In situ IR Spectroscopy as a Tool to Better Understand the Growth Mechanisms of Plasma Polymers Thin Films

Abstract

Aiming to get a better understanding of the growth mechanism during the plasma polymerization process of ethyl lactate, the surface reactivity of ester-bearing fragments has been determined by combining in situ FTIR spectroscopy and XPS measurements. While the plasma density of the reactive ester-bearing fragment decreases by one order of magnitude (from ∼2 × 1020 m-3 to ∼2 × 1019 m-3) as the power increases from 60 to 280 W, the ester group density in the plasma polymer films decreases from ∼1.5 × 1019 m-2/m2 to ∼1.7 × 1018 m-2. The associated incorporation efficiency of the reactive ester-bearings fragments in the films (σester) consequently increases from 2.6 × 10-6 to 1.3 × 10-4 when increasing the power. This behavior is attributed to higher activation the growing film surface.