Abstract: Soluble carboxymethyl silk fibroin was prepared from the waste silk by etherification of the water-fast silk fibroin and the monochloracetic acid in ethanol. Various factors on etherified degree of products(such as alkalized time, alkalized temperature, etherified time and etherified temperature, etc.) were discussed. The optimized etherification conditions for preparing the carboxymethyl silk fibroin are: alkalization time:90 min; etherification time:90 min; alkalization temperature:25 ℃, etherification temperature:70 ℃. The degree of etherification of the carboxymethyl silk fibroin is 0.7425. The critical micellar density of carboxymethyl silk fibroin is 1.25 g/L and the hydrophilic-lipophilic balance(HLB) value is 10. The fibroin solution is unsuitable for using as a foamer, even though it has some foaming ability, and the formed foam is stable in the mass ration range of 1.0%~1.2%. The silk fibroin solution has exhibited excellent emulsifying capacity and emulsion stability, which renders the silk fibroin can be used as good emulsifiers.

Key words: Carboxymethyl Silk Fibroin, Alkalization, Etherification, The degree of etherification, emulsification, foaming