methyl-1,3-dioxolan (98%), propylene sulfide, copper chloride (CuCl, 99.995%), ..... Left:1H NMR spectrum of benzyl thioacetate, which was obtained from the ...
Supplementary Information
Experimental part Materials Sodium
methoxide
solution
(0.5M
in
methanol),
2-bromoacetyl
bromide,
1,8-
diazabicyclo[5.4.0]undec-7-ene(1,5-5) (DBU, 98%) and sodium sulfate anhydrous were obtained from Fluka. Silica gel 60 (0.063-0.200 mm) was obtained from Merck (Darmstadt, Germany). Acetone, dichloromethane, methanol, hexane, tetrahydrofuran (laboratory reagent grade) and Spectra/Por BiotechCellulose Ester Dialysis Membranes (molecular weight cut-off 1000 and 3500 Da) were purchased from Fisher. Benzylmercaptan (99%), glacial acetic acid, tributylphosphine (97%), 2-bromoacetyl bromide (99%), ethylene glycol (99%), ethyl 2bromoisobutyrate (EBIB, 98%), 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA, 97%), -bromoisobutyryl bromide (98%), triethylamine (TEA, 99.5%), 2,3-dimethyl-4-hydroxy methyl-1,3-dioxolan (98%), propylene sulfide, copper chloride (CuCl, 99.995%), CDCl3 and DMSO-d6 were obtained from Sigma-Aldrich. Water was pre‐distilled and further purified using a Milli‐Q gradient A10 system (Millipore, UK). Unless otherwise stated all other reagents were obtained from Sigma-Aldrich and used without further purification. Physico-chemical characterisation 1
H NMR spectra were recorded using a 300 MHz Bruker NMR spectrometer.
FT-IR spectra were recorded in Attenuated Total Reflection (ATR) mode on a Tensor 27 Brucker spectrometer. Gel Permeation Chromatography (GPC) analysis was performed using a Polymer Laboratories PL-GPC50 comprising of a PLgel 5 µm Guard and two PolyPore 5 m columns operated at 30°C using THF as an eluent at a flow rate of 1.0 mL.min-1 with a refractive index detector and series of near-mono-dispersed linear polystyrene standards. Dynamic Light Scattering (DLS) measurements were carried out at 25 °C using a Brookhaven BI-200SM goniometer equipped with a BI-9000AT digital correlator and a HeNe laser (75 mW, 632.8 nm) at a fixed scattering angle of 90°. The intensity-average hydrodynamic diameter (D) of micellar aggregates were evaluated from cumulants analysis of the experimental correlation Page 1 of 14
function. Unless otherwise stated, 0.5% w/v aqueous copolymer solutions were used for all measurements. The copolymer solutions, if required, were ultrafiltered through 0.2 µm or 0.45 filters (Millipore) prior to DLS measurements. Transmission electron microscopy (TEM) analysis was performed on a Philips CM30 HRTEM operated at 300 kV. A 2% aqueous phosphotungstic acid solution (adjusted to pH 7.3 using NaOH 1 M) was used as a contrast enhancer. The grids (mesh 300 Cu, diameter 3.05 mm) were covered with a formvar film and then coated with carbon (Agar Scientific, Essex, UK). A drop of 1 mg/mL sample solution was left for 90 seconds on top of the grid and the excess solution was removed using filter paper. A drop of contrast solution was then placed on the grid and left for 90 seconds. The excess solution was removed with filter paper leaving a thin layer of solution and the grid was allowed to fully dry in air before analysis. Atomic Force Microscopy (AFM) imaging. AFM images were acquired at 25˚C in air using a Molecular Force Probe 3D AFM (MFP-3D, Asylum Research, Santa Barbara, CA) and a silicon cantilever (model AC240TS, Olympus) with a nominal spring constant, tip radius, tip height and resonance frequency, of 2 N/m, 97% mol.
