Study of xylan adsorption onto poly(ethylene terephthalate) using QCM-D

Abstract

Owing to superior mechanical properties, synthetic polymers like poly(ethylene terephthalate), polytetrafluorethylene, polypropylene, etc. keep an exceptional position in medical and technical fields. However, in many cases, their highly hydrophobic and inert surfaces represent an important drawback for many applications. Therefore, surface modifications are needed. The main aim of this investigation was to study the interaction of carboxymethylated xylans with poly(ethylene terephthalate) (PET) surfaces. Two different types of xylans, glucuronoxylan derived from wood, and arabinoxylan derived from oat spelt, were carboxymethylated in order to introduce hydrophilic entities. A quartz crystal microbalance with dissipation monitoring was used as a nanogram sensitive balance to detect the amount of deposited carboxymethylated xylans onto PET, as well as the behaviour of the bound xylan layers. The deposition/adsorption of xylans onto PET model films was studied in the dependence of the pH value and ionic strength, as well as of the presence of an anchoring polymer layer. Xylans deposit favourably at lower pH and higher ionic strengths, which are conditions leading to lower solubilities of xylans, manifesting that physical interactions between PET films and xylans are the driving force for the adsorption, which was reversible. When an intermediate layer of chosen functional polymer poly(ethyleneimine), a so-called anchoring agent was applied, the binding of xylans was improved significantly. The results showed that with the surface modifications and targeted introduction of derivatised xylans, it is possible to tailor surface hydrophilicities and reactivities of PET materials accurately.