Functionalisation of poly(ethylene terephthalate) (PET) surfaces with two cationised xylans by means of two anchoring polymers

The main aim of this investigation was to study the interaction of cationised xylans as antimicrobial substances with poly(ethylene terephthalate) (PET) model films, prepared by spin coating. A quartz crystal microbalance (QCM-D) with dissipation monitoring was applied as a nanogram sensitive balance to detect the amount of adsorbed cationised xylans. The xylan adsorption onto PET model films was studied as a function of pH and ionic strength. To improve the adsorption, positively charged polyethylenimid (PEI) and negatively charged polyvinyl-sulfonic acid (PVSA), as sodium salt, were applied as anchoring polymers. Surface free energies and hydrophilic/hydrophobic properties of surfaces were monitored by goniometry. Cationised xylans favourably deposited at pH 5, where beside electrostatic, physical interactions are possible, and adsorption may be driven by entropy gain. Higher ionic strengths of solutions also improved adsorption, due to the lower water solubilities of xylans. When intermediate layers of chosen anchoring polymers were applied on the PET surfaces, the binding of xylans as well as their coating durability were improved. Surface modifications presented in this work, provided important information regarding the adsorption/desorption phenomena between antimicrobial cationised xylans and synthetic PET surfaces. The latter is of great interest, when composing hydrophilic and antimicrobial PET surfaces for medical applications.