Influence of Selected Factors on the Adsorption Layer Structure of Polyamino Acids and Their Block Copolymers at the Solid–Aqueous Solution Interface

Abstract

The adsorption mechanism of different polymers containing ionic polyamino acids monomers in the chain structure at the solid–liquid interface was investigated. Initially, the influence of molecular weight and solution pH on simple polyamino acids (poly(L-aspartic acid) and poly(L-lysine) binding was determined. Considering the obtained dependencies, the polymer adsorption layer conformation was proposed in the systems containing block copolymers (both diblock and symmetrical triblock) consisting of polypeptide as well as poly(ethylene glycol) fragments. The presented studies focused on the application of two experimental methods. The polymer adsorption was carried out using the batch method and the adsorbate concentration was determined spectrophotometrically. Then, the turbidimetric measurements were taken. The analysis of the obtained results showed that the adsorption process of block copolymers depends on two factors. Firstly, the solution pH determines both the nature of the interactions of the copolymer structural units with the solid surface and the conformation of the polypeptide chains. The second parameter influencing the adsorption layer structure is the ratio of the lengths of both blocks. Introducing a short PEG fragment into the polymer main chain may improve the polymer adsorption properties by increasing the number of interactions with the adsorbent surface.