to provide further guidance, we
identified rate trends and studied their origins through comple-
mentary mechanistic studies. Density functional theory (DFT)
calculations suggest that formation of a Ru–O six-membered
chelate (which sequesters the catalyst in an unproductive form)
is significantly different for endo and exo isomers. Future stud-
ies will expand our understanding of the ROMP mechanism for
both diluents and macromonomers. Other factors that could af-
fect the ROMP kinetics, including for example solvent quality
and additives, will also be explored.
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This symmetry is perhaps surprising: although the block
volume fractions are equal (f = 0.50), the backbone lengths are
highly asymmetric: Nbb,A = 3Nbb,B. The graft polymer backbones
are clearly not fully extended as illustrated in Figure 11A. If the
backbone were fully extended, dA = 3dB is expected for all sam-
ples (Figure 12A). Every fourth diffraction peak (q4, q8, …)
would be weak, which is inconsistent with the SAXS data. In-
stead, the SAXS data indicates that the backbones are flexible
and that changing the side chain distribution affects the back-
bone conformation. Gradient distributions in which the grafting
density is either lowest (BP-2) or highest (BP-3) at the block-
block junction enable more efficient packing than uniform dis-
tributions (BP-1). Closer packing balances the backbone asym-
metry with the demands of equal block volumes, most likely via
bending of the A (PDMS) block backbone (Figure 12B).
Building on these results, we studied the copolymerization
kinetics of selected diluents and a poly(D,L-lactide) (PLA), pol-
ydimethylsiloxane (PDMS), or polystyrene (PS) macromono-
1
mer. The co-monomer concentrations were monitored by H
NMR, and the cross-propagation rate constants were calculated
by non-linear least squares regression based on the Mayo-Lewis
terminal model. Trends involving the measured self-propaga-
tion rate constants and the calculated reactivity ratios (r1 and r2)
were identified. In general, for the 26 co-monomer pairs stud-
ied, the greater the difference between homopolymerization
rates, the greater the gradient tendency (r1/r2 >> 1 or r1/r2 << 1).
The backbone sequence – and therefore the polymer architec-
ture – can be tailored simply by choosing the appropriate diluent
among the library introduced herein or by designing an appro-
priate monomer. We note that, at present, de novo prediction of
the reactivity ratios from the macromonomer and diluent chem-
ical structures is not possible. However, we anticipate that the
versatility of this design strategy, coupled with the broad func-
tional group tolerance of ROMP and its living character, should
enable the design and synthesis of graft polymers with almost
any desired graft chemistry and graft distribution.
Figure 12. Schematic illustration of the relationships between
chain dimensions and the lamellar period. (A) dA ≈ 3dB is expected
if the backbones are fully stretched (since Nbb,A = 3Nbb,B), but it is
consistent with SAXS data. (B) Instead, dA ≈ dB is observed. This
requires bending of the A block backbone. (C) Illustration of BP-3
and revised chain conformations.
For all samples, the backbones should be strongly stretched
at the domain interface as a consequence of segregation. In the
case of BP-2, the chains should have the highest local backbone
stiffness but also the greatest free volume at the free chain ends.
Compared to the uniformly grafted BP-1, this may better ac-
commodate high grafting density in the center of the domains.
In the case of BP-3, since the backbones are already strongly
stretched at the domain interfaces, the high grafting density may
not significantly stretch the backbones further, resulting in the
smallest d* among all three graft polymers. Low grafting den-
sity at the free chain ends should result in comparatively low
backbone stiffness and therefore better accommodate bending
in the A block (Figure 12C). Collectively, these results indicate
that the side chain distribution affects chain stretching and pack-
ing. This result indicates that molecular “shape” is indeed an
We further demonstrated the ease and versatility of this ap-
proach by synthesizing three AB graft diblock polymers that
differ only in the distribution of side chains along the backbone.
