Supporting Information
Synthesis of low molecular weight poly(vinyl acetate)
and its application as plasticizer
Daniel Heinzea,b, Thomas Mangb, Karin Petera, Martin Möllera and Oliver Weicholda,c
a
DWI an der RWTH Aachen e.V., Forckenbeckstr. 50, 52065 Aachen, Germany
b Aachen
c
University of Applied Sciences, Heinrich-Mußmann-Str. 1, 52428 Jülich, Germany
Institut für Bauforschung Aachen, Schinkelstraße 3, 52062 Aachen, Germany
1
EXPERIMENTAL
Materials
Vinyl acetate, carbon tetrachloride, and fluorene were obtained from Sigma Aldrich, acetone
was from Julius Hoesch, dried dimethyl sulfoxide, sodium borohydride, n-hexane, hydroquinone
and 1-dodecanethiol were from Merck, and 2,2’-azobisisobutyronitrile was purchased from
Fluka Chemicals. The commercial poly(vinyl acetate), referred to as PVAc-V, was Vinnapas B30
spezial (Tg = 40 °C and Mw = 50,000 g mol−1) from Wacker. Vinyl acetate was distilled under
argon flow before use to remove the inhibitor. All other chemicals were used as received.
Determination of chain transfer constants
A 250-ml three-neck round-bottom flask with argon gas inlet, reflux condenser, and mechanical
stirrer was loaded with freshly distilled vinyl acetate (5 g, 0.06 mol), AIBN (0.05 g, 0.31 mmol)
and the concentrations of 1-dodecanethiol, carbon tetrachloride, or fluorene shown in Table S1.
The flask was purged at room temperature with argon for 15 min while stirring at 120 rpm.
After heating the mixture to 70 °C under argon atmosphere and stirring, polymerization was
interrupted at low conversion by the addition of a small amount of hydroquinone and cooling to
room temperature. The time required to achieve low conversions in each polymerisation was
judged by pilot runs. For the transfer reactions using 1-dodecanthiol and fluorene, the reaction
mixtures were diluted with acetone and poured into n-hexane to remove unreacted VAc and
transfer agent. Concerning the polymerizations using CCl4 as transfer agent, VAc and CCl4 were
removed by distillation under reduced pressure. For all reactions, the yield was in the range of
2–7 % (Tab. S1). The molecular weights were determined using GPC.
2
TABLE S1 Results of the transfer reactions using vinyl acetate and 1-dodecanethiol, fluorene and CCl4
as transfer agents.
Run
1-Dodecanethiol
Fluorene
CCl4
w (1-Dodecanethiol)
Yield
Mn
w (fluorene)
Yield
Mn
w (CCl4)
Yield
Mn
%
%
g mol−1
%
%
g mol−1
%
%
g mol−1
1
0
6.8
82,140
0
6.8
82,140
0
6.8
82,140
2
1
3.2
36,100
0.25
4.3
52,140
5
4.4
4,680
3
2.5
6.2
20,800
0.5
3.4
40,470
10
5.2
2,390
4
5
3.5
9,480
1
2.8
20,260
15
2.1
1,590
5
10
5.1
5,280
2.5
6.1
7,620
20
4.2
1,100
6
15
3.7
3,290
5
5.0
4,840
25
3.7
820
0.11
0.10
0.09
Carbon tetrachloride y = 0.54322x + 0.0003
Fluorene
y = 0.48446x + 0.0002
1-Dodecanethiol
y = 0.33155x - 0.0001
0.08
1/Xn - 1/Xn,0
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
0.00
0.05
0.10
0.15
0.20
[AX]/[VAc]
FIGURE S1 Determination of transfer constants by plotting 1/Xn − 1/Xn,0 vs the transfer agent/vinyl
acetate molar ratio [AX]/[VAc].
3
Polymerization of VAc using 1-dodecanethiol as transfer agent: single addition
A 250-ml three-neck round-bottom flask with argon gas inlet, reflux condenser, and mechanical
stirrer was charged with freshly distilled VAc (15 g, 0.17 mol), AIBN (0.15 g, 0.91 mmol) and
1-dodecanethiol (8.61 g, 0.04 mol). The flask was purged at room temperature with argon for
15 min while stirring at a speed of 120 rpm, and then heated to 70 °C for 4 h with constant
stirring under argon. Polymerization was interrupted by the addition of a small amount of
hydroquinone and cooling to room temperature. The viscous and cloudy mixture was diluted
with acetone (60 ml) and poured into n-hexane (400 ml). The polymer was isolated by decanting
off the solvents and dried under vacuum at 50 °C to constant weight to give a solid and colorless
product designated PVAc-D1. Yield: 8.8 g (37 %). GPC: Mn = 21,170 g mol−1, Mw = 34,270 g mol−1.
