CO2-switchable viscoelastic fluids based on a âpseudoâ gemini ...
CO2-switchable viscoelastic fluids based on a “pseudo” gemini surfactant Yongmin Zhang†,‡ Yujun Feng*,†§ Yuejiao Wang†,‡ and Xiangliang Li§ †
Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041, People’s Republic of China
§
EOR Laboratory, Geological Scientific Research Institute, Shengli Oilfield Company of SINOPEC, Dongying 257013, People’s Republic of China
‡
University of the Chinese Academy of Sciences, Beijing 100049, People’s Republic of China
Experimental details Materials.
Sodium
dodecyl
sulfate
(SDS,
Sigma
Aldrich,
≥
99.0%),
N,N,N′,N′-tetramethyl-1,3-propanediamine (TMPDA, Aldrich, ≥ 99.0%). Other chemicals were analytical-grade and were used as received without further purification. Deionized water was used for all aqueous solutions. pH measurement. The pH of 250 mM “SDS-TMPDA” aqueous solution with bubbling CO2 was monitored by a Sartorius basic pH-meter PB-10 (± 0.01) at 25 °C. The gas flow rate was fixed at 0.1 L⋅min-1 under the pressure of 0.1 MPa. The variation of pH of pure water under bubbling CO2 at 25 °C was also recorded as a reference. Conductivity measurement. The conductivity of 250 mM “SDS-TMPDA” aqueous solution with bubbling CO2 was monitored by an FE30 conductometer (Mettler Toledo, USA) at 25 °C, and average values were calculated from three runs of measurements. The gas flow rate was fixed at 0.1 L⋅min-1. The conductivity of pure water under bubbling CO2 at 25 °C was also determined as a reference. NMR spectroscopy. Design amount of TMPDA and SDS-TMPDA were dissolved in D2O, respectively, and then their 1H NMR spectra were recorded at 25 °C on a Bruker 1
AV300 NMR spectrometer at 300 MHz. Next, they were treated with CO2 at ambient temperature for 5 min with the flow rate of 0.05 L⋅min-1 and their 1H NMR spectra were recorded again. Similarly, the 13C NMR spectra of TMPDA with CO2 was recorded at 75 M Hz. Chemical shifts (δ) are reported in parts per million (ppm) with reference to the internal standard protons of tetramethylsilane (TMS).
2
1
Additional results
2
Exhibited in Figure S1 is the Cole-Cole plot of the 250 mM “SDS-TMPDA” solution after
3
bubbling CO2. G′ and G″ can fit well Cole–Cole model in the low to medium frequency
4
range, but deviation occurs at high frequencies owing to non-repative effects,[1] suggesting
5
the formation of wormlike micelles.[2] Similar Cole-Cole plots have been also found in
6
CTAB/anthranilic acid,[3] cetyltrimethylammonium n-heptane sulfonate/NaBr,[4] or gemini
7
surfactants.[5]
8 9
Figure S1. The Cole-Cole plots of the 250 mM “SDS-TMPDA” solution after bubbling CO2.
10
As shown in Figures S2, with increasing CO2 bubbling duration, the conductivity of 250
11
mM “SDS-TMPDA” solution has an evident rise in conductivity from 17.5 to 27.0 mS·cm-1,
12
accompanied by a decrease in pH from approximately 12 to 8, pointing to the formation of
13
protonated species in solution including ammoniums, CO32- and HCO3-, and the amount of
14
protonated species increases over time. After 1 min of CO2 sparging, the protonation reaches
15
equilibrium; both conductivity and pH level off to a plateau value.
3
1 2
Figure S2. Evolution of conductivity and pH of the 250 mM “SDS-TMPDA” solution with
3
increasing CO2 bubbling time.
4
Shown in Figure S3 is the 13C NMR spectrum of TMPDA in the presence CO2. The signal
5
at ~160 ppm is attributed to the hydrogen carbonate ion according to the results reported by
6
Jessop.[6] Thus, bubbling CO2 induces the protonation of the terminal tertiary amine group of
7
TMPDA into ammonium hydrogen carbonate.