Analysis of the annealed, microphase-separated structures by
small-angle X-ray scattering (SAXS) indicated that the graft
block polymers all formed long-range-ordered lamellar struc-
tures. Differences in the lamellar periods and domain thick-
nesses reflect changes in the chain conformations. These results
demonstrate the physical consequences of varying the side
chain distribution. Ultimately, the design strategy outlined
herein provides extensive customizability in terms of polymer
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(16) Jeong, S. H.; Kim, J. M.; Baig, C. Macromolecules 2017, 50,
4491–4500.
(17) Liberman-Martin, A. L.; Chu, C. K.; Grubbs, R. H. Macromol.
Rapid Commun. 2017, 38, 1700058.
(18) Runge, M. B.; Bowden, N. B. J. Am. Chem. Soc. 2007, 129,
10551–10560.
(19) Sveinbjörnsson, B. R.; Weitekamp, R. A.; Miyake, G. M.; Xia,
Y.; Atwater, H. A.; Grubbs, R. H. Proc. Natl. Acad. Sci. U.S.A. 2012,
109, 14332–14336.
(20) Qiu, L. Y.; Bae, Y. H. Biomaterials 2007, 28, 4132–4142.
(21) Johnson, J. A.; Lu, Y. Y.; Burts, A. O.; Lim, Y.-H.; Finn, M.
G.; Koberstein, J. T.; Turro, N. J.; Tirrell, D. A.; Grubbs, R. H. J. Am.
Chem. Soc. 2011, 133, 559–566.
(22) Bhattarai, N.; Ramay, H. R.; Gunn, J.; Matsen, F. A.; Zhang,
M. J. Control. Release 2005, 103, 609–624.
(23) Bates, C. M.; Chang, A. B.; Momčilović, N.; Jones, S. C.;
Grubbs, R. H. Macromolecules 2015, 48, 4967–4973.
(24) Bates, C. M.; Chang, A. B.; Schulze, M. W.; Momčilović, N.;
Jones, S. C.; Grubbs, R. H. J. Polym. Sci., Part B: Polym. Phys. 2016,
54, 292–300.
(25) Jiang, F.; Wang, Z.; Qiao, Y.; Wang, Z.; Tang, C. Macromol-
ecules 2013, 46, 4772–4780.
(26) Zhang, J.; Schneiderman, D. K.; Li, T.; Hillmyer, M. A.; Bates,
F. S. Macromolecules 2016, 49, 9108–9118.
(27) Ma, H.; Wang, Q.; Sang, W.; Han, L.; Liu, P.; Chen, J.; Li, Y.;
Wang, Y. Macromol. Rapid Commun. 2015, 36, 726–732.
(28) Prudnikova, K.; Yucha, R. W.; Patel, P.; Kriete, A. S.; Han, L.;
Penn, L. S.; Marcolongo, M. S. Biomacromolecules 2017, 18, 1713–
1723.
(29) Noel, A.; Borguet, Y. P.; Wooley, K. L. ACS Macro Lett. 2015,
4, 645–650.
(30) Wang, Q.; Ma, H.; Sang, W.; Han, L.; Liu, P.; Shen, H.; Huang,
W.; Gong, X.; Yang, L.; Wang, Y.; Li, Y. Polym. Chem. 2016, 7, 3090–
3099.
(31) Grubbs, R. B.; Hawker, C. J.; Dao, J.; Fréchet, J. M. J. Angew.
Chem., Int. Ed. 1997, 36, 270–272.
(32) Shinoda, H.; Matyjaszewski, K. Macromolecules 2001, 34,
6243–6248.
(33) Börner, H. G.; Duran, D.; Matyjaszewski, K.; da Silva, M.;
Sheiko, S. S. Macromolecules 2002, 35, 3387–3394.
(34) Lee, H.-i.; Matyjaszewski, K.; Yu, S.; Sheiko, S. S. Macromol-
ecules 2005, 38, 8264–8271.
