Kolibaba_Capstone_Final

Kolibaba Capstone CHEM 499 Spring 2016
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Investigation of the phase behavior of a novel diblock copolymer electrolyte
system with potential applications in lithium-ion batteries by atomic force
microscopy
Thomas J. Kolibaba,
Pacific Lutheran University
Draft: 4/18/2016 AD
Abstract
Solid polymer electrolytes offer the possibility of combatting some of the safety issues
inherent in current lithium-ion batteries. However, in current polymer electrolytes, ionic
conductivity is directly tied to segmental rearrangement of the polymer backbone. A variety of
novel oligo(ethylene oxide) grafted diblock copolymers with bulky backbones were synthesized
from basic building blocks and characterized for use as solid polymer electrolytes which can
decouple ionic conductivity from local segmental dynamics. The phase behavior of these
systems was studied by atomic force microscopy and appears to deviate substantially from
standard theoretical random coil – random coil diblock systems. This deviation is believed to be
due to a conformational asymmetry in the two blocks studied this system, with this effect
seeming to be exaggerated as the oligo(ethylene oxide) sidechain lengths increase.
Background
Lithium-ion batteries are ubiquitous in our modern world: cell phones, laptops, even
some cars have lithium-ion batteries at their core. These batteries have even been discussed as a
possible solution to long-term storage of renewable wind or solar energy. However, the current
design of the lithium-ion battery is not without fault, as recent high profile failures like the
problems of Boeing’s 787 Dreamliner, exploding “hoverboards”, and flaming Tesla electric cars
have shown the world that lithium-ion batteries have several as of yet unsolved issues.
Chief among the potential hazards of current lithium-ion batteries is the fact that the
electrolytes currently used are flammable organic carbonates, such as ethylene, propylene, or
dimethyl carbonate. These organic carbonates (Fig. 1) are excellent electrolytes because they
have a low viscosity, allowing for fast lithium ion diffusion and as a result, greater ionic
conductivity.1
Finally, these organic carbonates are highly flammable with flashpoints around 30

2
°C, barely above room temperature.1
A leak of these flammable carbonates has been suspected as
playing part in the recent battery fires on the Boeing 787. Another hazard that goes along with
lithium-ion, and particularly lithium-metal, batteries is the formation of lithium dendrites. These
dendrites, which are essentially solid metal spikes of lithium, can connect the two terminals of
the battery and cause a short circuit.1
A short circuit within a flammable organic solvent can, and
of course often does, cause fires.
Some potential solutions to the battery issue have come from applying polymer
technologies to the battery electrolyte. However, the main polymer that has been utilized thus
far, poly(ethylene oxide) (PEO) has an issue in that it crystallizes below 60 °C. Since the
lithium-ion conductance is tied to the local segmental dynamics of the polymer, ionic
conductivity plummets when the polymer crystallizes and segmental motion all but ceases.1,2
Furthermore, PEO is a liquid when it’s not crystallized, meaning it can still leak out of a broken
cell. In addition, it has no ability to resist the growth of lithium dendrites, and like organic
carbonates, PEO is flammable. As a result, there is extreme interest in the idea of solid polymer
electrolytes (SPEs).
Diblock copolymer SPEs composed of a conductive block and a high-modulus block have
shown some promise in combatting many of the issues described above. First of all, these
polymers are solids, which means that they would not spill out of an electrochemical cell even if
something were to occur to compromise the cell’s integrity. The Balsara group has also
demonstrated that diblock copolymers of PEO and polystyrene (Fig. 2), due to the high modulus
of the poly(styrene) block, are able to suppress lithium dendrite formation through multiple
cycles of the battery, removing one of the primary safety concerns.3
The diblock copolymers are
able to reduce the formation of lithium dendrites because of the self-organization that diblock
Figure 1: From left to right - dimethyl, ethylene, and propylene
carbonates as well as poly(ethylene oxide).