8 9 10
Figure S3. 13C NMR spectrum of TMPDA-CO2 obtained by bubbling CO2 into TMPDA D2O solution. 4
1 2
Figure S4. Variation in surface tension with surfactant concentration at 25 oC.
3
Figure S4 shows the variation of surface tension against surfactants concentration in pure
4
water at 25 °C. The surface tension decreases with increasing surfactant concentration, and
5
then reaches a clear break point which is taken as the critical micelles concentration (cmc).
6
The amount of adsorbed surfactant (Γ) at the air–water interface can be calculated using the
7
Gibbs adsorption isotherm:[7]
8
Γ=−
1 ∂γ ( ) nRT ∂ ln C
(1)
9
where R is the gas constant (8.314 J⋅mol-1⋅K-1), T is the absolute temperature (K), C is the
10
surfactant concentration (mol⋅L-1), and ∂γ ∂ ln C refers to the slope below the cmc in the
11
surface tension plots. The value of n that stands for the number of species at the interface was
12
taken as 2 for SDS and SDS-TMPDA,[8] and 1 for SDS-TMPDA-CO2 because it can be
13
considered a net zero charge.[9] The area occupied (A) by a surfactant molecule at the
14
air–solution interface was obtained from the saturated adsorption as follows:
15
A=
1 N ⋅ Γcmc
(2)
5
1
where N is Avogadro’s number, and Γcmc is the maximum surface excess concentration at
2
cmc.
3
Table S1. Surface activity properties and packing parameters of SDS, SDS-TMPDA and
4
SDS-TMPDA-CO2 cmc
γcmc
Γcmc
Acmc
P
(mM)
(mN⋅m-1)
(10-3 mM)
(nm2)
SDS
7.95
38.13
3.04
0.60
0.34
SDS-TMPDA
3.75
35.20
0.90
1.95
0.11
SDS-TMPDA-CO2
0.71
30.30
2.23
0.82
0.45
12-3-12⋅2Br-[10]
0.91
35.00
2.37
1.05
/
5
As shown in Figure S3 and Table S1, before introducing CO2, the net charge of TMPDA is
6
zero, meaning that there is hardly any interaction between SDS and TMPDA. In other words,
7
the SDS-TMPDA mainly behaves as a conventional surfactant with one hydrophobic tail and
8
one hydrophilic headgroup. However, the fact that TMPDA molecule is also a small
9
molecular surface active compound, thus the cmc of SDS-TMPDA is lower than that of SDS
10
alone. Besides, the surface activity parameters particularly Γcmc and Acmc of SDS-TMPDA are
11
0.90×10-3 mM and 1.95 nm2, respectively.
12
While after bubbling CO2, the sample shows obvious differences in surface activity
13
parameters in comparison with SDS or SDS-TMPDA: cmc decreases to 0.71 mM, less than
14
1/10 and nearly 1/5 those of SDS and SDS-TMPDA without CO2; the γcmc decreases to ~30
15
mN⋅m-1 that is much lower than those of SDS and SDS-TMPDA. The Γcmc of the “pseudo”
16
gemini surfactant reaches 2.23 × 10-3 mM, much higher than that of the mixture, 0.90 × 10-3
17
mM, suggesting much more surfactant molecules intercalated at the air–solution interface
18
than that of the unprotonated mixture system. Accordingly, the Acmc of the
19
“SDS-TMPDA-CO2” is only less half that of “SDS-TMPDA”, implying more compacted
20
layer in the former case. Interestingly, besides γcmc, all other three surface active parameters
21
are very close to those of cationic gemini surfactant 12-3-12⋅2Br-.[10] 6
1
Generally, the morphology of surfactant micelles can be predicted by packing parameter
2
P=υ/al,[11] where a is the effective headgroup area and υ is the volume of the lipophilic chain
3
possessing maximum effective length l. When P < 1/3, spherical micelles are formed; when
4
1/3 < P < 1/2, wormlike micelles are found; and when 1/2 < P
Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041, People’s Republic of China
§
EOR Laboratory, Geological Scientific Research Institute, Shengli Oilfield Company of SINOPEC, Dongying 257013, People’s Republic of China
‡
University of the Chinese Academy of Sciences, Beijing 100049, People’s Republic of China
Experimental details Materials.