Page 4 of 14
1
H NMR (CDCl3): δ = 1.22-1.41 (broad, CH3 in PPS chain), 1.88 (s, -O-CO-C(CH3)2Br), 2.41-
2.63 (broad, CH in PPS chain), 2.65-2.94 (broad, CH2 in PPS chain), 3.26 (d, -S-CH2-CO-O-), 3.67 (s, Ar-CH2-S-), 4.33 (s, -CO-O-(CH2)2-O-CO-), 7.20-7.35 (m, Ar-CH2-S-) ppm. GPC: Mn = 2900 g/mol, Mw/Mn = 1.22. PPS with a degree of polymerisation of 40 was synthesized using above procedure using benzylmercaptan (248 mg, 2.00 mmol), TBP (2.5 mL, 10 mmol), propylene sulfide (5930 mg, 80 mmol), DBU (320 mg, 2.1 mmol) and 2 (1328 mg, 4.0 mmol). The product yield was 6.27 g (92% wt.). 1
H NMR (CDCl3): δ = 1.12-1.42 (broad, CH3 in PPS chain), 1.88 (s, -O-CO-C(CH3)2Br), 2.36-
2.65 (broad, one proton of CH2 in PPS chain), 2.65-3.10 (broad, one proton of CH2 and one proton of CH in PPS chain), 3.25 (d, -S-CH2-CO-O-), 3.68 (s, Ar-CH2-S-), 4.34 (s, -CO-O(CH2)2-O-CO-), 7.20-7.35 (m, Ar-CH2-S-) ppm. IR (liquid film): 2957 (νas CH3), 2916 (νas CH2), 2862 (νs CH2), 1736 (ν C=O, ester), 1447, 1371 (δ CH), 1258 (νCO-O, ester), 1167 (νC-O-C), 891 (ω CH, aromatic) cm-1 GPC: Mn = 3600 g/mol, Mw/Mn = 1.22.
DMM homopolymers ATRP of DMM was conducted in 50% wt. THF solutions at 20oC. Typically, EBIB initiator (117 mg, 0.599 mmol), DMM (6.0 g, 29.96 mmol, target DP = 50) and then HMTETA as a ligand (138.1 mg, 0.599 mmol) were introduced into a 25 mL round-bottomed flask. The mixture was bubbled with nitrogen for 30 min prior to the addition of nitrogen-degassed THF (6 mL). The copper catalyst (Cu(I)Cl, 59.3 mg, 0.599 mmol) was finally added while maintaining a slow nitrogen purge. The reaction mixture turned dark green, indicating the onset of the polymerisation. The polymerisation was carried out under magnetic stirring at 20oC for the required time and terminated by dilution with aerated THF. The solution turned from dark green to light-green/blue, indicating oxidation of the Cu(I) to Cu(II). This solution was then passed through a silica gel column to remove the copper catalyst, concentrated at the rotary evaporator and finally precipitated twice in hexane. For kinetic study, samples were taken after the required reaction times and added to CDCl3 for determining monomer conversion using 1H NMR, comparing the integrals of the vinyl peaks (δ = 6.15 and 5.59 ppm) to those of the methyl region (δ = 0.5-1.5 ppm from DMM in both polymeric Page 5 of 14
and monomeric form), which are unchanged during the polymerization. Other samples were diluted in THF for GPC analysis. 1
H NMR (DMSO-d6): δ = 0.70-1.10 (broad CH2C(CH3)- in PDMM chain), 1.30 and 1.36 (d
C(CH3)2 on isopropylidene ring), 1.72-2.04 (broad CH2C(CH3)- in PDMM chain), 3.76 (broad CHCH2 on isopropylidene ring), 4.08 (broad COO-CH2), 4.30 (CHCH2 on isopropylidene ring) ppm. FT-IR (film on ATR crystal): 2988 (asCH3), 2961 (asCH2), 2937 (sCH3), 2885 (sCH2), 1718 (ν C=O ester), 1454 ( O-CH2), 1371 (δ CH3 of acetonide group), 1213, 1082 (νas C-O-C acetal), 1058 (ν C-O-C ester), 842 and 509 (ring vibrations from acetonide group) cm-1. PPS-PDMM and PPS-PGMMA block copolymers Typically, PPS