supporting information 062315

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Supporting Information

Fine Tuning Surface Energy of Poly(3-hexylthiophene) by Heteroatom

Modification of the Alkyl Side Chains

Jenna B. Howard, Sangtaik Noh, Alejandra E. Beier, Barry C. Thompson*

Department of Chemistry, Loker Hydrocarbon Research Institute, University of Southern

California, Los Angeles, California 90089-1661, United States

*E-mail: [email protected]

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Materials and Methods: All reagents from commercial sources were used without further

purification, unless otherwise noted. All reactions were performed under dry N2, unless

otherwise noted. All dry reactions were performed with glassware that was flamed under high

vacuum and backfilled with N2. Flash chromatography was performed using a Teledyne

CombiFlash Rf instrument in combination with RediSep Rf normal phase disposable columns.

Solvents were purchased from VWR and used without further purification except for THF,

which was dried over sodium/benzophenone before being distilled.

All compounds were characterized by 1H NMR (400 MHz) and 13C NMR (100 MHz) on a

Mercury 400. Polymer 1H NMRs (500 MHz) were obtained on a Varian VNMRS-500. For

polymer molecular weight determination, polymer samples were dissolved in HPLC grade o-

dichlorobenzene at a concentration of 0.5 mg/ml, briefly heated and then allowed to turn to room

temperature prior to filtering through a 0.2 µm PTFE filter for P3HT and P3HT-co-MET

polymers or a 0.2 µm Nylon filter for P3HT-co-FHT polymers. SEC was performed using HPLC

grade o-dichlorobenzene at a flow rate of 0.6 ml/min on one 300 x 8.0 mm LT6000L Mixed

High Org column (Viscotek) at 60 °C using a Viscotek GPC Max VE 2001 separation module

and a Viscotek TDA 305 RI detector. The instrument was calibrated vs. polystyrene standards

(1,050 – 3,800 000 g/mol) and data was analyzed using OmniSec 4.6.0 software.

Cyclic voltammetry was collected using an EG&G instruments Model 263A potentiostat under

the control of PowerSuite Software. A standard three electrode cell based on a Pt wire working

electrode, a silver wire pseudo reference electrode (calibrated vs. Fc/Fc+ which is taken as 5.1 eV

vs. vacuum) and a Pt wire counter electrode was purged with nitrogen and maintained under

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nitrogen atmosphere during all measurements. Acetonitrile and chloroform were distilled over

CaH2 prior to use. Tetrabutyl ammonium hexafluorophosphate (0.1 M) was used as the

supporting electrolyte for polymer films. Polymer films were made by repeatedly dipping the Pt

wire in a 1% (w/w) polymer solution in chloroform or o-dichlorobenzene and dried under

nitrogen prior to measurement. Polymer solutions were prepared in chloroform at a concentration

of 0.1 mg/mL and tetrabutyl ammonium tetrafluoroborate (0.1 M) was used as the supporting

electrolyte.

Surface energy studies of the neat polymers film were performed on Ramé-Hart Instrument Co.

contact angle goniometer model 290-F1 and analyzed using Surface Energy (one liquid) tool

implemented in DROPimage 2.4.05 software. Polymer films were prepared from 10 mg/ml

chloroform solutions, spin-coated on the pre-cleaned glass slides. Water and glycerol were used

as two solvents in the two-liquid model to measure the contact angle and harmonic mean Wu

model

was used to calculate the average surface energy values for each film according to

following set of equations:

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where Zw and Zg are the contacts angles with water and glycerol, respectively; γtot is the total

surface energy, γp and γd are the polar and dispersive surface energy components.

