THE PROSPECTS OF USING ION-PLASMA MODIFICATION OF POLYURETHANES FOR CREATING DEFORMABLE BIOMEDICAL PRODUCTS

Abstract

Plasma treatment is a promising method for modifying materials. However, deformation of the elastic substrate can damage the modified layer that can lead to various undesirable consequences. Elastic polyurethanes (elastic modulus up to 30 MPa) were studied; the polymers were treated by plasma immersion ion implantation of nitrogen ions with energy from 0,1 to 3 keV. Materials were investigated by atomic force microscopy, spectroscopy, the wettability and free energy of the surface were measured. Mechanical uniaxial tests were carried out and then surfaces were re-examined. Proteins and bacteria adsorption was studied, including the damaged surfaces under mechanical loads. As a result of the treatment with ion energy from 1 keV, the relief gets folded, the stiffness and hydrophobicity of the surface significantly increases, the adhesion of both gram-positive (staphyloco-ccus) and gram-negative (Escherichia coli) bacteria decreases. Cyclic uniaxial deformation causes transverse cracks and longitudinal folds on treated surfaces. Such changes provoke the bacterial growth to values greater than their number on untreated materials. The lower plasma energies (up to 0,5 keV) resulted in a slight increase in the stiffness of the modified layer (by 1,5 ... 2 times compared to untreated material), which made it possible to avoid surface damage under stretching. Due to the increased hydrophobicity and surface energy, the treated materials showed improved protein adsorption, the number of bacteria has decreased. All the surface changes (treatment, damage) correlate both with the properties of the original substrate (polyurethane is a block copolymer) and with the treatment mode.