Biodegradability cleavable surfactants

The interest in cleavable surfactants has increased rapidly in recent years and the topic has been covered in review papers during the last decade [1-4]. This chapter begins with a relatively thorough discussion about the incentive for hydrolyzable surfactants, continues with a discussion about biodegradation of surfactants, which is important for understanding the concept of hydrolyzable surfactants, and then gives an account of the development of hydrolyzable surfactants with an emphasis on recent results. 

Hohnberg, K., Cleavable surfactants, mNovelSurfactants. Synthesis, Applications and Biodegradability, Ed., K. Hohnberg, Surfactant Science Series, Vol. 74, Marcel Dekker, New York, 1998. www.cler.com. 

Ono, D. Yamamura, S. Nakamura, M. Takeda, T. Masuyama, A. Nakatsuji, Y. Biodegradation of different carboxylate types of cleavable surfactants bearing a 1,3-dioxolane ring. J. Am. Oil Chemists Soc. 1995, 72, 853-856. 

As a consequence of this specific structure, esterquats upon hydrolysis decompose into non-surface-active fragments. They may be referred to as cleavable surfactants. As a matter of fact, esterquats usually biodegrade more rapidly than the related alkylquats. The hydrolytic instability, on the other hand, comprises a challenge to the user and formulator. While traditional alkylquats are virtually stable under the conditions of use, esterquats... 

A third and more recent example of where readily biodegradable surfactants have replaced surfactants that are more long-lived in the environment is the taking over of the market for textile softener surfactants by the ester quats from the stable quats. This transition is still in progress today but for several years the big soapers all base their softener formulations for the US and Western Europe markets on ester quats instead of traditional, stable quats. The change from stable quats to ester quats is probably the best example of the concept of introducing a cleavable bond in a given surfactant structure because the two types of products are very similar in structure and physical chemical charac-... 

The new structures place a cleavable functionality within the twin tails of the cationic surfactant which aids in biodegradation by separating the positively charged nitrogen hy-drophile from the hydrophobic portion as shown in Figure 6.2. 

A third important factor in biodegradation is the presence of cleavable bonds in the alkyl chain, which depend on branching. Extensive branching of the alkyl chain tends to reduce the rate of biodegradation. This is probably due to steric hindrance preventing close approach of the surfactant molecule into the active site of the enzyme. 

Masayama, A. Endo, C. Takeda, S. Nojima, M. Ono, D. Takeda, T. Ozone-cleavable gemini surfactants. Their surface-active properties, ozonolysis, and biodegradability. Langmuir 2000, 16, 368-373. 

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