1.4
1.2
Wlog molecular weight
1.0
0.8
0.6
0.4
0.2
0.0
10,000
100,000
Molecular weight (Da)
FIGURE S2 Molecular weight distribution of PVAc-D1.
4
Polymerization of VAc using 1-dodecanethiol as transfer agent: continuous addition
A 250-ml four-neck round-bottom flask with argon gas inlet, reflux condenser, mechanical
stirrer, and syringe pump (pump 11 plus, Harvard Apparatus) was charged with freshly distilled
VAc (10 g, 0.12 mol), AIBN (0.1 g, 0.61 mmol) and 1-dodecanethiol (0.74 g, 3.65 mmol) and
purged at room temperature with argon for 15 min while stirring at a speed of 120 rpm. The
mixture was heated to 70 °C with constant stirring under argon and 1-dodecanethiol (5 g,
0.03 mol) were added at a rate of 2 ml h−1 using the pump. Polymerization was interrupted by
the addition of a small amount of hydroquinone and cooling to room temperature. The viscous
and cloudy mixture was diluted in acetone (40 ml) and poured into n-hexane (300 ml). The
polymer was isolated by decanting off the solvents and dried under vacuum at 50 °C to constant
weight to give a solid and colorless product designated PVAc-D2. Yield: 7.8 g (49 %). GPC:
Mn = 1,690 g mol−1, Mw = 19,950 g mol−1.
1.6
1.4
Wlog molecular weight
1.2
1.0
0.8
0.6
0.4
0.2
0.0
1,000
10,000
100,000
Molecular weight (Da)
FIGURE S3 Molecular weight distribution of PVAc-D2.
5
Polymerization of VAc using fluorene as transfer agent
A 250-ml three-neck round-bottom flask with argon gas inlet, reflux condenser, and mechanical
stirrer was charged with freshly distilled VAc (15 g, 0.17 mol), AIBN (0.15 g, 0.91 mmol) and
fluorene (1.5 g, 9.02 mmol). The flask was purged at room temperature with argon for 15 min
while stirring at a speed of 120 rpm, and heated to 70 °C for 20 h with constant stirring under
argon. Polymerization was interrupted by the addition of a small amount of hydroquinone and
cooling to room temperature. The liquid mixture was diluted with acetone (30 ml) and poured
into n-hexane (250 ml). The polymer was isolated by decanting off the solvents and dried under
vacuum oven at 50 °C to constant weight to give a solid and yellow colored product designated
PVAc-F. Yield: 0.6 g (4 %). GPC: Mn = 3,670 g mol−1, Mw = 6,330 g mol−1.
1.4
1.2
Wlog molecular weight
1.0
0.8
0.6
0.4
0.2
0.0
1,000
10,000
Molecular weight (Da)
FIGURE S4 Molecular weight distribution of PVAc-F.
6
Characterization
Molecular weights were determined relative to PMMA standards (PSS Polymer Standards
Service) using gel permeation chromatography in tetrahydrofuran (THF), containing 250 g l−1
butylated hydroxytoluene, equipped with a refractive index detector (2031 plus, Jasco), a highpressure liquid chromatography pump (Model 6420, ERC), and four columns with MZ-Gel SDplus
from MZ-Analysentechnik. The tests were performed at 20 °C and a flow rate of 1 ml min−1.
Before measuring, the polymers were dissolved in THF to a concentration of 3–4 µg ml−1 and
purified employing syringe filters with a pore size of 0.2 µm.
1H-NMR-spectroscopy
was carried out with a Bruker AVANCETM III 400 MHz spectrometer in
chloroform-d containing 0.03 % tetramethylsilane as internal standard. The spectra were recorded at room temperature performing 64 scans and a relaxation delay of 2 s.