(35) Sutthasupa, S.; Shiotsuki, M.; Sanda, F. Polym. J. 2010, 42,
905–915.
(36) Bielawski, C. W.; Grubbs, R. H. Prog. Polym. Sci. 2007, 32,
1–29.
(37) Leitgeb, A.; Wappel, J.; Slugovc, C. Polymer 2010, 51, 2927–
2946.
(38) Lin, T.-P.; Chang, A. B.; Chen, H.-Y.; Liberman-Martin, A. L.;
Bates, C. M.; Voegtle, M. J.; Bauer, C. A.; Grubbs, R. H. J. Am. Chem.
Soc. 2017, 139, 3896–3903.
(39) Zhang, B.; Gröhn, F.; Pedersen, J. S.; Fischer, K.; Schmidt, M.
Macromolecules 2006, 39, 8440–8450.
(40) Sheiko, S. S.; Sumerlin, B. S.; Matyjaszewski, K. Prog. Polym.
Sci. 2008, 33, 759–785.
(41) Zhang, M.; Müller, A. H. E. J. Polym. Sci., Part A: Polym.
Chem. 2005, 43, 3461–3481.
(42) Lee, H.-i.; Pietrasik, J.; Sheiko, S. S.; Matyjaszewski, K. Prog.
Polym. Sci. 2010, 35, 24–44.
(43) Peng, S.; Bhushan, B. RSC Advances 2012, 2, 8557–8578.
(44) Pesek, S. L.; Li, X.; Hammouda, B.; Hong, K.; Verduzco, R.
Macromolecules 2013, 46, 6998–7005.
(45) Pesek, S. L.; Xiang, Q.; Hammouda, B.; Verduzco, R. J. Polym.
Sci., Part B: Polym. Phys. 2017, 55, 104–111.
(46) Gerle, M.; Fischer, K.; Roos, S.; Müller, A. H. E.; Schmidt,
M.; Sheiko, S. S.; Prokhorova, S.; Möller, M. Macromolecules 1999,
32, 2629–2637.
structure and functionality, illuminating new opportunities for
molecular and materials design.
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ASSOCIATED CONTENT
Supporting Information
Monomer synthesis and characterization information, kinetic anal-
ysis, compiled rate constants and reactivity ratios. This material is
available free of charge via the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
Corresponding Author
*rhg@caltech.edu
Author Contributions
‡A.B.C. and T.-P.L. contributed equally to this work.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENT
This work was supported by the Department of Energy under award
number DE-AR0000683 (ARPA-E Program) and by the National
Science Foundation under award number CHE-1502616. A.B.C.
thanks the U.S. Department of Defense for support through the
NDSEG Fellowship. A.L.L.-M. thanks the Resnick Sustainability
Institute at Caltech for fellowship support. The authors thank Prof.
J. C. Peters for access to computational resources. This research
used resources of the Advanced Photon Source, a US Department
of Energy Office of Science User Facility operated by Argonne Na-
tional Laboratory under Contract DE-AC02-06CH11357.
REFERENCES
(1) Hadjichristidis, N.; Pitsikalis, M.; Pispas, S.; Iatrou, H. Chem.
Rev. 2001, 101, 3747–3792.
(2) Polymeropoulos, G.; Zapsas, G.; Ntetsikas, K.; Bilalis, P.;
Gnanou, Y.; Hadjichristidis, N. Macromolecules 2017, 50, 1253–1290.
(3) Bates, C. M.; Bates, F. S. Macromolecules 2016, 50, 3–22.
(4) Matyjaszewski, K.; Tsarevsky, N. V. Nature Chem. 2009, 1,
276–288.
(5) Kikuchi, M.; Nakano, R.; Jinbo, Y.; Saito, Y.; Ohno, S.; To-
gashi, D.; Enomoto, K.; Narumi, A.; Haba, O.; Kawaguchi, S. Macro-
molecules 2015, 48, 5878–5886.