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copolymers have long been known to undergo.4
This microphase separation creates stiff, high
modulus structural regions that block the dendrite for mation, while simultaneously forming
conductive PEO channels for lithium ions to travel though, leading to a minimal loss in ionic
conductivity.5
Furthermore, polymers have generally low toxicity as compared to small
molecules, making them favorable over other more dangerous electrolyte alternatives.1
The Waldow research group has successfully synthesized a series of dicarboximide
functionalized oxanorbornyl diblock copolymers with lithium-ion conductive oligo(ethylene
oxide) sidechains (Fig. 3). Preliminary experiments have shown that the long-sidechain
homopolymer versions of this system (x=1, y=0, n ≥8) have ionic conductivity that is
competitive with pure PEO, without the possibility of crystallization occurring. Furthermore, due
to the bulky nature of the backbone, these polymers present the possibility of separating ionic
conductivity from segmental motion. In addition, due to the oligomeric length of the sidechain,
this system could maintain many of the advantages of small molecule electrolyte systems, since
they are free to move without backbone rearrangement. Importantly, these polymers have the
advantage of being synthetically easy to produce, since they are synthesized by the ring-opening
metathesis polymerization instead of by more challenging anionic means.6
Furthermore, the
ethylene oxide sidechain length is easily tunable, making a diblock system that incorporates it a
versatile platform for modification.
Figure 2: Poly(styrene)-block-(ethylene oxide), an example of a solid
polymer electrolyte.

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Like other diblock copolymers, this system undergoes microphase separation at
sufficiently high molecular weights, with the structures formed being a function of mass fraction
of each monomer and the overall degree of polymerization (N, the number of monomer units per
chain, which is thus proportional to the polymer molecular weight). This microphase separation
can be described by a phase diagram (Fig. 4) in order to predict the nanomorphology of a
polymer at a given molecular weight and composition.4
Figure 3: Novel dicarboximide functionalized oxanorbornyl diblock
copolymers with applications as SPEs. The x and y parameters refer to
the relative fraction of each monomer, and n refers to the number of
ethylene oxide units in the sidechain.

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In order to design optimal nanostructured lithium-ion battery electrolyte supports, the
nanomorphologies of the microphase separated diblock copolymers must be predictable, and the
obtained morphology must be such that it will not inhibit ionic conductivity (either gyroid or
lamellar) while providing the structural support necessary to prevent lithium dendritic growth.5
However, the phase diagram in (Fig. 4) is only theoretical, and most polymer systems deviate
from this phase diagram to a greater or lesser extent. As a result, knowledge of the specific phase
behavior of a diblock system must be probed and understood in order to take advantage of any
Figure 4:
a) Theoretical phase diagram for a random coil – random coil diblock
copolymer generated by Bates and Fredrickson.4
χ is the Flory-Huggins
interaction parameter, and N is the overall polymer degree of
polymerization. The x-axis is the volume fraction of one of the two
blocks.
b) Schematics of the phase formed as the volume fraction of the second
block (depicted as the black area) is increased relative to the volume
fraction of the primary block (depicted in red). Phases progress from
body centered cubic to hexagonally packed cylinders to bicontinuous
gyroid to lamellae.
a)
b)

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preferable nanomorphologies. Therefore, the phase diagram of novel dicarboximide
functionalized oxanorbornyl diblock copolymers with oligo(ethylene oxide) sidechains of
varying lengths was investigated by atomic force microscopy to determine this system’s phase
diagram in order to generate nanostructured battery electrolyte supports.
Materials and Methods
Materials:
Furan (99 %), N-phenyl maleimide (98 %), p-toluene sulfonyl chloride (99 %), ethyl
vinyl ether (98 %), cesium carbonate (98%), and n-ethylene glycol monomethyl ethers (n=2, 3,
98 %) were purchased from TCI-America. Diethyl ether (99 %), n=8 polyetheylene glycol
monomethyl ether (Mn= 350 kDa), lithium bistrifluoromethylsulfonimide (99%), hexanes (99
%), acetonitrile (99.8 %), methanol (99 %) and ethyl acetate (99 %) were purchased from Sigma
Aldrich. Dichloromethane (99%) was purchased from Fisher Chemical. Maleimide was
purchased from Oakwood Chemical. Grubbs GII catalyst was purchased from Materia Chemical.
CDCl3 and DMSO-d6 (99.8 D%) were purchased from Cambridge Isotope Laboratories. All
compounds used without further purification. Coverslips for AFM were Fisher’s Finest Glass
Coverslips and were mounted onto Fisher’s Finest Microscope Slides with Loctite Superglue.
AFM experiments were performed using Budget Sensors Tap300AI-G cantilevers with a
resonant frequency around 265 kHz.
Instruments:
Flash Chromatography was done via a Combiflash Redisep Rf instrument with 38-39 g
columns filled with Sorbitech silica gel loaded at 2 g theoretical yield/40 g silica. NMR
experiments were carried out in a Bruker 500 MHz NMR Spectrometer in CDCl3 or DMSO-d6
purchased from Cambridge Isotope Laboratories. Gel Permeation Chromatography experiments
were performed using a Polymer Laboratories PL-GPC 50 Plus with polystyrene reference
standards run in THF. AFM experiments were performed with an Asylum Research MFP-3D
atomic force microscope in tapping mode.

