| 1. |
- Karlberg, Maria, et al.
(author)
-
Mixed solutions of an associating polymer with a cleavable surfactant
- 2005
-
In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 21:21, s. 9756-9763
-
Journal article (peer-reviewed)abstract
- Mixtures of hydrophobically modified hydroxyethyl cellulose (HMHEC) and alkali-sensitive cleavable betaine ester surfactants have been studied by viscometry, H-1 NMR, absorbance measurements, and birefringence determinations. Before the hydrolysis, the surfactants behaved as conventional nondegradable surfactants in terms of the effect on the viscosity of increasing surfactant concentration. As the surfactants were hydrolyzed, systems with time-dependent viscosity were obtained. The viscosity either decreased monotonically or went through a maximum as a function of time, depending on the initial surfactant concentration. Different surfactant chain lengths gave rise to different viscosity profiles. The rate of hydrolysis, and thus the time-dependency of the surfactant concentration, could be controlled by changing the pH of the solution.
|
|
| 2. |
- Lundberg, Dan, 1975, et al.
(author)
-
Cleavable Surfactants
- 2010
-
In: Encyclopedia of Surface and Colloid Science, 2nd Ed..
-
Book chapter (other academic/artistic)
|
|
| 3. |
- Lundberg, Dan, 1975, et al.
(author)
-
Ester-based surfactants: Are they stable enough?
- 2023
-
In: Journal of Surfactants and Detergents. - : Wiley. - 1558-9293 .- 1097-3958. ; 26:3, s. 229-236
-
Research review (peer-reviewed)abstract
- Surfactants with an ester bond connecting the polar headgroup and the hydrophobic tail are common. They are easy to synthesize, they can often be made from natural raw materials and their biodegradation profile is generally good, partly due to lipase or esterase catalyzed breakdown of the ester bond in sewage plants. A labile ester bond in the molecule may cause problems, however. Surfactants are often formulated at relatively high pH and it is important that they remain intact for a given period of time. In this article we discuss alkaline hydrolysis of different types of ester-based surfactants—cationic, anionic and nonionic—and also of surfactant mixtures. We show that the ester bond in a surfactant has a different hydrolysis pattern than ester bonds in non-surface active uncharged molecules. Cationic ester-based surfactants are hydrolyzed rapidly while anionic and also nonionic ester-containing surfactants are relatively resistant to hydrolysis.
|
|
| 4. |
- Lundberg, Dan, 1975, et al.
(author)
-
Hydrolysis of Surfactants Containing Ester Bonds: Modulation of Reaction Kinetics and Important Aspects of Surfactant Self-Assembly
- 2011
-
In: Journal of Chemical Education. - : American Chemical Society (ACS). - 0021-9584 .- 1938-1328. ; 88:9, s. 1274-1277
-
Journal article (peer-reviewed)abstract
- The effects of self-assembly on the hydrolysis kinetics of surfactants that contain ester bonds are discussed. A number of examples on how reaction rates and apparent reaction orders can be modulated by changes in the conditions, including an instance of apparent zero-order kinetics, are presented. Furthermore, it is shown that the examples on reaction kinetics display parallels and connections to important physicochemical aspects of surfactant aggregates, namely, the "reservoir function" of micelles and the fact that the headgroup region of micelles constitutes an aqueous environment largely distinct from the bulk solution. The examples presented can be used in teaching organic as well as physical chemistry. The text is written with the intention to be largely self-contained, in order to make it accessible for readers with different background experience.
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Stjerndahl, Maria, 1975, et al.
(author)
-
Cleavable Surfactants: A Comparison between Ester, Amide, and Carbonate as the Weak Bond
- 2019
-
In: Journal of Surfactants and Detergents. - : Wiley. - 1558-9293 .- 1097-3958. ; 22:5, s. 1139-1145
-
Journal article (peer-reviewed)abstract
- Cleavable surfactants, i.e., surfactants in which a weak bond has deliberately been inserted into the molecule, are of interest when remaining surface-active material at a surface can cause problems. Ester and amide bonds are established as week linkages in surfactants but these generate an acid when they hydrolyze. For some applications, acidic degradation products are unwanted. Surfactants with a carbonate bond between the polar headgroup and the hydrophobic tail are of interest for such purposes. In this article, we compare the physical–chemical properties of nonionic carbonate surfactants with those of the corresponding ester and amide surfactants. The half-lives of the different cleavable surfactants are also compared and it was found that a carbonate bond is slightly more stable to alkaline hydrolysis than an ester bond when present in otherwise identical structures. A nonionic Gemini surfactant with a carbonate bond in the spacer, which on hydrolysis decomposes into two identical single-tailed nonionic amphiphiles, is also presented. The hydrolysis kinetics for this surfactant was studied in some detail and it was found that it degrades much faster at low temperature than at higher temperature. This anti-Arrhenius type of hydrolysis kinetics is proposed to be due to the reverse solubility versus temperature behavior of ethoxylated surfactants.
|
|
| 8. |
- Stjerndahl, Maria, 1975, et al.
(author)
-
NMR studies of aggregation and hydration of surfactants containing amide bonds
- 2007
-
In: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 111:8, s. 2008-2014
-
Journal article (peer-reviewed)abstract
- The consequences of including amide bonds into the structure of short-chain nonionic surfactants have been studied. Of particular interest were the possible effects of the hydrogen bonding ability of the amide group on the micellar shape. The aggregate structure and hydration of two different amide-containing surfactants, C7H15CO-NH-(CH2CH2O)(4)H and C7H15CO-(NH-C3H6-CO)(2)N(CH3)(2), were investigated using NMR diffusometry (pulsed gradient spin echo NMR) as the main technique. Data from experiments on the surfactants, the hydrophobic probe molecule hexamethyldisilane (HMDS), and water were interpreted to gain information about the solution structures, and the results were compared to those on a previously studied alcohol ethoxylate surfactant of similar size, C8E4. Both of the amide-containing surfactants form small micelles within the whole investigated concentration range. At the critical micelle concentration, the aggregates are most probably spherical, and with increasing surfactant concentration there are indications of either a minor aggregate growth or agglomeration of the micelles. In addition, it was found that the presence of amide groups in the surfactant inhibits the intermicellar transport of HMDS, which occurs in the C8E4 system. From measurements on water diffusion in the three surfactant systems, it could be concluded that the surfactant hydration is higher when amide bonds are present.
|
|
| 9. |
|
|
| 10. |
- Lundberg, Dan, 1975, et al.
(author)
-
Structural Evolution of Oleyl Betainate Aggregates: In Situ Formation of Small Unilamellar Vesicles
- 2010
-
In: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 26:11, s. 7996-8001
-
Journal article (peer-reviewed)abstract
- Betaine esters prepared from long-chain alcohols are a class of hydrolyzable cationic surfactants that is interesting both because the compounds can be designed to give harmless products on degradation and that the hydrolysis products can induce potentially useful changes in the properties of systems where such surfactants are present. In this work, the evolution in structure of aggregates formed by oleyl betainate during hydrolysis of the compound has been investigated using H-1 NMR and cryo-transmission electron microscopy (cryo-TEM). With an increasing extent of hydrolysis, and thus an increasing fraction of oleyl alcohol in the aggregates, the aggregate structure changes in a sequence consistent with an increase in the average packing parameter of the surfactant-alcohol mixture, from spherical micelles, via wormlike micelles, to vesicles. An important result front this work is that it demonstrates a means of in situ production of small unilamellar vesicles with a rather narrow size distribution.
|
|
