Polymeric Nanocontainers with High Loading Capacity of ... · Oana G. Schramm, Michael A. R. Meier, Richard Hoogenboom, Hannes H. P. van Erp, Jean-Francois Gohy, *Ulrich S. Schubert

Supplementary Material (ESI) for Soft Matter

This journal is (c) The Royal Society of Chemistry 2009

1

Polymeric Nanocontainers with High Loading

Capacity of Hydrophobic Drugs

Supporting Information

Oana G. Schramm, Michael A. R. Meier, Richard Hoogenboom, Hannes H. P. van Erp,

Jean-Francois Gohy, Ulrich S. Schubert*

Experimental Part

Materials

All reagents were used without further purification unless stated otherwise. Solvents were

purchased from Biosolve Ltd. (Valkenswaard, The Netherlands). Pentaerythritol, dipentaerithritol,

stannous octoate, ε-caprolactone, poly(ethylene glycol) methyl ether methacrylate (mPEGMA),

copper bromide and N,N,N′,N′,N′′-pentamethyl-diethylenetriamine (PMDETA) were purchased

from Aldrich (Oakville, On, Canada).

Instrumentation

GPC was measured on a Shimadzu system equipped with a SCL-10A system controller, a LC-

10AD pump, a RID-10A refractive index detector, a SIL-10AD autosampler and a Polymer

Laboratories Mixed-D column utilizing a chloroform:triethylamine:isopropanol (93:5:2) mixture

as eluent at a flow rate of 1 mL/min and a column temperature at 50 °C. Calibration was

performed utilizing linear poly(ethylene glycol) standards.

UV/vis spectra were recorded on a FlashScan S12 (AnalytikJena, Germany) in 96-well microtiter

plates (polypropylene, flat bottom) from Greiner (Greiner Bio-One, Germany) in a range from 250

2

to 700 nm. All spectra were referenced to an empty microtiter plate and measurements were

performed with four flashes. The actual time for the measurement of one microtiter plate with 96

full UV/Vis spectra was approximately 40 seconds.

NMR spectra were measured on a Varian Gemini 400 NMR spectrometer in CDCl3 and D2O. The

chemical shifts were calibrated to TMS.

DLS measurements were performed on a Brookhaven Instruments Corp. BI-200 apparatus

equipped with a BI-2030 digital correlator and a Spectra Physics He-Ne laser with a wavelength of

633 nm. The scattering angle used for the measurements was 90°. The experimental correlation

function was analyzed by the method of the cumulants, as described elsewhere.1 The

Stokes-Einstein approximation was used to convert diffusion coefficient into hydrodynamic

diameter (Dh).

General procedure for the synthesis of 4- and 6-arm starPCL-OH

Ring opening polymerizations of ε-caprolactone were performed at 130 °C for 8 h using 20.00 g

(20.60 mL, 0.18 mol) of monomer. The initiator amount was calculated according to the M/I ratio

of 48:1 and 72:1, respectively. The monomer, ε-caprolactone, and the initiator, pentaerythritol for

4-arm starPCL-OH or dipentaerythritol for 6-arm starPCL-OH, were added to a flask and stirred

for 15 min at 130 °C in order to obtain a homogeneous solution. Subsequently, the polymerization

was started by adding the catalyst, stannous octoate (n(cat) = 1/20 of n(OH-functional groups)).

After the reaction time was elapsed the very viscous reaction mixtures were cooled to room

temperature in an ice bath to stop the polymerization. The polymers were purified from residual

monomer and catalyst by precipitation from a concentrated dichloromethane solution into ice-cold

heptane resulting in powdery products. The yields were in the order of > 95%. The corresponding

analytical data are depicted in Table 1.



3

General procedure for the synthesis of 4- and 6-arm starPCL-Br macroinitiators

To a stirred solution of starPCL-OH (1.0 mmol; 5.6 g of 4-arm starPCL-OH or 8.5 g of 6-arm

starPCL-OH) and triethylamine (2.0 mmol/arm in 200 mL dry THF), 2.0 mmol/arm of

2-bromoisobutyryl bromide were added dropwise. The reaction was performed at room

temperature for 48 to 72 h. The reaction mixture was filtrated through a short pad of neutral

alumina to remove the quaternary ammonium salts. After the solvent evaporation and precipitation

from a small amount of THF in cold methanol, white powdery polymers were obtained in

quantitative yield.