Mobility was measured using a hole-only device configuration of ITO/PEDOT:PSS/Polymer/Al

in the space charge limited current regime. The dark current was measured under ambient

conditions. At sufficient potential the mobilities of charges in the device can be determined by

fitting the dark current to the model of SCL current and described by equation 4:

(4),

where JSCLC is the current density, ε0 is the permittivity of space, εR is the dielectric constant of

the polymer (assumed to be 3), µ is the zero-field mobility of the majority charge carriers, V is

the effective voltage across the device (V = Vapplied – Vbi – Vr), and L is the polymer layer

thickness. The series and contact resistance of the hole-only device (16 – 20 Ω) was measured

using a blank (ITO/PEDOT/Al) configuration and the voltage drop due to this resistance (Vr) was

subtracted from the applied voltage. The built-in voltage (Vbi), which is based on the relative

work function difference of the two electrodes, was also subtracted from the applied voltage. The

built-in voltage can be determined from the transition between the ohmic region and the SCL

region and is found to be about 0.6 V.

All steps of device fabrication and testing were performed in air. ITO-coated glass substrates (10

Ω/☐, Thin Film Devices Inc.) were sequentially cleaned by sonication in detergent, de-ionized

water, tetrachloroethylene, acetone, and isopropyl alcohol, and dried in a nitrogen stream. A thin

layer of PEDOT:PSS (Baytron® P VP AI 4083, filtered with a 0.45 μm PVDF syringe filter –

Pall Life Sciences) was first spin-coated on the pre-cleaned ITO-coated glass substrates and

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baked at 130 ºC for 60 minutes under vacuum. Solutions of polymers were prepared in

chloroform solvent at a concentration of 10 mg/ml and stirred for overnight. Subsequently, the

polymer active layer was spin coated (with a 0.45 µm PTFE syringe filter [Pall Life Sciences] for

P3HT and P3HT-co-MET polymers and 0.45 µm Nylon syringe filter [VWR International] for

P3HT-co-FHT polymers) on top of the PEDOT:PSS layer. Upon spin coating of polymers, films

were first placed under N2 for 30 min and then placed in the vacuum chamber for aluminum

deposition. At the final stage, the substrates were pumped down to high vacuum (< 9×10-7 Torr)

and aluminum (100 nm) was thermally evaporated at 3 – 4 Å/sec using a Denton Benchtop

Turbo IV Coating System onto the active layer through shadow masks to define the active area

of the devices as 5.18 mm2.

For thin film measurements, polymers were spin coated onto pre-cleaned glass slides from

chloroform solutions; 10 mg/mL for UV-Vis, 5 mg/mL for photoluminescence (PL) (with a 0.45

µm PTFE syringe filter [Pall Life Sciences] for P3HT and P3HT-co-MET polymers and 0.45 µm

Nylon syringe filter [VWR International] for P3HT-co-FHT polymers). UV-vis absorption

spectra were obtained on a Perkin- Elmer Lambda 950 spectrophotometer. PL spectra were

measured by a Horiba Jobin Yvon Nanolog spectrophotometer. The thickness and crystallinity of

the thin films and GIXRD measurements were obtained using Rigaku Diffractometer Ultima IV

using Cu Kα radiation source (λ= 1.54 Å) in the reflectivity and grazing incidence X-Ray

diffraction mode, respectively.

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Synthetic Procedures:

Synthetic procedures for the synthesis of 2-bromo-5-trimethyltin-3-hexylthiopehene and poly(3-

hexyl thiophene) were used without modifications as reported in the literature.1 Synthesis of

compounds 3 and 6 were modified from literature.

Scheme S1.

3-(4,4,5,5,6,6,7,7,7-nonafluorohept-1-en-1-yl)thiophene (1). A phosphonium ylide was

generated by adding PPh3 in one portion to a solution of 1H,1H, 2H, 2H-nonafluorohexyl iodide

(11.34g, 30.3 mmol) in DMF (15 mL). The solution was heated to 105 °C for 24 hours. After

cooling the reaction mixture, the solvent was removed by vacuum distillation to yield viscous

yellow oil. Dioxane/water (9:1, 170 mL) was added, followed by 3-carboxyaldehyde thiophene

(3.39 g, 30.3 mmol) and K2CO3 (5.44 g, 39.4 mmol). The reaction mixture was refluxed for 24

hours, cooled and extracted with CHCl3. The organic layer was washed with water three times

and brine three times, dried over Na2SO4 and concentrated in vacuo to yellow oil. The crude

material was purified on a column with hexanes to yield clear and faint yellow oil (8.82 g, 85%

yield), then carried onto hydrogenation. 1H NMR: (400 MHz, CDCl3) δ 7.43 (dd, 1H), 7.18, (dd,

1H), 7.05 (dd, 1H), 6.74 (dd, 1H), 5.69 (dt, 1H), 3.15 (td, 2H).

