Water-Insoluble Complexes of Poly(l-Lysine) with Mixed Alkyl Sulfates:  Composition-Controlled Solid State Structures

Abstract

Structures of the water-insoluble complexes of poly(L-lysine) with octyl and octadedecyl sulfates, and with the mixtures of these surfactants, were examined via X-ray diffraction, infrared spectroscopy, and differential scanning calorimetry. The solid-state structures of the complexes were shown to be governed by their compositions. In the stoichiometric poly(L-lysine) complex with octadecyl sulfate, surfactant chains crystallize on a hexagonal lattice. In the poly(L-lysine)-octyl sulfate complex of nearly stoichiometric composition, the surfactants are arranged on an alkane-type two-dimensional lattice. In the complex with 20 mol % octadecyl sulfate and about 75 mol % octyl sulfate, the longer surfactant chains form hexagonal crystalline blocks, and the shorter chains are arranged on an alkanetype two-dimensional lattice. In the poly(L-lysine) complex with 10 mol % octadecyl sulfate and about 85 mol % octyl sulfate, all surfactant chains are arranged on a two-dimensional alkane-type lattice. All complexes are organized in lamellar structures consisting of layers of poly(L-lysine) chains in /J-sheet conformations, separated by layers of surfactants. Complexes with crystalline and partially crystalline surfactants adopt lamellar structures with identical long periods and with interdigitated octadecyl chains. Complexes with two-dimensional order in the surfactant arrangement also adopt lamellar structures with identical long periods and with octyl chains packed tail to tail.

Liquid Crystalline Period Variations in Self‐Assembled Block Copolypeptides–Surfactant Ionic Complexes

“…The same structure has previously been reported for other stoichiometric polypeptide-surfactant complexes. [13,28] Particularly, PNiPAM 360 -b-PLG(C18) 108 -b-PLLys 344 gives a lamellae spacing of 3.81 nm, which is very close to the value of 3.93 nm reported in the literature for the nearly identical PLG-C18 complexes. [14] Also, its very pronounced second-order peak indicates sharply defined lamellar interfaces, consistent with the appearance of crystallization of the surfactant tails which can be inferred by the crystallization peak at 15.10 nm…”

Nonstoichiometric polymer-surfactant complexes obtained in a lamellar lyotropic medium

“…(13), it can be considered that 8 L w % 1 À d AOT d = , since the polymer concentration is small compared to the water content.…”

“…As a consequence of these two directing forces, PSCs usually present long-range order showing different types of organized structures, namely, lamellar [7,8], cubic [9,10], or hexagonal [11]. The type of structures formed depends on factors such as the global composition [12], the length of the surfactant alkyl chain [13], the length of the polymer chain [14], the charge density of the polyelectrolyte [15], or the presence of cosurfactants [16]. The composition of these complexes is usually assumed to be stoichiometric with equal amounts of the two species of opposite charge [3,6,[17][18][19], but in most of the systems studied, their detailed stoichiometry has not been characterized, and in a few cases, nonstoichiometric complexes have also been formed [20,21].…”

Assembled Materials: Polyelectrolyte-Surfactant Complexes

“…The properties of such kind of complexes offer a possibility to replace expensive and synthetically complicated chiral liquid-crystal systems. The MacKnight group extended their work to solid complexes formed by poly-L-lysine with mixed surfactants of SC 8 S and SC 18 S. [76] The solid-state structures of the complexes were controlled by the molar ratio of the two surfactants with different alkyl chain length. Dreja and Lennartz also reported polymerizable polyelectrolyte±surfactant complexes from monomeric ammonium cations and PSS.…”