Figures 3.17 and 3.18 show the CP variation of TX-114 aqueous solution with the concentration of polymers of PEG and PVP series, respectively. The results show that the CP decreases with an increasing polymer concentration. In general, for polymers of a homologous at the same concentration, one with a higher molecular weight has a stronger effect on lowering the CP. PEG-1000 is most effective while PEG-200 is least in decreasing CP. It seems that molecular weight of the polymer is playing some role. Trend observed with PVP addition is similar to PEG (shown in Figure 3.18): for PVPs of high molecular weight CP decreases, while with PVP of molecular weight 10000 (PVP K-15) CP remains constant up to 4 wt %. and above this it increases slowly. May be the low molecular weight PVPs are partitioning in the micelles and decreasing the hydration of micelles, whereas high molecular weight polymer hinders micelle formation.
Thermodynamics of clouding
Many attempts have been made to explain the process of phase separation in terms of thermodynauiics based on the mole-fractional solubility of the clouding species
in presence of additives [66, 67]. The clouding is considered as the formation of a separate phase in the solution where the clouding species become dehydrated and separate out in the solution. The CP, therefore, can be taken as the solubility limit of the clouding species at that temperature. The standard Gibbs energy of solution (here called clouding) (AGs) is then given by the relation
AGs° = RTlnx (3.1) where x, R and T are mole fractional solubility at CP, the gas constant and absolute
temperature respectively.
The standard enthalpy and entropy of the process can be calculated by the relation
( A G ; /T)/d( 1/T) = AHs° (3.2) and
TAS; = AHs°-AGs° (3.3) The values calculated from equations 3.1-3.3 are given in Table 3.19. The table
contains the parameters for pure 114 and 114 + additive systems. For pure TX-114 in the range of 0.33 mM to 2 mM, AG/values vary from -12.0 to -8.4 kJ m o l ' . In presence of additives, AGs values become more negative indicating more spontaneous process. TASs ° values for TX-114 + quaternary salt are negative (except for PrOsPhB) and positive for all long chain alcohols and amines. TASs° values for TX-114 + surfactant (except CPC) are negative. The clouding results in macroaggregate formation releasing heat and there is an overall ordering in the system. However, in some systems, at high additive concentrations, increase in temperature increases the disorderliness in the system and TASs becomes positive.
For the transfer of monomers into micelles the net heat change is due to two processes: (i) disruption of the water structure around the nonpolar tails of the surfactant molecules, and (ii) incorporation of the monomers into the micelles. The first process is endothermic and increases the entropy whereas the second one is exothermic and decreases the entropy. The energetic parameters reveal that the solubilization process is controlled by both enthalpy and entropy. These parameters also support our CP explanation. Positive TASs values mean that the micellization is favorable, i.e., cmc decreases in presence of these additives. Negative TASs" values indicate that these additives cause micellar breakdown which is evident from CP increase.
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Table 3.1. CP data for pure TX-114 aqueous solution.
[TX-114] CP
(M)
CQ_0.00033 27.5 0.00035 20.0 0.00040 19.5 0.00055 20.0 0.00060 21.0 0.00070 21.0 0.00080 23.0 0.00100 25.0 0.00150 25.0 0.00200 25.5 0.00275 25.5 0.00300 25.5 0.00400 26.0 0.00500 26.0 0.00600 26.0 0.00750 26.0 0.01000 26.5
XI CO H
"1 >/-J O O >n «0 p O in K 00 o (N >n 00 (N fN M m f<^ r<-) m
o
o
OH
e
O O O U-) O O O O
m fN ro >n VO
(N (N rj ' -H 00 >n ov r-co m •* rj- «n
OQ <
H
>n o O (O O >n rj- in in
1 vo o
OQ
OH
H
OQ
OQ
<
CM CO
3
o < n o o o o « n o o o o o o o o o o o o o o o o o o o — i r s ( N « n O T t o o o i n o o o o o o o o o O O O O O O O ^ H - — ' C N r ' ^ ' ^ - ' ^ i n o o o i n o i n O i n O 2 Q O O O O O O O O O O O O O ' — ' — (NfNCir'^'^
p p p p p p o o o o o o o o o o o o o o o c o o o o o o o o o o o o o o o o o o o o o o "
IT) O O O O O ( ^ Tt « o iri l o >>d CM (N CN CN (N CN
r-i
o o o o o o o o o o o o o o
>/^ O O O >0 O O
rf in ^ oo oo o\ o p O O O O O —H
o o o c5 o o o
Table 3.3. CP data for x mM TX-114 aqueous solution with added TBuAB.