3-(4,4,5,5,6,6,7,7,7-nonafluoroheptyl)thiophene (2). To a solution of methanol (40 mL) and 1

(5.00 g, 14.6 mmol) in a 3-necked RBF fitted with a condenser, stir bar, and rubber septa with a

vent needle at the top of the condenser, dry Pd/C 10% (550 mg, 10% w/w) was carefully added.

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To a separate 3-necked RBF fitted with an addition funnel and rubber septa, NaBH4 was added

with a stir bar. A solution of methanol and acetic acid (10% v/v solution) was added to the

addition funnel. A cannula was place to connect the atmosphere of the NaBH4 vessel to the

solution of 1. The solution was heated to 50 °C with vigorous stirring while the acidic methanol

solution was set to slowly add to the NaBH4, allowing hydrogen gas to bubble through the

solution. Progress of the reaction mixture was monitored by sampling aliquots by 1H NMR, and

was typically complete after 24 h. The reaction mixture was concentrated in vacuo and Pd/C was

filtered off through a pad of Celite. The crude material was purified on a column with hexanes to

yield a clear, colorless oil (4.61 g, 92% yield). 1H NMR: (400 MHz, CDCl3) δ 7.28 (dd, 1H),

6.97, (dd, 1H), 6.95 (dd, 1H), 2.74 (t, 2H), 2.09 (m, 2H), 1.96 (m, 2H).

2-bromo-3-(4,4,5,5,6,6,7,7,7-nonafluoroheptyl)thiophene (3). To a solution of 2 (2.57 g, 7.47

mmol) and acetic acid (0.6 M, 12.5 mL), freshly recrystallized NBS (1.46 g, 8.23 mmol) was

added in one portion. The reaction mixture was left to stir at room temperature for 24 h and then

transferred to a separatory funnel with ether and water. The organic layer was washed with 2 M

NaOHaq three times, dried with MgSO4 and concentrated in vacuo to yellow oil. The crude

material was purified on silica column with hexanes followed by a vacuum distillation to yield

clear and colorless oil (2.17 g, 69% yield). 1H NMR: (400 MHz, CDCl3) δ 7.24 (d, 1H), 6.81, (d,

1H), 2.69 (t, 2H), 2.09 (m, 2H), 1.91 (m, 2H).

(5-bromo-4-(4,4,5,5,6,6,7,7,7-nonafluoroheptyl)thiophen-2-yl)trimethylstannane 4. To a

solution of diisopropylamine (0.76 mL, 5.40 mmol) and THF at -78 °C, n-BuLi (1.6 M, 2.83 mL,

4.353 mmol) was added drop wise and left to stir for 15 minutes. The solution was warmed to

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room temperature for 15 minutes, then subsequently cooled to -78 °C. The LDA solution was

then cannulated to a solution of 3 (1.88 g, 4.40 mmol) and THF at -78 °C. The reaction mixture

was left to stir for 1 h, then trimethyl tin chloride (1.0 M, 5.40 mL, 5.40 mmol) was added drop

wise at -78 °C. The final solution was left to slowly warm to room temperature overnight. The

reaction mixture was transferred to a separatory funnel with ether and water. The organic layer

was washed with diluted HClaq three times, dried over Na2SO4, and concentrated in vacuo to red

oil. The crude material was vacuum distilled to yield clear, faint yellow oil (1.33 g, 52% yield).

1H NMR: (400 MHz, CDCl3) δ 6.85 (s, 1H), 2.68 (t, 2H), 2.11 (m, 2H), 1.92 (m, 2H), 0.36 (s,

9H); 13C NMR: (500 MHz, CDCl3) δ 140.91, 139.00, 135.73, 114.32, 30.29, 29.86, 29.04, 28.40,

22.59, 20.53, 14.07, -8.26.

