oligomeric surfactants as novel type of amphiphiles ... ?· oligomeric surfactants as novel type...
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Universitt Potsdam Arbeitsgruppe Prof. A. Laschewsky
Oligomeric Surfactants as Novel Type of Amphiphiles:
Structure Property Relationships and Behaviour with Additives
zur Erlangung des akademischen Grades
Doktor der Naturwissenschaften (Dr. rer. nat.)
in der Wissenschaftsdisziplin
Kolloid- und Polymerchemie
eingereicht an der Mathematisch-Naturwissenschaftlichen Fakultt
der Universitt Potsdam
geboren am 16.06.1980 in Lesquin
Potsdam, im Dezember 2006
Not in knowledge is happiness, but in the acquisition of knowledge
Edgar Allan Poe, The Power of Words (1850)
I want to express my profound gratitude to the staffs of scientists and technicians and other
persons directly or indirectly involved in the completion of this work. The findings within this
dissertation would never have been so fruitful without the help of these people.
First of all, I would like to thank sincerely Prof. Andr Laschewsky (University of Potsdam
and Fraunhofer Institute for Applied Polymer Research) for giving me the opportunity to carry out my
PhD thesis under his supervision, on a research topic of colloid and polymer science. I enjoyed the
multiple fields addressed within this PhD work, including surfactant chemistry (synthesis and
analysis) and physics (characterization), as well as polymer science. I am indebted to him for his
helpful guidance throughout these three years, especially when precise practical or theoretical
problems arose. Furthermore, I am grateful for the real autonomy he gave me so that I could explore
the topic by myself and fulfill my own ideas. I appreciated his availability for discussions, during
which I definitely benefited from his great knowledge and experience in chemistry. Likewise, I thank
him for his encouragement and trust, and for interesting conversations on open subjects. Finally I
gratefully acknowledge him for giving me the opportunity to develop cooperations on the topic with
other scientists and also for allowing me to present our results at international conferences.
I am grateful to Dr. R. H. Rakotoaly (Universit Catholique de Louvain, Louvain-la-Neuve,
Belgium) for the synthesis of the cationic oligomers, leaving enough material to start the first
measurements of my work.
I would like to thank Prof. J.-L. Habib-Jiwan (UCL) for his hospitality during my stay in
Louvain-la-Neuve and for allowing me to perform time-resolved fluorescence quenching
measurements (TRFQ) with a first-rate Laser equipment. I greatly appreciated his comments on the
use of an uncommon fluorescent probe for the determination of micellar aggregation numbers.
Moreover, I am extremely grateful to A. Moussa for his valuable help with the TRFQ measurements
and his involvement during my stay in Louvain-la-Neuve.
I am thankful to Dr. K. Lunkenheimer (Max Planck Institute of Colloids and Interfaces,
Golm) for determination of the critical micellization concentrations of the cationic dimers and for
interesting discussions about surface tension measurements. Likewise, I gratefully acknowledge Dr.
M. Arotarna and A. Baudoult (UCL) for technical assistance with CMC determination via
fluorescence, Prof. J. Ktz and Dr. S. Kosmella (Universitt Potsdam) for interesting discussions on
colloid chemistry and for providing access to the surfactant selective electrodes, C. Note for help with
phase diagram determination and turbidimetric measurements, Dr. B. Tiersch for the cryo-SEM
pictures, Dr. M. Heydenreich and A. Krtitschka for help with NMR spectroscopy, Dr. V. Strehmel for
her help with TGA and DSC measurements as well as with administrative issues, Dr M. Page (MPI)
for stimulating discussions on worm-like micelles, Dr. R. Sigel and Dr. S. Kubowicz (MPI) for
discussions about static and dynamic light scattering. Special thanks go to S. Ra (Ecole Nationale
Suprieure de Chimie de Lille, France) for her practical help with counterion-modified gemini
surfactants: her 2-month placement was a good experience to test my abilities as a supervisor. I also
wish to thank Prof J.-M. Aubry (ENSCL, France) who kindly introduced me to Prof. Laschewsky in
2003, and Dr. V. Rataj for her interest in dimeric surfactants for new developments in catalytic
reactions. Prof. M. Gradzielski and Dr. S. Prvost (Technische Universitt Berlin) are acknowledged
for their interest in catanionic mixtures with gemini surfactants.
