Preparation and Properties of A-B-A Tri-Block Copolymer Membranes Consisting of N-Hydroxyethyl-L-glutamine as the A Component and L-Leucine as the B Component

Abstract

A-B-A type tri-block copolymer consisting of N-hydroxyethyl-L-glutamine as the A component and L-leucine as the B component as well as the corresponding random copolymers and homopolymers were prepared by carrying out an aminoalcoholysis reaction with 2-amino-1-ethanol, together with a crosslinking reaction with octamethylenediamine on membranes of the starting polymer membranes including γ-benzyl L-glutamate residue. It was shown that the effective crosslink density was proportional to the percent crosslinker in the reaction mixture. The relation between their bulk structure and membrane properties was investigated, such as the degree of swelling in water, aqueous vapor permeability, tensile properties, and enzymatic degradation behavior of the membranes in pseudo-extracellular fluid (PECF) solution. The tensile properties of the hydrophilic membranes were highly dependent on the degree of swelling in PECF, and on the hydrophobic portions in molecular chains, whose behavior was typical of an elastomer. A common relation was observed between the rate of water vapor permeation and the degree of swelling QW(%) of membranes in PECF in the higher QW region, in spite of the difference of the nature of the side chains. Biodegradation of samples in vitro by proteases indicated that the degradation was a bulk rather than a surface phenomenon, and that the rate of degradation was also highly dependent on the QW values of sample membranes in PECF.