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Synthesis of exo-4-Aza-10-oxatricyclo[5.2.1.02,6
]dec-8-ene-3,5-dione (oxanorbornene-
maleimide, ONMI): Maleimide (6.12 g, 63 mmol, 1 equiv) was dissolved in ethyl acetate
(135mL) in a round bottomed flask which was allowed to begin heating in an 80 °C oil bath. As
the solution was heating, furan (18.3 mL, 17.16 g, 252 mmol, 4 equiv) was injected into the
flask, which was then affixed with a reflux condenser. The reaction was allowed to reflux for 5
hours, after which the flask was lifted out of the oil bath and allowed to cool to room
temperature. Very small crystals were allowed to form overnight. These crystals were then
vacuum filtered, rinsed with ethyl acetate, and then allowed to dry. If necessary, the product can
be recrystallized from hot ethyl acetate. 63% yield. 1
H NMR (500 MHz, DMSO-d6): δ 11.16
(1H, s) 6.53 (2H, s), 5.11 (2H, s), 2.85 (2H, s).
Synthesis of exo-4-Aza-10-oxa-4-phenyltricyclo[5.2.1.02,6
]dec-8-ene-3,5-dione (phenyl-
oxanorbornenemaleimide, Ph-ONMI): N-phenylmaleimide (10.91 g, 63 mmol, 1 equiv) was
dissolved in ethyl acetate (135mL) in a round bottomed flask which was allowed to begin
heating in an 80 °C oil bath. As the solution was heating, furan (18.3 mL, 17.16 g, 252 mmol, 4
equiv) was injected into the flask, which was then affixed with a reflux condenser. The reaction

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was allowed to reflux for 5 hours, after which the flask was lifted out of the oil bath and allowed
to cool to room temperature. Very small crystals were allowed to form overnight. These crystals
were then vacuum filtered, rinsed with ethyl acetate, and then allowed to dry. If necessary, the
product can be recrystallized from hot ethyl acetate. 87% yield. 1
H NMR (500 MHz, DMSO-d6):
δ 7.49 (2H, m), 7.42 (1H, m), 7.21 (2H, m), 6.61 (2H, s), 5.26 (2H, s), 3.08 (2H, s).
Synthesis of tosylated monofunctional PEGs: Following the protocol of Kazemi et al.,7
a
mortar was charged with monofunctional poly(etheyle glycol) (130 mmol, 1 equiv) p-toluene
sulfonyl chloride (37.2 g, 195 mmol, 1.5 equiv) and anhydrous potassium carbonate (63 g, 455
mmol, 3.5 equiv) and ground into a homogenous mixture for 5 minutes. Potassium hydroxide
(36.5 g, 650 mmol, 5 equiv) was ground into this paste for 5 minutes, along with a few drops of
isopropanol. The mixture was then transferred to a beaker and washed with 800 mL of diethyl
ether. This solution was then vacuum filtered, dried over magnesium sulfate, and vacuum filtered
again. The final solution was concentrated in vacuum to yield the product as a viscous, amber
oil. 48 % yield. 1
H NMR (500 MHz, CDCl3): d), 7.33 (2H, d), 4.15 (2H, t), 3.68
(Varying H, m), 3.59 (Varying H, m), 3.52 (Varying H, m), 3.36 (3H, s), 2.44 (3H, s).

