Cleavable Cationic Gemini Surfactants
Doktorsavhandling, 2012

This research project concerns investigations of ester-containing cationic gemini surfactants (esterquat and betaine ester types). These dimeric surfactants are compared with their monomeric counterparts. Series of both stable and ester-containing cationic gemini and monomeric surfactants were synthesized and their physical-chemical properties were investigated. The critical micelle concentration (CMC) values of the ester-containing gemini surfactants were generally 10-20 times smaller than those of the corresponding monomers. The alkyl chain length was decisive of the CMC while the length and the nature of spacer did not affect the CMC much. The low CMC of the gemini surfactants resulted in very high efficiency in covering surfaces in adsorption experiments, in stabilizing emulsions and foams, and in solubilizing hydrophobic dyes. The micellar aggregation number of the surfactants was determined with steady state and with time-resolved fluorescence quenching. Based on calculations of diffusion coefficients obtained from NMR measurements, a growth of the micelles with increasing surfactant concentration was observed for some of the gemini surfactants and a structure of interdigitated micelles was proposed for all the geminis. Studies of the chemical hydrolysis showed that the betaine ester type surfactants were much more susceptible to alkaline hydrolysis than the esterquat type surfactants. It was also found that the ester-containing geminis hydrolyzed more readily than the ester-containing monomeric surfactants, which was attributed to an anchimeric assistance by the second quaternary ammonium head group. In contrast to the results from the chemical hydrolysis the monomeric ester-containing surfactants biodegraded faster than the corresponding gemini surfactants. The low rate of biodegradation of the ester-containing geminis was found to be due to the dicationic species formed on hydrolysis of the two ester bonds being very resistant to further biodegradation.

chemical hydrolysis

esterquat

gemini

biodegradation

adsorption

cleavable

synthesis

betaine ester

surfactant

solubilization

shape and size of micelle

10an
Opponent: Prof. Per Claesson

Författare

Ali Tehrani

Chalmers, Kemi- och bioteknik

Cationic Ester-Containing Gemini Surfactants: Physical-Chemical Properties

Langmuir,; Vol. 26(2010)p. 9276-9282

Artikel i vetenskaplig tidskrift

Cationic ester-containing gemini surfactants: Adsorption at tailor-made surfaces monitored by SPR and QCM

Langmuir,; Vol. 24(2008)p. 6140-6145

Artikel i vetenskaplig tidskrift

Cationic ester-containing gemini surfactants: Chemical hydrolysis and biodegradation

J Colloid Interface Sci,; Vol. 312(2007)p. 444-452

Artikel i vetenskaplig tidskrift

Cleavable surfactants

Curr. Opinion Colloid Interface Sci,; Vol. 12(2007)p. 81-91

Artikel i vetenskaplig tidskrift

Tensider är ytaktiva ämnen som är viktiga ingredienser i hygienprodukter, rengöringsmedel, färger och många andra konsumentprodukter. De används också i en lång rad industriella tillämpningar. I utvecklingen av nya och förbättrade tensider ligger tyngdpunken på två aspekter: (i) ökad effektivitet så att man kan klara sig med mindre mängd tensid i formuleringen, samt (ii) förbättrad bionedbrytbarhet så att påverkan på miljön blir mindre. Målsättningen är att de nya tensider som presenteras i avhandlingen skall uppfylla båda dessa önskemål. De tensider som avhandlingen beskriver är katjoniska s.k. geminitensider. Gemini är latin för tvilling, och det handlar om en ny tensidtyp som består av två sammankopplade konventionella tensidmolekyler. Sådana tvillingtensider har visat sig vara mycket mer effektiva än konventionella tensider. I många fall kan man uppnå samma effekt i en applikation med upp till tio gånger mindre tensid i formuleringen om man använder en geminitensid istället för en konventionell tensid. I avhandlingen beskrivs ett sätt att markant öka nedbrytningshastigheten hos katjoniska geminitensider genom att bygga in hydrolyskänsliga esterbindningar, en i vardera tensidhalvan, i molekylerna. Ett stort antal hydrolyskänsliga geminitensider har syntetiserats och karakteriserats med avseende på struktur och fysikalisk-kemiska egenskaper.

Surfactants are among the most versatile products of the chemical industry and they have many applications in industry. Surfactants are also present in many products that we use in our daily life such as soaps, detergents, shampoos, shower gels, creams, cosmetics, foods, drugs, etc. The search for novel surfactants with higher efficiency and better performance gave birth to the concept of gemini surfactants. Gemini or dimeric surfactants represent a novel class of surfactants made up of two conventional single-chain surfactants which are chemically bonded by a linker between, or close to, the hydrophilic head groups. Gemini surfactants can replace single chain conventional surfactants in a wide range of applications. Before this can happen, two other criteria must be met, however. The first and most important one is the production cost of these new surfactants in comparison to conventional surfactants and the second one concerns the environmental legislations. In this study the concept of cationic gemini surfactants with higher efficiency and performance has been combined with the concept of cleavable surfactant by inserting a hydrolyzable bond in the alkyl tails near the quaternary head group. This study aims at understanding the relation between the chemical structure of ester-containing gemini surfactants and their physical-chemical properties, rate of chemical hydrolysis and rate of biodegradation.

Ämneskategorier

Materialteknik

Annan materialteknik

Styrkeområden

Materialvetenskap

ISBN

978-91-7385-638-6

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 0

10an

Opponent: Prof. Per Claesson