supplementary information · ©20 10 macmillan publishers limited. all rights reserved. s1...

© 2010 Macmillan Publishers Limited. All rights reserved.

S1

Supplementary Information

Monodisperse cylindrical micelles by

crystallization-driven living self-assembly

Joe B. Gilroy1, Torben Gädt1, George R. Whittel1l, Laurent Chabanne1, John M. Mitchels1,

Robert M. Richardson2*, Mitchell A. Winnik3*, Ian Manners1*

1School of Chemistry, University of Bristol, Bristol, United Kingdom, BS8 1TS, 2H. H. Wills

Physics Laboratory, University of Bristol, United Kingdom, BS8 1TL, and 3Department of

Chemistry, University of Toronto, Toronto, Ontario, Canada, M5S 3H6

[email protected], [email protected], [email protected]

Experimental Details……………………………………………………………………S2

Additional Figures………………………………………………………………………S10

References………………………………………………………………………………S17

SUPPLEMENTARY INFORMATIONdoi: 10.1038/nchem

nature chemistry | www.nature.com/naturechemistry 1


S2

Experimental Details

Equipment and Materials

All reactions and manipulations were performed under an atmosphere of prepurified N2 using

either standard Schlenk techniques or in an inert atmosphere glovebox. All anionic

polymerizations were carried out in an inert atmosphere glovebox. PFS block copolymers

were prepared by previously reported methods1,2. All polymers together with their properties

are listed in Table S1. n-Butyllithium (1.6 M) in n-hexanes, sec-butyllithium (1.4 M) in

cyclohexane and isoprene were all purchased from Aldrich. Isoprene was first distilled from

CaH2 followed by a distillation from n-butyllithium and stored at -40 C.

Hexamethylcyclotrisiloxane (D3) was dissolved in dry n-hexanes and stirred over CaH2 for 12

h. Subsequently, the n-hexanes was distilled off and the D3 was distilled under reduced

pressure and dissolved again in dry n-hexanes. Bu2Mg in heptane (1.0 M, Aldrich) was added

to this solution and the volatile solvents were distilled off under reduced pressure followed by

a vacuum distillation of D3. Tetrahydrofuran was distilled from Na/benzophenone under static

vacuum immediately before use.

Polymer characterization.

Gel permeation chromatography was carried out on diblock copolymers and aliquots of the

first block using a Viscotek VE 2001 Triple-Detector Gel Permeation Chromatograph,

equipped with an automatic sampler, a pump, an injector, an inline degasser and a column

oven (30 °C). The elution columns consist of styrene / divinyl benzene gels with pore sizes of

500 Å and 100,000 Å. Detection was conducted by mean of a VE 3580 refractometer, a four-

capillary differential viscometer and a 90° and low angle (7°) laser light (λ0 = 670 nm)

scattering detector, VE 3210 & VE 270. THF (Fisher) was used as the eluent, with a flow rate

of 1.0 mL min-1. Samples were dissolved in the eluent (2 mg mL-1) and filtered with a

Ministart SRP 15 filter (polytetrafluoroethylene membrane of 0.45 μm pore size) before

2 nature chemistry | www.nature.com/naturechemistry

SUPPLEMENTARY INFORMATION doi: 10.1038/nchem


S3

analysis. The calibration was conducted using a PolyCALTM polystyrene standard (PS115K)

from Viscotek.

To determine the molecular mass of the obtained block copolymers aliquots of the first block

were taken and the molecular mass of the first block was determined by GPC. The molecular

weights of the diblocks were then determined by combining the molecular weight Mn of the

first block from GPC measurements with the block ratio of the diblock copoylmer which was

obtained by integrating the 1H NMR spectroscopy signal intensities of the respective blocks.

The characteristics of the polymers used in this study are listed in Table S1.

Table S1. Polymer data.