Sodium
dodecyl
sulfate
(SDS,
Sigma
Aldrich,
≥
99.0%),
N,N,N′,N′-tetramethyl-1,3-propanediamine (TMPDA, Aldrich, ≥ 99.0%). Other chemicals were analytical-grade and were used as received without further purification. Deionized water was used for all aqueous solutions. pH measurement. The pH of 250 mM “SDS-TMPDA” aqueous solution with bubbling CO2 was monitored by a Sartorius basic pH-meter PB-10 (± 0.01) at 25 °C. The gas flow rate was fixed at 0.1 L⋅min-1 under the pressure of 0.1 MPa. The variation of pH of pure water under bubbling CO2 at 25 °C was also recorded as a reference. Conductivity measurement. The conductivity of 250 mM “SDS-TMPDA” aqueous solution with bubbling CO2 was monitored by an FE30 conductometer (Mettler Toledo, USA) at 25 °C, and average values were calculated from three runs of measurements. The gas flow rate was fixed at 0.1 L⋅min-1. The conductivity of pure water under bubbling CO2 at 25 °C was also determined as a reference. NMR spectroscopy. Design amount of TMPDA and SDS-TMPDA were dissolved in D2O, respectively, and then their 1H NMR spectra were recorded at 25 °C on a Bruker 1
AV300 NMR spectrometer at 300 MHz. Next, they were treated with CO2 at ambient temperature for 5 min with the flow rate of 0.05 L⋅min-1 and their 1H NMR spectra were recorded again. Similarly, the 13C NMR spectra of TMPDA with CO2 was recorded at 75 M Hz. Chemical shifts (δ) are reported in parts per million (ppm) with reference to the internal standard protons of tetramethylsilane (TMS).
2
1
Additional results
2
Exhibited in Figure S1 is the Cole-Cole plot of the 250 mM “SDS-TMPDA” solution after
3
bubbling CO2. G′ and G″ can fit well Cole–Cole model in the low to medium frequency
4
range, but deviation occurs at high frequencies owing to non-repative effects,[1] suggesting
5
the formation of wormlike micelles.[2] Similar Cole-Cole plots have been also found in
6
CTAB/anthranilic acid,[3] cetyltrimethylammonium n-heptane sulfonate/NaBr,[4] or gemini
7
surfactants.[5]
8 9
Figure S1. The Cole-Cole plots of the 250 mM “SDS-TMPDA” solution after bubbling CO2.
10
As shown in Figures S2, with increasing CO2 bubbling duration, the conductivity of 250
11
mM “SDS-TMPDA” solution has an evident rise in conductivity from 17.5 to 27.0 mS·cm-1,
12
accompanied by a decrease in pH from approximately 12 to 8, pointing to the formation of
13
protonated species in solution including ammoniums, CO32- and HCO3-, and the amount of
14
protonated species increases over time. After 1 min of CO2 sparging, the protonation reaches
15
equilibrium; both conductivity and pH level off to a plateau value.
3
1 2
Figure S2. Evolution of conductivity and pH of the 250 mM “SDS-TMPDA” solution with
3
increasing CO2 bubbling time.
4
Shown in Figure S3 is the 13C NMR spectrum of TMPDA in the presence CO2. The signal
5
at ~160 ppm is attributed to the hydrogen carbonate ion according to the results reported by
6
Jessop.[6] Thus, bubbling CO2 induces the protonation of the terminal tertiary amine group of
7
TMPDA into ammonium hydrogen carbonate.