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Synthesis of exo-4-Aza-4-di/tri/oligo(ethylene oxide)-10-oxatricyclo[5.2.1.02,6
]dec-8-ene-3,5-
dione, (n=2/n=3/n=8 ONMI monomers): ONMI (3.17 g, 19.2 mmol, 1 equiv), cesium
carbonate (12.5 g, 38.9 mmol, 2 equiv), and the appropriate tosylated ether (57.6 mmol, 3 equiv)
were stirred into a round bottomed flask containing 100 mL of acetonitrile. The flask was capped
with a septum and placed in a 55 °C oil bath and allowed to react for 48 hours. The flask’s
contents were vacuum filtered and washed with more acetonitrile. Celite (30 g) was then added
to the filtrate, which was concentrated by rotary evaporation. The resultant solid was split into
three aliquots, which were then purified by flash chromatography (40 g column, 0 – 100 %
EtOAc : Hexane). For the n=8 monomer, flash chromatography was performed utilizing the
same column size, but was run from 100 % EtOAc to 0 % versus a 10 % (v/v) MeOH/CH2Cl2
mixture. The product-containing fractions were again concentrated by rotary evaporation to yield
a viscous, amber oil. 88 % yield. 1
H NMR (500 MHz, CDCl3): δ 6.48 (2H, t), 5.23 (2H, t), 3.73-
3.48 (Varying H, m), 3.34 (3H, s), 2.83 (2H, s).

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Synthesis of Grubbs Generation III Catalyst: (Adapted from Colin Peterson and Doug Smith)
Adapted from procedure by Love, et al.8
To a 20 mL vial, 0.255g Grubb’s Generation II catalyst
and a stir bar were added. The vial was flushed gently with argon and capped with a septum. Via
syringe, 3-bromopyridine (0.3 mL, 10 molar equivalents) was stirred into the solution, turning
the mixture from maroon to dark green. After five minutes of stirring, pentane was layered over
the solution without mixing. The vial was stored in a freezer overnight. The mixture was then
vacuum filtered, and the solid was washed four times with pentane. The resulting green powder
was vacuum-dried overnight and resulted in a 99% yield.
Synthesis of poly(exo-4-Aza-4-oligo(ethylene oxide)-10-oxatricyclo[5.2.1.02,6
]dec-8-ene-3,5-
dione)-block-poly(exo-4-Aza-10-oxa-4-phenyltricyclo[5.2.1.02,6
]dec-8-ene-3,5-dione)
(n=2/3/8 diblock): Grubbs generation III catalyst was placed in an argon-flushed flask and
dissolved in anhydrous dichloromethane (0.5 mL/mg catalyst). The n=2/3/8 ONMI monomer and
Ph-ONMI were each degassed and dissolved in anhydrous dichloromethane (2 mL / gram of EO
monomer, 15 mL/ gram of phenyl monomer) in separate containers. An aliquot of the n=2/3/8
monomer (chosen according to planned mass fraction of the n=2/3/8 block) was then removed
and added into the stirring solution of the Grubbs Generation III catalyst. After 18 minutes
elapsed, a complimentary aliquot of the phenyl monomer was added and allowed to react for 18
more minutes. Following this, ethyl vinyl ether (1800 molar equivalents relative to the catalyst)