Table 1 Analytical data of the synthesized star-shaped polymers

Mn (GPC) obtained using linear poly(ethylene glycol) calibration.

polymer M/I units of CL per arm Mn (GPC) Mn (1H NMR) PDI yield

4-arm starPCL-OH 48 12 4100 5600 1.18 98%

6-arm starPCL-OH 72 12 6600 8500 1.18 96%

4-arm starPCL-Br - 12 4600 6200 1.17 ∼100%

6-arm starPCL-Br - 12 7000 9300 1.17 ∼100%

4

4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0

(b)

(a)

he

g

b+dc

a

f

ec

b+da

O

OO

O

n

OR2R2O

R2O O

OBr

ab cd

e

g

a bc dh

O

OO

O

n

R1O

R1O OH

OR1

ab cd

e

f

a bc d

δ / ppm

Fig. S1 1H NMR spectra of starPCL-OH (a) and star-PCL-Br (b).

General procedure for the synthesis of 4- and 6-arm starPCL-p(mPEGMA)s

The catalyst CuBr (0.05 mmol) and the ligand PMDETA (0.05 mmol) were added to 5 mL of

toluene previously purged with argon for 10 minutes. A solution of macroinitiator (0.05 mmol)

and monomer mPEGMA in 15 mL of toluene was purged with argon for 10 minutes and then

added to the catalyst suspension. The amount of monomer was calculated according to the M/I

ratios. The reaction mixture was stirred for 3 to 4 h at 70 ºC under an inert atmosphere. The



5

reaction was stopped by cooling to room temperature and dilution with toluene in air. The content

was then passed through a short pad of alumina to remove the copper catalyst. After solvent

evaporation, the polymer was precipitated from a small amount of toluene in diethyl ether, filtered

and dried under vacuum for several hours. The conversions (48-85%) were determined by 1H

NMR spectroscopy. A typical 1H NMR spectrum and GPC traces of star PCL-p(mPEGMA)s are

depicted in Figure S2 and S3, respectively.

Fig. S2 Representative 1H NMR spectrum for 4- and 6-arm star-PCL-p(mPEGMA)s.

4 3 2 1

δ / ppm

R3O OR3

O

OO

OBr

n

OR3O

R3O

O O

p

O

O

O

x

R3O

j

j

a

b

c

d

e

f

g h

i j

j k

l

O

OO

OBr

n

OR3R3O

R3O

O O

p

O

O

O

x

j

a

b

c

d

e

f

g h

i j

j

j k

la b+d

c

e+i

j+k

l

hgf

or

6

The molar masses of all star-shaped polymers were calculated according to the DP of the PCL, DP

of the pPEGMA shell and the number of arms. The degree of polymerization (DP) of mPEGMA

related to the DP of PCL (12/arm) was determined by 1H NMR spectroscopy from the integrated

ratios of the signal at 4.1 ppm corresponding to the resonances of the methylenic protons from the

PCL core and the signals at 3.4 ppm assigned to the methoxy protons from the

starPCL-pPEGMAs.

Fig. S3 GPC traces of starPCL-p(mPEGMA), P5-P8.

The semilogaritmic plot of the conversion versus time of the polymerizations at 90 °C and

70 °C are linear, except a fast activation step, suggesting that at the beginning of polymerization,

elevated temperatures induce a fast monomer consumption as well as radical terminations.2 This

fast initiation step could be diminished by reducing the temperature (Fig. S4).

8 12 16 20

7 00032 10065 40083 400

170 000

PDI 1.176-arm starPCL-BrP5, PDI 1.29P6, PDI 1.3P7, PDI 1.18P8, PDI 1.15

Mn - 1H NMR (Da)

elution volume/ mL



7

Fig. S4 Semi-logarithmic kinetic plot for ATRP of mPEGMA at different temperatures.

