The impact of chemical modification on charge injection at metal/polyolefin interfaces

The process of charge injection at metal/polymer interfaces is crucial to many areas of research and technology, such as organic light emitting and harvesting devices, high-voltage capacitors and cables. In this work, we study charge injection at metal/polymer interfaces for two polymers commonly used in high-voltage applications, namely polyethylene (PE) and polypropylene (PP). Using first-principles electronic structure methods, we compute charge injection barriers at model aluminium/PE and aluminium/PP interfaces. We show that the introduction of polar chemical groups (e.g., -COOH, -CH₂Cl, and -CHO) in the polymer chains at the interface can tune the intrinsic charge injection barrier significantly. We take into account of thermal disorder by averaging over a large ensemble of interface structures obtained from first-principles molecular dynamics trajectories. Our results suggest the possibility of rational design of metal/polymer interfaces via localised chemical modification.