Amino acid polymers for biomedical applications. I. Permeability properties of L‐leucine DL‐methionine copolymers

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Abstract
A series of DL‐methionine/L‐leucine copolymers was prepared from the coresponding N‐carboxy‐anhydrides. The copolymers formed clear flexible films having low water vapor transmission rates. Peroxide oxidation of the pendant methyl‐theioethyl groups to methyl‐sulfinoethyl groups enhanced the hydrophilic properties of the membranes, and the water vapor transmission rates rapidly increased with an increase in the number of pendant methyl‐sulfinoethyl groups. Increasing the leucine content of the membranes produced a 13‐fold increase in the carbon dioxide permeability and a 6‐fold increase in oxygen permeability, whereas, an increase in the methionine content doubled the carbon dioxide‐oxygen separation factor.Synthetic poly (α‐amino acids) are very similar to naturally occurring proteins with respect to composition and conformation. Because of these similarities, they are being considered in aerosol spray bandages, synthetic skin applications and as coatings for plastic prostheses. The unusual permeability characteristics of the DL‐methionine/L‐leucine copolymers make them interesting membranes for possible use in artificial kidney machines and blood oxygenators.