Table 3.4. CP data for 0.8 tnM TX-114 aqueous solution with added alcohols.
Table 3.5. CP data for 0.8 niMTX-114aqaeous solution with added alcohols.
Table 3.6. CP data for 0.8 mMTX-114aqueoussolution with added amines.
Table 3.7. CP data for 0.8 mM TX-114 aqueous solution with added amines.
Table 3.8. CP data for 0.8 mMTX-114 aqueous solution with added alcohols.
[Cyclopentanol]
(M) 0.00000 0.00432 0.00540 0.00620 0.00720 0.00864 0.01080
CP
rc)
23.0 22.5 20.5 19.0 17.0 16.0 14.0
[Ethanediol]
(M) 0.000 0.120 0.169 0.211 0.282 0.338 0.423
CP
CO
23.0 23.0 23.0 23.0 23.0 23.0 22.5
[Propanediol]
(M) 0.000 0.227 0.302 0.318 0.377 0.412 0.453
CP
CO
23.0 23.0 24.0 24.5 25.0 26.0 27.0
Table 3.9. CP data for 0.8 mM TX-114 aqueous solution with added hydrocarbons.
Table 3.10. CP data for 0.8 inMTX-114 aqueous solution with added ureas.
0.725
-Table 3.11. CP data for 0.8 mM TX-114 aqueous solution with added sugars.
1
i
Table 3.13. CP data for 0.8 mM TX-114 aqueous solution with added cationic conventional
Table 3.14. CP data for 0.8 mM TX-114 aqueous solution with added cationic gemini surfactants.
[16-4-16]
(10"^M) 0.000 3.315 6.630 9.950 13.260 16.575 19.890
CP
ro
23.0 27.0 29.0 31.0 33.5 35.0 37.0
[16-6-16]
(10-'M) 0.00 3.28 6.56 9.84 13.12
CP CC) 23.0 27.0 30.0 39.0 46.0
Table 3.15. CP data for 0.8 mM TX-114 aqueous solution with added anionic surfactants.
[SDS]
(10"^ M) 0.000 0.068 0.090 0.135 0.270 0.360 0.540 1.080 1.450 1.940 2.480 3.460 4.380
CP
ro
23.0 22.5 23.5 24.5 26.0 27.0 28.5 30.0 31.0 32.5 33.0 34.0 35.0
[SDBS]
(10-^ M) 0.000 0.034 0.068 0.100 0.200 0.410 0.500 0.580 0.700 0.875
CP
CO
23.0 22.5 24.5 26.0 28.0 29.5 30.5 31.5 32.0 33.0
Table 3.16. CP data for 0.8 mM TX-114 aqueous solution with added nonionic surfactants.
Table 3.17. CP data for 0.8 mM TX-114 aqueous solution with added polymers (polyethylene glycol PEG).
Table 3.18. CP data for 0.8 mM TX-114 aqueous solution with added polymers (polyvinyl pyyrolidon PVP).
[K-15]
Table 3.19. The energetic parameters for clouding in 0.80 mM TX-114 + additive systems.
Additives Pure TX-114
TBuAB
Mole fraction of the additive
7.2x10'
TASs°/kJ mor' -91.1
TPeAB
CsOH
3.9x10"
CPC
1.9x10"**
1.2x10-1.8xl0' 2.4xl0'
-31.7 -31.0 -30.5
-53.4 -54.1 -54.6
0.000
rTX-114](M)
Figure 3.1. Variation of cloud point (CP) with concentration of TX-114 aqueous solution.
80
60
^
-S 50
. 2 40
30-— I 30-— 0.00
— I —
0.02 0.04 O06 0.08
[Quatemaiy salts] (M)
OlO
— I — 012
Figure 3.2. Variation of cloud point (CP) of 0.8 mM TX-U4 aqueous solution with the concentration of various quaternary salts.
o
70 65 60 5 5 5 0
-1 **
o
Q- 40-1
•o O 35 O
30 25-1 20
0.00 0.02
-A-3.62x10''MTX-114 -•—8x10^MTX-114
— I —
0.04 0.06 0.08 0.10 0.12 [TBuAB] (M)
Figure 3.3. Variation of cloud point (CP) of TX-114 aqueous solution with the concentration ofTBuAB.