(6) Liang, H.; Cao, Z.; Wang, Z.; Sheiko, S. S.; Dobrynin, A. V.
Macromolecules 2017, 50, 3430–3437.
(7) Paturej, J.; Sheiko, S. S.; Panyukov, S.; Rubinstein, M. Sci. Adv.
2016, 2, e1601478.
(8) Rathgeber, S.; Pakula, T.; Wilk, A.; Matyjaszewski, K.; Beers,
K. L. J. Chem. Phys. 2005, 122, 124904.
(9) Abbasi, M.; Faust, L.; Riazi, K.; Wilhelm, M. Macromolecules
2017, 50, 5964–5977.
(10) Dalsin, S. J.; Hillmyer, M. A.; Bates, F. S. Macromolecules
2015, 48, 4680–4691.
(11) Hu, M.; Xia, Y.; McKenna, G. B.; Kornfield, J. A.; Grubbs, R.
H. Macromolecules 2011, 44, 6935–6943.
(12) Daniel, W. F. M.; Burdynska, J.; Vatankhah-Varnoosfaderani,
M.; Matyjaszewski, K.; Paturej, J.; Rubinstein, M.; Dobrynin, A. V.;
Sheiko, S. S. Nat. Mater. 2016, 15, 183–189.
(13) Mai, D. J.; Marciel, A. B.; Sing, C. E.; Schroeder, C. M. ACS
Macro Lett. 2015, 4, 446–452.
(14) Kapnistos, M.; Kirkwood, K. M.; Ramirez, J.; Vlassopoulos,
D.; Leal, L. G. J. Rheol. 2009, 53, 1133–1153.
(15) Read, D. J.; Auhl, D.; Das, C.; den Doelder, J.; Kapnistos, M.;
Vittorias, I.; McLeish, T. C. B. Science 2011, 333, 1871–1874.
(47) Dettmer, C. M.; Gray, M. K.; Torkelson, J. M.; Nguyen, S. T.
Macromolecules 2004, 37, 5504–5512.
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Journal of the American Chemical Society
(48) Matyjaszewski, K.; Ziegler, M. J.; Arehart, S. V.; Greszta, D.;
Pakula, T. J. Phys. Org. Chem. 2000, 13, 775–786.
(49) Sun, X.; Luo, Y.; Wang, R.; Li, B. G.; Zhu, S. AIChE J. 2008,
54, 1073–1087.
(50) Wang, R.; Luo, Y.; Li, B.-G.; Zhu, S. AIChE J. 2007, 53, 174–
186.
(51) Radzinski, S. C.; Foster, J. C.; Scannelli, S. J.; Weaver, J. R.;
Arrington, K. J.; Matson, J. B. ACS Macro Lett. 2017, 6, 1175-1179.
(52) Grubbs, R. H.; Khosravi, E.: Handbook of Metathesis: Polymer
Synthesis; Wiley, 2015.
(53) Moatsou, D.; Hansell, C. F.; O'Reilly, R. K. Chem. Sci. 2014,
5, 2246–2250.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(54) Slugovc, C.; Demel, S.; Riegler, S.; Hobisch, J.; Stelzer, F.
Macromol. Rapid Commun. 2004, 25, 475–480.
(55) Radzinski, S. C.; Foster, J. C.; Chapleski, R. C.; Troya, D.;
Matson, J. B. J. Am. Chem. Soc. 2016, 138, 6998–7004.
(56) Rosso, V. W.; Lust, D. A.; Bernot, P. J.; Grosso, J. A.; Modi,
S. P.; Rusowicz, A.; Sedergran, T. C.; Simpson, J. H.; Srivastava, S.
K.; Humora, M. J.; Anderson, N. G. Org. Process Res. Dev. 1997, 1,
311–314.
(57) Xia, Y.; Kornfield, J. A.; Grubbs, R. H. Macromolecules 2009,
42, 3761–3766.