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was injected and allowed to stir in the solution for 1 hour. The polymer was then precipitated in
cold stirring methanol (n=2,3) or cold diethyl ether (n=8) and vacuum filtered. The solid product
was dried in a vacuum oven overnight.
Atomic Force Microscopy:
Samples for atomic force microscopy were prepared on coverslips wiped with low-
residue isopropanol. Under a nitrogen atmosphere, 180 µL of a 2% (wt/wt) solution of polymer
was spun cast onto a coverslip (5 s, 500 rpm, followed by 60s 2000 rpm). After mounting via
superglue to a microscope slide, the sample was imaged, and then placed into a 270 mL jar
flushed with argon and wrapped with Teflon tape. After the sample was placed in the jar (leaning
on the side of the jar), 0.5 mL (0.3 mL for polymers where Mn < 30 kDa) of dichloromethane
was introduced into the bottom of the jar and the jar was tightly capped for 60-70 minutes. After
the annealing was complete, the sample was transferred into a vacuum oven as fast as possible
and allowed to dry for at least 10 minutes. The sample was then reimaged for a post- solvent
annealing image.
Samples loaded with LiTFSI for the “salt loading” experiments were prepared by adding
desiccator-dried salt to a vial, into which was then added the vacuum oven dried solid polymer.
Dry dichloromethane was added to the solid mixture to make a 2% (wt/wt) solution with respect
to the dissolved polymer. Samples were otherwise prepared as all of the others from spin coating
onward. Care was taken to perform solvent annealing with dry solvents.
Results and Discussion
Polymers with a wide variety of compositions and molecular weights for the n=2
(meaning two ethylene oxide units on the sidechain of the conductive block), n=3 and n=8 were
successfully synthesized in yields ranging from 60% to 90%. Compositions spanned a range
from 19% EO monomer (wt/wt) to 65%. Furthermore, all polymers for which GPC data has been
acquired had PDI ≤ 1.11 (Tables 1-3). These observations indicate that the living polymerization
went as intended, granting us control over molecular weight and composition of the diblocks as
well as yielding monodisperse products. The molecular weight determined from the GPC data
shows generally much lower molecular weights than were planned by the stoichiometry of the

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polymerization, due to the fact that all GPC data were acquired using only the refractive index
detector rather than light scattering data.
The images that followed the solvent vapor annealing phase of sample preparation
showed samples with much longer range order than their pre-annealing counterparts (Fig. 5).
Furthermore, the nanomorphologies that were observed were almost always the same before and
after annealing. Introduction of solvent vapor merely seemed to help foster and lengthen ordering
that was already present on the surface, and allowed for accurate phase assignments.
The phase diagrams were created solely by the analysis of topographical AFM images.
The phase images of these experiments are not shown, but showed images similar to those from
the topography data, indicating phase assignments matching what was observed via topography
images. It is important to note that in the phase diagrams that are reported in this study, mass
fraction of the EO containing monomer is reported on the x-axis rather than the volume fraction.
n=2 Phase Diagram:
The n=2 diblock system had the largest number of samples to study (Table 1), and as
such, a much more comprehensive phase picture was available (Fig. 6). The diblock system
demonstrated lamellar, cylindrical, and gyroidal phases, as well as a disordered phase. This
phase diagram is somewhat “shifted” towards the EO-containing side, rather than being centered
about fEO = 0.5. However, this could be a consequence of using mass fraction rather than volume
Figure 5: Pre (left) and post (right) solvent vapor annealing AFM
images of a 60% EO n=2 diblock copolymer.

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fraction for the phase diagram. It is important to note that AFM, by nature of being a purely
topographical technique, cannot with certainty distinguish between lamellar and cylindrical
morphologies. This is because what appears lamellar could potentially also be sideways-lying
cylinders. As a result, what are predicted now to be lamellar morphologies are reported as L*
instead of L for the remainder of the paper. Most interestingly, however, is the very large gyroid
phase in this diblock system. All of the phase diagrams have this morphology noted as G*, rather
than G, due to the fact that the phase could also potentially be perforated lamellae. AFM lacks
the ability to resolve the difference between perforated lamellae and gyroid, so the phase cannot
be assigned with much certainty. Either way, the large prevalence of this phase is very abnormal
for most diblock systems.
n=2
%EO (wt/wt)a
Mn (kDa)b
PDI
19% 19 1.03
33% 21 1.04
41% 24 1.02
53% 22 1.03
60% 22 1.03
69% 14 1.01
79% 14 1.38
43% 25 1.01
57% 23 1.02
38% 35 1.02
50% 35 1.05
55% 38 1.03
60% 41 1.03
65% 56 1.09
a: Mass fraction of EO-containing block
b: Molecular weights with respect to PS standards in THF
Table 1: Composition, molecular weight, and dispersity of synthesized
diblocks with 2 EO units on the sidechain.