Electrospray ionization mass spectroscopy (ESI-MS) of PVAc-C was done by means of a
micrOTOF-QTM mass spectrometer from Bruker Daltonik, equipped with an Apollo IITM electrospray ionization source, in positive ion mode. PVAc-C was dissolved in a mixture of acetonitrile
and 0.1 % aqueous formic acid to a concentration of 500 µg ml −1 and directly injected into the
ESI source, held at a temperature of 180 °C, with a flow rate of 180 µl h−1. The solution was
nebulized using a voltage of 4.5 kV and by coaxial flow of nitrogen at 0.4 bar. Desolvation was
enhanced by a countercurrent flow of drying nitrogen of 4 l min−1.
Thermogravimetric analysis was performed by means of the thermobalance TG 209 F1 Iris®
from Netzsch coupled to the Bruker infrared spectrometer IFS 28. For the measurements of
PVAc-C and PVAc-R, polymers (15–20 mg) were placed in porcelain crucibles (Al2O3) and heated
7
to 600 °C at a rate of 10 K min−1 under nitrogen flow. Concerning the isothermal TGA measurements of the blended PVAc films, samples (5–15 mg) were placed in the crucibles, heated at a
rate of 10 K min−1 to 80 °C and held isothermally for 6 h under argon.
Three point bending tests were done on a Zwick Z030 universal testing machine using rectangular specimens (58  12  2 mm3) and a 30 kN load cell. Samples were tested at room
temperature with a crosshead speed of 10 mm min−1 either until break or a deflection of 3 mm
and the load deflection curves were recorded. Before measuring, the width and thickness of
each specimen were determined at three different points and the average value was calculated.
The flexural stress σf and flexural strain εf values were calculated from the data of the load
deflection curves using
𝜀f =
600 ∙ 𝑠 ∙ ℎ
%
𝐿2
and
𝜎f =
3∙𝐹∙𝐿
2 ∙ 𝑏 ∙ ℎ2
where F is the applied load, L is the span, s is the deflection and b and h are the width and
thickness of the specimens. The flexural modulus Ef was calculated from the slope of the initial
section of the flexural stress-flexural strain curves by the use of the equation
𝐸f =
𝜎f2 − 𝜎f1
𝜀f2 − 𝜀f1
where εf1 is 0.05 % and εf2 is 0.25 %, and σf1 and σf2 are the flexural stresses at these flexural
strains. Three specimens of each material were examined and the average values were calculated. The span L depends on the medial thickness of each specimen set.
8
The oxygen transmission rates OTR trough the PVAc films were measured using the MOCON
OX-TRAN® Model 702 in accordance with the standard ASTM D-3985. The test conditions were
controlled at 23 °C and 0 % relative humidity and the O2 driving force gradient across the film Δp
was 1 bar. The test gas was oxygen and the carrier gas was a nitrogen/hydrogen mixed gas. Due
to their small size, the samples were fixed into aluminum masks and glued. Then the correct test
areas of the films were determined. The measurements were performed on two samples of
each film type until the constant transmission rates were obtained. These were measured twice
per sample. The final transmission rate per film type in cm3 m−2 d−1 was calculated by averaging
the values. The amount of oxygen, permeating through the film sample and carried to the
sensor by the carrier gas, was determined by the Coulox® sensor. The oxygen permeability
coefficients (P) were calculated using the equation
𝑃=
𝑂𝑇𝑅 ∙ 𝑙
∆𝑝
where OTR is the oxygen transmission rate, l is the thickness of the sample and Δp is the oxygen
driving force gradient across the film. Before measuring, the thickness of each sample was
measured at random points with the MTS Adamel Lhomargy model MI20 micrometer and the
average values were calculated.
Rheological properties of the blends were examined using the Anton Paar Physica MCR 501
rheometer, equipped with parallel plate geometry, and shear rate dependent rotational
measurements on the injection moulded plates. The samples were directly moulded between
the plates and the tests were done under compressed air atmosphere from 0.1 s −1 to 20 s−1
(logarithmically ramped) at 85 °C. The distance gap was 0.2 mm.
9
A Netzsch DSC 200 PC Phox® attached to a dewar flask filled with liquid nitrogen was used for
differential scanning calorimetry test. Samples (10–20 mg) were placed in aluminium crucibles
and the measurements were carried out at a heating and cooling rate of 10 K min−1 from
–100 °C to 100 °C under nitrogen flow. The reference material was air. Three runs (heatingcooling-heating) were performed and the second heating cycle was used to determine the Tg.