macro-initiator (0.592 g, 0.2278 mmol), DMM (2.737 g, 13.668 mmol) and HMTETA (52.7 mg, 0.2278 mmol) were introduced into a Schlenk flask and degassed with nitrogen for approximately 20 minutes. Degassed THF (3.3 mL) was added and the reaction flask was heated using 60oC water bath under stirring. CuCl (22.5 mg, 0.2278 mmol) was then added to start the polymerisation. The conversion of the monomer reached 83% after 6.5 hours as determined by 1H NMR. The polymerisation mixture was then exposed to air, diluted with THF (3.5 mL) and the polymer was precipitated into hexane. The obtained polymer was then redissolved in THF (100 mL) and passed through a silica column to remove the spent ATRP catalyst. The resulting solution was then concentrated and the polymer was again precipitated into hexane before being dried under vacuum to afford 2.36 g of an off-white solid. Yield: 82 %wt. 1
H NMR (DMSO-d6): δ = 0.70-1.10 (broad CH2C(CH3)- in PDMM chain),1.12-1.42 (broad,
CH3 in PPS chain and C(CH3)2 on isopropylidene ring), 1.72-2.04 (broad CH2C(CH3)- in PDMM chain), 2.36-2.65 (broad, one proton of CH2 in PPS chain), 2.65-3.10 (broad, one proton of CH2 and one proton of CH in PPS chain), 3.76 (broad CHCH2 onisopropylidene ring), 4.08 (broad COO-CH2), 4.30 (CHCH2onisopropylidene ring) 7.20-7.35 (m, Ar-CH2-S-) ppm. FT-IR (film on ATR crystal): 2984 (νas CH3), 2939 (νas CH2), 2887 (νs CH2), 1726 (ν C=O, ester), 1452, 1382 and 1372 (δ CH3), 1082 (ν C-O-C from acetal group), 1058 (ν C-O-C from ester group) 847 and 509 (ring vibrations from acetonide) cm-1.
Page 6 of 14
A literature procedure was used for the deprotection step with formic acid[2]; whereas other methods provided less quantitative results, e.g. 1N HCl/THF for up 5 days and temperatures up to 40oC. Typically, 0.2 g of PPS30-PDMM60 diblock copolymer was added to 2 g of a 80% formic acid solution and stirred at 20oC for 2 days. The polymer was separated by pouring the reaction mixture into brine solution, dissolved in THF, precipitated in hexane and washed with brine before being dried affording an off-white solid. To remove any PPS homopolymer, 1 mL hexane was added drop-wise to the solution of 0.1 g PPS-PGMMA block copolymers in 1 mL DMF. The precipitated polymers were then re-dispersed in THF and precipitated in hexane (50/50 v/v). The resulting PPS-PGMMA diblock copolymers were dried in a vacuum oven at 20oC to yield an off-white polymer. 1
H NMR (DMSO): δ = 0.70-1.10 (broad CH2C(CH3)- in PGMMA chain),1.12-1.42 (broad, CH3
in PPS chain), 1.72-2.04 (broad CH2C(CH3)- in PGMMA chain), 2.36-2.65 (broad, one proton of CH2 in PPS chain), 2.65-3.10 (broad, one proton of CH2 and one proton of CH in PPS chain), 3.76
(broad
CHCH2
(CHCH2onisopropylidene
onisopropylidene
ring),
ring),
(broad,
3.63-4.41
4.08
(broad
COO-CH2),
-CH2CH(OH)CH2(OH),
5.06
4.30 (s,
CH2CH(OH)CH2(OH), 5.35 (s, CH2CH(OH)CH2(OH), 7.20-7.35 (m, Ar-CH2-S-) ppm. FT-IR (film on ATR crystal): 3750-3000 (ν OH), 2951 (νas CH2), 2882 (νs CH2), 1717 (ν C=O, ester), 1481, 1389 and 1372 (δ CH3), 1058 (ν C-O-C from ester group) cm-1.