Also, I am grateful to Dr. U. Buller and Dr. H.-P. Fink who permitted me to work in the
laboratories of the Fraunhofer institute (IAP). Particularly, I wish to express my appreciation to the
scientists and technicians of the FB 4 (division of water-based polymer systems) for the friendly
environment and practical help. Dr. E. Goernitz is gratefully acknowledged for his useful comments
on rheology and expertise with the rheometer. In addition, I would like to thank Dr. B. Paulke for
access to the tensiometer, as well as Dr. J. Storsberg, Dr. S. Bruzzano, Dr. J.-F. Lutz for motivating
scientific discussions. Special thanks to the lab and office mates for the nice work atmosphere: Dr. J.-
F. Baussard, Dr. M. Mertoglu, Dr. S. Garnier, K. Skrabania, J. Kristen, F. Salles, N. Zuber, A.
Bivigou-Koumba, P. Ott, O. Mauger, E. Mller, Dr. M. Pch.
I send my heartfelt thanks to my brother Alexis, sister Mlanie and friends in France and
Berlin-Brandenburg for their important support all over these years and for giving me precious thesis-
unrelated moments. I do not forget to thank my football mates of the S.G. Saarmund for their warm
welcome in the club and for providing great times of entertainment.
I am forever indebted to my parents Dany and Rgine for their understanding, help and
encouragement whatever I have carried out in my life. Finally, I wish to express my love to Carine
and thank her for her endless patience and support in every-day life, and for always being at my side
whenever I need it.
All contributed to make my PhD work abroad a great experience and an enjoyable time.
Merci vous tous,
The properties of a series of well-defined new surfactant oligomers (dimers to tetramers) were examined. From a molecular point of view, these oligomeric surfactants consist of simple
monomeric cationic surfactant fragments coupled via the hydrophilic ammonium chloride head groups
by spacer groups (different in nature and length).
Properties of these cationic surfactant oligomers in aqueous solution such as solubility,
micellization and surface activity, micellar size and aggregation number were discussed with respect
to the two new molecular variables introduced, i.e. degree of oligomerization and spacer group, in
order to establish structure property relationships. Thus, increasing the degree of oligomerization
results in a pronounced decrease of the critical micellization concentration (CMC). Both reduced
spacer length and increased spacer hydrophobicity lead to a decrease of the CMC, but to a lesser
extent. For these particular compounds, the formed micelles are relatively small and their aggregation
number decreases with increasing the degree of oligomerization, increasing spacer length and sterical
hindrance. In addition, pseudo-phase diagrams were established for the dimeric surfactants in more
complex systems, namely inverse microemulsions, demonstrating again the important influence of the
spacer group on the surfactant behaviour.
Furthermore, the influence of additives on the property profile of the dimeric compounds
was examined, in order to see if the solution properties can be improved while using less material.
Strong synergistic effects were observed by adding special organic salts (e.g. sodium salicylate,
sodium vinyl benzoate, etc.) to the surfactant dimers in stoichiometric amounts. For such mixtures, the
critical aggregation concentration is strongly shifted to lower concentration, the effect being more
pronounced for dimers than for analogous monomers. A sharp decrease of the surface tension can also
be attained. Many of the organic anions produce viscoelastic solutions when added to the relatively
short-chain dimers in aqueous solution, as evidenced by rheological measurements. This behaviour
reflects the formation of entangled wormlike micelles due to strong interactions of the anions with the
cationic surfactants, decreasing the curvature of the micellar aggregates. It is found that the associative
behaviour is enhanced by dimerization. For a given counterion, the spacer group may also induce a
stronger viscosifying effect depending on its length and hydrophobicity.
Oppositely charged surfactants were combined with the cationic dimers, too. First, some
mixtures with the conventional anionic surfactant SDS revealed vesicular aggregates in solution. Also,
in view of these catanionic mixtures, a novel anionic dimeric surfactant based on EDTA was
synthesized and studied. The synthesis route is relatively simple and the compound exhibits
particularly appealing properties such as low CMC and CMC values, good solubilization capacity of
hydrophobic probes and high tolerance to hard water. Noteworthy, mixtur