Sample Mn first block (g mol-1) Block ratio Mn diblock (g mol-1) PDI

PI550-b-PFS50 37500 11:1 49600 1.02

PFS28-b-PDMS560 6700 1:20 48200 1.02

Transmission Electron Microscopy (TEM)

The samples for electron microscopy were prepared by drop casting one drop (ca. 10 μL) of

the micelle colloidal solution onto a carbon coated copper grid which was placed on a piece of

filter paper to remove excess solvent. Bright field TEM micrographs were obtained on a

JEOL1200EX II microscope operating at 120 kV and equipped with an SIS MegaViewIII

digital camera. No staining of the samples was necessary. Images were analyzed using the

ImageJ software package developed at the US National Institute of Health. For the statistical

length analysis, 400-500 cylinders were carefully traced by hand to determine the contour

length. Each TEM micrograph was analyzed completely, i.e. every cylindrical micelle in each

image was counted in order to reduce subjectivity. From this data Ln and Lw of each sample




S4

of monodisperse cylindrical micelles was calculated as shown below (L = length of object, N

= number).

∑

∑

=

== n

ii

n

iii

n

N

LNL

1

1 (S1) ∑

∑

=

== n

iii

n

iii

w

LN

LNL

1

1

2

(S2)

The data was fit to Gaussian distribution curves using the following probability function

where L = measured length, σ = standard deviation, and μ = mean length.

⎟⎟⎠

⎞⎜⎜⎝

⎛ −−= 2

2

2)(exp

21)(

σμ

πσLLf (S3)

The standard deviations (σ) of the measured lengths are related to length dispersity (Lw/Ln)

through the following expression3,4.

2

1 ⎟⎟⎠

⎞⎜⎜⎝

⎛=−

nn

w

LLL σ (S4)

The small values of σ/Ln (Table 1, main text) suggest that the distributions reported in Figure

3e are at the Poisson limit of the Gaussian distribution, a characteristic of living

polymerization for the case in which initiation is much faster than propagation.

Atomic Force Microscopy (AFM)

Tapping mode and phase images were obtained using a Multimode V atomic force

microscope equipped with a Nanoscope V controller (Veeco Instruments Ltd, Santa Barbara,

USA). Nanosensors (Neuchatel, Switzerland) PPP NCHR10 cantilevers with a rotated

monolithic silicon probe with a tip radius of approximately 2 nm were employed. Tip

analysis studies were conducted in order to confirm the tip remained intact during the

acquisition of the data presented. The samples were prepared as follows: a colloidal solution

of 0.1 mg mL-1 PFS28-b-PDMS560 cylindrical micelles was drop cast onto freshly cleaved

highly ordered pyrolytic graphite (RMS background 0.15 nm), and the sonicated PFS-b-




S5

PDMS crystallites were adsorbed to silicon by dipping a silicon wafer into a 1.0 mg mL-1

colloidal solution (RMS background 0.20 nm). Imaging was conducted in air at ambient

temperature. Images were analyzed using Gwyddion, an open source software program for

SPM images (www.gwyddion.net).

Small Angle X-ray Scattering (SAXS)

Samples were prepared in 1.5 mm diameter quartz capillary tubes (Capillary Tube Supplies

Ltd) by adding 40 μL of decane to the tube before the appropriate amount of cylindrical

micelles was added as a concentrated colloidal solution in n-hexane. The tubes were

submerged in a 60 °C oil bath for 48 h, at which time it was assumed that all of the n-hexane

had boiled off. The density of the cylindrical micelles was taken as the density of the PI550-b-

PFS50 diblock copolymer, which was calculated from the density of the PFS (assumed to be

1.33 g cm-3) and PI (assumed to be 0.92 g cm-3) blocks.

