though the understanding of the degradation mechanism is The influence of the chemical structure of siloxane alkyl ammoof great importance in the synthesis of degradable surfactants nium bromides on their long-term stability in aqueous solution has (4). Rossmy (5) proposed a mechanism for hydrolytic been investigated by means of the change of the double layer cleavage of the siloxane bonds in trisiloxanes which is recapacity at the mercury/electrolyte interface and by mass spectrolated to the concentration of the monomolecularly dissolved scopic measurements. Generally, the degradation of the surfacsurfactant in water. The hydrolysis reduces the surface activtants is caused by a hydrolytic cleavage of the siloxane bonds, ity of the siloxane. Gru Β¨ning et al. (1) have shown that in leading to a loss of surface activity. Such a loss could be detected the range 7 Γ΅ pH Γ΅ 9 hydrolysis of trisiloxanes proceeds only in concentrated solutions (10 01 M), not in those Β°10 04 M.
only very slowly. Furthermore, the hydrolytic attack is as-In the case of branched trisiloxanes, the successive addition of a few methylene groups to one alkyl chain at the nitrogen atom sumed to involve predominantly the monomolecularly resulted in a dramatic decrease of the rate of hydrolysis. This solved part of the molecule whereas trisiloxane micelles are effect is consistent with the assumption that polar groups, located much more stable. Knoche et al. (6) reported a sudden at the surface of siloxane micelles, protect the siloxane bonds increase in the surface tension due to degradation of monoagainst hydrolytic attack and that this protection increases sigmers of the organosilicone surfactant L-77 and the occurnificantly with increasing alkyl chain length. α§ 1998 Academic Press rence of a lag period above the cmc. The longest time period