8 9 10
Figure S3. 13C NMR spectrum of TMPDA-CO2 obtained by bubbling CO2 into TMPDA D2O solution. 4
1 2
Figure S4. Variation in surface tension with surfactant concentration at 25 oC.
3
Figure S4 shows the variation of surface tension against surfactants concentration in pure
4
water at 25 °C. The surface tension decreases with increasing surfactant concentration, and
5
then reaches a clear break point which is taken as the critical micelles concentration (cmc).
6
The amount of adsorbed surfactant (Γ) at the air–water interface can be calculated using the
7
Gibbs adsorption isotherm:[7]
8
Γ=−
1 ∂γ ( ) nRT ∂ ln C
(1)
9
where R is the gas constant (8.314 J⋅mol-1⋅K-1), T is the absolute temperature (K), C is the
10
surfactant concentration (mol⋅L-1), and ∂γ ∂ ln C refers to the slope below the cmc in the
11
surface tension plots. The value of n that stands for the number of species at the interface was
12
taken as 2 for SDS and SDS-TMPDA,[8] and 1 for SDS-TMPDA-CO2 because it can be
13
considered a net zero charge.[9] The area occupied (A) by a surfactant molecule at the
14
air–solution interface was obtained from the saturated adsorption as follows:
15
A=
1 N ⋅ Γcmc
(2)
5
1
where N is Avogadro’s number, and Γcmc is the maximum surface excess concentration at
2
cmc.
3
Table S1. Surface activity properties and packing parameters of SDS, SDS-TMPDA and
4
SDS-TMPDA-CO2 cmc
γcmc
Γcmc
Acmc
P
(mM)
(mN⋅m-1)
(10-3 mM)
(nm2)
SDS
7.95
38.13
3.04
0.60
0.34
SDS-TMPDA
3.75
35.20
0.90
1.95
0.11
SDS-TMPDA-CO2
0.71
30.30
2.23
0.82
0.45
12-3-12⋅2Br-[10]
0.91
35.00
2.37
1.05
/
5
As shown in Figure S3 and Table S1, before introducing CO2, the net charge of TMPDA is
6
zero, meaning that there is hardly any interaction between SDS and TMPDA. In other words,
7
the SDS-TMPDA mainly behaves as a conventional surfactant with one hydrophobic tail and
8
one hydrophilic headgroup. However, the fact that TMPDA molecule is also a small
9
molecular surface active compound, thus the cmc of SDS-TMPDA is lower than that of SDS
10
alone. Besides, the surface activity parameters particularly Γcmc and Acmc of SDS-TMPDA are
11
0.90×10-3 mM and 1.95 nm2, respectively.
12
While after bubbling CO2, the sample shows obvious differences in surface activity
13
parameters in comparison with SDS or SDS-TMPDA: cmc decreases to 0.71 mM, less than
14
1/10 and nearly 1/5 those of SDS and SDS-TMPDA without CO2; the γcmc decreases to ~30
15
mN⋅m-1 that is much lower than those of SDS and SDS-TMPDA. The Γcmc of the “pseudo”
16
gemini surfactant reaches 2.23 × 10-3 mM, much higher than that of the mixture, 0.90 × 10-3
17
mM, suggesting much more surfactant molecules intercalated at the air–solution interface
18
than that of the unprotonated mixture system. Accordingly, the Acmc of the
19
“SDS-TMPDA-CO2” is only less half that of “SDS-TMPDA”, implying more compacted
20
layer in the former case. Interestingly, besides γcmc, all other three surface active parameters
21
are very close to those of cationic gemini surfactant 12-3-12⋅2Br-.[10] 6
1
Generally, the morphology of surfactant micelles can be predicted by packing parameter
2
P=υ/al,[11] where a is the effective headgroup area and υ is the volume of the lipophilic chain
3
possessing maximum effective length l. When P < 1/3, spherical micelles are formed; when
4
1/3 < P < 1/2, wormlike micelles are found; and when 1/2 < P