Fig. S5 1H NMR spectra of (a) p(mPEGMA) from the acid-catalysed hydrolysis of 6-arm starPCL-

p(mPEGMA), (b) 6-arm star-PCL-p(mPEGMA) (P8), (c) 6-arm starPCL-Br.

0 50 100 150 200 250 3000.0

0.2

0.4

0.6

0.8

1.0

1.2

ln([M

0]/[M

])

time/ minutes0 50 100 150 200 250 300

0.0

0.2

0.4

0.6

0.8

1.0

1.2

ln([M

0]/[M

])

time, minutes

Temperature 90 ºC Temperature 70 ºC

0.51.01.52.02.53.03.54.04.55.0

0.51.01.52.02.53.03.54.04.55.0

0.51.01.52.02.53.03.54.04.55.0

(a)

(b)

(c)

δ / ppm

H2O

8

The degradation of the PCL core was also performed using a lipase from Rhizopus arrhizus

(enzyme/polymer 1:5 (w/w)), in phosphate buffer solution (PBS, pH = 7.0). Every 24 h, new

amounts of enzyme were added, to enssure that the enzyme present in the PBS solution is

catalytically active. The starPCL core was completely degraded after 4 days of stirring at 37 °C, as

determined by GPC measurements.

General procedure for the UV/Vis polymer titrations

For the preparation of a [1]:[1] molar ratio [dye]/[polymer] aqueous solution, 4.84 mg,

(0.02 mmol) of disperse orange 3 were added to a solution of polymer, 0.02 mmol, in 200 mL of

demineralized water. After ultrasonication for 2 minutes at 40 ºC when the dye was completely

dissolved and 10 mL of this solution were placed into a separated vial. To the rest of the solution

4.35 mg of dye were added, corresponding to a [dye]/[polymer] ratio of [2]:[1] and after

ultrasonication at 40 ºC for 2 minutes, another 10 mL were placed into a separated vial. The

procedure has been repeated for all 10 or 15 solutions of different ratio [dye]/[polymer] ratios. The

solutions were then diluted with 30 mL of water and their UV/Vis absorptions were measured. A

control UV/Vis spectrum was recorded for a suspension of 1.21 mg of dye in 10 mL of water, (0.5

mM) in the absence of polymer (see Figure S6, S7).

Fig. S6 Different aqueous solutions for the titration of polymer with guest 1.



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Fig. S7 UV/Vis data obtained from titration of P7 with guest 1 ([P7] = 15 μM).

8 6 4 2 0

f d+e cba

SCl

NH

OO

ONH2

OHO

a

bc

d e

f

DMF

DMFH2O

P4 + guest 2

P3 + guest 2

P2 + guest 2

guest 2 + DMF in D2O

P1 + guest 2

δ / ppm

Fig. S8 1H NMR spectra of polymer encapsulated guest 2 in D2O (DMF as internal standard).

12 16 20 24 28

0.6

0.8

1.0

1.2

abso

rptio

n at

443

nm

/ a.u

.

no. of encapsulated molecules of guest 1 per molecule of P7

300 400 500 600 700

0.0

0.4

0.8

1.2

[dye]/[polymer]ab

sorp

tion/

a.u

.

wavelength/ nm

26:1 24:1 22:1 20:1 18:1 16:1 14:1 12:1

10

8 6 4 2 0

ba

NH

NHSS

O

ONH2

Cl

OOa

b

H2ODMF DMF

P4 + guest 3

P3 + guest 3

P2 + guest 3

P1 + guest 3

guest 3 +DMF in D2O

δ / ppm

Fig. S9 1H NMR spectra of polymer encapsulated guest 3 in D2O (DMF as internal standard).



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References

1 B. J. Berne, R. J. Pecora, Dynamic Light Scattering; John Wiley and Sons: Toronto, 1976. 2 K Matyjaszewski, J. Xia, Chem. Rev. 2001, 101, 2921-2990.

Documents

Polymeric Nanocontainers with High Loading Capacity of ... · Oana G. Schramm, Michael A. R. Meier, Richard Hoogenboom, Hannes H. P. van Erp, Jean-Francois Gohy, *Ulrich S. Schubert