SAXS measurements were performed at the University of Bristol Physics Department. The

diffraction measurements were made using copper Kα X-rays (wavelength, λ = 0.154 nm)

from a Bede Microsource generator with a polycapillary focussing optic and a graphite

monochromator. The diffraction pattern was detected using a 200 mm square flat multi-wire

area detector from Molecular Metrology. It was placed 1 m from the sample with an

evacuated path to reduce air scatter. The sample to detector distance was calibrated using a

silver behenate standard5. The electric field was applied to the sample using two brass

electrodes covered with an insulating Kapton film placed either side of the sample tube with a

gap of ca. 1.7 mm so that the field was horizontal. A 1 kHz signal was applied across the gap

using a Trek high voltage amplifier. The magnetic field was applied using an electromagnet

with the poles placed at the same location as the electrodes. The scattering vector, Q , for each

pixel on the detector was determined from the scattering angle, θ2 .




S6

λθπ /sin4=Q The scattering from a narrow ring at constant scattering vector, Q =0.047 Å-1 was analysed to

deterime the order parameter of the scattering. This is the second Legendre polynomial,

)(cos2 φP , where φ is the azimuthal angle between a point on the ring and the direction of the

electric field. The order parameter of the scattering is the average value of )(cos2 φP where

the average is weighted by the intensity of the ring.

φφφ

φφφφ

π

π

dQQI

dQIP

i

scattering

∫

∫

=

⎟⎠⎞

⎜⎝⎛ −=

=

0

0

2

,2

sin),(

sin21cos

23),047.0(

This was determined numerically from the intensity vs. φ profile of the ring. The next step is

to calculate the order parameter of the rod axes from that of the scattering. The order

parameter of the rods is defined by an average over the normalized orientational distribution

function, )(βf , where β is the angle between a rod and the field direction. It is often given

the symbol, S.

ββββπ

dfPS rods ∫ ⎟⎠⎞

⎜⎝⎛ −==

0

2,2 sin

21cos

23)(

If the orientational distribution fuction, )(βf , has uniaxial symmetry, there is a simple

relationship between the order parameter of the scattering and the order parameter of the

rods6. For objects that have a scattering feature in a plane perpendicular to their long axes, the

following relationship holds.

scatteringrods PPS ,2,2 2−==

Thus the orientational order parameter was determined from the azimuthal distribution of the

scattering. These values reflect the orientational ordering of completely rigid rods, but may

also contain a contribution from orientations made possible by the potential flexibility of PFS-

based cylindrical micelles.




S7

Dynamic Light Scattering (DLS)

Dynamic light scattering (173°) experiments were performed using a nano series Malvern

zetasizer instrument equipped with a 633 nm red laser. Samples were analyzed in 1 cm glass

cuvettes at concentrations of 0.5 mg mL-1, 0.25 mg mL-1, and 0.13 mg mL-1 in n-hexane at 25

°C. For the purpose of the light scattering studies the refractive index of the block

copolymers involved was assumed to be 1.60. The results of dynamic light scattering studies

are reported as apparent hydrodynamic radius (RH,app), acknowledging that the particles have

been modelled as spheres in the experiments conducted.

Polarized Optical Microscopy (POM)

The experiments were conducted in a cell comprised of two Indium Tin Oxide (ITO) covered

glass (sheet resistance 8 Ω) slides coated with a layer of Hyprez Type W lubricant (Engis

Ltd.), wiped unidirectionally with a lense wipe to remove excess liquid. The glass slides were

held at a distance of 25 μm from one another using Kapton tape, and the sample in decane

was loaded via capillary action. The electric field was generated using a Thandar TG102

signal generator attached to leads soldered to the ITO using indium metal. The signal was

amplified using a home-made amplifier capable of delivering 100 V peak to peak. The AC

frequency was a constant 1 kHz. Liquid crystalline behavior was studied using an Olympus

B50 polarized light optical microscope (POM) fitted with a digital camera.

Cylindrical Micelle Preparation

Preparation of PI550-b-PFS50 cylindrical micelles

To a vial containing 2.5 mg of PI550-b-PFS50 was added 2.5 mL of n-hexane and the sealed

vial was immersed into an oil bath and heated to 70 ºC for 1 h. The clear yellow solution was

cooled to room temperature and allowed to age for 48 h.