Scheme S2.

2-(2-bromothiophen-3-yl)ethan-1-ol (5). To a solution of 2(3-thienyl)ethanol (3.46 g, 27.0

mmol) in THF (34 mL) at 0 °C, freshly recrystrallized NBS (5.00 g, 28.1 mmol) was slowly

added. The reaction mixture was covered from light and left to slowly warm to room temperature

overnight. After 24 h, reaction mixture was transferred into a separatory funnel with ether and

water. The organic layer was washed with water three times, dried over MgSO4 and concentrated

in vacuo to brown oil. The extract was eluted through a silica column with 8:2 hexanes to ethyl

acetate solvent, concentrated to an oil, then vacuum distilled to yield a clear and colorless oil

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(4.88 g, 87% yield). 1H NMR: δ 7.20 (d, 1H), 6.85 (d, 1H), 3.77 (t, 2H), 2.82 (t, 2H); 13C NMR:

δ 138.03, 128.59, 125.65, 110.28, 61.90, 32.74.

2-bromo-3-(2-(2-methoxyethoxy)ethyl)thiophene (6). Freshly powdered KOH (3.96 g, 70.7

mmol) was added to a solution of 5 (4.88 g, 23.6 mmol), 2-chloroethylmethyl ether (5.57 g, 58.9

mmol), and Aliquat 336 (0.3 mL). The reaction mixture was left to stir for 4 days at 80 °C.

Reaction mixture was cooled to room temperature and transferred into a separatory funnel with

ether and water. The organic layer was washed three times with dilute HCl(aq), dried over

MgSO4, then concentrated to a yellow oil. Extract eluted through a silica column with 9:1

hexanes to ethyl acetate solution, concentrated to an oil, then vacuum distilled to yield a clear

and colorless oil (3.18 g, 51% yield). 1H NMR: δ 7.18 (d, 1H), 6.86 (d, 1H), 3.64 (t, 2H), 3.55

(m, 4H), 3.38 (s, 3H), 2.89 (t, 2H); 13C NMR: δ 138.20, 128.62, 125.31, 109.92, 71.91, 70.25,

70.11, 59.08, 29.64.

(5-bromo-4-(2-(2-methoxyethoxy)ethyl)thiophen-2-yl)trimethylstannane (7). A solution of 6

(1.48g, 5.58 mmol) in THF (11.2 mL) was cooled to -78 °C followed by the dropwise addition of

TMP MgCl LiCl in THF/Toluene solution (0.65 M, 9.45 mL). The reaction mixture was stirred

at -78 °C for 3 h, followed by the dropwise addition of trimethyl tin chloride in hexanes solution

(1.0 M, 6.14 mL), then slowly warmed to room temperature over night. The reaction mixture was

transferred to a separatory funnel with ether and water. The organic layer was washed with water

three times, dried over MgSO4, then concentrated to a red oil. Extract was vacuum distilled to

yield a clear and yellow oil (1.62 g, 69% yield). 1H NMR: 13C NMR: 1H NMR: δ 6.92 (s, 1H),

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3.65 (t, 2H), 3.56 (m, 4H), 3.39 (s, 3H), 2.90 (t, 2H); 13C NMR: δ 139.16, 138.27, 136.61,

114.55, 71.95, 70.40, 70.09, 59.10, 29.66, -8.23.

Scheme S3.

Stille Copolymerizations for P3HT-co-FHT Polymers. Monomers 4 and 2-bromo-5-

trimethyltin-3-hexylthiopehene were added to 3-necked RBFs at varied molar ratios via syringe.

Dry DMF (0.04 M) was added via syringe followed by quickly adding palladium

tetrakis(triphenyphosphine) Pd(PPh3)4 (0.04 eq) in one portion. The solution was degassed with

N2 for 20 m, then heated to 95 °C for 24 h. Reaction mixtures were cooled to room temperature

and precipitated into cold stirring methanol, followed by addition of ammonium hydroxide.