10
RESULTS AND DISCUSSION
Synthesis of thermally stable PVAc Oligomers
1.6
1.4
Wlog molecular weight
1.2
1.0
0.8
0.6
0.4
0.2
0.0
1,000
10,000
Molecular weight (Da)
FIGURE S5 Molecular weight distribution of chlorinated PVAc-C.
1.0
0.9
HCl
Transmittance
0.8
CH3
0.7
C-O
0.6
0.5
0.4
C=O
0.3
1,000
1,500
2,000
2,500
3,000
3,500
-1
Wavenumber (cm )
FIGURE S6 Thermal behaviour of PVAc-C containing C–Cl end groups: FTIR spectra of the volatile
components at 235 °C.
11
1.6
1.4
Wlog molecular weight
1.2
1.0
0.8
0.6
0.4
0.2
0.0
1,000
10,000
Molecular weight (Da)
FIGURE S7 Molecular weight distribution of reduced PVAc-R.
0.94
0.92
0.90
CH3
Transmittance
0.88
0.86
C-H
ar
0.84
0.82
C-O
0.80
C=O
0.78
0.76
0.74
1,000
1,500
2,000
2,500
3,000
3,500
-1
Wavenumber (cm )
FIGURE S8 Thermal behaviour of PVAc-R containing C–H end groups: FTIR spectrum of the volatile
components at 449 °C.
12
Plasticizing effect of oligomeric PVAc
0.36
0.32
6
8
-1
Heat flow (mW mg )
0.28
7
0.24
1
0.20
5
0.16
4
3
0.12
2
0.08
9
0.04
0.00
-0.04
-40
-20
0
20
40
60
80
Temperature (°C)
FIGURE S9 DSC thermograms of the pure PVAc-V (1), of the PVAc blends containing 5 wt.-% (2),
10
wt.-% (3), 15 wt.-% (4), 20 wt.-% (5), 25 wt.-% (6), 50 wt.-% (7) and 90 wt.-% PVAc-R (8) as well as of the
pure PVAc-R (9).
99
98
PVAc-V
TG (%)
97
96
5 wt.-% PVAc-R
95
7.5 wt.-% PVAc-R
10 wt.-% PVAc-R
94
12.5 wt.-% PVAc-R
93
15 wt.-% PVAc-R
92
50
100
150
200
250
300
350
400
Time (min)
FIGURE S10 Isothermal TGA thermograms of evaporation of PVAc-R from the blended PVAc films
containing different PVAc-R concentrations.
13
1.00
0.98
Transmittance
0.96
0.94
0.92
0.90
0.88
CO2
0.86
a
0.84
1000
1500
2000
2500
3000
3500
4000
-1
Wavenumber (cm )
1.00
Transmittance
0.95
0.90
H2O
H 2O
0.85
0.80
CO2
0.75
b
0.70
1000
1500
2000
2500
3000
3500
4000
-1
Wavenumber (cm )
FIGURE S11 Isothermal thermogravimetry of evaporation of PVAc-R from the PVAc films: FTIR spectra of
the volatile components of pure PVAc-V (a) and B12.5 (b).
14
DMSO
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
ppm
FIGURE S12 1H-NMR spectrum of reduced PVAc-R.
TABLE S2 Formulations and properties of blended PVAc materials.
DSC
Sample
Three point bending test
Rheometer
w (PVAc-R)
Tg
Ef
σfB
εfB
η0
%
°C
MPa
MPa
%
Pas
PVAc-V
0
40.5
3,520 ± 460
31.3 ± 4.2
1.0 ± 0.1
15,000
B5
5
35.9
2,990 ± 195
46.6 ± 9.4
1.7 ± 0.3
10,700
B10
10
32.2
2,270 ± 197
30.9 ± 2.6
1.4 ± 0.0
5,550
B15
15
28.6
960 ± 423
-a
-a
3,360
B20
20
24.8
720 ± 165
-a
-a
2,290
b
B25
25
21.4
-
-
-
-
B50b
50
5.9
-
-
-
-
B90b
90
-7.2
-
-
-
-
PVAc-Rb
100
-6.1
-
-
-
-
a
No fracture was observed in the strain region under investigation. b samples with more than 20 wt.-%
PVAc-R are too soft to be considered for three point bending tests.
15