Ichizo Aoki

ON THE INTERACTION OF SURFACE ACTIVE AGENTS WITH SERICIN (PART 2)

The interaction of surface active agents with sericin has been studied with regard to reelability of cocoon in the process of raw silk production. The following results were obtained. 1) Anionic and cationic surface active agents were adsorbed on sericin at co-ion regions respectively, and the adsorption of the later took place at pH 2.5 where COOH groups of sericin scarecely dissociated. 2) In the co-ion region, the charge density of AgI sol particles covered with sericin became noticeable at about 10-4M concentration of surface active agents, and at about cmc it increased remarkably. Also, the surface active agents which have the same polar groups increased the charge density of AgI sol particles covered with sericin at lower concentrations with the increase in chain length of alkyl groups. 3) The increment of charge density of AgI sol particles covered with sericin by adsorption of surface active agents was observed in the order of counter ion> isoelectric point > co-ion region. This was also found in the adsorption test using cocoon layers. 4) The effect of surface active agents on the swelling ratio of cocoon layer was in the order of co-ion> isoelectric point >counter ion region. In the counter ion region, the swelling ratio decreased at around the concentration at which the charge of sericin was neutralized with surface active agent, while in the co-ion region it increased remarkably at about cmc. Similar phenomena were found in the solubility test of sericin with sodium lauryl sulfate. From these results, it is concluded that the interaction of surface active agent with sericin is due to both van der Waals force and electrostatic force (Coulombs force) and the swelling ratio of cocoon layer treated with surface active agent is influenced by intermolecular electrostatic repulsion of sericin due to the adsorption as well as by lowering of the surface tention or contact angle etc. (Received March 31, 1972)