Polymers were decanted into a thimble and purified via Soxhlet extraction with methanol,

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hexanes, dichloromethane and then collected in chloroform. Polymer chloroform solutions were

concentrated in vacuo and precipitated in cold MeOH and collected via filtration.

P3HT-co-FHT-10%: Yield: 31% (69 mg). 1H NMR (500 MHz, CDCl3) δ 2.83 (m, 0.11H), 2.74

(m, 1H).

P3HT-co-FHT-20%: Yield: 46% (104 mg). 1H NMR (500 MHz, CDCl3) δ 2.83 (m, 0.26H),

2.74 (m, 1H).


2.74 (m, 1H).


2.74 (m, 1H).


2.74 (m, 1H).

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Figure S1. 1H NMR of P3HT-co-FHT and P3HT Polymers. Singlet at 2.10 ppm is acetone and

1.50 ppm is water.

Stille Copolymerizations for P3HT-co-MET Polymers. Monomers 7 and 2-bromo-5-

trimethyltin-3-hexylthiopehene were added to 3-necked RBFs at varied molar ratios via syringe.

Dry DMF (0.04 M) was added via syringe followed by quickly adding palladium

tetrakis(triphenyphosphine) Pd(PPh3)4 (0.04 eq) in one portion. The solution was degassed with

N2 for 20 m, then heated to 95 °C for 48 - 120 h. Reaction mixtures were cooled to room

temperature and precipitated into cold stirring methanol, followed by addition of ammonium

hydroxide. Polymers were decanted into a thimble and purified via Soxhlet extraction with

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methanol, hexanes, and then collected in chloroform. Polymer chloroform solutions were

concentrated in vacuo and precipitated in cold MeOH and collected via filtration.

P3HT-co-MET-10%: Yield: 31% (56 mg). 1H NMR (500 MHz, CDCl3) δ 3.80 (m, 0.17H), 3.67

(m, 0.17H), 3.59 (m, 0.17H), 3.41 (s, 0.26H), 3.14 (m, 0.15H), 2.82 (m, 1.61H).


(m, 0.35H), 3.59 (m, 0.35H), 3.41 (s, 0.54H), 3.14 (m, 0.31H), 2.82 (m, 1.49H).


(m, 0.56H), 3.59 (m, 0.58H), 3.41 (s, 0.86H), 3.14 (m, 0.51H), 2.82 (m, 1.32H).


(m, 0.81H), 3.59 (m, 0.84H), 3.41 (s, 1.26H), 3.14 (m, 0.73H), 2.82 (m, 1.04H).


(m, 1.04H), 3.59 (m, 1.03H), 3.41 (s, 1.46H), 3.14 (m, 0.87H), 2.82 (m, 0.84H).

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Figure S2. 1H NMR of P3HT-co-MET and P3HT Polymers.

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One Liquid Model Data

Figure S3. Surface energy as calculated by the One-Liquid Model for as cast (solid line) and thermally annealed (dotted line) thin films of P3HT-co-MET (blue) and P3HT-co-FHT (red).

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Wu Model Data

Figure S4. Surface energy as calculated by the harmonic mean Wu Model for a) as cast and b) thermally annealed thin films of P3HT-co-MET (blue) and P3HT-co-FHT (red).

a

b

a

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Table S1. Calculated surface energy measurements with standard deviations of polymers using the one-liquid method and Wu Model.

One-Liquid Surface Energy Wu Model Surface Energy Polymer As Cast Annealed As Cast Annealed P3HT 19.94 ± 0.27 18.73 ± 0.32 19.78 ± 0.73 21.37 ± 0.87