Preparation of PFS-b-PDMS crystallites

To a vial containing 7.5 mg of PFS28-b-PDMS560 was added 15 mL n-hexane and the sealed

vial was immersed into an oil bath and heated to 70 °C for 1 h. The clear yellow solution was




S8

cooled to room temperature and allowed to age for 4 weeks. TEM and AFM micrographs of

the resulting long cylindrical micelles of PFS28-b-PDMS560 are shown in Figure 2. A vial

containing the micelle colloidal solution was flushed with nitrogen and capped with a rubber

septum. The sonotrode was introduced into the colloidal solution through the rubber septum

before the solution was cooled to -78 °C. The colloidal solution was then subjected to

ultrasound with stirring for 4 h (ultrasonic processor: Hielscher UP50H operating at 30 kHz

and 50 W equipped with a Hielscher MS1 titanium sonotrode). TEM and AFM micrographs

of the sonicated micelles are shown in Figure 2. An aliquot of the sonicated PFS-b-PDMS

cylindrical micelles was then removed, dried in vacuo, and dissolved in THF before being

analyzed by GPC (conventional calibration, RI detection) to study the effect of sonication on

the PFS28-b-PDMS560 block copolymers that make up the micelles. The signal obtained from

the colloidal solution of sonicated micelles was very slightly broadened (Mn = 49900, PDI =

1.13) relative to a sample of micelles analyzed before sonication (Mn = 50100, PDI = 1.07).

In addition, a new very small signal with a negligible UV response at 450 nm (indicative of

PDMS oligomers) corresponding to a low molecular weight species (Mn ≈ 350) was observed.

The results indicate that negligible degradation of the block copolymer occurs under the

sonication conditions employed.

Preparation of monodisperse cylindrical micelles

To a 100 μL aliquot of the 0.5 mg mL-1 colloidal solution of stub-like PFS-b-PDMS

crystallites in n-hexane was added a further 2 mL n-hexane. The colloidal solution was stirred

at 600 rpm and 25, 50, 100, 200 μL PI550-b-PFS50 in THF (10 mg mL-1) were injected rapidly.

After 10 seconds the stirring was stopped and the solution was allowed to age for 24 h. TEM

micrographs of the resulting cylindrical micelles are shown in Figure 3.

Larger scale (~30 mg) preparation of cylindrical micelles

For each experiment a new batch of stub-like PFS-b-PDMS cylinders were prepared as

discussed previously. Each batch differs in the size and overall number of stub-like




S9

cylindrical micelles present. The target unimer:seed ratio was therefore assessed by

conducting ‘small-scale’ test experiments, analyzing the size distribution by TEM, and

adjusting the ratio according to the desired cylinder length.

Monodisperse 188 nm cylindrical micelles

To a 12.0 mL aliquot of a freshly sonicated colloidal solution of stub-like PFS-b-PDMS

crystallites (0.5 mg mL-1 in n-hexane) was added an additional 240 mL of n-hexane. The

colloidal solution was stirred at 600 rpm and 2.4 mL PI550-b-PFS50 in THF (10 mg mL-1) was

added dropwise over 30 s. The solution was allowed to stir for 1 min before it was allowed to

age for 36 h.

Monodisperse 731 nm cylindrical micelles

To a 2.5 mL aliquot of a freshly sonicated colloidal solution of stub-like PFS-b-PDMS

crystallites (0.5 mg mL-1 in n-hexane) was added an additional 50 mL of n-hexane. The

colloidal solution was stirred at 600 rpm and 2.2 mL PI550-b-PFS50 in THF (10 mg mL-1) was

added dropwise over 30 s. The solution was allowed to stir for 1 min before it was allowed to

age for 36 h.