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n=3 Phase Diagram:
The n=3 diblock system exhibits many of the same trends as the n=2 system, but more
exaggerated. There were slightly fewer samples of this system (Table 2), and they were all of
Figure 6: The phase diagram for the n=2 system, theoretical phase
boundary lines drawn in for easier viewing. Selected images are
representative of the observed structures. 1) 50% EO, 35 kDa gyroidal
diblock, 2) 65% EO, 51 kDa cylindrical structure, 3) 58% EO, 23 kDa
lamellar structure of small domain spacing, and 4) 60% EO, 41 kDa
lamellar structure with much larger domain spacing. Scale bars are all
200 nm.
1 2
1
2
3
4
3
A
4
A

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much higher molecular weight. Due to the larger molecular weights of these samples, none of
them exhibited a disordered phase at room temperature, therefore only the lamellar, cylindrical,
and gyroidal phases were observed in this phase diagram (Fig. 7). The lower phase boundary on
this diagram is purely a guess, and is included only as a visual aid. Once again, this phase
diagram seems to be off-center, and also appears to be “tilted”. Rather than having vertical
symmetry about some composition, the phase diagram as a whole seems to slope towards one
side. Furthermore, the gyroid phase in this system is once again quite large, and dominates a very
large portion of the explored phase space.
n=3
%EO (wt/wt)a
Mn (kDa)b
PDI
42% 35 1.06
42% 38 1.07
41% 56 1.01
54% 41 1.05
53% 58 1.08
54% 74 1.01
58% 47 1.04
65% 60 1.05
65% 71 1.11
a: Mass fraction of EO-containing block
b: Molecular weights with respect to PS standards in THF

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n=8 Phase Diagram:
The n=8 diblock system exhibited a further exaggeration of the trends from the n=2 and
n=3 systems. For this diblock system, there were substantially fewer samples (Table 3), and we
boundary lines drawn in for easier viewing. Selected images are
representative of the observed structures. 1) 42% EO, 38 kDa gyroidal
diblock, 2) 54% EO, 74 kDa gyroidal structure with larger dimensions,
3) 65% EO, 60 kDa cylinder structure, and 4) 58% EO, 47 kDa lamellar
structure. Scale bars are all 200 nm.
1
2
3
4
1 2 4
A
3
A

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were unable to obtain molecular weight characterization. As a result, only planned molecular
weight could be utilized for phase diagram purposes. Once again, no disordered phase was
observed in the phase diagram (Fig. 8), so the lower phase boundary is drawn in purely as a
visual aid. This time, only two phases were observed with some certainty: gyroid and cylinder.
Like other samples, the gyroid phase could not be differentiated from the possibility of a
perforated lamellae phase. Once again the gyroid phase is dominant over the explored phase
space, and a “tilting” of the phase diagram is observed. The ability of these polymers to absorb
water from the air is more of a concern in this system, and could also influence the phase
diagram. Particularly in the 90 kDa/62% EO polymer, what was assigned as being cylinders
could be influence by the formation of worm-like micelles that collapsed upon the removal of
solvent during solvent annealing. The formation of micelles is thought to be at least partially a
result of the long EO sidechain on this polymer. With 8 EO units, the polymer has potential to be
much more “bottlebrush-like” and hygroscopic, leading to the potential formation of micelles in
solution or during solvent annealing. The phase noted with a question mark in the diagram was
so difficult to acquire data on that no phase assignment could be made. This too could be a result
of the high amount of EO in the polymer for this sample, which, when combined with the larger
molecular weight could lead to micelle formation and enough water absorption to make the
phase unclear.
The microphase separation of this system also makes it clear that  increases as a
function of EO sidechain length. As the EO sidechain increases, so too does the monomer’s
molecular weight. Thus, polymers of the same overall molecular weight have a lower degree of
polymerization as the sidechain length increases. The polymers studied had the same target
molecular weights as the n=3 diblocks, but possess a much lower degree of polymerization due
to how massive the n=8 monomer is. Despite this, microphase separation readily occurred, and it
can thus be assumed that  increases with EO sidechain length to preserve the requisite N >
10.5 condition for microphase separation.
n=8
%EO (wt/wt) Theoretical Mn PDI
44% 60 TBD

