WATER-INSOLUBLE COMPLEXES OF POLY(L-LYSINE) WITH MIXED ALKYL SULFATES- COMPOSITION-CONTROLLED SOLID-STATE STRUCTURES

Structures of the water-insoluble complexes of poly(L-lysine) with oct yl and octadedecyl sulfates, and with the mixtures of these surfactant s, were examined via X-ray diffraction, infrared spectroscopy, and dif ferential scanning calorimetry. The solid-state structures of the comp lexes were shown to be governed by their compositions. In the stoichio metric poly(L-lysine) complex with octadecyl sulfate, surfactant chain s crystallize on a hexagonal lattice. In the poly(L-lysine)-octyl sulf ate complex of nearly stoichiometric composition, the surfactants are arranged on an alkane-type two-dimensional lattice. In the complex wit h 20 mol % octadecyl sulfate and about 75 mol % octyl sulfate, the lon ger surfactant chains form hexagonal crystalline blocks, and the short er chains are arranged on an alkane-type two-dimensional lattice. In t he poly(L-lysine) complex with 10 mol % octadecyl sulfate and about 85 mol % octyl sulfate, all surfactant chains are arranged on a two-dime nsional alkane-type lattice. All complexes are organized in lamellar s tructures consisting of layers of poly(L-lysine) chains in beta-sheet conformations, separated by layers of surfactants. Complexes with crys talline and partially crystalline surfactants adopt lamellar structure s with identical long periods and with interdigitated octadecyl chains . Complexes with two-dimensional order in the surfactant arrangement a lso adopt lamellar structures with identical long periods and with oct yl chains packed tail to tail.