(58) Miyake, G. M.; Weitekamp, R. A.; Piunova, V. A.; Grubbs, R.
H. J. Am. Chem. Soc. 2012, 134, 14249–14254.
(59) Radzinski, S. C.; Foster, J. C.; Matson, J. B. Polym. Chem.
2015, 6, 5643–5652.
(60) Wolfe, P. S.; Wagener, K. B. Macromolecules 1999, 32, 7961–
7967.
(61) Rule, J. D.; Moore, J. S. Macromolecules 2002, 35, 7878–7882.
(62) Pollino, J. M.; Stubbs, L. P.; Weck, M. Macromolecules 2003,
36, 2230–2234.
(63) Seehof, N.; Grutke, S.; Risse, W. Macromolecules 1993, 26,
695–700.
(64) Liu, P.; Taylor, B. L. H.; Garcia-Lopez, J.; Houk, K. N.: Com-
putational Studies of Ruthenium-Catalyzed Olefin Metathesis. In
Handbook of Metathesis; Wiley-VCH Verlag GmbH & Co. KGaA,
2015; pp 199–252.
(65) Sanford, M. S.; Love, J. A.; Grubbs, R. H. J. Am. Chem. Soc.
2001, 123, 6543–6554.
(66) Adlhart, C.; Chen, P. J. Am. Chem. Soc. 2004, 126, 3496–3510.
(67) Vyboishchikov, S. F.; Bühl, M.; Thiel, W. Chem. Eur. J. 2002,
8, 3962–3975.
(68) Walsh, D. J.; Lau, S. H.; Hyatt, M. G.; Guironnet, D. J. Am.
Chem. Soc. 2017, 139, 13644–13647.
(69) See SI for the full derivation. We could not exclude the possi-
bility that cycloaddition is the rate-limiting step, which would result in
a more complicated rate expression.
(70) Further discussion of the ROMP mechanism can be found in
the SI. We note that, at present, we cannot conclusively rule out the
stepwise or concerted associative/dissociative pathway.
(71) Fürstner, A.; Thiel, O. R.; Lehmann, C. W. Organometallics
2002, 21, 331–335.
(72) Benitez, D.; Tkatchouk, E.; Goddard, W. A. Organometallics
2009, 28, 2643–2645.
(73) In-depth DFT investigation of the ROMP mechanism, includ-
ing calculation of transition-state structures and identification of the
rate-limiting step, will be the subject of future work.
(74) Mayo, F. R.; Lewis, F. M. J. Am. Chem. Soc. 1944, 66, 1594–
1601.
(75) In order to account for pyridine binding, it is critical to use the
same [G3]0 concentration in both homo- and copolymerization reac-
tions. Further details can be found in the preceding section and SI.
(76) Odian, G.: Principles of Polymerization; 4th ed.; Wiley-Inter-
science: Hoboken, New Jersey, 2004.
(77) Meijs, G. F.; Rizzardo, E. J. Macromol. Sci., Polym. Rev. 1990,
30, 305–377.
(78) Lin, T.-P.; Chang, A. B.; Luo, S.-X.; Chen, H.-Y.; Lee, B.;
Grubbs, R. H. ACS Nano 2017, Article ASAP, DOI:
10.1021/acsnano.7b06664.
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Figure 1. Grafting-through ROMP of a small-molecule diluent (white) and a macromonomer (black). Since
the side chains (red) are connected to certain backbone units, control over the backbone sequence directly
determines the side chain distribution: (A) uniform, (B) gradient, etc. The anticipated average cross-
sectional radius of gyration (Rc) is indicated. For ease of visualization, chains are illustrated in the limit of
fully extended backbones.
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Chart 1. Monomer design for ring-opening metathesis copolymerization.
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Figure 2. Homopolymerization rate constants (khomo) for substituted endo,exo-norbornenyl diester
monomers (left to right: 1a–j). khomo decreases with increasing steric bulk (R = Me to tBu, 1a–f). khomo does
not change significantly with electronic changes via fluorination (1g) or para-substitution of a phenyl ring
(1h–j).
