Cleavable surfactants

Abstract

Cleavable surfactants are of interest for several reasons. Above all, the development of surfactants with weak bonds deliberately built into the structure is driven by the need for improved biodegradability of amphiphiles. The breakdown may be catalyzed by enzymes, and biodegradation would be the normal mechanism in sewage plants. Alternatively, the surfactant may degrade by chemical means, e.g., induced by acid, alkali, ultraviolet (UV) light, heat, or ozone. Acid-and alkali-labile surfactants have attracted particular attention, and there is often a compromise between required stability at one stage and ease of breakdown at a subsequent stage. The paper reviews the main routes used to prepare cleavable surfactants and points out advantages and disadvantages of the different approaches. Emphasis is placed on the development during recent years. Cyclic and acyclic acetals, ketals, and ortho esters are the most important types of bonds for the preparation of acid-labile surfactants, whereas alkali-labile amphiphiles usually are based on ester bonds. The ester bond approach has been particularly important for cationic surfactants, and so-called ester quats have rapidly taken a large share of the traditional market for quats. Betaine esters constitute a special class of ester with very pronounced pH dependence. UV-labile surfactants based, for instance, on an azo bond, offer promise for the future.Paper no. S1174 in JSD 3, 81-91 (January 2000). KEY WORDS: Acetal, betaine ester, choline ester, cleavable surfactant, ester quat, isethionate ester, ketal, labile surfactant, ortho ester, UV degradation. SCHEME 17 SCHEME 16amples of environmentally benign amphiphiles. These surfactants, which contain unsaturated bonds, break down easily during ozonization of water, which is a water purification process of growing importance (64).

Tuning the Amphiphilicity of Building Blocks: Controlled Self‐Assembly and Disassembly for Functional Supramolecular Materials

“…[52][53][54] Some pH-responsive groups for the fabrication of controllable surfactants or amphiphilic polymers have been well reviewed. [55][56][57][58][59][60] Some new and important progresses in the tuning of molecular amphiphilicity and material properties by pH stimuli need to be highlighted. For example, Kataoka and coworkers recently reported a pH-responsive block copolymer that can perform a chargeconversion on one block by external pH stimulus.…”

Ortho ester‐based cleavable cationic surfactants

“…The present paper shows that this new family of cleavable surfactants can be extended to corresponding cationic products as well. In recent years, there has been a strong trend toward the development of surfactants containing a weak bond that connects the polar head group and the hydrophobic tail of the surfactant (2). This is largely valid also for the subgroup of cationic surfaceactive agents, as has been demonstrated by a number of very recent publications.…”

Controlled Release of Volatiles under Mild Reaction Conditions: From Nature to Everyday Products

“…[124] Betaine esters have also been explored for the development of cleavable surfactants. [127,128] The hydrolysis of the betaine esters is strongly pHdependent [124,125,129] and, as a consequence of their micelleforming properties, further increased by micellar catalysis. [128] Betaine ester 56, for example, is completely hydrolyzed within about 20 minutes under alkaline conditions (pH > 8) and only by about 20 % after one hour under acidic conditions (pH < 6).…”