可裂解的表面活性剂(英)(待续)

可裂解的表面活性剂值得关注有几方面的原因。首先，弱键联接的表面活性剂分子结构迎合了改善两亲性物质生物降解能力的发展趋势。裂解可以被酶催化，其生物降解作用可能与污水处理的一般发机理相符合。另外，这些表面活性剂也可以妥，例如，用酸、碱、此一（ＵＶ）、热或臭氧诱发降解反应，对酸、碱不稳定的表面活性剂已引起特别关注，因为在初始步骤所需的稳定性与其在后续步骤中应易裂解并不冲突。综述了制可裂解性表面活性剂的主

Cleavable Surfactants

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.