P3HT90-co-FHT10 18.09 ± 0.23 17.94 ± 0.06 17.39 ± 0.34 17.20 ± 0.87 P3HT80-co-FHT20 17.46 ± 0.11 18.21 ± 0.02 16.85 ± 0.72 15.97 ± 0.95 P3HT70-co-FHT30 16.92 ± 0.19 18.13 ± 0.43 15.39 ± 0.47 15.36 ± 0.42 P3HT60-co-FHT40 16.03 ± 0.15 17.19 ± 0.54 13.61 ± 0.13 14.62 ± 0.94 P3HT50-co-FHT50 14.17 ± 0.21 15.67 ± 0.92 12.27 ± 0.14 13.85 ± 0.53 P3HT90-co-MET10 21.17 ± 0.09 20.99 ± 0.12 18.18 ± 0.10 20.53 ± 0.34 P3HT80-co-MET20 22.86 ± 0.21 22.84 ± 0.29 18.97 ± 0.24 22.44 ± 0.61 P3HT70-co-MET30 24.09 ± 0.18 24.05 ± 0.26 19.86 ± 0.13 21.62 ± 0.45 P3HT60-co-MET40 25.05 ± 0.26 25.62 ± 0.19 20.70 ± 0.29 22.21 ± 0.33 P3HT50-co-MET50 27.02 ± 0.08 26.34 ± 0.05 22.34 ± 0.14 22.53 ± 0.27

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UV-Vis Spectroscopy

Figure S5. Absorption profiles of a) annealed P3HT-co-FHT, and b) annealed P3HT-co-MET films; i) P3HT, ii) P3HT90-co-FHT10, iii) P3HT80-co-FHT20, iv) P3HT70-co-FHT30, v) P3HT60-co-FHT40, vi) P3HT50-co-FHT50, vii) P3HT90-co-MET10, viii) P3HT80-co-MET20, ix) P3HT70-co-MET30, x) P3HT60-co-MET40, and xi) P3HT50-co-MET50.

a

b

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Photoluminescence

Figure S6. Photoluminescence responses of a) as cast and b) annealed P3HT-co-FHT films; c) as cast and d) annealed P3HT-co-MET; black) P3HT (i), blue) P3HT90-co-FHT10 (ii) or P3HT90-co-MET10 (ii), orange) P3HT60-co-FHT40 (iii) or P3HT60-co-MET40 (iii), red) P3HT50-co-FHT50 (iv) or P3HT50-co-MET50 (iv).

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GIXRD

Figure S7. GIXRD data of a) as-cast P3HT-co-FHT and b) as cast P3HT-co-MET films; i) P3HT, ii) P3HT90-co-FHT10, iii) P3HT80-co-FHT20, iv) P3HT70-co-FHT30, v) P3HT60-co-FHT40, and vi) P3HT50-co-FHT50. vii) P3HT90-co-MET10, viii) P3HT80-co-MET20, ix) P3HT70-co-MET30, x) P3HT60-co-MET40, and xi) P3HT50-co-MET50.

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Cyclic Voltammetry

Figure S8. P3HT90-co-FHT10 Film CV

Figure S9. P3HT90-co-FHT10 Solution CV

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Figure S18. P3HT90-co-MET10 Film CV

Figure S19. P3HT90-co-MET10 Solution CV

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Figure S28. P3HT Film CV P3HT Solution CV available in previously published Supporting Information.4 Differential Scanning Calorimetry P3HT DSC Trace available in previously published Supporting Information.5

Figure S29. P3HT90-co-FHT10 DSC trace.

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Figure S34. P3HT90-co-MET10 DSC trace.


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References (1) Burkhart, B.; Khlyabich, P. P.; Cakir Canak, T.; LaJoie, T. W.; Thompson, B. C.

Macromolecules 2011, 44 (6), 1242. (2) Tanba, S.; Sugie, A.; Masuda, N.; Monguchi, D.; Koumura, N.; Hara, K.; Mori, A.

Heterocycles 2010, 82 (1), 505. (3) Costanzo, P. J.; Stokes, K. K. Macromolecules 2002, 35 (18), 6804. (4) Burkhart, B.; Khlyabich, P. P.; Thompson, B. C. Macromolecules 2012, 45 (9), 3740. (5) Rudenko, A. E.; Wiley, C. A.; Tannaci, J. F.; Thompson, B. C. J. Polym. Sci. Part A:

Polym. Chem. 2013, 51 (12), 2660.

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