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49% 90 TBD
49% 120 TBD
62% 60 TBD
62% 90 TBD
62% 120 TBD
boundary lines drawn in for easier viewing. Note: theoretical molecular
weight is plotted on the y-axis instead of measured molecular weight.
Selected images are representative of the observed structures. A) 44%
EO, 60 kDa gyroidal diblock, B) 49% EO, 120 kDa gyroidal structure
with larger dimensions, C) 62% EO, 60 kDa cylindrical structure, and
D) 62% EO, 90 kDa cylindrical structure. Scale bars are all 200 nm.
1 4
A
2 3
A
1
2
3
4

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Analysis of Phase Diagrams
The three-component nature of these diblock systems makes for very unique phase
diagrams. There have been very few theoretical studies done on any polymers like these ones,
leading to less certainty in what should be expected. However, a number of years ago, Matsen
and Schick published a paper discussing the theoretical phase diagram of a polymer with
conformational asymmetry.9
The theoretical phase diagram generated by this system (Fig. 9)
exhibited many of the properties noted in this study: the phase diagram was not centered around f
= 0.5, the gyroid region was larger, and the phase diagram as a whole appeared “tilted”. The
conformational asymmetry that Matsen and Schick discuss has to do with a ratio of the Kuhn
lengths of the two blocks that deviates substantially from unity. The Kuhn length of a polymer is
related to the distance that must be travelled along the polymer backbone before a significant
change in direction is observed. It can be thought of as the “stiffness” of the backbone, or its
resistance to bending and turning.
One potential explanation for the way that the phase diagrams of our diblock systems
behave is that the Kuhn lengths of the EO blocks vary substantially from the phenyl block.
Figure 9: Comparison of a standard random coil – random coil
theoretical diblock phase diagram (left) from Bates et al. and the
theoretical phase diagram of a diblock copolymer with conformational
asymmetry (right) from Matsen and Schick.4,9
Note that C (Cylinders) in
the left image corresponds to H (Hexagonally packed cylinders) in the
right, and that S (spheres) in the left image corresponds to C (body
centered cubic spheres) in the right. Note in the right image the
asymmetric nature of the phase diagram as well as the smaller range on
the x-axis.

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Inherently, this assumption makes some sense, as the space taken up by the ethylene oxide
sidechain increases, each monomer will take up more space, and it will be harder for the polymer
backbone to bend back on itself without hitting some part of the sidechain. This effect will cause
the polymer to have an increasing Kuhn length as the EO sidechain grows longer, which would
cause more and more asymmetry in the backbone. This is observed with the results acquired in
this study, as the apparent asymmetry and “tilt” of the phase diagram appears to increase as the
EO sidechain length increases.
One prevalent issue throughout the discussion of these phase diagrams has been the
question of whether or not what is reported as lamellar is actually lamellar or if it is a cylindrical
phase where the cylinders are lying parallel to the glass surface that the polymers are spuncast
onto. By utilizing a little bit of geometry (Fig. 10), it is possible to determine what the expected
displacement between the top of a cylinder and the bottom of the gap between the cylinders
would be. The factors at play in this are the radii of the cylinders, and the radius of curvature of
the cantilever tip. These two combine to together to generate an expected vertical displacement
of around 10 nm for a 50 nm gap between two formations, if a cylindrical phase were formed. A
smaller vertical displacement would be support for the judgement in this paper that lamellae
were formed instead of cylinders. Analysis of a cross-section of a polymer shown earlier (see
Fig. 5 right image) supports this judgement, as the maximum height discrepancy is around 5 nm,
as opposed to the expected 10 nm if sideways lying cylinders were at fault (Fig. 11).
Furthermore, other studies of the phase behaviors of diblocks have assigned a lamellar
designation to polymers that generated extremely similar formations as the ones depicted as
lamellae in this paper, further supporting the designation of the systems in this paper as forming
lamellae.10
Without x-ray scattering data, it’s impossible to know for sure, but these two pieces
of analysis lend credence to an assumption of a lamellar formation in the systems studied in this
paper.

