Monolayers of poly(L,D, and DL)alanine and their mixtures with arachidic acid

Abstract

Monolayers of poly(L,D, DL)alanine were studied on substrates containing Ca 2+, Na +, and K + and in mixtures with arachidic acid. Application of the theory of Huggins shows that the most stable isomeric form, from a thermodynamic standpoint, is the L form, while the least thermodynamically stable is the DL species. It has been seen that poly(L and D)alanine, which are present at the interphase as α helixes, show preferential interactions between the polymeric chains, while poly(DL)alanine, which is present in the β conformation, shows preferential interactions with the support. The presence of the Ca 2+ ions increases considerably the interactions between the polymer and the substrate. Mixtures of the three isomers show incompatibility which arachidic acid even if interactions are present between the lipidic chains and the macromolecular micelles in the “bad fit” zones of the latter.