S10

Additional Figures S1-S9 and Tables S2 and S3

-1

0

1

2

3

4

5

6

7

8

9

0 50 100 150 200 250 300 350

Hei

ght (

nm)

Distance (nm)A B

-1

0

1

2

3

4

5

6

7

8

9

0 50 100 150 200 250 300 350

Hei

ght (

nm)

Distance (nm)A B

-1

0

1

2

3

4

5

6

7

8

9

0 50 100 150 200 250 300 350

Hei

ght (

nm)

Distance (nm)A B

ab

c d

Figure S1 | AFM characterization of PFS28-b-PDMS560 cylindrical micelles illustrating

their structural dimensions. a, AFM height image of PFS28-b-PDMS560 cylindrical micelles

on highly ordered pyrolytic graphite (before sonication), b, height profiles across a single

micelle (brown trace) and three neighbouring micelles (black trace), c, height profiles across

two neighbouring micelles (light blue and red traces), and d, height profiles along a graphite

step (green trace) and along the corona of one of the micelles (dark blue trace). The green

trace illustrates how flat the substrate is, and the yellow trace shows clearly that the small

cylinder-like features observed in the image are less than 1 nm high, and therefore are not

attributed to PFS-containing cylindrical micelles. The scale bar corresponds to 200 nm.




S11

-1

0

1

2

3

4

5

6

7

8

9

0 50 100 150 200 250 300 350

Hei

ght (

nm)

Distance (nm)A B

-1

0

1

2

3

4

5

6

7

8

9

0 50 100 150 200 250 300 350

Hei

ght (

nm)

Distance (nm)A B

-1

0

1

2

3

4

5

6

7

8

9

0 50 100 150 200 250 300 350

Hei

ght (

nm)

Distance (nm)A B

ab

c d

Figure S2 | AFM characterization of stub-like PFS-b-PDMS crystallites illustrating

their structural dimensions. a, AFM height image of stub-like PFS-b-PDMS crystallites on

silicon (after sonication), b, height profiles across three densely spaced crystallites (black and

light blue traces), c, height profiles across three less densely spaced crystallites (dark blue and

brown traces), and d, height profiles along silicon surface (green trace) and across two

crystallites and a larger aggregate of several crystallites (red trace). The scale bar corresponds

to 200 nm.




S12

Figure S3 | High magnification images of stub-like PFS-b-PDMS crystallites. a, TEM

micrograph and b, AFM phase image on silicon of stub-like PFS-b-PDMS crystallites after

sonication. The scale bars correspond to 200 nm.

Figure S4 | A comparison of the contour length distributions of seed cylinders for the

living crystallization-driven self-assembly of PFS-containing block copolymers. a,

previously reported PI264-b-PFS48 cylindrical micelles seeds (Ln = 96 nm, Lw = 143 nm, Lw/Ln

= 1.49, and σ/Ln = 0.47)7 and b, PFS-b-PDMS stub-like crystallites (Ln = 23 nm, Lw = 24 nm,

Lw/Ln = 1.04, and σ/Ln = 0.13) (this work).




S13

0

5

10

15

20

25

1 10 100 1000 10000

Num

ber I

nten

sity

(%)

RH,app (nm) Figure S5 | Representative DLS (173°) trace for the stub-like PFS-b-PDMS crystallites

as a 0.25 mg mL-1 colloidal solution in n-hexane.

Table S2. Results of DLS (173°) experiments for a colloidal solution of stub-like PFS-b-

PDMS crystallites in n-hexane.

Concentration 0.50 mg mL-1 0.25 mg mL-1 0.125 mg mL-1 Run 1 2 1 2 1 2

RH,app (nm) 22.89 22.35 21.29 22.31 20.25 19.59 21.02 22.89 21.76 19.94 20.78 17.50 22.45 22.09 20.09 20.59 21.97 18.04

Average RH,app (nm) 22.3 ± 0.7 21.0 ± 0.9 19.7 ± 1.7 Overall Average RH,app (nm) 21.0 ± 1.6




S14

a b

c d

fe

Figure S6 | Contour length distributions of monodisperse PI550-b-PFS50 cylindrical

micelles grown from stub-like PFS-b-PDMS crystallites. a, Ln = 236 nm, b, Ln = 452 nm,

c, Ln = 966 nm, d, Ln = 1787 nm, e, Ln = 188 nm (30 mg scale), and f, Ln = 731 nm (30 mg

scale). The data sets were fit to Gaussian distributions (blue lines), and the corresponding

data shown in Table S3.