Page 7 of 14
Supplementary figures and tables
Figure S1. Synthesis of DMM via reaction of isopropylidene glycerol with methacryloyl chloride in dichloromethane (see experimental part). 1H NMR (left) and IR (right) spectra of the reaction product after distillation, which afforded the product in very high purity (e.g. complete absence of OH stretching in the IR spectrum)
Figure S2. Synthesis of BisBr from ethylene glycol through two successive esterification reactions. As a result of the second reaction, the NMR peaks of the ethylene bridge merge into a broad singlet at 4.44 ppm (left), while the OH stretching disappears from the IR spectrum (right).
Page 8 of 14
Figure S3.Left:1H NMR spectrum of benzyl thioacetate, which was obtained from the acetylation of benzyl mercaptane.
Table 1SI. Composition and molecular weight of PPS macroinitiators and PPS-PGMMA diblock copolymers before and after removal of the acteonide protecting groups. PPS Polymera
PPS-PDMM DMM conv. (% mol)d
(g/mol)
74%
PPS-PGMMA
M w c,e Dh f (nm) Mn
Mw c Mn
(g/mol)
5100
1.29
8100
1.26
128
83%
11100
1.36
14300
1.18
190
PPS30-PGMMA77
58%
14500
1.37
16000
1.20
26
PPS39-PGMMA23
80%
6900
1.31
9700
1.20
122
82%
14000
1.28
15900
1.23
48
51%
16700
1.39
19000
1.25
28
DPb
Mn
c
(g/mol)
Mw c Mn
PPS30-PGMMA13 PPS30-PGMMA53
PPS39-PGMMA75 PPS39-PGMMA89
30
39
2900
3600
1.22
1.22
a The final composition was calculated by comparing the integration of methyl groups of PPS and PGMMA backbone an using the DP of PPS. b From 1 H NMR spectra using PPS CH3 residues (peak 4 in Figure 1, δ = 1.22-1.41 ppm) and the benzyl CH2 group (peak 1, δ = 3.75-3.85 ppm ). c GPC in THF using polystyrene standard calibration d based on DMM monomer conversion using 1H NMR e The OH groups of the purified PPS-PGMMA block copolymers were reacted with acetyl chloride/triethyl amine
Mn
c
Mn
c,e
(five equivalents to the OH group) in dried DMF for 2 days. The obtained copolymers were precipitated in methanol and the solvent was evaporated before being re-dissolving the polymers in THF for GPC. f Hydrodynamic diameter (nm) was obtained using Dynamic Light Scattering; 5 mg/mL amphiphilic block copolymer solutions were prepared by adding the copolymers directly into 5 mM NaNO3 solution and shaking at 1000 rpm using an IKA vibrax VXR orbital shaker.
Page 9 of 14
1.5 6000 1.4
4000
1.3
3000 1.2
Mw/Mn
Mn, GPC (g/mol)
5000
2000 1.1
1000 0
1.0 0
10
20
30
40
50
60
70
80
90
Monomer conversion (%)
Figure S4. Molecular weight (GPC in THF) and polydispersity index vs. monomer conversion (from 1H NMR) during ATRP using EBIB as initiator at 60°C (theoretical DP = 30).
Figure S5. Comparison of GPC traces. Due to the chain transfer effect of disulfide impurities in benzyl mercaptan the PPS macroinitiator will be present in mixture with a “monomeric” (terminal disulfide and identical molecular weight) and a “dimeric” (internal disulfide and double molecular weight) non-functional PPS. The GPC trace of PPS30 allows to clearly identify the latter as a shoulder at 16.5 – 17 minutes. The PPS30PDMM13 block copolymer has a more extended shoulder in the low molecular weight region, which comprises both non-functional PPS that did not take part to ATRP. These components were finally removed with hexane extraction of the deprotected (and reacetylated) amphiphilic polymers.