Q. o
•O 30 O O
25-- • 25-- C , O H - • - C ^ H - A - C , O H
—I ' 1 < 1 ' T"
0.0 0.2 0.4 0.6 0.8
[Alcohols] (M)
I ' I
1.0 1.2 1.4
Figure 3.4. Variation of cloud point (CP) of 0.8 mM TX-114 aqueous solution with the concentration of various alcohols.
24-,
22-
20-O
^^
18-o
"- 16-o
^
14-
12--0
.
I II
1
^
- * - C ^ O H
-m-cpH -•-cpn -A-cpu
- ^ - C , O H
1 1 1 1 1 1 • 1 i 1 I 1
1 0.0 0.1 0.2 0.3 0.4 0.5
*
' 1 ' 1 ' 1 0.6 0.7 0,8 [Alcohols] (M)
Figure 3.5. Variation of cloud point (CP) of 0.8 mM TX-114 aqueous solution with the concentration of various alcohols.
50
45
40-i 35H
T3
O 30
25
20
C,NK
—I ' 1 ' 1 ' 1 ' 1 — 0.0 0.1 0.2 0,3 0.4
[Amines] (M)
— I — 0.5
— I — 0.6
Figure 3.6. Variation of cloud point (CP) of 0.8 mM TX-114 aqueous solution with the concentration of various amines.
1 — • — I — ' — I — ' — I — ' — I — ' — r -0.01 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07
[Amines] (M)
Figures.?. Variation of cloud point (CP) of 0.8 mM TX-114 aqueous solution with the concentration of various amines.
28
26
24
O 22
O 20
J 18
16-
14-r
- cyclopentanol ethanediol - propanediol
— I —
0.0
—r-0.1 — I — 0.2 — I —
0.3 0.4 0.5 [Alcohols] (M)
Figure 3.8. Variation of cloud point (CP) of 0.8 mM TX-114 aqueous solution with the concentration of various alcohols.
so
[Hydrocarbons] (M)
Figure 3.9. Variation of cloud point (CP) of 0.8 mM TX-114 aqueous solution with the concentration of various hydrocarbons.
Figure 3.10. Variation of cloud point (CP) of 0.8 mM TX-114 aqueous solution with the concentration of various ureas.
24
22-
f-•o
16-s
1 4
1 2
-— I -— 0.0
->—xylose -B—sort>ose -»— arabinose - • — dextrose -A—fructose -*— mannose
— I 1 1 1 1 1 1 — 0.2 0.4 0.6 0.8
— I — 1.0 [Sugars] (M)
Figure 3.11. Variation of cloud point (CP) of TX-114 aqueous solution with the concentration of various sugars.
alanine proline aspartic actd histidine phenylalanine leucine Isoeucine methionine tryptophan
>— glutamine glycine threonine serine asparagine
0.06 0.08 [Amino acids] (M)
0.10
Figure 3.12. Variation of cloud point (CP) of 0.8 mM TX-114 aqueous solution with the concentration of various amino acids.
[Surfactants] (10^ M)
Figure 3.13. Variation of cloud point (CP) of 0.8 mM TX-114 aqueous solution with the concentration of various cationic conventional surfactants.
45
40 O
c 35 o J 30
25
-»—16-4-16 - A ^ 16-6-16
— I — 0.0
— I — 0.5
— I —
1.0 — I —
1.5 2.0 [Surfactants] (lO^M)
Figure 3.14. Variation of cloud point (CP) of 0.8 mM TX-114 aqueous solution with the concentration of various cationic gemini surfactants.
[Surfactants] (10* M)
Figure 3.15. Variation of cloud point (CP) of 0.8 mM TX-114 aqueous solution with the concentration of various anionic surfactants.
80
70
6 0 -O
c o O.
? 4 0 o
30
20-TX-100 - Tween-20
[Surfactants] (10 M)
Figure 3.16. Variation of cloud point (CP) of 0.8 mM TX-114 aqueous solution with the concentration of various nonionic surfactants.
24
22
20
O 18
o 16.
7T U O
12-
10-PEG-200 -PEG-300 PEG-600 PEG-1000
T - r
2 4 6
[Polymers] (wt%)
Figure 3.17. Variation of cloud point (CP) of 0.8 mM TX-114 aqueous solution with the concentration of various polymers.
25
§.0
•3
T • •
^r. 0
. . . , . . . T . .
- • - P V P K - 1 5 - T - P V P K - 2 5 - A - PVP K-30 - O - P V P K - 9 0
. , — , ,. _ j
g 10 [Polyjners] (wt %)
Figure 3.18. Variation of cloud point (CP) of 0.8 mM TX-114 aqueous solution with the concentration of various polymers.