S15

Table S3. Parameters obtained from Gaussian distribution curves (Fig. S6).

Ln from TEM data (nm) Ln (nm)a σ/Ln (nm)b R2c

236 261 0.17 0.998

452 476 0.14 0.994

966 999 0.09 0.963

1787 1813 0.08 0.996

188 208 0.21 0.992

731 758 0.12 0.996 aCalculated from Eq. S1, bCalculated from Eq. S3, cR = correlation coefficient of data fit

Figure S7 | A comparison of the contour length distributions of PI-b-PFS cylindrical

micelles of similar length grown from different PFS-based initiators. a, previously7

reported PI264-b-PFS48 cylindrical micelles grown from sonicated polydisperse cylinders (Ln =

510 nm, Lw = 815 nm, Lw/Ln = 1.60, and σ/Ln = 0.48) fit to a Zimm-Shulz expression (red)

and b, PI550-b-PFS50 cylindrical micelles grown from monodisperse stub-like PFS-b-PDMS

crystallites (Ln = 731 nm, Lw = 743 nm, Lw/Ln = 1.02, and σ/Ln = 0.13) fit to a Gaussian

distribution (red, this work).

a b




S16

Er

a b

Figure S8 | A depiction of the proposed alignment behavior of PFS-containing

cylindrical micelles. a, before application, and b, after application of an electric field.

Figure S9 | Study of the electric field responsiveness of PFS-containing cylindrical

micelles as a 50 mg mL-1 colloidal solution of 731 nm cylinders in decane using

polarizing optical microscopy. a, before application of an electric field (after 10 min), b, in

a 4.2 V μm-1 field (after 10 min). The bright features that make a diagonal pattern across the

surface are small dust particles. The scale bars correspond to 100 μm.




S17

References

1. Massey, J. A. et al. Self-assembly of organometallic block copolymers: The role of

crystallinity of the core-forming polyferrocene block on the micellar morphologies

formed by poly(ferrocenylsilane-b-dimethylsiloxane) in n-alkane solvents. J. Am.

Chem. Soc. 122, 11577-11584 (2000).

2. Ni, Y., Rulkens, R. & Manners, I. Transition metal-based polymers with controlled

architectures: Well-defined poly(ferrocenylsilane) homopolymers and multiblock

copolymers via the living anionic ring-opening polymerization of silicon-bridged

[1]ferrocenophanes. J. Am. Chem. Soc. 118, 4102-4114 (1996).

3. Rogošić, M., Mencer, H. J. & Gomzi, Z. Polydispersity index and molecular weight

distributions of polymers. Eur. Polym. J. 32, 1337-1344 (1996).

4. Henderson, J. F. & Szwarc, M. The use of living polymers in the preparation of

polymer structures of controlled architecture. Macromol. Rev., 317-401 (1969).

5. Huang, T. C., Toraya, H., Blanton, T. N. & Wu, Y. X-ray powder diffraction analysis

of silver behenate, a possible low-angle diffraction standard. J. Appl. Crystallogr. 26,

180-184 (1993).

6. Lovell, R. & Mitchell, G. R. Molecular-orientation distribution derived from an

arbitrary reflection. Acta Crystallogr., Sect. A: Found. Crystallogr. 37, 135-137

(1981).

7. Wang, X. et al. Cylindrical block copolymer micelles and co-micelles of controlled

length and architecture. Science 317, 644-647 (2007).



supplementary information · ©20 10 macmillan publishers limited. all rights reserved. s1...

Documents