Effects of Cationic Surfactants with an Alkyl Group of Different Chain Lengths on Permeability across Polymer Membranes Having Poly(L-glutamic acid) Domains

Abstract

Effects of five cationic surfactants, decyl (C10), dodecyl (C12), tetradecyl (C14), hexadecyl (C16), and octadecyl (C18) trimethylammonium chlorides, were investigated on the conformation of poly(L-glutamic acid) (PLGA) in a membrane composed of poly(butyl methacrylate)–poly(L-glutamic acid) graft copolymer, and on the permeability of phenyl-1,2-ethanediol across the membrane. For the membrane treated with NaOH, C10, C12, and C14 induced the coil-to-helix transition, but not C16 and C18, On the contrary, for the membrane treated with HCl, C16, and C18 induced the helix-to-coil transition of PLGA, but not C10, C12, and C14. In most cases, treatment of the membrane with surfactants brought about decrease in the permeability of phenyl-1,2-ethanediol, except for the effect of C16 and C18 to enhance the permeability across the membrane pretreated with HCl. These effects are considered due to increase in the hydrophobicity of the permeating pathway composed of PLGA chains, and/or their conformational transition in the membrane.