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Figure 3. (A) Homopolymerization rate constants (khomo) for monomers with exo,exo-diester (xx, green),
endo,exo-diester (dx, red), and endo,endo-diester (dd, yellow) anchor groups. Comparison of khomo for
monomers with R = Me, Et, nPr, and nBu supports the steric influences of stereochemistry and substituent
size. (B) khomo for Me- and nBu-substituted monomers with each of the five anchor groups; endo-imide (d-I,
blue) and exo-imide (x-I, purple).
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Figure 4. Plot of khomo values for all monomers studied herein. The monomers are sorted according to their
anchor groups: left to right: endo,exo-diester (red, 1a–j), endo,endo-diester (yellow, 2a–d), exo,exo-
diester (green, 3a–d), endo-imide (blue, 4a–c), and exo-imide (purple, 5a–c and macromonomers). khomo
values for methyl-substituted monomers are provided for comparison.
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Figure 5. (A) Proposed dissociative ROMP pathway for G3. (B) DFT-calculated free energy diagram
corresponding to one ROMP cycle for endo- (2a, blue) and exo-substituted (3a, red) norbornenyl
monomers. The following intermediates were calculated: (a) six-membered Ru–O chelate, (b) 14-electron
vacant species, (c) olefin adduct, and (d) metallacyclobutane.
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Figure 6. Propagation reactions for the copolymerization of a discrete diluent (M2, dx-DE shown for
example) and a macromonomer (M1) according to a terminal model. M2* and M1* are the corresponding
propagating alkylidene species. (A) Diluent self-propagation (k22), (B) cross-propagation (k21), (C)
macromonomer self-propagation (k11), (D) cross-propagation (k12).
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Figure 7. (A) Copolymerization scheme: the same macromonomer (PLA, M1) was copolymerized with 13
different diluents (M2). The feed ratio (x/y = 1) and total backbone length (x + y = 200) were fixed. (B) M2
arranged in order of increasing k22. (C) PLA/diluent copolymerization data. Left axis, black: self-propagation
rate constants (k22: filled circles, k11: open circles). Right axis, red: reactivity ratios (r2: solid line, r1: dotted
line).
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Figure 8. Simulated sequences and (inset) graft polymer architectures for the copolymerization of PLA with
different diluents: (A) 4a, (B) 1a, or (C) 5a. For ease of visualization, the simulated structures show fully
extended side chains and backbones.
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Figure 9. Data for the copolymerization of M1 = PDMS (left) or PS (right) with different diluents. Left axis,
black: self-propagation rate constants (k22: filled circles, k11: open circles). Right axis, red: reactivity ratios
(r2: solid line, r1: dotted line).
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Figure 10. Reactivity ratio map. The copolymerization kinetics studied for PLA, PDMS, and PS are
interpreted in terms of the quotient r1/r2, plotted on the x-axis. For ease of visualization, the simulated
structures show fully extended side chains and backbones.
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Figure 11. (A) Illustrations of three AB graft diblock polymers, differing only in the side chain distribution:
uniform (BP-1), gradient (BP-2), and inverse-gradient (BP-3). The horizontal dotted line indicates the
junction between blocks. (B) SAXS patterns corresponding to the annealed block polymers: (i) BP-1, (ii)
BP-2, (iii) BP-3. The white “x” indicates the first-order diffraction peak, q*.
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Journal of the American Chemical Society
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Figure 12. Schematic illustration of the relationships between chain dimensions and the lamellar period. (A)
dA ≈ 3dB is expected if the backbones are fully stretched (since Nbb,A = 3Nbb,B), but it is consistent with SAXS
data. (B) Instead, dA ≈ dB is observed. This requires bending of the A block backbone. (C) Illustration of BP-
3 and revised chain conformations.
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