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Salt Loading
Loading the polymers with a lithium salt is important to understand how the diblock
system will behave when utilized in realistic situations. It has been demonstrated in the literature
that lithium salt loading increases in diblock systems.11,12
Therefore, salt effects on this diblock
Figure 10: Schematic of how a cantilever tip (modeled as a circle) would
interact with two sideways-lying cylinders on one of the studied surfaces.
Geometry indicates that for a 50 nm gap, a 10 nm difference between
the peak and the valley would be expected.
Figure 11: Cross section of a 41 kDa, 60% EO n=2 diblock shown in
figure 4 (right side) and in figure 6.4. I0n areas where the peak to peak
gap is around 50 nm, (as in the schematic of fig. 10) the maximum
vertical displacement is only around 2 nm.

22
system were investigated to understand if any nonideal effects were observed in terms of this
system’s potential for use in batteries. The results of this investigation (Fig. 12) yielded results
consistent with literature predictions for other diblock systems. Low molecular weight polymers
demonstrated order where they previously had not at room temperature, and a morphology
change was observed from a gyroid to lamellae via the addition of salt.
Figure 12: Two examples of salt-loading on the studied diblock
copolymers.
Top: On the left is an example n=2 before solvent annealing (non-salted
morphology was gyroidal after annealing). The right is the same
polymer with a 7:1 EO:Li ratio and no solvent annealing, bearing a
much different morphology (lamellar rather than disordered).
Bottom: Another example, this time with n=8. Both left and right images
are solvent annealed, but there is a 4:1 EO:Li doping on the right
sample. A distinct change from gyroids to lamellae is observed in this
case as well.

23
Conclusion:
These novel oligo(ethylene oxide) functionalized oxanorbornyl diblock copolymers can
be readily produced and customized with synthetic control over composition, molecular weight,
and EO sidechain length. At sufficiently high molecular weights, they microphase separate like
other diblock systems. However, they exhibit a rather larger than usual gyroidal or perforated
lamellar phase when doing so. The techniques used in this study are not conclusive however, and
scattering experiments would still be necessary to confirm the phase assignments. Despite that
uncertainty, it is clear that this polymer system forms useful morphologies for lithium-ion battery
systems. Future work will further study the AFM data to attempt to arrive at a more conclusive
phase assignment. Furthermore, time-resolved electrostatic force microscopy experiments are
planned to study the movement of lithium salts within the microphase separated system.
References
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(2) Agapov, A. L.; Sokolov, A. P. Decoupling Ionic Conductivity from Structural Relaxation:
A Way to Solid Polymer Electrolytes? Macromolecules 2011, 44, 4410–4414.
(3) Stone, G. M.; Mullin, S. A.; Teran, A. A.; Hallinan, D. T.; Minor, A. M.; Hexemer, A.;
Balsara, N. P. Resolution of the Modulus versus Adhesion Dilemma in Solid Polymer
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(4) Bates, F. S.; Fredrickson, G. H. Block Copolymers—Designer Soft Materials. Phys. Today
1999, 52, 32.
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24
(7) Kazemi, F.; Massah, A. R.; Javaherian, M. Chemoselective and Scalable Preparation of
Alkyl Tosylates under Solvent-Free Conditions. Tetrahedron 2007, 63, 5083–5087.
(8) Love, J. A.; Morgan, J. P.; Trnka, T. M.; Grubbs, R. H. A Practical and Highly Active
Ruthenium-Based Catalyst That Effects the Cross Metathesis of Acrylonitrile. Angew.
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(9) Matsen, M. W.; Schick, M. Microphases of a Diblock Copolymer with Conformational
Asymmetry. Macromolecules 1994, 27, 4014–4015.
(10) Rüttiger, C.; Appold, M.; Didzoleit, H.; Eils, A.; Dietz, C.; Stark, R. W.; Stühn, B.; Gallei,
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J. Phys. Chem. B 2014, 118, 4–17.
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