A THEORETICAL-STUDY OF THE INTERFACES BETWEEN ALUMINUM AND POLY(ETHYLENE-TEREPHTHALATE), POLYCAPROLACTONE, AND POLYSTYRENE - ILLUSTRATION OF THE REACTIVITY OF ALUMINUM TOWARDS ESTER GROUPS AND PHENYL RINGS

The interfaces between aluminium and poly(ethylene terephthalate), pol y(epsilon-caprolactone), and polystyrene are investigated theoreticall y in order to assess the reactivity of aluminium towards the functiona l groups (i.e., ester functions and phenyl rings) present at the surfa ce of the polymers. The theoretical approach consists in performing qu antum-chemical calculations on small molecular model systems interacti ng with a few Al atoms. The geometric structures of the organometallic complexes are optimized and their stabilities and changes in charge d ensities due to Al bonding are evaluated. The results are compared to experimental X-ray photoelectron spectroscopy data collected during th e early stages of interface formation following aluminium deposition o n the polymer surfaces. in agreement with experimental data, it emerge s from this study that aluminium interacts strongly with both polyeste rs by forming covalent bonds with the carbon and oxy gen atoms of the ester functions. The attack of the poly(ethylene terephthalate) phenyl rings occurs only for high metal coverage and does not hamper the int eraction with the ester sites. Furthermore, our theoretical investigat ion has confirmed, on one hand, that the aluminium/polystyrene interac tions are weak, and on the other hand, the absence of strong reactions at the interfaces between aluminium and saturated hydrocarbon polymer s.