Page 10 of 14
A
6
B
Y=1.88
5
Height (nm)
4 3 2 1 0 0.0
0.5
1.0
1.5
2.0
2.5
X (m)
Figure S6. Tapping mode 2D AFM image (A) and the surface profile at Y = 1.88 µm (B) for PPS30PGMMA75 deposited on mica. The aggregates have a kind of pancake morphology, typically only a few (2-4) nanometers tall and about 50-150 nm large.
A
B
Y = 80nm
2.0
Height (nm)
1.5
1.0
0.5
0.0
-0.5 0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
X (m))
Figure S7. Tapping mode 3D AFM image of a PPS30PGMMA75 aggregate deposited on mica (A) and its surface profile at Y = 80 nm(B).
Page 11 of 14
AFM analysis The root mean square (RMS) roughness of control areas was calculated through the Asylum Research AFM software (Version 101010+1202, Wavemetrics, Portland, OR) in order to select an appropriate threshold to segment the images. The RMS roughness value of the flat surface (black/gray region) were estimated to be 0.4 nm using a 50nm x 50nm mask and this value was used as threshold to discriminate the PPS-PGMMA aggregates from the surface.
0.1 nm
0.4 nm
0.8 nm
Figure S8.A threshold value of 0.4nm, i.e. identical to the surface roughness, allowed to discriminate the surface of the mica disk from the PPS30PGMMA75 aggregates.
Figure S8.AFM height image (left) and its segmentation (right) obtained with a threshold = 0.4 nm
The volume of 467 aggregates was measured and the corresponding volume distribution was then fitted with different probability distributions using the Statistic Toolbox of MATLAB (version 7.12.0). The final best-fit model was selected on the basis of the Akaike Information Criterion (AIC). For each model, the log-likelihood parameter (measured with MATLAB) was Page 12 of 14
, where k represents the
used to calculate the AIC value, expressed as
number of parameters in the statistical model and L is the likelihood function for the estimated model (ln(L)=log-likelihood). The model with the lowest AIC is the one that best fits the data. The best fit was obtained using the lognormal distribution described as where V is the volume and μ and σ are the distribution parameters related to the mean of the data . The most probable micellar volume was Vm=2513 nm3 (with μ = 7.36
(Vm) through
and σ = 0.96. The standard error of the fitting on μ and σ was 0.05 and 0.04 respectively). The volume of a single macromolecule was calculated as the sum of the volumes of the two , where n, MW, ρ represent the degree of
blocks, which were calculated as
polymerization, molecular weight of the repeating units and density of the two polymers (MWPS = 74 g/mol; MWGMMA = 160 g/mol; ρPPS = 1.10 g/cm3 [3]; ρPGMMA was assumed to be equal to that of poly(2-hydroxyethyl methacrylate), 1.15 g/cm3)[4] and NA is the Avogadro number (6.022x1023 molecules/mol).
Diameter Histogram LogNormal Fit
0.12
Count / Total Count
0.10 0.08 0.06 0.04 0.02 0.00 0
10
20
30
40
50
60
Diameter (nm)
Figure S9. Diameter distribution and its fitting. The distribution was calculated from the volume distribution. Since the correlation between the volume and the diameter is not linear, the mean diameter obtained fitting the above distribution differs from the mean diameter calculated from the mean volume. The mean diameter obtained from the fitting of the above distribution was Dm1 = 16.8 nm (µ = 2.35 and σ = 0.68 with a standard error of 0.03 and 0.02, respectively). Please realize that mean and peak values substantially differ.
Page 13 of 14
References [1] H. Mori, A. Hirao, S. Nakahama, Macromolecules 1994, 27, 35. [2] C. Gao, S. Muthukrishnan, W. W. Li, J. Y. Yuan, Y. Y. Xu, A. H. E. Muller, Macromolecules 2007, 40, 1803. [3] J. Masamoto, "Poly(propylene sulfide)", in Polymer Data Handbook, J.E. Mark, Ed., Oxford University Press, Oxford, 1999. [4] Y. Luo, P. D. Dalton, M. S. Shoichet, Chem. Mater. 2001, 13, 4087.
Page 14 of 14
